An acid hydrolysis method for quantification of plasma free and total carnitine by flow injection tandem mass spectrometry

ObjectivesTo develop a tandem mass spectrometry (MS/MS) method for plasma free and total carnitine, incorporating acid hydrolysis for total carnitine measurement, for improved accuracy and sample throughput.Design and methodsLimit of detection (LOD), limit of quantitation (LOQ), linearity, accuracy, precision coefficient of variation (CV), method comparison with a radioenzymatic assay (REA) and liquid chromatography tandem mass spectrometry assay (LC-MS/MS) were performed. The method was tested for interferences and for long-term performance.ResultsThe method LOD and LOQ were 0.87 and 1.36 μmol/L for free carnitine and 1.79 and 2.54 μmol/L for total carnitine, respectively. No interferences were detected. Long-term measurement CVs for both free and total carnitine were < 4%.ConclusionsThe method shows acceptable performance characteristics with improved speed and low level accuracy compared to existing REA and MS/MS methods.