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GC USP-Methods
Users from the regulated environment (e.g. the pharmaceutical industry) are often bound to so-called monograph methods of the European or US Pharmacopoeia(Ph. Eur. or USP). The specifications laid down in the pharmacopoeias for the analysis of the substances to be analysed must be followed. These are mainly laid down in Chapter 621 of the USP.
Chapter 621 of the USP explicitly contains practical recommendations that allow deviations from the method specifications in a monograph without the need to revalidate the method. The adjustment is considered necessary to fulfil the system suitability test (SST) criteria. The following tables provide an overview of the parameters that can be varied and the limits permitted in each case.
| Parameters | Permitted deviation* |
| Column length | +/- 70 % |
| Packing material | Any (as long as SST criteria are met and the column or support category (GXX or SXX) remains the same ("remaining same chemistry") |
| Injection and split volume | The injection and split volume can be adjusted if detection and repeatability are satisfactory. |
| Oven temperature | +/- 10 °C |
| Oven temperature programme | The temperatures may be adjusted as specified above. If the specified temperature must be maintained or if the temperature must be changed from one value to another, an adjustment of up to ±20% is permitted. |
| Flow rate | +/- 50% (Note - If the monograph specifies a linear velocity parameter, the allowable flow rate adjustment is between +50% and -25%, provided the carrier gas system can be kept under control at the desired setpoints). |
| Particle size | Changing particle sizes of a GC mesh support is allowed as long as the chromatography fulfils the system suitability requirements and the same particle size range ratio is maintained. The particle size ratio is defined as the diameter of the largest particle divided by the diameter of the smallest particle. |
* Modifications outside the specified limits are considered "changes" that require revalidation of the method used
For more detailed information, see the adjacent information from USP. ->
MZ-AT USP <621> Supplement to USP 40-NF 35