This content is current only at the time of printing. This document was printed on 28 September 2020. A current copy is located at https://apvma.gov.au/node/26436
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Standard for metazachlor active constituent
The material shall consist of metazachlor together with related manufacturing impurities and shall be in the form of a colourless solid with a faint aromatic odour, free from visible extraneous matter and added modifying agents. The material may be formulated directly into products as a wet cake, without full removal of residual water, in which case the active content must still comply with the minimum dry weight purity (see composition below)
Active constituent: 950 g/kg minimum (dry weight basis)
- The analytical method used for the determination of the active constituent and toxicological significant impurities must be validated in accordance with the APVMA guidelines for the validation of analytical methods.
- The APVMA guidelines on validation of analytical methods state that 'Analytical methods described in CIPAC handbooks and AOAC International Manual, and in recognized pharmacopoeias [BP, BP (Vet), Ph Eur and USP] for a particular active constituent or formulation are regarded as validated and do not require revalidation'. However, the suitability of these methods must be verified under actual conditions of use ie, the selectivity and accuracy of the method should be demonstrated for the published method when applied to the relevant sample matrix and laboratory conditions.
- When a CIPAC or AOAC method is used for the assay of an active constituent in a bulk active constituent, there is no matrix. The registrants need to check the specificity of the method to ensure there is no interference from impurities or degradation products. However, determination of accuracy of the method is not required as there is no potential for the product matrix to have an effect on the determination of the active constituent. However, when a CIPAC or AOAC method is used for the assay of an active constituent in a formulated product, determination of both specificity and accuracy is required as the matrix is relevant in formulated products (formulated products have different composition and quantities of excipients).
- Unless the scope of the collaborative method (CIPAC and AOAC) also includes toxicologically significant impurities in the active constituent, validation data for impurities are required.