Enantioselective Determination of Carnitine Enantiomers in Food and Supplement Samples by Chiral Liquid Chromatography-Tandem Mass Spectrometry

Carnitine (CAR) is an essential compound for animals and plays several physiological roles related to energy production. These functions are possessed by only the l-forms, while the d-forms are known to inhibit the uptake of the l-forms, thus causing a CAR deficiency. Therefore, it is required to determine dl-CAR in various samples such as foods, supplements, and drugs by an enantioselective analytical method. In this study, we developed a chiral liquid chromatography-tandem mass spectrometry (LC-MS/MS) method using derivatization. The CAR enantiomers derivatized with 4-nitrophenylhydrazine were successfully separated on a CHIRALPAK ZWIX (-) column (resolution = 1.64) and detected with high sensitivity and selectivity by MS/MS. The developed method was well validated and applied to the analysis of eight kinds of foods and an l-CAR supplement. Only the l-forms were found in all the tested food samples and were abundant in meat, milk, and yogurt. The system was also applicable for a supplement sample and could detect the d-CAR contamination at the 2.5% level, suggesting its potential for use in the purity test of CAR preparations.