Quantitation of Butyrylcarnitine, Isobutyrylcarnitine, and Glutarylcarnitine in Urine Using Ultra-Performance Liquid Chromatography-Tandem Mass Spectrometry (UPLC-MS/MS).

Acylcarnitines are formed when an acyl group is transferred from coenzyme A to a molecule of L-carnitine. In organic acidemias, and in fatty acid oxidation disorders, specific acylcarnitine species accumulate in a pattern that is characteristic for each disease. For this reason, acylcarnitine analysis is widely used for screening and diagnosis of inherited disorders of metabolism. The most common method for acylcarnitine analysis uses flow injection tandem mass spectrometry. Flow injection analysis allows for high throughput, however, does not provide separation of isomeric and isobaric compounds. Among the acylcarnitine species which can be affected by the presence of isomeric/isobaric compounds, C4-carnitine and C5DC-carnitine are probably the ones encountered most often. The method presented here is performed on urine and utilizes butanolic HCL to derivatize acylcarnitines, ultra-performance liquid chromatography to resolve C4- and C5-DC isomers and isobars, and quantitation of these species using multiple-reaction monitoring (MRM).