TROUBLESHOOTING FINDER

Something wrong with an instrument?

Describe the symptom and see the likely causes and what to do — 358 problems across 72 instruments.

358 of 358 problems

HPLCHigh back-pressure
Likely causes
- • Blocked column frit or guard column
- • Precipitated buffer in tubing
- • Blocked in-line filter
What to do
- • Replace the guard column or in-line filter
- • Back-flush the column if the supplier allows
- • Flush the system with warm water to dissolve buffer salts
HPLCPressure fluctuating
Likely causes
- • Air bubble in the pump head
- • Faulty or dirty check valve
- • Leaking pump seal
What to do
- • Degas mobile phase and purge the pump
- • Sonicate or replace check valves
- • Replace pump seals
HPLCRetention time shifting
Likely causes
- • Change in mobile-phase composition or pH
- • Column temperature not controlled
- • Flow rate error or leak
- • Column not equilibrated
What to do
- • Prepare fresh mobile phase exactly as per the method
- • Use the column oven
- • Check for leaks and verify flow rate
- • Equilibrate for longer
HPLCBaseline drift or noise
Likely causes
- • Contaminated mobile phase
- • Lamp near end of life
- • Air in the detector cell
- • Room temperature changes
What to do
- • Use fresh HPLC-grade solvents
- • Check lamp energy and replace if low
- • Flush the flow cell
- • Keep the instrument away from draughts and direct sunlight
HPLCPeak tailing
Likely causes
- • Column degradation or void
- • Secondary interactions with silanol groups
- • Mobile-phase pH close to analyte pKa
What to do
- • Replace the column
- • Use an end-capped column or adjust buffer
- • Adjust pH as permitted by the method
HPLCGhost / extra peaks
Likely causes
- • Carry-over from a previous injection
- • Contaminated diluent or vials
- • Late-eluting peaks from an earlier run
What to do
- • Increase needle wash; run blanks
- • Use fresh diluent and clean vials
- • Extend run time or add a wash step
HPLCNo peaks
Likely causes
- • Lamp off or failed
- • Injection did not happen (empty vial, needle blocked)
- • Wrong wavelength
What to do
- • Check lamp status
- • Check vial volume and needle
- • Verify method settings
Analytical balanceReading drifts continuously
Likely causes
- • Draught or open door
- • Sample warmer or colder than the room
- • Static charge on the container or sample
- • Sample is absorbing moisture or evaporating
What to do
- • Close all doors and remove draught sources
- • Let the sample reach room temperature
- • Use an anti-static gun or ionising bar, or a metal container
- • Weigh quickly in a closed weighing bottle
Analytical balanceReading does not return to zero
Likely causes
- • Material left on the pan
- • Pan touching the draught shield
- • Temperature change since the last zero
What to do
- • Clean the pan and press zero again
- • Re-seat the pan correctly
- • Allow the balance to stabilise and re-zero
Analytical balanceUnstable reading, stability indicator never appears
Likely causes
- • Vibration from nearby equipment or traffic
- • Balance not level
- • Air conditioning blowing on the balance
What to do
- • Move the balance to an anti-vibration table away from pumps and centrifuges
- • Level the balance
- • Redirect the air flow or fit a cover
Analytical balanceDaily check fails
Likely causes
- • Balance not adjusted after a temperature change
- • Dirty or damaged check weight
- • Weight handled with bare fingers
What to do
- • Run the internal adjustment and repeat
- • Clean the weight with a lint-free cloth; use another calibrated weight
- • Always handle weights with forceps or gloves
Analytical balanceDifferent readings at different pan positions
Likely causes
- • Eccentricity error in the weighing cell
- • Pan bent or not seated
What to do
- • Always place samples in the centre
- • Re-seat the pan; call service if the eccentricity test fails
Analytical balanceError message or 'overload'
Likely causes
- • Load above capacity
- • Pan missing or blocked
- • Internal fault
What to do
- • Remove the load and check capacity
- • Fit the pan correctly
- • Restart the balance; call service if it continues
pH meterSlow or drifting reading
Likely causes
- • Blocked or dirty junction
- • Low ionic strength sample (e.g. purified water)
- • Old electrode
- • Refill hole closed
What to do
- • Clean the junction; soak in warm KCl
- • Use a low-ionic-strength electrode or add KCl as the method allows
- • Replace the electrode
- • Open the refill hole during measurement
pH meterSlope below 95%
Likely causes
- • Aged or dehydrated glass membrane
- • Contaminated or expired buffers
- • Deposits on the bulb
What to do
- • Rehydrate in storage solution for some hours
- • Use fresh buffers from a new bottle
- • Clean the electrode; replace it if the slope stays low
pH meterOffset outside ±30 mV
Likely causes
- • Contaminated reference electrolyte
- • Poisoned reference (e.g. sulfide, proteins)
- • Wrong buffer used for the first point
What to do
- • Replace the reference electrolyte
- • Clean or replace the electrode
- • Check buffer identity and value
pH meterUnstable, jumping reading
Likely causes
- • Air bubble in the bulb
- • Electrolyte level too low
- • Damaged cable or connector
- • Static or earth loop with the stirrer
What to do
- • Shake the electrode downwards like a thermometer
- • Top up electrolyte
- • Check or replace the cable
- • Stop the stirrer briefly or earth the set-up
pH meterCheck buffer reads outside limit after a passing calibration
Likely causes
- • Check buffer contaminated or at a different temperature
- • Electrode response not linear across the range
What to do
- • Use fresh check buffer at the same temperature
- • Recalibrate with buffers closer to the sample pH; replace the electrode if it persists
pH meterReading changes with stirring speed
Likely causes
- • Junction potential problem
- • Low ionic strength sample
What to do
- • Clean the junction
- • Use a constant stirring rate for buffers and samples, or read without stirring as the method states
Conductivity meterReading higher than expected in purified water
Likely causes
- • Carbon dioxide absorbed from air
- • Contaminated sampling container
- • Cell not rinsed
- • Real water system problem
What to do
- • Measure immediately, minimise air contact; continue to Stage 2/3 if needed
- • Use a clean, dedicated container
- • Rinse the cell repeatedly with sample
- • Check the water system and online trend
Conductivity meterUnstable or noisy reading
Likely causes
- • Air bubbles on the electrodes
- • Cell not fully immersed
- • Electrical interference from a stirrer or pump
What to do
- • Tap the cell to dislodge bubbles
- • Increase immersion depth
- • Move away from interference or earth the set-up
Conductivity meterCell constant drifts from its nominal value
Likely causes
- • Coating or deposits on the electrodes
- • Damaged electrode surface
- • Old or contaminated standard
What to do
- • Clean the cell as recommended
- • Replace the cell if damaged
- • Use a fresh standard in date
Conductivity meterStandard check fails
Likely causes
- • Wrong cell constant entered in the meter
- • Temperature compensation set incorrectly for the standard
- • Standard contaminated by air or by a dirty cell
What to do
- • Re-enter or re-determine the cell constant
- • Use the certificate value at the measured temperature, or the correct compensation
- • Pour a fresh portion of standard; rinse cell with standard first
Conductivity meterTemperature reading wrong
Likely causes
- • Faulty temperature sensor
- • Cell not fully immersed so sensor is in air
What to do
- • Check against a reference thermometer and replace if needed
- • Immerse the cell fully
UV-VisNoisy or drifting baseline
Likely causes
- • Lamps not fully warmed up
- • Deuterium lamp near end of life
- • Dirty optics or cuvette windows
- • Temperature changes in the room
What to do
- • Allow a longer warm-up
- • Check lamp energy and replace the lamp if low
- • Clean the cuvettes; get optics cleaned by service
- • Keep the instrument away from draughts and direct sunlight
UV-VisNegative absorbance readings
Likely causes
- • Blank absorbs more than the sample
- • Baseline taken with a dirty or different cuvette
- • Cuvettes not matched
What to do
- • Prepare the blank from the same solvent lot
- • Repeat the baseline with clean cuvettes
- • Use a matched pair or always use the same cell
UV-VisResults not reproducible
Likely causes
- • Cuvette placed in different orientations
- • Air bubbles or particles in the solution
- • Fingerprints on the optical faces
What to do
- • Mark the cuvette and always insert it the same way
- • Tap out bubbles; filter or centrifuge turbid solutions
- • Wipe the cuvette with lint-free tissue
UV-VisAbsorbance lower than expected at high concentration
Likely causes
- • Stray light at high absorbance
- • Solution outside the linear range
- • Chemical effects such as association at high concentration
What to do
- • Dilute so the reading falls in the linear range
- • Check stray-light performance
- • Use the dilution specified in the method
UV-Visλmax shifted from the expected value
Likely causes
- • Wavelength calibration error
- • Wrong solvent or pH (many drugs shift with pH)
- • Contaminated sample
What to do
- • Run a wavelength accuracy check (holmium oxide or deuterium lines)
- • Check the solvent and pH specified in the monograph
- • Prepare a fresh solution
UV-VisVery high or 'over-range' absorbance in the low UV
Likely causes
- • Solvent cut-off (solvent absorbs strongly)
- • Glass or plastic cuvette used in the UV
- • Lamp failure
What to do
- • Use a solvent with a suitable UV cut-off
- • Use quartz cuvettes below about 320 nm
- • Check lamp status and energy
FTIRLarge water vapour or CO₂ bands
Likely causes
- • Old background spectrum
- • Exhausted desiccant or no purge
- • Sample compartment left open
What to do
- • Collect a new background just before the sample
- • Replace the desiccant or restore purge
- • Keep the compartment closed and allow it to settle
FTIRWeak spectrum, low band intensities (ATR)
Likely causes
- • Poor contact between sample and crystal
- • Too little sample
- • Hard crystalline sample
What to do
- • Increase clamp pressure to the set position
- • Cover the whole crystal area
- • Grind the sample finely before measuring
FTIRCloudy KBr disc or sloping baseline
Likely causes
- • Wet KBr
- • Sample not ground finely enough (scattering)
- • Too much sample
What to do
- • Dry the KBr and work quickly in low humidity
- • Grind sample and KBr together thoroughly
- • Reduce the amount of sample
FTIRBroad band near 3400 cm⁻¹ and band near 1640 cm⁻¹ in a KBr spectrum
Likely causes
- • Moisture absorbed by KBr
What to do
- • Dry the KBr, store it in a desiccator and prepare discs quickly
- • Compare against a blank KBr disc
FTIRFlat-topped (saturated) bands
Likely causes
- • Disc too concentrated or too thick
What to do
- • Reduce the amount of sample in the disc or use ATR
FTIRLow energy or no interferogram
Likely causes
- • Source failure
- • Misalignment
- • Laser fault
- • Fogged KBr optics from humidity
What to do
- • Check the diagnostic page
- • Run the auto-alignment if available
- • Call service for source, laser or optics replacement
FTIRSample and reference spectra differ but the material is expected to be correct
Likely causes
- • Different polymorph or hydrate
- • Different measurement technique (ATR vs KBr)
- • Contamination on the crystal
What to do
- • Follow the monograph's instructions to recrystallise or dissolve and evaporate both sample and reference, then repeat
- • Use the same technique for both
- • Clean the crystal and re-measure
KF titrator (volumetric)High or unstable drift
Likely causes
- • Leaking septum or ground-glass joint
- • Exhausted molecular sieve
- • Exhausted solvent
- • Side reaction with the sample
