Measurement of urinary free and acylcarnitines: quantitative acylcarnitine profiling in normal humans and in several patients with metabolic errors.

A method for determining urinary concentrations of carnitine and acylcarnitine esters is described that employs fast atom bombardment mass spectrometry, stable isotope dilution techniques, and a novel deutero-methyl esterification that permits unambiguous identification and quantitation of free carnitine and acylcarnitines. It is rapid, does not require chromatographic or other isolation procedures, and is immune to analyte losses in sample preparation. Urinary concentrations are reported for adult control subjects and for others with various metabolic disorders.