SOP on Operation and cleaning of FTIR spectrophotometer



To lay down a procedure for operation and cleaning of FTIR spectrophotometer.


This procedure is applicable for the operation and cleaning of FTIR spectrophotometer.


QC officer : Responsible for the operation and maintenance of the instrument.

QC Head/ Manager : Responsible for accountability and effective implementation of the standard procedure for operation of instrument.

Definition  : FTIR stands for Fourier Transform Infrared. In infrared spectroscopy, IR radiation is passed through a sample. Some of the infrared radiation is absorbed by the sample and some of it is passed through (transmitted). The resulting spectrum represents the molecular absorption and transmission, creating a molecular fingerprint of the sample. Like a fingerprint no two unique molecular structures produce the same infrared spectrum. Infrared spectrophotometers are used for recording spectra in the region of 4000- 650 cm-1 (2.5-15.4 µm).



  • Always use the clean and dry mortar pestle for sample preparation to avoid contamination.
  • Do not prepare the sample near to the instrument to avoid spillage of chemical on the instrument.
  • Do not allow to test the corrosive and strong acid or base samples as it damage the sample holder.
  • After each operation clean the sample holder and instrument properly and discard the sample in a waste bin.
  • Do not locate the FTIR instrument in an environment with condensing moisture and excessive dust.
  • If any major problem arise in the operation of instrument then call the service engineer for troubleshooting.


  1. Before operation ensure that the instrument is clean and calibrated.
  2. Turn ON the main power of the instrument and computer connected with the instrument.
  3. Wait for at least 15 minutes until the initialization succeeded for proper stabilization of the instrument.
  4. Before operation check the sample holder or cleanliness, if it is not clean properly it will contaminate the current sample and gives inaccurate results, so clean the sample die or sample holder with acetone or ethanol and dry with tissue paper.
  5. To run the software double click on the software icon on the computer desktop.
  6. To open the main functioning window enter the individual user ID and password.
  7. Set the general parameters as follow: Resolution : 4 cm-1, Measurement mode : % transmittance, No. of scans : 1 to 20, Scanning range : 4000 to 400 cm-1 or as per requirement
  8. To execute the background click on the background or reference.
  9. Crush the dry(dried in oven) moisture free potassium bromide (KBr) of spectroscopic grade in a clean mortar and pestle, and then fill the KBr alone in sample holder , scan the KBr as a background.
  10. In case of ATR (Attenuated total reflection) assembly, fix the assembly in the sample compartment, ensuring that sample holder is empty and take air as a background scan the air without any sample in the sample compartment.
  11. For sample (sample may be solid, liquid, gaseous) measurement prepare the sample as described in the respective STP, fill the sample in the sample holder and place in the sample compartment in the front of IR beam.
  12. In general sample is prepared by mixing it with KBr in a mortar pestle, about 1 to 2 mg of sample is mixed with the 200 mg of KBr powder.
  13. Once the sample is placed close the chamber of sample compartment and scan the sample to acquire the sample spectrum.
  14. Save the sample spectrum file as per desired path.
  15. Compare the sample spectrum with the standard spectrum select the spectrum of standard from previous saved data of standard file and open the required standard spectrum. (Note: if standard spectrum is previously not saved then prepare the standard in same manner as sample and scan the standard to get the spectra of standard)
  16. Merge the sample and standard IR spectrum together and splits the peaks to get the % purity of sample.
  17. Execute the print of spectrum in a desired template.
  18. For Packing material testing the packing material is fixed in a Multiple internal reflectance assembly and record the spectrum.
  19. After completion of operation close the software make all the necessary entries in the respective log books.


  1. Before cleaning switch off the instrument, Clean the outer surface of the instrument with dry  clean lint free cloth.
  2. If required then clean the outer surface of instrument with lukewarm water and keep the surface dry.
  3. Clean the sample holder with IPA or methanol and keep the sample holder and sample compartment in a dry condition.


  • FTIR :Fourier transform Infrared
  • QC:    Quality Control
  • KBr:   Potassium bromide
  • STP:  Standrad testing procedure

Related Articles

Basics of FTIR

Sample Preparation Techniques for IR Analysis

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Article prepared by Quality Control desk and reviewed by pharmapathway team.


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