What to do
- • Replace the septum and check all joints
- • Replace or regenerate the molecular sieve
- • Exchange the solvent
- • Use a reagent or solvent suitable for the sample, or a KF oven
KF titrator (volumetric)Endpoint never reached (titration runs on)
Likely causes
- • Side reaction consuming iodine, for example with ketones or aldehydes
- • Very large water content
- • Contaminated or wet solvent
What to do
- • Use ketone-compatible reagents for such samples
- • Reduce the sample mass
- • Replace the solvent
KF titrator (volumetric)Results too high
Likely causes
- • Moisture picked up during weighing or transfer
- • Wrong titre (too old, or determined incorrectly)
- • Drift not corrected
What to do
- • Weigh quickly and add the sample promptly
- • Redetermine the titre
- • Check drift correction is enabled
KF titrator (volumetric)Results too low or poor repeatability
Likely causes
- • Sample not fully dissolved, so water is not released
- • Endpoint criteria too loose (stop too early)
- • Sample mass too small
What to do
- • Use a co-solvent (for example formamide), longer extraction or a KF oven
- • Review endpoint and stop-drift settings
- • Increase sample mass so more reagent is consumed
KF titrator (volumetric)Slow titrations
Likely causes
- • Exhausted solvent
- • Dirty platinum electrode
- • pH outside the optimum range
What to do
- • Exchange the solvent
- • Clean the electrode
- • Buffer the solvent for acidic or basic samples
KF titrator (volumetric)Air bubbles in the burette
Likely causes
- • Loose tubing connection
- • Reagent outgassing
- • Empty reagent bottle
What to do
- • Tighten connections
- • Run several prepare / rinse cycles to expel bubbles
- • Refill the reagent bottle
Potentiometric titratorNo clear equivalence point
Likely causes
- • Wrong electrode for the titration type
- • Very weak acid or base in the chosen solvent
- • Sample mass too small
What to do
- • Use the electrode the method specifies
- • Use a non-aqueous solvent system if the method allows
- • Increase sample mass to consume more titrant
Potentiometric titratorNoisy or drifting potential
Likely causes
- • Blocked or dirty diaphragm
- • Low reference electrolyte
- • Static or poor earthing in non-aqueous solvents
- • Air bubble under the glass membrane
What to do
- • Clean the diaphragm or replace the electrode
- • Refill electrolyte and open the refill port during titration
- • Use an electrode suited to non-aqueous media
- • Shake the electrode to remove the bubble
Potentiometric titratorResults high or low compared with expected
Likely causes
- • Old or wrong titre of the titrant
- • Air bubbles in the burette
- • Blank not subtracted
- • Wrong sample mass entry
What to do
- • Restandardise the titrant
- • Flush the burette
- • Run and apply the blank
- • Check the mass transfer from the balance
Potentiometric titratorSlow electrode response
Likely causes
- • Ageing glass membrane
- • Protein or fat film on the membrane
- • Electrode stored dry
What to do
- • Clean or recondition the membrane as per supplier
- • Replace the electrode if slope and response remain poor
Potentiometric titratorTwo or more equivalence points detected
Likely causes
- • Polyprotic analyte or impurity
- • Equivalence point recognition set too sensitive
What to do
- • Confirm which point the method uses
- • Adjust the recognition threshold or window within the validated range
Potentiometric titratorLeaking burette tip or dripping
Likely causes
- • Worn piston seal or valve
- • Loose tubing connection
What to do
- • Tighten fittings
- • Replace the seal or service the burette unit
Hot air ovenOven does not reach set temperature
Likely causes
- • Failed heating element
- • Door seal damaged or door left open
- • Controller fault
What to do
- • Have the element checked and replaced
- • Replace the gasket and close the door properly
- • Service the controller
Hot air ovenTemperature overshoots or cycles widely
Likely causes
- • Poorly tuned controller
- • Sensor displaced or faulty
What to do
- • Retune the PID controller
- • Reposition or replace the sensor and recalibrate
Hot air ovenDisplay reading differs from reference thermometer
Likely causes
- • Sensor drift
- • Controller offset not adjusted
What to do
- • Recalibrate and apply the offset as per SOP
- • Replace the sensor if drift is large
Hot air ovenPoor uniformity (hot or cold spots)
Likely causes
- • Fan not working
- • Overloaded shelves
- • Blocked vents
What to do
- • Repair the fan
- • Reduce load and space containers
- • Clear the vents and repeat mapping
Hot air ovenLOD results variable between analysts
Likely causes
- • Different shelf positions
- • Samples weighed while warm
- • Inconsistent cooling time in the desiccator
What to do
- • Use only mapped positions
- • Cool to room temperature before weighing
- • Fix the cooling time in the method
Hot air ovenOver-temperature alarm or cut-out trips
Likely causes
- • Controller failure
- • Cut-out set too close to the working temperature
What to do
- • Stop use and have the controller checked
- • Set the cut-out as per manufacturer guidance
Dissolution testerResults lower than expected or highly variable
Likely causes
- • Dissolved air forming bubbles on the unit or basket
- • Coning of powder under the paddle
- • Vessel not centred or shaft wobbling
- • Incorrect paddle or basket height
What to do
- • Deaerate the medium as per the method
- • Confirm coning is real and discuss with method owners (the method, not the analyst, decides on changes)
- • Recheck centring, wobble and height
- • Repeat the mechanical calibration
Dissolution testerOne vessel always gives different results
Likely causes
- • Scratched or deformed vessel
- • Damaged paddle or bent shaft at that position
- • Vessel not seated in its centring ring
- • Local temperature difference
What to do
- • Swap the vessel and paddle to another position to find the cause
- • Replace the damaged part
- • Check temperature in that vessel with a calibrated probe
Dissolution testerResults higher than expected
Likely causes
- • Vibration from nearby equipment or a worn drive
- • Sampling too close to the paddle
- • Rotation speed too high
- • Evaporation of medium without covers
What to do
- • Isolate the bench from vibration sources
- • Use the correct sampling position
- • Verify speed with a tachometer
- • Use vessel covers
Dissolution testerTemperature out of range
Likely causes
- • Low bath water level
- • Heater or circulator fault
- • Medium added cold
- • Faulty temperature sensor
What to do
- • Top up the bath
- • Service the heater or pump
- • Pre-warm the medium
- • Check the sensor against a calibrated thermometer
Dissolution testerUnits floating
Likely causes
- • Capsule shells trapping air
- • Low-density formulation
What to do
- • Use the sinker type specified or permitted by the method
- • Use the basket apparatus only if the method allows it
Dissolution testerFilter blocked or slow sampling
Likely causes
- • High excipient load
- • Unsuitable filter pore size or material
What to do
- • Use the validated filter and pre-filter if the method allows
- • Check filter compatibility and adsorption during validation
Dissolution testerFailed performance verification test
Likely causes
- • Mechanical parameters at the edge of tolerance
- • Poor deaeration
- • Vibration
- • Analyst technique (timing, sampling, filtration)
What to do
- • Repeat the mechanical checks
- • Review deaeration and sampling
- • Investigate as per your SOP before repeating; do not just retest until it passes
Disintegration testerDisintegration time longer than usual
Likely causes
- • Fluid temperature low
- • Stroke rate slow
- • Product hardness higher than usual (compression force)
- • Wrong or old immersion fluid
What to do
- • Check temperature and stroke rate
- • Review in-process hardness data
- • Prepare fresh fluid
Disintegration testerFragments pass through too quickly (false pass)
Likely causes
- • Torn or enlarged mesh
- • Wrong mesh fitted
What to do
- • Replace the mesh with one of the correct aperture and check it against the drawing
Disintegration testerUnits float or stick to the mesh
Likely causes
- • Air trapped in capsules
- • Sticky coating or soft gelatin
What to do
- • Use discs only if the monograph allows
- • Record the observation and follow the monograph instructions for that dosage form
Disintegration testerRack movement uneven or noisy
Likely causes
- • Worn drive or loose arm
- • Rack not hung correctly
What to do
- • Re-seat the rack
- • Service the drive and recalibrate the stroke
Disintegration testerTemperature not stable
Likely causes
- • Low bath level
- • Heater or sensor fault
What to do
- • Top up the bath
- • Check against a calibrated thermometer and service the heater
Hardness testerReadings drift or do not return to zero
Likely causes
- • Load cell fault
- • Debris on the jaw
- • Temperature change
What to do
- • Clean the jaws and re-zero
- • Recalibrate; service the load cell if it still drifts
Hardness testerHigh variability between tablets
Likely causes
- • Inconsistent orientation
- • Variable compression on the press
- • Laminated or capped tablets
What to do
- • Standardise orientation
- • Check press settings and weight variation
- • Inspect tablets for capping
Hardness testerResults differ between two testers
Likely causes
- • Different loading rates
- • Calibration difference
- • Different jaw geometry
What to do
- • Compare settings
- • Check both calibrations
- • Use the same tester for trend data
Hardness testerTablet slips or rotates in the jaws
Likely causes
- • Curved or irregular shape
- • Wrong orientation fixture
What to do
- • Use the specified fixture or orientation and document it in the procedure
Friability testerWeight gain after the test
Likely causes
- • Tablets absorbed moisture
- • Uneven dedusting
What to do
- • Test in controlled humidity and weigh promptly
- • Dedust consistently
Friability testerTablets do not tumble (slide or jam)
Likely causes
- • Large or unusual tablet shape
- • Damaged drum projection
What to do
- • Use the tilted-drum set-up permitted by the chapter
- • Replace the drum
Friability testerRevolution count or time wrong
Likely causes
- • Motor speed drift
- • Counter fault
What to do
- • Verify speed with a stopwatch or tachometer and service the drive
Friability testerHigh friability on a batch that is usually fine
Likely causes
- • Low hardness from the press
- • Capping or lamination
What to do
- • Check in-process hardness and press settings
- • Inform production and investigate
GCNo peaks
Likely causes
- • FID flame not lit or blown out
- • Syringe blocked or empty vial
- • Column broken or not connected
- • Carrier gas cylinder empty
What to do
- • Check hydrogen and air flows and re-ignite
- • Replace the syringe and check vial volume
- • Inspect the column and its connections
- • Replace the cylinder and purge the lines
GCGhost peaks or rising baseline
Likely causes
- • Septum bleed (siloxane peaks)
- • Carry-over from a previous injection
- • Contaminated carrier gas or saturated traps
- • Column bleed at high temperature
What to do
- • Use a low-bleed septum and replace it
- • Increase syringe washes and run blanks
- • Replace gas traps or cylinder
- • Condition the column; stay below its temperature limit
GCPeak tailing
Likely causes
- • Active sites in a dirty liner or column inlet
- • Poorly cut column end or wrong insertion depth
- • Column contamination
What to do
- • Replace the liner (deactivated)
- • Recut the column squarely and reinstall at the correct depth
- • Trim the front of the column
GCRetention time shifting
Likely causes
- • Leak at the inlet or septum
- • Changed column length after trimming
- • Wrong carrier gas pressure or flow
- • Oven temperature not reproducible
What to do
- • Leak-check and replace the septum
