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 acquired 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 chromatography (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. Samples 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 be recommended as a substitute for GC/MS, primarily because of poorer sensitivity. Although the data set is limited, and justifiably represents only the starting point for conventional method development, the purpose at hand was served adequately. This work demonstrates the utility of LC/MS for rapid regulatory response, provided there is a framework of quality assurance checks.