Acylcarnitines ionization

Costa CG, Struys EA, Bootsma A, et al (1997) Quantitative analysis of plasma acylcarnitines using gas chromatography chemical ionization mass fragmentography. J Lipid Res 38 173-182... 

Paglia G, D Apolito O, Corso G. Precursor ion scan profiles of acylcarnitines by atmospheric pressure thermal desorption chemical ionization tandem mass spectrometry. Rapid Commun Mass Spectrom 2008 22 3809-3815. 

Reference values for the acylcarnitines are derived from >500 patients, mostly pediatric (0.2-16 yrs), evaluated for metabolic disorders in the author s laboratory but with no manifest biochemical evidence of disease. Individuals with any markedly abnormal values were discounted. The analytical method used was tandem mass spectrometry with electrospray ionization. Internal standards used were stable isotope-labeled analogs of acetyl, propionyl, butyryl, octanoyl and palmitoyl carnitine. The values for straight-chain C2, C3, C4, C5, C6, C8, CIO, C14, C16 and Cl8 1 species are in pmol/1 and are derived from calibration curves using analytical standards all other values are ratios of the signal for the compound to an appropriate internal standard. All values are mean + 2 std. dev. except where a range is given... 

Analysis of carnitine and acylcarnitines by MS/MS is now considered routine in those laboratories that possess the appropriate technology. The ionization techniques commonly used with MS/MS are fast atom (or fast ion) bombardment and electrospray. Both are sufficiently sensitive to detect abnormally elevated concentrations of specific metabolites in all types of specimen, although the latter is much more widespread and is the more sensitive of the two, especially for long-chain acylcarnitines. The method is quantitative or at least semi-quantitative for most analytes, and uses stable isotope-labeled forms of the analytes as internal standards. The acylcarnitines are analyzed simultaneously in the positive ion mode as their methyl or butyl esters using a precursor ion scan function [14, 23] that detects the parent (molecular) ions. Free carnitine and total carnitine are determined by assaying the same specimen before and after alkaline hydrolysis, without derivatization, using Hs-carnitine as internal standard [17]. The value for acylcarnitine is determined by difference. This value includes the contribution of short, medium and long-chain acylcarnitines. Analysis time for each method is approximately 2 min. 

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