- • Update column dimensions in the method and adjust flow
- • Verify flow with a calibrated flow meter
- • Check oven calibration
GCPoor area precision
Likely causes
- • Septum leak or cored septum
- • Syringe plunger sticking or air bubbles
- • Liner packed with septum fragments
- • Split ratio drifting
What to do
- • Replace the septum
- • Replace or clean the syringe; adjust draw speed
- • Replace the liner
- • Check split vent flow and trap
GCSplit or broad peaks
Likely causes
- • Solvent and stationary phase poorly matched in splitless mode
- • Initial oven temperature too high for solvent focusing
- • Column installed too high in the inlet
What to do
- • Use a solvent compatible with the phase or a retention gap
- • Start the oven 10–20 °C below the solvent boiling point
- • Reinstall at the correct insertion depth
GCFID noise or spikes
Likely causes
- • Dirty jet or collector
- • Incorrect hydrogen/air ratio
- • Particles from a broken column or septum
What to do
- • Clean or replace the jet
- • Reset gas flows to the manufacturer's values
- • Clean the detector and replace the septum
HeadspaceLow or variable peak areas
Likely causes
- • Vial not sealed properly or septum punctured
- • Equilibration time too short
- • Inconsistent fill volume or sample weight
What to do
- • Recrimp with a new cap and check the crimper setting
- • Extend equilibration time to the plateau
- • Use calibrated pipettes and weigh accurately
HeadspaceCarry-over in blank
Likely causes
- • Loop or transfer line too cold so analytes condense
- • Contaminated needle
- • High-concentration sample run just before
What to do
- • Keep loop and line hotter than the vial oven
- • Purge or clean the needle
- • Add blank vials after high samples
HeadspaceSolvent peaks in blank
Likely causes
- • Contaminated vials, septa or diluent
- • Laboratory air contaminated with solvent
What to do
- • Use fresh headspace-grade diluent and baked vials
- • Prepare vials away from solvent-handling areas
HeadspacePressure or leak error
Likely causes
- • Worn needle seal
- • Loose transfer-line fitting
- • Bent needle
What to do
- • Replace the seal
- • Tighten the fitting and leak-check
- • Replace the needle
HeadspaceBroad early peaks
Likely causes
- • Split ratio too low for 1 mL gas injection
- • Transfer line dead volume
- • Inlet liner unsuitable
What to do
- • Increase split ratio within method allowance
- • Check connections and use a narrow-bore liner
- • Use the liner type the method specifies
HeadspaceResponse falls over the sequence
Likely causes
- • Vials waiting too long in a heated oven
- • Gas supply pressure dropping
What to do
- • Use timed overlap so each vial gets the same heating time
- • Check the cylinder and regulator
TLCStreaking or tailing spots
Likely causes
- • Sample overloaded
- • Sample too polar or ionised
- • Spot not dried before development
What to do
- • Apply less sample or dilute it
- • Add a little acid or base (e.g. acetic acid or ammonia) to the mobile phase if the method allows
- • Dry spots fully before developing
TLCUneven or curved solvent front
Likely causes
- • Chamber not saturated
- • Plate touching the filter paper or wall
- • Uneven layer or damaged plate edge
What to do
- • Saturate for longer with a paper lining
- • Position the plate carefully
- • Use a new plate
TLCAll spots near the origin
Likely causes
- • Mobile phase not polar enough
- • Wrong plate type
What to do
- • Check mobile-phase composition against the method
- • Confirm plate type and activation
TLCAll spots near the solvent front
Likely causes
- • Mobile phase too polar
- • Plate deactivated by humidity
What to do
- • Check mobile-phase composition
- • Activate plates and store them dry
TLCRf values differ from expected
Likely causes
- • Temperature or humidity differences
- • Different plate batch
- • Old or evaporated mobile phase
What to do
- • Always compare with a reference on the same plate
- • Use fresh mobile phase each time
- • Control saturation time
TLCSpots not visible
Likely causes
- • Compound does not absorb at 254 nm
- • Too little sample applied
- • Wrong visualisation reagent
What to do
- • Use a suitable chemical reagent or iodine
- • Increase application volume within the method
- • Check the reagent preparation and heating step
AutoclaveBowie-Dick test sheet shows a pale or uneven centre
Likely causes
- • Air leak into the chamber
- • Inadequate vacuum pulses
- • Non-condensable gases in the steam supply
What to do
- • Run a vacuum leak test and replace the door gasket or leaking valves
- • Have the vacuum pump and air removal stage serviced
- • Check steam quality and the feed water
- • Do not use the autoclave for porous loads until the test passes
AutoclaveCycle does not reach set temperature or heat-up is very slow
Likely causes
- • Low steam supply or generator water level
- • Blocked drain or steam trap
- • Overloaded chamber
- • Faulty heating element
What to do
- • Check water and steam supply
- • Clean the drain strainer and trap
- • Reduce the load to the validated pattern
- • Call service for the heater or generator
AutoclaveBiological indicator shows growth
Likely causes
- • Cold spot in the load not reaching temperature
- • Air trapped in the load
- • Indicator placed in a non-validated position or mishandled
- • Cycle time too short for the load
What to do
- • Treat the load as not sterile and quarantine it
- • Investigate the cycle record and load configuration
- • Check positive and negative controls of the indicator
- • Repeat mapping and BI challenge after correction
AutoclaveMedia boil over or bottles lose volume
Likely causes
- • Containers overfilled
- • Pressure released too quickly at the end of the cycle
- • Wrong cycle selected (porous instead of liquid cycle)
What to do
- • Fill containers to no more than two-thirds
- • Use the liquid cycle with slow exhaust
- • Check the cycle programme settings
AutoclaveWet load at the end of a porous cycle
Likely causes
- • Wet steam or a blocked steam trap
- • Load packed too densely or wrapped in non-breathable material
- • Drying vacuum too short
What to do
- • Check steam quality and the trap
- • Repack the load as per the validated pattern
- • Review the drying phase settings
AutoclavePressure and temperature do not agree with the steam table
Likely causes
- • Air in the chamber
- • Faulty temperature probe or pressure transducer
- • Superheated steam
What to do
- • Repeat air removal and run a Bowie-Dick test
- • Check the instruments against a calibrated reference
- • Investigate the steam supply
AutoclaveDoor will not open after the cycle
Likely causes
- • Chamber still under pressure or above the safe temperature
- • Vacuum remaining in the chamber
- • Faulty door switch or seal
What to do
- • Wait for the cycle to finish and the chamber to vent
- • Do not force the door; call maintenance if it remains locked
LAFLow air velocity
Likely causes
- • Blocked or loaded pre-filter or HEPA filter
- • Fan speed set too low or motor fault
- • Obstruction in front of the filter face
What to do
- • Replace the pre-filter and check differential pressure
- • Adjust fan speed and re-measure
- • Replace the HEPA filter if loaded, then re-qualify
LAFHigh particle counts in the work zone
Likely causes
- • HEPA filter leak or damaged seal
- • Turbulence from room air or operator movement
- • Unit switched on too recently
- • Dirty work surface
What to do
- • Run a HEPA integrity (aerosol) test and repair or replace the filter
- • Check room airflow, close doors and reposition the unit
- • Allow the full stabilisation time
- • Clean the unit and repeat the count
LAFMicrobial growth on Grade A settle or contact plates
Likely causes
- • Poor aseptic technique
- • Inadequate cleaning or disinfectant contact time
- • Airflow disturbed or filter leak
- • Contaminated plates or materials
What to do
- • Raise a deviation and investigate as per the EM procedure
- • Identify the organism to find the likely source
- • Check air velocity and filter integrity
- • Review cleaning and operator training
LAFDifferential pressure gauge reading rising
Likely causes
- • HEPA or pre-filter loading with dust
What to do
- • Replace the pre-filter first
- • If the reading stays high and velocity drops, plan HEPA replacement
LAFDifferential pressure suddenly drops
Likely causes
- • Filter seal failure or torn filter
- • Fan failure or belt slip
What to do
- • Stop using the unit
- • Inspect the filter and fan; call service; re-qualify after repair
LAFAlarm or unusual noise from the blower
Likely causes
- • Worn motor bearing
- • Loose panel or fan imbalance
What to do
- • Switch off and call maintenance
- • Do not use until the fault is fixed and velocity is re-checked
IncubatorTemperature above set point
Likely causes
- • Faulty sensor or controller
- • Room too hot for a heating-only unit
- • Refrigeration failure (BOD)
- • Heater relay stuck on
What to do
- • Check the reading with a calibrated thermometer
- • Move the unit or use a BOD incubator
- • Call service for the compressor or relay
- • Assess plates incubated during the excursion
IncubatorTemperature below set point
Likely causes
- • Door left open or poor gasket seal
- • Heater failure
- • Ice build-up on the evaporator (BOD)
What to do
- • Close the door and replace a damaged gasket
- • Call service for the heater
- • Defrost and check the defrost cycle
IncubatorPoor uniformity between shelves
Likely causes
- • Overloading or blocked air paths
- • Fan failure
- • Plates against the walls or fan
What to do
- • Reduce load and leave space between stacks
- • Check fan operation
- • Use only mapped positions
IncubatorDisplay differs from reference thermometer
Likely causes
- • Sensor drift
- • Wrong calibration offset
What to do
- • Recalibrate and apply the correct offset
- • Replace the sensor if drift continues
IncubatorCondensation inside plates or chamber
Likely causes
- • Plates not inverted
- • Large temperature difference between media and chamber
- • Water spills or humid samples
What to do
- • Incubate plates inverted
- • Pre-warm or dry plates before use
- • Clean and dry the chamber
IncubatorFrequent alarms
Likely causes
- • Alarm limits set too tight
- • Frequent door opening
- • Monitoring probe in an unrepresentative position
What to do
- • Review alarm limits against the requirement
- • Plan access to reduce door openings
- • Relocate the probe to a mapped representative position
UHPLCPressure rising steadily over a sequence
Likely causes
- • Particles from samples collecting on the column inlet frit
- • Blocked in-line filter
- • Buffer precipitating in high organic
What to do
- • Replace the in-line filter
- • Filter or centrifuge samples more thoroughly
- • Check buffer solubility at the highest organic content in the gradient
UHPLCBroad or split peaks on a new column
Likely causes
- • Fitting not fully seated (dead volume)
- • Sample solvent much stronger than the starting mobile phase
- • Injection volume too large for the column
What to do
- • Remake the connection with the correct fitting
- • Dissolve the sample in a solvent close to the starting mobile phase
- • Reduce the injection volume
UHPLCPeaks look flat-topped or jagged
Likely causes
- • Data rate too low
- • Detector time constant too long
What to do
- • Increase the sampling rate so there are at least 15–20 points per peak
- • Use a shorter filter time constant
UHPLCRetention times differ from the HPLC method after transfer
Likely causes
- • Different dwell volume
- • Gradient not scaled to the new column
- • Frictional heating in the column
What to do
- • Add an isocratic hold or adjust the gradient start to compensate for dwell volume
- • Re-scale gradient time and flow to the new column dimensions
- • Use a narrower column or control temperature
UHPLCCarry-over in blanks
