Impurity results from three validation

TABLE I Impurity Results from Three Validation Batches Using the New Suppliers Drug Substance. Specifications Are <0.1%... 

Validation of methods for quantitative determination of impurities includes precision studies. Repeatability is generally assessed by analysis of the same sample or samples prepared by the same analyst in replicate assays within a short duration of time. Repeatability should be assessed using (i) a minimum of nine determinations covering the specified range for the procedure (e.g., three concentrations/three replicates each) or (ii) a minimum of six determinations at 100% of the test concentration. Repeatability is evaluated by averaging the mean results from replicate assays and calculating the standard deviation (SD) and RSD. Repeatability of the method can be stated as either SD or RSD values. If an instrument is required for assay performance, then the same instrument should be used for the replicate assays. 

The validation process begun in Phase I is extended during Phase II. In this phase, selectivity is investigated using various batches of drugs, available impurities, excipients, and samples from stability studies. Accuracy should be determined using at least three levels of concentration, and the intermediate precision and the quantitation limit should be tested. For quality assurance evaluation of the analysis results, control charts can be used, such as the Shewart-charts, the R-charts, or the Cusum-charts. In this phase, the analytical method is refined for routine use. 

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