QUANTITATIVE-ANALYSIS OF PLASMA ACYLCARNITINES USING GAS-CHROMATOGRAPHY CHEMICAL-IONIZATION MASS FRAGMENTOGRAPHY

A stable isotope dilution gas chromatography chemical ionization mass spectrometry (GC-CI-MS) method was developed for the quantitative prof iling of plasma acylcarnitines. The clean-up procedure was comprised o f a solid-phase cation exchange extraction using PRS-columns from whic h the acylcarnitines were eluted with a barium chloride solution. Isol ated acylcarnitines were transformed into acyloxylactones and analyzed by positive GC-CI-MS using isobutane as reactant gas. The selected mo nitoring of a common ion at m/z [85](+) and the protonated molecular i on enabled a selective and sensitive detection of all C-2-C-18 acylcar nitines. An accurate quantitation was achieved by the use of stable is otope-labeled internal standards (C-2-C-18) and acylcarnitines could b e analyzed in the sub-nanomolar range. Control values for C-2-C-18 acy lcarnitines in plasma were established. Concentrations ranged from 0.0 2 mu mol/L for C-14-acylcarnitine to 4.90 mu mol/L for C-14-acylcarnit ine. The diagnostic suitability of the method was demonstrated for pat ients with medium-chain acyl-CoA dehydrogenase deficiency and very lon g-chain acyl-CoA dehydrogenase deficiency.