Likely causes
- • Weak needle wash
- • Sample adsorbed on the needle seat or rotor seal
What to do
- • Use a stronger or two-solvent needle wash
- • Replace the needle seat or rotor seal
HPTLCRf values differ from the reference
Likely causes
- • Chamber not saturated
- • Humidity or temperature different
- • Mobile phase prepared wrongly or reused
What to do
- • Saturate for the specified time
- • Condition the plate to controlled humidity
- • Prepare fresh mobile phase each time
HPTLCSmile or curved solvent front
Likely causes
- • Uneven saturation
- • Plate not vertical
- • Edge effects
What to do
- • Use a twin-trough chamber with filter paper
- • Check the plate sits level
- • Keep tracks away from the plate edges
HPTLCDiffuse or tailing zones
Likely causes
- • Sample applied in too strong a solvent or too large a volume
- • Overloaded track
- • Plate too active or contaminated
What to do
- • Use spray-on band application and a weaker solvent
- • Reduce the amount applied
- • Pre-wash and activate plates
HPTLCUneven colour after derivatisation
Likely causes
- • Hand spraying
- • Uneven heating
What to do
- • Use a dipping or automatic spraying device
- • Use a calibrated plate heater
ICHigh background conductivity
Likely causes
- • Suppressor exhausted or failing
- • Contaminated eluent or water
- • Eluent too concentrated
What to do
- • Regenerate or replace the suppressor
- • Prepare fresh eluent with ultrapure water
- • Check eluent concentration and generator settings
ICRetention times getting shorter
Likely causes
- • Column capacity lost through contamination
- • Eluent concentration too high
- • Temperature change
What to do
- • Clean the column as per the supplier's guide or replace it
- • Re-prepare eluent
- • Use the column oven
ICGhost peaks of chloride or sulfate in blanks
Likely causes
- • Contaminated water, vials or filters
- • Contaminated eluent reservoir
What to do
- • Use fresh ultrapure water and IC-grade vials
- • Rinse filters and vials before use
- • Clean the reservoir
ICNoisy or drifting baseline
Likely causes
- • Air bubble in the conductivity cell
- • Unstable cell temperature
- • Pump pulsation
What to do
- • Purge the cell
- • Check the cell and column temperature control
- • Service check valves
ICPoor peak shape for early ions
Likely causes
- • Sample matrix too concentrated
- • Carbonate interference
- • Overloaded column
What to do
- • Dilute the sample
- • Use eluent generation with a carbonate trap
- • Reduce injection volume
GPC / SECMolecular weights drifting between runs
Likely causes
- • Flow rate variation
- • Temperature change
- • Column ageing
What to do
- • Verify flow and use a flow marker correction
- • Control column and detector temperature
- • Re-run calibration standards; replace the column if needed
GPC / SECLate-eluting tail or peaks after total permeation
Likely causes
- • Adsorption of sample to the packing
- • Wrong salt concentration or pH
What to do
- • Increase ionic strength or adjust pH as the method allows
- • Use a column with a more inert surface
GPC / SECUnstable RI baseline
Likely causes
- • Reference cell not purged
- • Temperature fluctuation
- • Mobile phase not degassed or changing
What to do
- • Purge the reference cell with fresh mobile phase
- • Stabilise room and detector temperature
- • Degas and use a single mobile-phase batch
GPC / SECIncreasing back-pressure
Likely causes
- • Undissolved sample or gel particles
- • Microbial growth in aqueous systems
What to do
- • Filter samples; dissolve more completely
- • Use fresh buffer with an antimicrobial agent for storage
GPC / SECUnexpected aggregate peak in protein samples
Likely causes
- • Sample handling (shaking, freeze–thaw)
- • Carry-over from a previous sample
What to do
- • Handle samples gently and as per stability data
- • Run blanks and clean the injector
LC-MSLoss of sensitivity
Likely causes
- • Dirty ion source or cone
- • Ion suppression from matrix
- • Detector ageing
- • Wrong tune or mass calibration
What to do
- • Clean the source
- • Improve sample clean-up or chromatographic separation
- • Increase detector voltage within limits or replace the detector
- • Re-tune and recalibrate
LC-MSUnstable spray or noisy signal
Likely causes
- • Partly blocked ESI needle or capillary
- • Air in the LC flow
- • Gas supply problems
What to do
- • Clean or replace the needle
- • Degas solvents and purge the LC
- • Check nitrogen pressure and purity
LC-MSMass shift / wrong m/z
Likely causes
- • Calibration out of date
- • Room temperature change affecting the analyser
What to do
- • Recalibrate with the reference solution
- • Stabilise room temperature; use a lock mass on HRMS
LC-MSHigh background ions
Likely causes
- • Contaminated solvents or additives
- • Plasticisers from tubing or containers
- • Column bleed
What to do
- • Use fresh LC-MS grade solvents
- • Use MS-compatible tubing and glass containers
- • Condition or replace the column
LC-MSVacuum fault
Likely causes
- • Leak at a seal
- • Rough pump failing
- • Turbo pump fault
What to do
- • Stop work and contact service
- • Check pump oil and running noise
- • Do not run samples until vacuum is restored
GC-MSHigh air / water in tune (m/z 18, 28, 32)
Likely causes
- • Leak at the column nut or transfer line
- • Recently vented system not fully pumped down
- • Leaking vent valve or seal
What to do
- • Check and tighten fittings; use a leak-check gas
- • Allow longer pump-down
- • Replace the faulty seal
GC-MSTune fails / electron multiplier voltage high
Likely causes
- • Dirty ion source
- • Ageing detector
- • Low calibrant level
What to do
- • Clean the source
- • Replace the electron multiplier if voltage is near its maximum
- • Refill or check the PFTBA vial
GC-MSPeak tailing of active compounds
Likely causes
- • Dirty or active inlet liner
- • Column contamination at the inlet end
What to do
- • Replace the liner with a deactivated one
- • Trim 10–50 cm from the column inlet
GC-MSRising baseline with siloxane ions (m/z 207, 281)
Likely causes
- • Column bleed at high temperature
- • Septum bleed
What to do
- • Use a low-bleed MS column and stay within its temperature limit
- • Use low-bleed septa and replace them regularly
GC-MSPoor library match
Likely causes
- • Co-eluting peaks
- • Background not subtracted
- • Spectral skew from scanning a fast peak
What to do
- • Improve separation
- • Subtract background near the peak
- • Increase scan speed or use more points across the peak
AASLow absorbance (poor sensitivity)
Likely causes
- • Nebuliser partly blocked
- • Burner not aligned or wrong height
- • Lamp weak or wrong current
- • Wrong fuel/oxidant ratio
What to do
- • Clean or replace the nebuliser
- • Re-optimise burner position with a standard
- • Check lamp energy and replace if needed
- • Re-optimise gas flows
AASNoisy or drifting signal
Likely causes
- • Lamp not warmed up
- • Salt build-up on burner slot
- • Unstable aspiration rate
What to do
- • Allow full lamp warm-up
- • Clean the burner head
- • Check capillary tubing and nebuliser
AASResults biased high in a heavy matrix
Likely causes
- • Background absorption not corrected
- • Spectral overlap
What to do
- • Switch on deuterium or Zeeman correction
- • Use an alternative line or matrix-matched standards
AASResults biased low for Ca or Mg
Likely causes
- • Chemical interference from phosphate or silicate
What to do
- • Add a lanthanum or strontium releasing agent
- • Use a nitrous oxide–acetylene flame
AASFlame will not ignite
Likely causes
- • Low gas pressure
- • Burner head not seated
- • Drain trap interlock open
- • Exhaust interlock
What to do
- • Check cylinder and regulator
- • Re-seat burner head
- • Fill the drain trap
- • Confirm exhaust is on
ICP-OESPlasma will not ignite or goes out
Likely causes
- • Air leak in torch or connections
- • Low argon pressure
- • Wet or contaminated torch
- • Sample too high in solids or organics
What to do
- • Check torch fitting and O-rings
- • Check argon supply
- • Dry and clean the torch
- • Dilute the sample; use organic-solvent settings if needed
ICP-OESPoor precision (high %RSD)
Likely causes
- • Worn pump tubing
- • Partly blocked nebuliser
- • Air bubbles in sample line
What to do
- • Replace pump tubing
- • Clean nebuliser by back-flushing (never with a wire)
- • Check uptake tube and connections
ICP-OESSignal drift during the run
Likely causes
- • Salt deposits on injector
- • Temperature changes
- • Plasma not stable
What to do
- • Use internal standard correction
- • Clean the torch injector
- • Allow longer warm-up
ICP-OESUnexpected high result for one element
Likely causes
- • Spectral interference from a matrix element
- • Contamination or carry-over
What to do
- • Check a second line for the same element
- • Run blanks; extend rinse time
ICP-OESWavelength calibration fails
Likely causes
- • Spectrometer temperature not stable
- • Wrong or old calibration solution
What to do
- • Allow the optics to reach temperature
- • Prepare fresh calibration solution and repeat
ICP-MSLow sensitivity in tune
Likely causes
- • Dirty or worn cones
- • Partly blocked nebuliser
- • Worn pump tubing
- • Dirty ion lenses
What to do
- • Clean or replace cones
- • Clean the nebuliser
- • Replace pump tubing
- • Clean lenses as per manual
ICP-MSHigh oxide (CeO⁺/Ce⁺) ratio
Likely causes
- • Nebuliser gas flow too high
- • Spray chamber temperature too high
- • Torch position not optimised
What to do
- • Re-tune nebuliser gas flow
- • Check spray chamber cooling
- • Re-optimise torch alignment
ICP-MSHigh arsenic or selenium in blanks
Likely causes
- • Polyatomic interference (ArCl⁺, ArAr⁺)
- • Contaminated reagents
What to do
- • Use helium collision or reaction mode
- • Use high-purity acids and fresh blank
ICP-MSMercury carry-over
Likely causes
- • Hg adsorbing to tubing and spray chamber
What to do
- • Add HCl or gold to rinse and solutions
- • Lengthen rinse time
ICP-MSInternal standard recovery falling during run
Likely causes
- • Matrix deposits on cones
- • High dissolved solids
- • Drift
What to do
- • Dilute samples further
- • Clean cones
- • Re-calibrate and repeat affected samples
ICP-MSVacuum fault
Likely causes
- • Interface or cone O-ring leak
- • Rotary pump oil low or degraded
What to do
- • Check cone seating and O-rings
- • Service the rotary pump
FluorimeterWeak or no signal
Likely causes
- • Lamp failed or near end of life
- • Wrong wavelengths or slits
- • Shutter closed
- • PMT voltage too low
What to do
- • Check lamp and replace
- • Check method settings
- • Check shutter status
- • Increase PMT voltage within the linear range
FluorimeterSignal saturating
Likely causes
- • Concentration too high
- • PMT voltage too high
- • Slits too wide
What to do
- • Dilute the sample
- • Lower PMT voltage
- • Narrow the slits
FluorimeterCalibration curve bends at high concentration
Likely causes
- • Inner-filter effect
- • Self-quenching
What to do
- • Work at lower concentrations
- • Keep absorbance at λex low
FluorimeterUnexpected peak in blank
Likely causes
- • Solvent Raman band
- • Fluorescent impurity in solvent or cuvette
- • Second-order scatter
What to do
- • Change λex to move the Raman band
- • Use fluorescence-grade solvent and clean cuvettes
- • Use an emission cut-off filter
FluorimeterReadings drift
Likely causes
- • Lamp not warmed up
- • Sample temperature changing
- • Photobleaching
What to do
- • Allow full warm-up
- • Use a thermostatted holder
- • Reduce slit width or exposure time
NIRKnown good material fails library identity
Likely causes
- • New supplier, grade or particle size not represented in the library
- • Different packaging film or measurement through a fold
- • Moisture uptake by the material
- • Instrument drift since the library was built
What to do
- • Re-measure on a clean, flat part of the bag or in a vial
