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How to calibrate FTIR?
Table of Contents
- Calibration description
- FTIR calibration frequency
- Procedure for verification of the wavenumber
- Procedure for control of Resolution performance
- Frequently asked questions
Calibration description
Following are the main sections for the calibration of FTIR
Objective
The purpose of this SOP is to detail the for the calibration of FTIR
Scope
This procedure applies to all FTIR instruments of xxxx (where xxx is the company name)
Scope
The procedure applies to all FTIR at QC /Analytical Laboratory of xxx (where xxx is the company name)
Responsibility
Research scientists/Chemists/Analysts responsible for the calibration of the FTIR
HOD
To ensure the implementation of this SOP in the department (QC or Analytical or as applicable)
FTIR calibration Frequency
Once in three months ± 5 days
Calibration procedure
- Operate the instrument as per operational SOP
- Make sure the instrument must be clean
- Use Polystyrene film reference standard with valid COA for calibration. The Thickness of the Polystyrene film should be 38 µm (micron) or 0.038mm
- Set the Polystyrene film in the sample chamber of the instrument and set the instrument parameters as mentioned below:
- Resolution: 2 cm-1
- Measurement mode: % transmittance ratio
- Number of Scan: 1 to 20
- Scan range: 4000 to 400 cm-1
Note: The scan range may be different for some of the instruments. Therefor scan range must be set as per Instrument requirement
Procedure for the verification of the Wavenumber
The wavenumber is verified using the calibrated Polystyrene film, which has transmittance minima (absorption maxima) at wavenumbers (in cm-1) shown below table – 1:
Table-1
| Std Wavenumber(cm-1) | Tolerance(cm-1) | Acceptance criteria(cm-1) |
| 3060 | ±1 | 3059 to 3061 |
| 2849.5 | ±1 | 2848.5 to 2850.5 |
| 1942.9 | ±1 | 1941.9 to 1943.9 |
| 1601.2 | ±1 | 1600.2 to 1602.2 |
| 1583 | ±1 | 1582 to 1584 |
| 1154.5 | ±1 | 1153.5 to 1155.5 |
| 1028.3 | ±1 | 1027.3 to 1029.3 |
Procedure for control of Resolution performance
- Record the spectrum of Polystyrene reference standard
- Check the % absorbance at the absorption minimum at 2870 cm-1 and that at the absorption maximum at 2849.5cm-1.The difference (say X) in % absorbance between the two should be greater than 0.33
- Check the % absorbance at the absorption minimum at 1589 cm-1 and that at the absorption maximum at 1583 cm-1.The difference (say Y) in % absorbance between the two should be greater than 0.08
Frequently asked questions and answers
Read this article
Abbreviations:
- FTIR: Fourier transform infrared spectroscopy
- HOD: Head of the department
- QC: Quality control
References:
- Pharma Knowledge Forum
- Indian Pharmacopoeia
- USP: United state pharmacopeia
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