Development of a chiral liquid chromatography-tandem mass spectrometry for simultaneous determination of carnitine and acetylcarnitine enantiomers in food samples

l -Carnitine (CAR) and acetyl- l -carnitine (ACA) are essential compounds involved in energy production and are used as supplements and drugs. On the other hand, the opposite enantiomer, the d -forms, don’t have the same functions as the l -forms. d -CAR is known to inhibit the l -CAR absorption causing CAR deficiency, and d -ACA has recently been reported to enhance the efficacy of pharmaceuticals for the Pompe disease. Since the physiological actions of the d - and l -forms differ, the enantioselective analysis of CAR and ACA is expected in foods, drugs, and biological specimens. However, conventional methods still present some analytical challenges in separating the enantiomers and achieving selective detection. In the present study, a chiral liquid chromatography-tandem mass spectrometric (LC-MS/MS) method has been developed with the combination of pre-column derivatization. The CAR and ACA enantiomers were separated as their 3-nitrophenylhydrazine derivatives on a CHIRALPAK ZWIX (-) column with resolution values higher than 1.57. After the successful method validation, the developed system was applied to the content analysis of meat, milk, and soybean fermented food samples, and l -CAR and l -ACA were found in all the tested products. Furthermore, trace amounts of d -CAR were discovered in Hama-natto, which is a local traditional food in Japan. • A chiral LC-MS/MS method was developed for the separation of CAR and ACA enantiomers • 3-NPH derivatization improved the retention and separation of the enantiomers • Trace amounts of d -CAR were found in the Japanese fermented soybean food, Hama-natto