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

Abstract

AbstractA 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 β‐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 β‐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.