Chromatography
Thin-Layer Chromatography (TLC)
Separates compounds as a solvent climbs up a thin layer of adsorbent on a glass, aluminium or plastic plate. Simple and cheap; used in pharma QC mainly for identification and limit tests for related substances.
- Pharmaceutical
- Herbal & natural products
- Chemicals
- Forensic
- Education
TROUBLESHOOTING
Common problems, causes and fixes
Streaking 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
Uneven 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
All 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
All 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
Rf 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
Spots 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
In LimsPulse · Calibration Management
Keep every TLC in control: usage logs, calibration and maintenance schedules, and automatic blocking of overdue instruments.