- • Check the performance test and calibration
- • Investigate and, if justified, add new representative lots to the library under change control
NIRTwo different materials both pass as each other
Likely causes
- • Library uses a simple correlation that cannot separate similar materials
- • Threshold set too wide
What to do
- • Use a more selective algorithm (e.g. PCA/Mahalanobis or SIMCA) for that pair
- • Re-validate specificity with challenge samples
NIRNoisy spectrum
Likely causes
- • Lamp near end of life
- • Dirty window or probe
- • Too few scans or poor contact with the sample
What to do
- • Check energy and replace the lamp
- • Clean the window
- • Increase scans and press the probe firmly
NIRPerformance test fails wavelength check
Likely causes
- • Internal standard contaminated or damaged
- • Laser or interferometer fault (FT-NIR)
- • Temperature change
What to do
- • Clean or replace the standard
- • Call service
- • Let the instrument stabilise and repeat
NIRQuantitative predictions biased
Likely causes
- • Model built on a different instrument or old lamp
- • Samples outside the calibration range
- • Changed sample presentation
What to do
- • Check outlier statistics; do not report outliers
- • Transfer or update the model
- • Standardise the presentation method
RamanLarge sloping background, no clear bands
Likely causes
- • Fluorescence from the sample, impurities or the packaging
- • Coloured sample
What to do
- • Increase integration time or use fluorescence-reduction settings if validated
- • Measure in a glass vial instead of the bag
- • Use a 1064 nm instrument or another identity test
RamanAuthentic material fails
Likely causes
- • Different polymorph, hydrate or grade from the library material
- • Measurement through a fold, label or tinted bag
- • Probe not in contact or misaligned
What to do
- • Re-measure on a clear, flat area
- • Check the library contains this grade or form
- • Investigate before adding material to the library
RamanWeak signal
Likely causes
- • Laser power low
- • Dirty window
- • Sample out of focus
What to do
- • Check laser power
- • Clean optics
- • Use the correct nose cone or vial position
RamanSample discoloured or burnt
Likely causes
- • Laser power too high for a dark or absorbing sample
What to do
- • Reduce power, defocus or use a rotating stage
- • Use another identity method
RamanWavenumber check fails
Likely causes
- • Temperature drift
- • Contaminated reference standard
- • Spectrograph misalignment or laser wavelength change
What to do
- • Let the instrument stabilise and repeat
- • Use a fresh standard
- • Call service and recalibrate
NMRCannot lock
Likely causes
- • Wrong solvent selected
- • Too little deuterated solvent
- • Sample not at the correct depth
What to do
- • Select the correct solvent
- • Make the sample to the correct volume
- • Reset the depth with the gauge
NMRBroad or distorted lines
Likely causes
- • Poor shimming
- • Solid particles or paramagnetic impurities in the sample
- • Low-quality or scratched tube
What to do
- • Re-shim or load a good shim file
- • Filter the sample
- • Use a good-quality tube
NMRPoor signal-to-noise
Likely causes
- • Too little sample
- • Probe not tuned
- • Too few scans
What to do
- • Use more sample or a smaller-volume tube
- • Tune and match
- • Increase the number of scans
NMRqNMR purity too low or variable
Likely causes
- • Relaxation delay too short
- • Weighing error with small masses
- • Overlapping signals
- • Poor baseline or phasing
What to do
- • Measure T1 and set delay ≥ 5 × T1
- • Use a microbalance and larger masses
- • Choose non-overlapping signals or another internal standard
- • Correct the phase and baseline carefully
NMRLarge water signal
Likely causes
- • Wet solvent or hygroscopic sample
What to do
- • Use fresh, dry solvent ampoules
- • Use solvent suppression if validated
XRPDAll peaks shifted by the same amount
Likely causes
- • Sample surface above or below the reference plane (displacement)
- • Goniometer zero error
What to do
- • Re-prepare the sample level with the holder rim
- • Run the silicon standard; realign if it fails
XRPDRelative intensities differ from the reference
Likely causes
- • Preferred orientation
- • Large crystallites (grainy pattern)
- • Different sample thickness
What to do
- • Use back-loading or side-loading and spin the sample
- • Gently reduce particle size
- • Use the same holder and preparation as the reference
XRPDUnexpected extra peaks
Likely causes
- • Another polymorph or hydrate present
- • Contamination
- • Peaks from the holder or Kβ radiation
What to do
- • Compare with known forms and investigate
- • Run a blank holder
- • Check the filter or monochromator
XRPDBroad hump, few sharp peaks
Likely causes
- • Amorphous or poorly crystalline material
- • Very small crystallite size
What to do
- • Confirm with DSC or other techniques
- • Investigate the process step that caused amorphisation
XRPDLow intensity overall
Likely causes
- • Ageing X-ray tube
- • Wrong slits or generator settings
- • Too little sample
What to do
- • Check tube hours and intensity trend
- • Load the correct method
- • Fill the holder properly
MicrobalanceReading drifts up or down by many micrograms
Likely causes
- • Static charge on the container or sample
- • Sample or container not at room temperature
- • Draught from air-conditioning or an open door
What to do
- • Use the ioniser and anti-static containers
- • Allow more time to equilibrate; handle with forceps
- • Close doors, redirect air flow, use a smaller draught shield
MicrobalanceStability symbol never appears
Likely causes
- • Vibration from nearby equipment or people walking
- • Balance not level
- • Weighing table touching the bench or wall
What to do
- • Move vibrating equipment away; weigh at quieter times
- • Level the balance
- • Make sure the stone table stands free
MicrobalanceZero is not stable after removing the sample
Likely causes
- • Material left on the pan
- • Temperature changed since the last tare
- • Pan touching the draught shield
What to do
- • Clean the pan and re-zero
- • Wait for stabilisation, then re-zero
- • Re-seat the pan correctly
MicrobalanceRepeatability or minimum weight check fails
Likely causes
- • Poor environment at the place of use
- • Weight handled with fingers
- • Worn or dirty weighing cell parts
What to do
- • Improve the environment and repeat
- • Use forceps and a clean, calibrated weight
- • Call service; raise the working minimum weight until fixed
MicrobalanceReading slowly increases for a hygroscopic sample
Likely causes
- • Sample absorbs moisture from the air
What to do
- • Weigh quickly in a closed container
- • Weigh by difference
- • Control the room humidity
PolarimeterUnstable or noisy reading
Likely causes
- • Air bubble in the light path
- • Turbid sample
- • Temperature not yet stable
What to do
- • Refill the tube and move bubbles into the bubble trap
- • Filter the solution
- • Wait until the cell temperature is stable
PolarimeterBlank does not read zero
Likely causes
- • Dirty or strained windows
- • Tube placed in a different orientation
- • Contaminated solvent
What to do
- • Clean or replace the windows
- • Always insert the tube the same way
- • Use fresh solvent
PolarimeterLow light / 'low transmission' error
Likely causes
- • Strongly coloured or concentrated sample
- • Lamp ageing
- • Dirty optics
What to do
- • Use a shorter tube or dilute as the monograph allows
- • Replace the lamp
- • Clean the windows and compartment
PolarimeterQuartz plate check out of limit
Likely causes
- • Plate dirty or at the wrong temperature
- • Instrument scale drift
- • Wrong wavelength selected
What to do
- • Clean the plate and let it equilibrate
- • Repeat; if it still fails, call service
- • Check the wavelength setting
PolarimeterResults drift during a series
Likely causes
- • Mutarotation of the sample
- • Room or cell temperature changing
- • Evaporation of a volatile solvent
What to do
- • Measure at the time the monograph states
- • Check temperature control
- • Cap the tube and measure quickly
RefractometerBlurred or no light–dark boundary
Likely causes
- • Too little sample
- • Bubbles or particles on the prism
- • Sample too dark or opaque
What to do
- • Cover the prism fully
- • Clean and reload without bubbles
- • Use reflected light mode or another method if the sample is opaque
RefractometerWater check reads wrong
Likely causes
- • Prism not at 20 °C
- • Residue on the prism
- • Water not fresh or not pure
What to do
- • Wait for temperature stability
- • Clean the prism thoroughly
- • Use fresh purified water
RefractometerReadings drift with time
Likely causes
- • Evaporation of a volatile sample
- • Temperature not stable
What to do
- • Close the cover and read quickly
- • Allow more time for equilibration
RefractometerColour fringes on the boundary (Abbe)
Likely causes
- • Compensator not adjusted with white light
What to do
- • Turn the compensator knob until the boundary is sharp and colourless
RefractometerResults differ between two instruments
Likely causes
- • Different temperatures
- • One instrument out of calibration
What to do
- • Measure both at the same temperature
- • Check both with the reference liquid
ViscometerReading keeps falling with time
Likely causes
- • Shear-thinning or thixotropic sample
- • Sample warming from friction or room
What to do
- • Read at a fixed time as the STP states
- • Check bath temperature and container immersion
ViscometerError or 'EEEE' / reading above 100% torque
Likely causes
- • Sample too thick for spindle/speed combination
What to do
- • Use a smaller spindle or lower speed as the STP permits
ViscometerVery low % torque, poor repeatability
Likely causes
- • Sample too thin for the spindle/speed
- • Instrument not zeroed
What to do
- • Use a larger spindle or higher speed
- • Auto-zero with no spindle attached
ViscometerViscosity standard reads out of tolerance
Likely causes
- • Wrong temperature
- • Bent spindle
- • Wrong container size or guard leg missing
- • Instrument not level
What to do
- • Check temperature with a calibrated probe
- • Replace the spindle
- • Use the container and guard leg the calibration requires
- • Level the instrument
ViscometerResults differ between analysts
Likely causes
- • Different immersion depth or air bubbles
- • Different sample mixing or reading time
What to do
- • Immerse to the mark at an angle
- • Write exact mixing and reading time into the STP
Density meterWater check reads high
Likely causes
- • Residue or deposit in the tube
- • Bubble in the tube
- • Water not pure or not degassed
What to do
- • Clean the tube thoroughly and dry
- • Refill slowly; check the camera
- • Use fresh, freshly boiled and cooled purified water
Density meterAir reading does not match
Likely causes
- • Tube not dry
- • Solvent vapour still in the tube
What to do
- • Dry longer with the air pump
- • Rinse with a volatile solvent, then dry
Density meterUnstable readings
Likely causes
- • Bubbles forming as the sample warms
- • Temperature not stable
- • Vibration from nearby equipment
What to do
- • Degas the sample
- • Wait for temperature stability
- • Move the instrument away from vibration sources
Density meterResults higher than expected for a thick syrup
Likely causes
- • Viscosity effect not corrected
What to do
- • Turn on viscosity correction or use a method designed for viscous samples
Density meterDuplicates disagree
Likely causes
- • Sample not mixed
- • Particles settling in the tube
What to do
- • Mix before filling
- • Filter if the method allows, or use another technique
OsmometerSample freezes too early (pre-freeze)
Likely causes
- • Dirty probe or tube
- • Particles or ice crystals in the sample
- • Cooling bath too cold
What to do
- • Clean the probe and use a new tube
