Scheme for validation of an analytical protocol: semiautomated Kjeldahl nitrogen determination.

Definitive validation of an analytical protocol is not always possible. A scheme for performing an alternative type of validation is presented. The scheme is tested on a commonly used chemical procedure for assaying total nitrogen. This alternative validation scheme uses 5 approaches: tests of robustness to recovery of working standards, assay of fortified in-house control materials to assess recovery from typical material, prescribed means of measuring within-and between-batch precision of the assay of typical material, comparison with alternative assay procedures, and determination of analogous certified reference materials to enable calculation of total error. The scheme uses the results of the 5 approaches to obtain a performance profile for the assay. The scheme does not rely on involved statistical modeling or data treatment, yet provides the laboratory worker with a systematic approach to a within-laboratory validation of an analytical protocol.