(2) Validation Program Conforming to Japanese Pharmacopoeia
I will describe the validation program used with the FTIR- 8400S/IRPrestige-21. There are 5 inspection items: power spectrum, resolution (resolving power), wave number accuracy, wave number reproducibility, and transmittance reproducibility. The performance of the system is inspected by comparing measurement results with criteria values.
The specification for resolving power shown on the right is given in supplement 1 to the fourteenth edition of the Japanese Pharmacopoeia and in EP4.0.
The respective differences in transmittance are measured and if they both are no less than the criteria values then system performance regarding this item is judged to be satisfactory.
|When the spectrum of a polystyrene film about 0.04 mm thick is recorded, the depth of the trough from the maximum absorption at about 2850 cm-1 to the minimum at about 2870 cm-1 should be not less than 18 % transmittance and that from the maximum at about 1583 cm-1 to the minimum at about 1589 cm-1 should not be less than 12 % transmittance.|
Wavenumber Accuracy The specification for wavenumber accuracy shown on the right is given in supplement 1 to the fourteenth edition of the Japanese Pharmacopoeia and in EP4.0. With this program, the peak wavenumbers measured for a polystyrene-film spectra with the wavenumbers used for evaluation given above are obtained. If all the peak wavenumbers are within the respective permissible ranges, system performance regarding this item is judged to be satisfactory.
The wave number (cm-1) scale is usually calibrated by the use of several characteristic absorption wave numbers (cm-1) of a polystyrene film shown below. The number in parentheses indicates the permissible range.
The specification for wavenumber repeatability shown on the right is given in supplement 1 to the fourteenth edition of the Japanese Pharmacopoeia.
With this program, 3 peak wavenumber points are specified and the actual peak wavenumbers at these points are obtained for two measurements of polystyrene film. If the peak wavenumbers for the specified wavenumbers are all within the respective ranges, system performance regarding this item is judged to be satisfactory. There is no specification for wavenumber repeatability in EP4.0.
|As the repeatability of transmittance and wave number ... when the spectrum of a polystyrene film is measured twice at several wave numbers from 3000 to 1000 cm-1... the difference of wave number should be within 5 cm-1 at about at about 3000 cm-1 and within 1 cm-1 at about at about 1000 cm-1.|
The following specification for transmittance repeatability is given in supplement 1 to the fourteenth edition of the Japanese Pharmacopoeia.
|As the repeatability of transmittance and wave number, the difference of transmittance should be within 0.5 % when the spectrum of a polystyrene film is measured twice at several wave numbers from 3000 to 1000 cm-1.|
With this program, 3 peak wavenumber points are specified and the transmittance values at these points are obtained for two measurements of polystyrene film. If the differences between the transmittance values are all within the respective ranges, system performance regarding this item is judged to be satisfactory.
The Japanese Pharmacopoeia-based validation program is incorporated, as a standard feature, in the IRsolution software that controls FTIR-8400S/IRPrestige-21. It can be executed simply by selecting it from the IRsolution menu and operation can be performed simply by following the instructions that are displayed. Inspection can be completely automated by using the Beam Switching Kit, which incorporates polystyrene film.
Reports summarizing inspection results can also be automatically printed out when measurement is completed.
Polystyrene Film Used for Inspections
The polystyrene film that is packed together with Shimadzu FTIR systems can be used for inspections. If traceability is required, however, use NIST (National Institute of Standards and Technology) standard polystyrene film: SRM 1921a - Infrared Transmission Wavelength Standard (Polystyrene Film).
In SRM 1921a, polystyrene film with a thickness of approx. 38 µm and a diameter of 25 mm is mounted to a paper holder of dimensions 5 × 11 cm.
The handling method, storage method, and use-by date are all detailed on the certificate provided with the product. As of December 2004, film that could be used up to December 31, 2008 was available.
When not using polystyrene film, cover it with the cover provided and store it in a desiccator. Do not touch the surface of the polystyrene film and blow off the dust that may accumulate on the surface using clean, dry air. The polystyrene film cannot be used if it is damaged or contaminated.
Use of NIST SRM 1921a polystyrene film is recommended, but NIST was out of stock as of June 27, 2005. Accordingly, NIST traceable polystyrene test film from International Crystal Laboratories (ICL), the secondary standard, is also recommended.