- • Filter or centrifuge the sample if the method allows
- • Check the cooling system
OsmometerSample does not freeze
Likely causes
- • Freeze-induction wire not working
- • Sample volume wrong
What to do
- • Check and adjust the wire
- • Pipette the correct volume
OsmometerReference solution reads out of limit
Likely causes
- • Standard contaminated or evaporated
- • Probe dirty
- • Calibration drift
What to do
- • Use a fresh ampoule of standard
- • Clean the probe
- • Recalibrate with certified standards
OsmometerPoor repeatability
Likely causes
- • Inconsistent sample volume
- • Bubbles in the sample
- • Carry-over between samples
What to do
- • Check the pipette
- • Pipette slowly to avoid bubbles
- • Clean and dry the probe between samples
OsmometerResults drift upwards when sample tubes stand open
Likely causes
- • Evaporation of water from the sample
What to do
- • Measure immediately after pipetting; keep tubes covered
Turbidity meterReading high and unstable
Likely causes
- • Air bubbles in the sample
- • Particles settling or rising
What to do
- • Let the sample stand, invert gently or degas
- • Read promptly after gentle mixing
Turbidity meterBlank (low-turbidity water) reads too high
Likely causes
- • Scratched or dirty cuvette
- • Fingerprints or condensation
- • Contaminated water
What to do
- • Clean or replace the cuvette
- • Wipe and handle only by the top
- • Use freshly filtered water
Turbidity meterResults differ when the cuvette is turned
Likely causes
- • Cuvette not uniform or scratched
- • Orientation mark not aligned
What to do
- • Index the cuvette (find the lowest reading position) and always use that position
- • Replace the cuvette
Turbidity meterVerification standard out of limit
Likely causes
- • Standard expired or contaminated
- • Lamp ageing
- • Calibration drift
What to do
- • Use a new standard
- • Replace the lamp
- • Recalibrate with formazin
Turbidity meterColoured sample reads lower than expected
Likely causes
- • Colour absorbs the scattered light
What to do
- • Use ratio mode if available, or follow the monograph's visual method
Melting point apparatusMelting points consistently too high
Likely causes
- • Heating rate too fast
- • Capillary too thick-walled or too wide
- • Sensor out of calibration
What to do
- • Use the specified ramp rate
- • Use pharmacopoeial capillaries
- • Calibrate with reference standards
Melting point apparatusWide melting range
Likely causes
- • Sample impure or not dried
- • Powder too coarse or loosely packed
- • Column too tall
What to do
- • Dry the sample as per the monograph
- • Grind finely and pack well
- • Fill to about 3 mm only
Melting point apparatusDuplicates disagree
Likely causes
- • Different packing in each capillary
- • Capillaries inserted at different start temperatures
What to do
- • Pack each capillary the same way
- • Insert all capillaries at the same stabilised start temperature
Melting point apparatusSample darkens or bubbles before melting
Likely causes
- • Melting with decomposition
- • Residual solvent or moisture
What to do
- • Follow the monograph instructions for decomposing substances
- • Dry the sample properly
Melting point apparatusAutomatic detection gives a wrong point
Likely causes
- • Dirty window or poor lighting
- • Sample shrinks or sublimes before melting
What to do
- • Clean the optics
- • Review the video and confirm visually; set the evaluation threshold as validated
DSCNoisy or drifting baseline
Likely causes
- • Contaminated sensor
- • Unstable purge gas flow
- • Pan not sitting flat
What to do
- • Clean the cell by bake-out
- • Check gas regulator and flow
- • Use flat, undamaged pans
DSCIndium onset out of limits
Likely causes
- • Calibration out of date
- • Wrong heating rate or pan type compared with the calibration
- • Contaminated indium
What to do
- • Recalibrate
- • Calibrate under the same conditions as the method
- • Use fresh indium
DSCUnexpected sharp exotherm
Likely causes
- • Decomposition
- • Pan burst or lid moved
What to do
- • Check the sample by TGA
- • Use vented pans and lower end temperature
DSCBroad, unclear melting peak
Likely causes
- • Large or uneven sample
- • Heating rate too high
- • Impure or mixed polymorphic sample
What to do
- • Use a smaller, flatter sample
- • Reduce the heating rate
- • Confirm with XRPD or microscopy
DSCSmall endotherm near 100 °C
Likely causes
- • Water in the sample or condensation in the cell
What to do
- • Use a pierced lid or dry the sample
- • Check the purge gas is dry
TGANoisy mass signal
Likely causes
- • Vibration or draughts
- • Gas flow too high or unstable
- • Pan touching the furnace
What to do
- • Move the instrument to a stable bench
- • Reduce and stabilise gas flow
- • Re-centre the pan
TGAApparent mass gain at start
Likely causes
- • Buoyancy effect
- • Oxidation in air
What to do
- • Subtract a blank curve
- • Use nitrogen if oxidation is not wanted
TGAStep temperatures shifted
Likely causes
- • Temperature calibration out of date
- • Different heating rate or sample mass from the method
What to do
- • Recalibrate with Curie point standards
- • Use the method conditions
TGAMass loss does not match theory for a hydrate
Likely causes
- • Sample partly dehydrated or extra surface water
- • Weighing error at the start
What to do
- • Check storage and sample handling
- • Let the starting mass stabilise; check mass calibration
TGAResidue sticks in pan
Likely causes
- • Sample melted and charred
- • Wrong pan material
What to do
- • Clean by heating in air
- • Use a platinum or alumina pan as appropriate
Muffle furnaceSlow to reach set point
Likely causes
- • Ageing heating element
- • Door seal damaged
- • Supply voltage low
What to do
- • Have elements checked and replaced
- • Replace the seal
- • Check the electrical supply
Muffle furnaceTemperature overshoots
Likely causes
- • Controller tuning poor
- • Thermocouple loose or moved
What to do
- • Re-tune the PID controller
- • Refit the thermocouple
Muffle furnaceDisplay differs from reference thermocouple
Likely causes
- • Controller thermocouple drifted
- • Probe placed in a cooler zone
What to do
- • Calibrate or replace the thermocouple
- • Measure in the working zone
Muffle furnaceSulphated ash results variable
Likely causes
- • Crucibles placed near the door
- • Cooling time not controlled
- • Incomplete charring
What to do
- • Use the central working zone
- • Use a fixed desiccator cooling time
- • Char completely before ignition
Vacuum ovenVacuum not reached
Likely causes
- • Leaking door gasket
- • Vent valve open
- • Pump oil contaminated
What to do
- • Clean or replace the gasket
- • Close the vent valve
- • Change the pump oil
Vacuum ovenPressure rises when the valve is closed
Likely causes
- • Leak in fittings or door
- • Sample still releasing vapour
What to do
- • Leak-test fittings
- • Allow longer drying
Vacuum ovenResults higher than expected
Likely causes
- • Powder lost when vacuum applied or released
- • Temperature too high
What to do
- • Apply and release vacuum slowly
- • Check temperature accuracy
Vacuum ovenSlow drying
Likely causes
- • Poor shelf contact
- • Overloaded chamber
What to do
- • Use flat-bottomed containers on the shelf
- • Dry fewer samples at a time
Moisture analyserResults lower than oven LOD
Likely causes
- • Temperature too low
- • Switch-off criterion too loose
- • Sample too thick
What to do
- • Re-validate method settings
- • Tighten the criterion
- • Use a thinner, even layer
Moisture analyserSample burns or turns brown
Likely causes
- • Temperature too high
- • Sample sensitive to heat
What to do
- • Lower the temperature and lengthen the time
- • Use a glass fibre filter over the sample
Moisture analyserUnstable reading
Likely causes
- • Draughts or vibration
- • Instrument not level
What to do
- • Move to a stable location
- • Level the instrument
Moisture analyserPoor repeatability
Likely causes
- • Variable sample mass or spreading
- • Non-uniform sample
What to do
- • Use the same mass and spreading each time
- • Mix the sample before sampling
Laser diffraction PSAHigh or noisy background
Likely causes
- • Dirty or scratched cell windows
- • Air bubbles in the wet unit
- • Contaminated dispersant
What to do
- • Clean or replace windows
- • Degas the dispersant and lower the stirrer speed
- • Use fresh, filtered dispersant
Laser diffraction PSAResults keep getting smaller across replicates
Likely causes
- • Agglomerates still breaking up
- • Sample dissolving in the dispersant
- • Sonication too strong, breaking primary particles
What to do
- • Extend the pre-measurement dispersion time
- • Use a saturated or different dispersant
- • Review sonication settings during method development
Laser diffraction PSAUnexpected coarse peak
Likely causes
- • Agglomerates not dispersed
- • Air bubbles seen as large particles
- • Dust in the cell
What to do
- • Increase dispersion energy within the validated range
- • Remove bubbles; avoid vigorous stirring
- • Clean the cell and re-run background
Laser diffraction PSAHigh fit residual
Likely causes
- • Wrong refractive index
- • Obscuration outside range
- • Non-spherical particles
What to do
- • Confirm optical properties in the method
- • Adjust sample amount
- • Check shape by microscopy and document it
Laser diffraction PSACannot reach obscuration
Likely causes
- • Blocked feeder (dry)
- • Sample sticking to tray
- • Too little sample
What to do
- • Clean the feeder and venturi
- • Adjust feed rate or vibration
- • Add more sample
Laser diffraction PSACRM check fails
Likely causes
- • Misalignment
- • Dirty optics
- • Poor CRM dispersion or handling
What to do
- • Run alignment and clean optics
- • Repeat with fresh CRM using the certificate conditions
- • Call service if it fails again
Tap density testerPoor repeatability between duplicates
Likely causes
- • Different filling technique
- • Sample not sieved or not representative
- • Uneven powder surface
What to do
- • Standardise pouring; train analysts
- • Sieve and mix before sampling
- • Read at the mean level of the surface
Tap density testerVolume keeps decreasing after many taps
Likely causes
- • Very cohesive or fragile powder
- • Particles breaking under tapping
What to do
- • Continue tapping in increments as the method allows
- • Report the number of taps used
Tap density testerTap count wrong
Likely causes
- • Faulty counter or sensor
- • Belt slipping
What to do
- • Verify by manual count; service the counter
- • Replace the belt
Tap density testerDrop height out of tolerance
Likely causes
- • Worn cam or anvil
- • Loose holder
What to do
- • Replace worn parts and recalibrate
- • Tighten fixings
Sieve shakerMass balance poor (loss above limit)
Likely causes
- • Dust escaping
- • Material stuck in sieves
- • Weighing errors
What to do
- • Fit the lid and seals properly
- • Brush out sieves and re-weigh
- • Check balance and tare values
Sieve shakerResults coarser than expected
Likely causes
- • Sieve blinding
- • Sieving time too short
- • Agglomerated or electrostatically charged powder
What to do
- • Clean sieves; use sieving aids if validated
- • Confirm the end-point
- • Condition the sample or use air-jet sieving
Sieve shakerResults finer than expected
Likely causes
- • Torn or stretched mesh
- • Granule attrition during shaking
What to do
- • Inspect and replace damaged sieves
- • Reduce amplitude or time within validated limits
Sieve shakerShaker noisy or stack moving
Likely causes
- • Loose clamp
- • Worn rubber mounts
What to do
- • Tighten the clamp
- • Replace mounts
Optical microscopeImage blurred
Likely causes
- • Dirty lens or slide
- • Wrong cover slip thickness
- • Oil on a dry objective
What to do
- • Clean optics
- • Use the correct cover slip
- • Clean the objective with lens tissue
Optical microscopeUneven illumination
Likely causes
- • Condenser not centred
