Direct analysis by electrospray ionization and matrix-assisted laser desorption ionization mass spectrometry of standard and urinary acylcarnitines - Comparison with fast atom bombardment and gas chromatography chemical ionization mass spectrometry

A simple method using matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) is described for the characterization of acylcarnitines in standard solutions and urinary samples from controls and patients with beta-oxidation deficiency disorders. This mass spectrometric approach is compared with other techniques currently utilized for studying acylcarnitines: fast atom bombardment mass spectrometry (FABMS), gas chromatography/chemical ionization mass spectrometry (GC/CIMS) and electrospray ionization mass spectrometry (ESI-MS), MALDI-MS was found to compare favourably with the recently described ESI-MS analysis of acylcarnitines. Both ESI-MS and MALDI-MS share the following advantages: (i) non-requirement of a derivatization step; (ii) easy detection of acylcarnitine esters in standard preparations and urinary samples from human subjects; (iii) detection of fatty acid oxidation disorders from the urinary acylcarnitine profiles in patients suffering from medium-chain acyl-CoA dehydrogenase deficiency (MCADD), multiple acyl-CoA dehydrogenase deficiency (MADD) and mitochondrial carnitine palmitoyltransferase type II (CPT II) deficiency; (iv) sensitivity comparable to FABMS and GC/CIMS, the two reference methods most widely utilized for routine detection of acylcarnitines; and (v) ability (like FABMS but in contrast with GC/CIMS) to detect long-chain acylcarnitines, suggesting that these esters might have been previously underestimated in body fluids from patients with beta-oxidation deficiency disorders, MALDI-MS, like ESI-MS, provides a fast and sensitive method for determining carnitine and its esters, with the potential for routine application in neonatal screening for inherited metabolic disorders involving acylcarnitine metabolism.