SOP for Calibration of FT-IR Spectrometer : Pharmaceutical Guidelines

SOP for Calibration of FT-IR Spectrometer

Standard operating procedure to calibrate the Fourier Transforms Infra Red Spectrometer using polystyrene film.


To describe the procedure for operation and calibration of FT-IR Spectrometer.


This SOP is applicable for the operation and calibration of FT-IR Spectrometer.


Officer/ Executive - Quality Control.


Manager - Quality Control


5.1 Procedure for General Cleaning

5.1.1 Ensure that the power to the instrument is switched OFF before cleaning Clean the instrument with clean dry cloth daily.

5.2 Operation of Instruments

5.2.1  Ensure that the instrument is properly connected to the power supply.
5.2.2  Switch ON the main switch and power switch of the instrument situated at backside panel.
5.2.3  Switch the computer ON by the switches situated on right of the monitor and PC respectively.
5.2.4  Switch on the instrument, kept it for 10-15 minutes to get warm.
5.2.5  Click on software & select collect mode
5.2.6  In collect mode you select background & put file name or as per your requirement (in case of DRA assembly put KBr powder).
5.2.7  Now click on ‘ok collect’ so that it will scan background spectra.
5.2.8  After completion of background spectra, put sample pellet (in case of DRA put mixture of KBr & sample).
5.2.9  Again click on collect & select normal, transmittance mode, select scanning range (4000-5000 cm-1 or as per your requirement). Select number of scan (1-20 or as per your requirement).
5.2.10  After completion of scanning you will get spectrum of actual sample.
5.2.11  For peak marking click on view & select ‘peaks’.
5.2.12  For comparison with your previous standard just right click on main screen & select overlaid or stacked mode as per your requirement 
5.2.13  Now open your previous standard spectrum by click on file – open trace. 
5.2.14  You can also add the data on screen by right click on main screen & select add text.
5.2.15  For printouts click on file – print & select ‘display current’.
5.2.16  Same way you can check no. of samples

5.3  For Solids

5.3.1  Preparation of potassium bromide disc: Take about 200 mg of potassium bromide in pestle and mortar and grind it to a fine powder. Add about 2-3 mg of substance being examined and again grind to fine powder, Mix well the contents
5.3.2  Clean the Die and it components with soft cloths or tissue paper. Do not use a cloth having hard abrasive texture to wipe to wipe the polished surface.
5.3.3  Ensure that the rubber seal is properly fixed in the groove of the die.
5.3.4  Carefully place on the pellets (polished face in up side position ) into the bore of the cylinder .
5.3.5  Using a clean thin stainless steel spatula, transfer the fine powder sample + Kbr preparation in the bore of the cylinder. Tape the side of die gently so that the powder is evenly distributed across the face of the police face. Insert the second pellet with police facing down.
5.3.6  Place the die assembly under “hydraulic press “ Evacuate die assembly. Then apply pressure of 10 tons to the plunger to produce transparent disc.
5.3.7  Remove die base from cylinder leaving plunger in released position.
5.3.8  Put cylinder bore below the cylinder and place them “hydraulic press” Apply pressure across the plunger until the pellet immersed from the cylinder followed by disc .
5.3.9  Remove the disc carefully and put into plastic tweezer switch is further fixed into the sample compartment of the instrument

5.4  For Liquids 

5.4.1  Prepare the blank and sample solution as directed in the STP.
5.4.2  Fill the blank /test solution into the cell, preferably with a syringe.
5.4.3  Rinse the cell 2 times with the solution and finally fill the cell taking care that no air bubble is trapped inside.