- • Lamp misaligned
What to do
- • Set Köhler illumination
- • Re-align the lamp
Optical microscopeParticles all clumped
Likely causes
- • Poor dispersion
- • Wrong mounting fluid
What to do
- • Disperse more gently and use less sample
- • Choose a fluid with suitable wetting
Optical microscopeSize results differ between analysts
Likely causes
- • Different particle selection
- • Graticule not calibrated
What to do
- • Use a defined field-scanning pattern
- • Calibrate and document for each objective
Leak testerCannot reach set vacuum
Likely causes
- • Worn lid gasket
- • Pump oil low or contaminated
- • Leaking tubing
What to do
- • Replace the gasket; grease if allowed
- • Change pump oil
- • Replace tubing
Leak testerAll packs fail (vacuum decay)
Likely causes
- • Chamber or seal leak
- • Wet or dirty containers
- • Wrong recipe
What to do
- • Run an empty-chamber test
- • Clean and dry samples
- • Load the validated recipe
Leak testerPositive control passes
Likely causes
- • Blocked defect in the control
- • Test time too short
- • Transducer drift
What to do
- • Use a new, certified positive control
- • Check the recipe
- • Recalibrate transducers
Leak testerFaint dye in pockets
Likely causes
- • Inadequate rinse
- • Borderline leak
What to do
- • Rinse properly and re-inspect
- • Treat as a fail and investigate the sealing process
Franz cellLow, variable release in some cells
Likely causes
- • Air bubble under the membrane
- • Uneven dosing
- • Membrane wrinkled
What to do
- • Remove bubbles before dosing
- • Weigh the dose and spread evenly
- • Mount membrane flat
Franz cellReceptor medium leaking
Likely causes
- • Clamp loose
- • Chipped joint
What to do
- • Tighten clamp
- • Replace damaged cell
Franz cellRelease levels off early
Likely causes
- • Loss of sink conditions
- • Product drying out
What to do
- • Use a larger receptor volume or add solubiliser
- • Occlude the donor chamber
Franz cellTemperature out of range
Likely causes
- • Water bath set wrongly
- • Poor circulation
What to do
- • Adjust bath to give 32 °C at the membrane
- • Check circulation tubing
Liquid particle counterHigh blank counts
Likely causes
- • Dirty glassware or water
- • Contaminated sensor
- • Poor environment
What to do
- • Re-clean glassware; use freshly filtered water
- • Flush the sensor with detergent then water
- • Work in LAF and wear gloves
Liquid particle counterCounts falling between portions
Likely causes
- • Bubbles settling or dissolving
- • Particles settling
What to do
- • Degas properly before running
- • Stir gently during measurement
Liquid particle counterVery high counts at small sizes
Likely causes
- • Air bubbles
- • Product precipitating
What to do
- • Degas and re-run
- • Check product compatibility; consider the microscopic method
Liquid particle counterCount accuracy check fails
Likely causes
- • Coincidence errors
- • Wrong volume
- • Sensor drift
What to do
- • Check dilution
- • Verify syringe volume
- • Recalibrate the sensor
BSCAirflow alarm sounds during work
Likely causes
- • Sash raised above the working height
- • Front grille blocked by arms or items
- • HEPA filters loaded with dust
- • Exhaust duct fan failure (ducted cabinets)
What to do
- • Return the sash to the marked height
- • Clear the grille
- • Stop work, close cultures and call service if the alarm stays on
- • Check the building exhaust system
BSCLow inflow velocity at certification
Likely causes
- • Exhaust filter loading
- • Fan speed set too low
- • Exhaust damper or duct partly closed
What to do
- • Adjust the fan speed and re-balance by a certified engineer
- • Replace the exhaust filter if adjustment is not enough
- • Check the duct and damper settings
BSCSmoke escapes from the front opening during the smoke test
Likely causes
- • Inflow too low or downflow too high
- • Air currents in the room from doors, vents or traffic
What to do
- • Re-balance the cabinet
- • Relocate the cabinet away from doors and supply vents
- • Repeat the smoke and velocity tests
BSCLeak found in HEPA filter scan
Likely causes
- • Damaged filter media
- • Gasket or seal leak
- • Filter not seated correctly
What to do
- • Repair within the allowed area or replace the filter
- • Reseat the filter or replace the gasket
- • Repeat the integrity test
BSCContamination on negative controls handled in the cabinet
Likely causes
- • Poor disinfection
- • Cluttered work area disturbing airflow
- • Filter leak
- • Poor aseptic technique
What to do
- • Review the cleaning record and disinfectant
- • Reduce items in the cabinet
- • Check filter integrity
- • Retrain the analyst
Colony counterAutomated count much higher than manual count
Likely causes
- • Debris, bubbles or precipitate counted as colonies
- • Detection threshold too low
What to do
- • Review the image and edit marks
- • Re-set the detection parameters within the validated range
- • Filter or dilute samples that leave particles
Colony counterAutomated count lower than manual count
Likely causes
- • Small or pale colonies missed
- • Merged colonies counted as one
- • Poor lighting
What to do
- • Adjust lighting and threshold within the validated settings
- • Use the separation tool or count manually
Colony counterPen does not register counts
Likely causes
- • Pen tip worn or cable loose
- • Battery low
What to do
- • Replace the pen tip or battery
- • Check the connection
Colony counterDifferent analysts get different counts
Likely causes
- • Unclear rules for spreading or merged colonies
- • Training gaps
What to do
- • Define counting rules in the SOP
- • Run periodic analyst comparison counts
Air samplerFlow error alarm during sampling
Likely causes
- • Blocked head holes
- • Fan or sensor fault
- • Low battery
What to do
- • Clean the head and check holes
- • Charge or replace the battery
- • Send for service and recalibration
Air samplerUnexpected growth on Grade A air samples
Likely causes
- • Contaminated head or poor plate handling
- • Real excursion in the area
- • Sampler placed in turbulent air
What to do
- • Review handling and head sanitisation
- • Start an investigation with particle data and other EM results
- • Identify the isolate and check placement
Air samplerAgar surface dried or cracked after sampling
Likely causes
- • Large sample volume in one plate
- • Low agar fill volume
What to do
- • Split the volume across plates or use thicker plates
- • Validate the maximum volume per plate
Air samplerCalibration shows flow outside tolerance
Likely causes
- • Sensor drift
- • Worn fan or leaking seal
What to do
- • Adjust and recalibrate
- • Assess impact on results since the last passing calibration
Particle counterCounts with the purge filter fitted
Likely causes
- • Contaminated sensor or inlet
- • Leak at the filter connection
- • Electronic noise or laser fault
What to do
- • Purge for longer and re-check
- • Refit the filter
- • Send for cleaning and service
Particle counterFlow alarm
Likely causes
- • Blocked inlet or kinked tubing
- • Pump wear
What to do
- • Clear the inlet and straighten tubing
- • Service and recalibrate the pump
Particle counterSudden high counts in Grade A
Likely causes
- • Real excursion: intervention, HEPA leak or HVAC failure
- • Probe disturbed or touched
What to do
- • Follow the excursion SOP and assess the impact on product
- • Check the HVAC and filter status
- • Review video and operator activity
Particle counterVery low ≥5.0 µm counts compared with history
Likely causes
- • Long tubing or bends losing large particles
- • Sensor degraded
What to do
- • Shorten tubing
- • Check calibration and counting efficiency
Endotoxin readerStandard curve |r| below 0.980
Likely causes
- • Poor CSE dilution or vortexing
- • Pipetting errors
- • Temperature not uniform
What to do
- • Prepare fresh standards with full vortexing
- • Check pipette calibration and technique
- • Check reader temperature calibration
Endotoxin readerNegative control shows endotoxin
Likely causes
- • Contaminated LRW, tips or tubes
- • Environmental contamination during set-up
What to do
- • Use a new lot of LRW and consumables
- • Clean the work area and repeat
Endotoxin readerPPC recovery below 50%
Likely causes
- • Product inhibition (pH, chelators, protein binding)
- • Spike added incorrectly
What to do
- • Dilute further (not beyond the MVD)
- • Adjust pH or use a dispersing buffer
- • Repeat with correct spiking
Endotoxin readerPPC recovery above 200%
Likely causes
- • Product enhancement
- • Glucan interference
- • Endotoxin contamination of the spiked sample
What to do
- • Dilute further
- • Use a glucan-blocking buffer or glucan-insensitive reagent
- • Repeat with fresh consumables
Endotoxin readerVery short onset in all wells
Likely causes
- • Contaminated LAL reagent
- • Reader temperature too high
What to do
- • Use a new reagent vial
- • Check temperature
Filtration unitFiltration very slow or stops
Likely causes
- • Sample with particles or high viscosity
- • Weak vacuum or leak
What to do
- • Pre-dilute or use several membranes
- • Check seals and pump
Filtration unitGrowth on negative controls
Likely causes
- • Non-sterile funnels or rinse fluid
- • Poor aseptic technique
- • Contaminated environment
What to do
- • Check sterilisation records
- • Retrain analyst and review EM data
- • Repeat with fresh materials
Filtration unitLow recovery in method suitability
Likely causes
- • Residual antimicrobial on the membrane
- • Wrong membrane type
What to do
- • Increase rinse volume or add neutraliser
- • Try another membrane material
Filtration unitLiquid in vacuum line
Likely causes
- • Trap full
- • Hydrophobic filter missing or wet
What to do
- • Empty trap and replace filter
- • Service the pump
KF titrator (coulometric)High or unstable drift
Likely causes
- • Worn septum or leaking joint
- • Exhausted molecular sieve
- • Wet glassware or electrodes after cleaning
- • Exhausted or contaminated anolyte
What to do
- • Replace the septum and grease or tighten joints
- • Replace the molecular sieve
- • Dry the glassware before filling
- • Replace the reagent
KF titrator (coulometric)Low recovery of the water standard
Likely causes
- • Error in syringe weighing
- • Standard opened too long or past expiry
- • Reagent near the end of its capacity
- • Endpoint settings too loose
What to do
- • Weigh by difference on a calibrated balance
- • Use a fresh ampoule of standard
- • Replace the reagent
- • Review the endpoint and stop-drift settings
KF titrator (coulometric)High recovery or results that keep increasing
Likely causes
- • Moisture picked up by the syringe or needle
- • Side reaction with the sample
- • Drift not correctly subtracted
What to do
- • Dry syringes and needles; rinse with sample
- • Use a KF oven or suitable reagent
- • Check drift correction
KF titrator (coulometric)Error message about generator electrode
Likely causes
- • Catholyte exhausted or contaminated
- • Deposits on the diaphragm or electrode
- • Cable or connector fault
What to do
- • Replace the catholyte
- • Clean the generator electrode as advised by the supplier
- • Check connections; call service if the fault remains
KF titrator (coulometric)Very long determination times
Likely causes
- • Sample contains too much water
- • Sample dissolves slowly
- • Reagent nearly exhausted
What to do
- • Reduce sample size or use volumetric KF
- • Use a co-solvent or a KF oven
- • Replace the reagent
TOC analyserHigh blank values
Likely causes
- • Contaminated reagent water
- • Dirty vials or caps
- • Contaminated reagent
- • Carry-over from a high sample
What to do
- • Use fresh TOC-free reagent water
- • Use certified low-TOC vials
- • Replace reagents
- • Run extra rinses or blanks after high samples
TOC analyserResponse efficiency outside 85–115%
Likely causes
- • UV lamp or catalyst losing performance
- • Wrong standard concentration
