Measurement of free carnitine and acylcarnitines in plasma by HILIC-ESI-MS/MS without derivatization

•A method for measurement of acylcarnitines has been developed using HILIC-MS/MS.•Acylcarnitines were detected without derivatization.•IDA experiment was performed to explore fragment pattern of unusual acylcarnitines.•Dicarboxylic and hydroxyl acylcarnitine isomers could be separated.•It can be used for high-risk screening and diagnosis of inborn errors of metabolism.

Measurement of carnitine and acylcarnitines in plasma is important in diagnosis of fatty acid β-oxidation disorders and organic acidemia. The usual method uses flow injection tandem mass spectrometry (FIA-MS/MS), which has limitations. A rapid and more accurate method was developed to be used for high-risk screening and diagnosis. Carnitine and acylcarnitines were separated by hydrophilic interaction liquid chromatography (HILIC) without derivatization and detected with a QTRAP MS/MS System. Total analysis time was 9.0 min. The imprecision of within- and between-run were less than 6% and 17%, respectively. Recoveries were in the range of 85–110% at three concentrations. Some acylcarnitine isomers could be separated, such as dicarboxylic and hydroxyl acylcarnitines. The method could also separate interferent to avoid false positive results. 216 normal samples and 116 patient samples were detected with the validated method, and 49 patients were identified with fatty acid oxidation disorders or organic acidemias.