ICH Q7 - Good Manufacturing Practice Guide for Active Pharmaceutical Ingredients 14.1-14.2: Quarantine and record the disposition of out-of-specification material, and reprocess only by repeating established steps, building routine reprocessing into the process and evaluating any repeated reaction

What does 14.1-14.2 require?

Intermediates and APIs that fail specification should be identified and quarantined, and their final disposition recorded; they may be reprocessed or reworked as below. Returning material, even non-conforming material, to the process and repeating a crystallisation or another chemical or physical step that already belongs to the established process (such as distillation, filtration, chromatography or milling) is generally acceptable, but reprocessing used for most batches should become part of the standard process. Continuing a step after an in-process test shows it is incomplete is normal processing, not reprocessing. Returning unreacted material and repeating a chemical reaction counts as reprocessing unless part of the established process, and should first be carefully evaluated for by-products and over-reacted material.