- • Oxidiser exhausted
What to do
- • Replace the lamp or catalyst
- • Prepare fresh standards and check calculations
- • Replace the oxidiser reagent
TOC analyserPoor repeatability
Likely causes
- • Air bubbles in the sample line
- • Contamination during sampling
- • Detector or membrane problem
What to do
- • Purge lines and check fittings
- • Review sampling technique and gloves
- • Inspect and replace the membrane or call service
TOC analyserSudden rise in online TOC
Likely causes
- • Real contamination of the water system
- • Sanitisation residues
- • Sensor fault
What to do
- • Take a grab sample and test offline
- • Check recent maintenance or sanitisation activities
- • Verify the sensor with a standard
TOC analyserResults higher than expected after calibration
Likely causes
- • Calibration standards prepared in water with high TOC
- • Blank not subtracted correctly
What to do
- • Prepare standards in fresh reagent water and repeat
- • Review the blank correction settings
DO meterReadings drift continuously
Likely causes
- • Probe not fully polarised
- • Temperature not stable
- • Membrane damaged or fouled
What to do
- • Allow the full polarisation time
- • Let the probe reach the sample temperature
- • Replace the membrane or sensor cap
DO meterCalibration fails (slope out of range)
Likely causes
- • Wrong pressure or salinity setting
- • Dry membrane or wrinkled membrane
- • Exhausted electrolyte or old sensor cap
What to do
- • Correct the settings
- • Refit the membrane
- • Replace electrolyte or sensor cap
DO meterReadings too low in a flowing sample
Likely causes
- • Insufficient flow or stirring (electrochemical sensor)
- • Air bubble on the membrane
What to do
- • Increase stirring or flow
- • Remove bubbles by tapping the probe gently
DO meterZero reading too high
Likely causes
- • Zero solution old or exposed to air
- • Slow sensor response
What to do
- • Use freshly prepared zero solution
- • Wait longer or service the sensor
Lab water systemResistivity below specification
Likely causes
- • Exhausted ion-exchange cartridge
- • Poor feed water quality
- • Faulty or dirty resistivity cell
What to do
- • Replace the polishing cartridge
- • Check pretreatment and RO performance
- • Verify the sensor and clean or replace it
Lab water systemTOC rising
Likely causes
- • UV lamp at end of life
- • New cartridge not rinsed
- • Contaminated reservoir
What to do
- • Replace the UV lamp
- • Rinse new cartridges as instructed
- • Sanitise the reservoir
Lab water systemLow flow at dispenser
Likely causes
- • Blocked point-of-use filter
- • Low reservoir level
- • Pump fault
What to do
- • Replace the final filter
- • Check RO production
- • Call service
Lab water systemMicrobial counts out of limit
Likely causes
- • Infrequent sanitisation
- • Contaminated outlet or filter
- • Water standing in lines
What to do
- • Sanitise the system
- • Replace the final filter and clean the outlet
- • Increase recirculation or use frequency
MicropipetteDrop forms at the tip or volume falls
Likely causes
- • Tip not fitted tightly
- • Worn seal or O-ring
- • Damaged tip cone
What to do
- • Use the correct tip and fit it firmly
- • Replace the seal
- • Replace the tip cone
MicropipetteDelivered volume consistently low
Likely causes
- • No pre-wetting
- • Tip immersed too deep or aspiration too fast
- • Pipette warmer than liquid
What to do
- • Pre-wet tips
- • Improve technique
- • Equilibrate pipette and liquid
MicropipettePoor precision
Likely causes
- • Inconsistent plunger speed
- • Holding the pipette at an angle
- • Hand warming the pipette
What to do
- • Train for a steady rhythm
- • Aspirate vertically
- • Do not hold the pipette for long periods; rest it on the stand
MicropipettePlunger stiff or jerky
Likely causes
- • Dried liquid in the shaft
- • Damaged piston
What to do
- • Clean and grease as instructed
- • Send for service
Burette & glasswareDrops cling to the inside wall
Likely causes
- • Grease or dirt on the glass
What to do
- • Clean with laboratory detergent or a suitable cleaning solution and rinse well
Burette & glasswareBurette reading drifts with stopcock closed
Likely causes
- • Leaking stopcock
What to do
- • Tighten or replace the stopcock
Burette & glasswareAir bubble in the tip changes during titration
Likely causes
- • Tip not cleared before setting zero
What to do
- • Run titrant through the tip before setting zero
Burette & glasswareGravimetric check fails
Likely causes
- • Chipped tip
- • Wrong delivery or waiting time
- • Temperature not recorded or wrong Z factor
What to do
- • Withdraw chipped glassware
- • Follow the delivery time marked
- • Measure water temperature and use the correct Z factor
Thermometer / loggerReading differs from reference by more than the limit
Likely causes
- • Sensor drift
- • Poor thermal contact or immersion
- • Not stabilised
What to do
- • Recalibrate or replace the sensor
- • Improve immersion and stirring
- • Wait longer before reading
Thermometer / loggerGaps in logged data
Likely causes
- • Battery failure
- • Memory full
- • Logger not started correctly
What to do
- • Replace the battery
- • Download and clear memory as per procedure
- • Check start settings
Thermometer / loggerErratic or jumping readings
Likely causes
- • Damaged cable or connector
- • Electrical interference
What to do
- • Replace the probe or cable
- • Move away from sources of interference
Stability chamberRH below set point
Likely causes
- • Humidifier water supply empty
- • Scaled or failed humidifier element
- • Door gasket leaking
What to do
- • Refill with purified water and check the supply line
- • Descale or replace the humidifier element
- • Replace the door gasket
Stability chamberRH above set point
Likely causes
- • Dehumidifying coil iced or not cooling
- • Wet samples or open water container inside
- • Blocked condensate drain
What to do
- • Defrost and check the refrigeration system
- • Remove the source of moisture
- • Clear the drain
Stability chamberTemperature slowly drifting high
Likely causes
- • Dirty condenser coil
- • Low refrigerant
- • Room too warm around the chamber
What to do
- • Clean the condenser
- • Call service to check refrigerant
- • Improve room ventilation or air conditioning
Stability chamberDisplay and monitoring system disagree
Likely causes
- • Sensor drift
- • Probes in different positions
- • Monitoring probe out of calibration
What to do
- • Calibrate both sensors against a reference
- • Check probe locations against the mapping report
- • Recalibrate or replace the drifting probe
Stability chamberFrequent short alarms
Likely causes
- • Frequent or long door openings
- • Alarm delay set too short
- • Controller tuning poor
What to do
- • Plan sample pulls together
- • Set a justified alarm delay in the SOP
- • Ask service to re-tune the controller
Stability chamberUneven conditions between shelves
Likely causes
- • Overloading or blocked air paths
- • Fan fault
What to do
- • Reduce load and keep space around packs
- • Check and repair fans; re-map if needed
Fridge / freezerTemperature too high
Likely causes
- • Door left open or not sealing
- • Dirty condenser
- • Overloading blocking airflow
- • Compressor fault
What to do
- • Close the door and replace a worn gasket
- • Clean the condenser
- • Reduce the load
- • Call service
Fridge / freezerTemperature below 2 °C in a refrigerator (risk of freezing)
Likely causes
- • Controller set point drifted
- • Items touching the cold evaporator plate
- • Room very cold
What to do
- • Recalibrate or reset the controller
- • Move items away from the cold plate
- • Relocate the unit
Fridge / freezerHeavy ice build-up in freezer
Likely causes
- • Frequent door opening
- • Door seal leaking
- • Defrost failure
What to do
- • Reduce door openings
- • Replace the seal
- • Defrost and service the unit
Fridge / freezerLogger and display disagree
Likely causes
- • Probes in different positions
- • Air probe versus buffered probe
- • Calibration drift
What to do
- • Compare positions with the mapping report
- • Remember buffered probes respond more slowly
- • Calibrate both against a reference
Fridge / freezerFrequent alarms
Likely causes
- • Alarm limits too tight or no delay
- • Defrost cycle
- • Unit near a heat source
What to do
- • Set justified alarm limits and delay
- • Check defrost schedule
- • Relocate the unit
SonicatorWeak or no cavitation
Likely causes
- • Water level too low or too high
- • Fresh water not degassed
- • Transducer or generator failure
What to do
- • Fill to the marked line
- • Run in degas mode before use
- • Have the unit serviced
SonicatorLow or variable assay recovery
Likely causes
- • Sonication time too short
- • Flask in a dead spot
- • Sample overheated and degraded
What to do
- • Follow the method time exactly
- • Use the same rack positions; use sweep mode
- • Control bath temperature, add ice if needed
SonicatorBath gets very hot
Likely causes
- • Long continuous runs
- • Heater left on
What to do
- • Change or cool the water between runs
- • Switch off the heater when not required
SonicatorTank floor pitted or leaking
Likely causes
- • Abrasive material on the floor
- • Long-term cavitation erosion
What to do
- • Always use a basket or rack
- • Replace the tank or unit
CentrifugeImbalance alarm or vibration
Likely causes
- • Unequal tube masses
- • Tubes not placed opposite each other
- • Missing bucket
What to do
- • Re-balance tubes by mass
- • Load symmetrically
- • Fit all buckets, even if empty
CentrifugeSupernatant still cloudy
Likely causes
- • RCF too low
- • Time too short
- • Fine colloidal particles
What to do
- • Check the method RCF and radius
- • Increase time within method limits
- • Use a higher-speed rotor or filtration as allowed
CentrifugeLid will not open
Likely causes
- • Rotor still turning
- • Power failure
What to do
- • Wait for the rotor to stop
- • Use the manual emergency release only after confirming the rotor has stopped
CentrifugeDoes not reach set speed
Likely causes
- • Worn motor brushes or drive fault
- • Rotor not recognised
What to do
- • Call service
- • Check rotor seating and identification
CentrifugeTubes cracked
Likely causes
- • Tube RCF rating exceeded
- • Old or solvent-damaged tubes
What to do
- • Use tubes rated for the RCF
- • Use solvent-compatible tubes and replace old stock
Water bathTemperature below set point
Likely causes
- • Lid left off
- • Water level low
- • Heater or controller fault
What to do
- • Close the lid
- • Top up the water
- • Have the unit serviced
Water bathDifferent temperatures at different positions
Likely causes
- • No circulation
- • Overloaded tank
What to do
- • Use a circulating model or stir
- • Reduce load and leave gaps
Water bathGreen or cloudy water
Likely causes
- • Algae and bacterial growth
What to do
- • Drain, disinfect and refill; add an approved antimicrobial additive; change water weekly
Water bathHeater cuts out
Likely causes
- • Low-level or over-temperature protection tripped
What to do
- • Top up and reset; call service if it repeats
Fume hoodLow-flow alarm
Likely causes
- • Sash raised too high
- • Fan or belt fault
- • Damper closed
What to do
- • Lower the sash
- • Report to engineering for fan repair
- • Check and open the damper
Fume hoodOdours escaping into the lab
Likely causes
- • Working too close to the opening
- • Clutter blocking baffles
- • Cross-draughts from doors or air vents
What to do
- • Work 15 cm inside the hood
- • Clear the hood
- • Redirect air vents or relocate activities
Fume hoodFace velocity uneven across the opening
Likely causes
- • Blocked baffle slots
- • Large equipment inside
What to do
- • Clear the slots
- • Raise or move equipment
Fume hoodSash will not stay in place
Likely causes
- • Broken counterweight cable
What to do
- • Stop using the hood and arrange repair