5.5  For Sample in Mineral Oil Dispersion 

5.5.1  Take about 200 to 300 mg of the sample in the clean mortar and add about 3 to 5 drops of liquid paraffin (AR grade) and grind it to a fine paste. Mix the contents properly.
5.5.2  Clean the sodium chloride cell with a tissue paper mildly so that no fiber /small piece of tissue paper stick to it.
5.5.3  Hold a cell horizontally and pour 2 to 3 drops of the sample preparation on it and spread it evenly slightly tilting.
5.5.4  Place the second cell horizontally on the first and press it mildly so that it stick together.
5.5.5  Now place these cell horizontally, inside the window and tighten the screws

5.6  Scanning 

5.6.1  Open the sample compartment by raising the left hand side cover of spectrum one FT-IR Spectrometer and insert the sample holder into sample the compartment.
5.6.2  Close the sample compartment
5.6.3  Click the scan display on right sight of the screen.
5.6.4  The spectrum appears on the screen.
5.6.5  Compare the spectrum obtained with standard spectra that is stored in the computer, by proceeding as follows.
5.6.6  Select file on the top left hand side then open.
5.6.7  In open choose the relevant spectra and clicking the one that is needed . If relevant standard spectra not available in computer scan standard also with same operation parameter.
5.6.8  Two spectra are displayed on the screen, the test in black colour and the standard over laying it in blue colour.
5.6.9  After comparison take the spectra by print command.
5.6.10  The spectrum is printed by the printer.
5.6.11  Current official reference standard shall be chronogram and the spectra shall be kept in the file.
5.6.12  These spectra shall be updated once every year /or whenever there change in lot no. of the official reference.

5.7  Calibration

5.7.1  Switch on the system.
5.7.2  Set instrument parameter as follows.
RANGE 4000-400 cm-1 
5.7.3  Allow the instrument to warm for 30 minutes.
5.7.4  Operate the instrument as per operation SOP.
5.7.5  Open the sample compartment cover of FTIR 1600 and place the polystyrene film in the sample holder and the close the cover.
5.7.6  Click OK in the SCAN MODE.
5.7.7  The spectrum of the polystyrene film is displays on the screen.
5.7.8  PRINT the spectrum by going to print function.
5.7.9  When the printer of the spectra is completely go to DATA and then to PEAK.
5.7.10  The peak data’s of the spectra of the polystyrene film is displays on the screen.
5.7.11  PRINT out these data’s by going to print function.
5.7.12  Compare the wave function accuracy with the following limit .
Limit of wave Number Accuracy
3060.0 (±1.5)  2849.5 (±1.5)  1942.9 (±1.5)  1601.2 (±1.0)
1583.0 (±1.0)  1154.5 (±1.0)  1026.3 (±1.0)
Resolution performance of the apparatus
Record the spectrum of the polystyrene film 0.04 mm in thickness. The difference x 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 (3.51µm ) should greater than 16. The difference y between the percentage transmittance at the transmission maximum C at 1589 cm-1 (5.29 µm) and that at the transmission minimum D at 1583 cm –1 (5.32 µm) should be greater than 12.
5.7.13  Record the observation in the calibration record (Annexure –II ). Affix a “CALIBRATION LABEL “on the instrument.
5.7.14  Report any discrepancy observed during calibration or operation of the instrument to QA Manager and notify the defect to Engineering. Dept / Service. Affix an ‘UNDER MAINTENANCE; label on the instrument.

5.8  Frequency of Calibration 

5.6.1  Once in three month and after each maintenance job.


6.1  SOP - Standard Operating Procedure
6.2  Kbr - Potassium Bromide
6.3  FTIR - Fourier Transforms Infra Red
6.4  AR - Analytical Reagent Grade

Material Name
Batch No./
Lot No.
Started at
Completed On

                        CALIBRATION REPORT OF FTIR
Asset  ID No.

Ref. SOP No.


Model No.

Limit of Wave Number Accuracy :
By Polystyrene Film

Sr. No.
Wave Number
3060.0 (±1.5)


2849.5 (±1.5)


1942.9 (±1.5)


1601.2 (±1.0)


1583.0 (±1.0)


1028.3 (±1.0)


Resolution Performance
By Polystyrene Film

Sr. No.
Wave Number
Transmittance Deference Between X and Y
Limit Greater Than in %






Remarks : The instrument is working satisfactorily/not satisfactorily as per SOP.
Next calibration due on :

________________                              ____________________                               _________________________
Date of calibration                       Calibrated by (name/sign)                     Checked by (name/sign)/on

Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of Pharmaceutical Guidelines, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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