SOP on Calibration of FTIR Spectrophotometer



To lay down a procedure for calibration of FTIR Spectrophotometer.  


This procedure is applicable for the Calibration of FTIR spectrophotometer


  • QC officer/ Executive : Responsible for carry out calibration and to review and check the results of calibration of the instrument.
  • QC Head/ Manager : Responsible for accountability and effective implementation of the standard procedure for operation of instrument and to finally approve the report of calibration.



  • Operate the instrument as per its standard operating procedure.
  • Ensure that before performing the calibration instrument is clean.
  • Use reference standard polystyrene film for calibration along with its certificate traceable to NIST(5) standrads        
  • Thickness of the polystyrene film is 38 µ (micron) or 0.038 mm.
  • Polystyrene film used for calibration of FTIR because it shows absorption bands covers the complete range of IR region.
  • Polystyrene film is made up of polymers of styrene and stable at any temperature and highly durable.
  • Set the polystyrene film in a sample chamber of an instrument and set the instrument parameters as mentioned below :

Resolution : 2 cm-1

Measurement mode : % transmittance & ratio

No. of scans : 1 to 20

Scanning range : 4000 to 400 cm-1 or as per requirement.

  • Verification of the wave number scale:The wave-number scale may be verified using a calibrated polystyrene film, which has transmission minima (absorption maxima) at   the wave numbers (in cm–1) shown in below

Standard wave number ( cm-1)       Tolerance

3060.0                                                 ± 1.0 cm-1

2849.5                                                 ± 1.0 cm-1

1942.9                                                  ± 1.0 cm-1

1601.2                                                  ± 1.0 cm-1

1583.0                                                  ± 1.0 cm-1

1154.5                                                  ± 1.0 cm-1

1028.3                                                  ± 1.0 cm-1

  • Control of resolution performance : Record the spectrum of a polystyrene  film approximately 35 µm in thickness. The difference  between the percentage transmittance at the transmission maximum A at 2870  cm-1 (3.48 µm) and that at the transmission minimum B at 2849.5 cm-1 (3.51 µm)  must be greater than 18. The difference  between the percentage transmittance at  the transmission maximum C at 1589 cm-1 (6.29 µm) and that at the transmission  minimum D at 1583 cm-1 (6.32 µm) must be greater than 10.
  • After calibration, affix the label” CALIBRATED” on the instrument.
  • Frequency of calibration is quarterly.



  • FTIR :Fourier transform Infrared
  • QC:    Quality Control
  • NIST:  National institute of standard and technology
  • %:  Percentage


Related Articles

Basics of FTIR

SOP on preparation & calibration of FTIR

Sample preparation techniques for IR Analysis



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