LimsPulse
Spectroscopy

Fourier Transform Infrared (FTIR) Spectrometer

Records the infrared absorption spectrum of a sample, which acts as a molecular fingerprint. The standard technique for identification of APIs and excipients in pharma QC.

  • Pharmaceutical
  • Polymers & plastics
  • Chemicals
  • Forensics
  • Food
  • Academic research
Photo of a Fourier Transform Infrared (FTIR) Spectrometer
Photo: Wang, F., Zhang, L., Zhang, X., Li, H. and Wu, S., CC BY 4.0 (cropped), via Wikimedia Commons
TROUBLESHOOTING

Common problems, causes and fixes

Large 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
Weak 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
Cloudy 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
Broad 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
Flat-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
Low 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
Sample 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
In LimsPulse · Calibration Management

Keep every FTIR in control: usage logs, calibration and maintenance schedules, and automatic blocking of overdue instruments.

See how