Liquid chromatography/mass spectrometry for timely response in regulatory analyses: Identification of pentobarbital in dog food

A limited liquid chromatography/mass spectrometry (LC/MS) data set was acqu ired under conditions which called for timely response without benefit of a fully developed method. Quality assurance elements verified that an LC/MS procedure developed in a short time was sufficiently under control to meet its purpose. LC/MS was used to rule out a potential problem with a gas chro matography (GC)/MS method that had been developed for regulatory purposes. The LC/MS data set showed that signals identified by GC/MS as diagnostic of pentobarbital (PB) were not artifacts of derivatization or GC analysis, Sa mples of dry dog food identified by GC/MS as containing PB were also shown by LC/MS to contain PB. The LC/MS method would not he recommended as a subs titute for GC/MS, primarily because of poorer sensitivity. Although the dat a set is limited, and justifiably represents only the starting point for co nventional method development, the purpose at hand was served adequately. T his work demonstrates the utility of LC/MS for rapid regulatory response, p rovided there is a framework of quality assurance checks.