Simultaneous Analysis of L-Carnitine and Acetyl-L-Carnitine in Food Samples by Hydrophilic Interaction Nano-Liquid Chromatography

L-Carnitine (L-CAR) and acetyl-L-carnitine (Acetyl L-CAR) are the essential cofactor compounds in lipid metabolism and are used in the treatment of various diseases. The European Food Safety Authority (EFSA) has reported that Acetyl-L-CAR contributes to normal cognitive function and has a beneficial physiological effect. Therefore, the sensitive separation and determination of L-CAR and Acetyl-L-CAR in foodstuffs can provide critical information. A notable trend in modern food analysis is the increasing use of miniaturized analytical columns with a narrow inner diameter (ID). In this study, a new, green analytical method for food analysis was developed to analyze L-CAR and Acetyl-L-CAR in food samples by nano-LC/UV with a hydrophilic monolithic 100 µm ID capillary. This is the first time that the preparation and application of a hydrophilic monolithic nano-column for the analysis of L-CAR and Acetyl-L-CAR in food samples by nano LC/UV has been reported. The hydrophilic monolith was prepared using in situ co-polymerization of glyceryl methacrylate (GMM) and ethylene dimethacrylate (EDMA). Following preparation and characterization, the hydrophilic monolith was used to analyze L-CAR and Acetyl-L-CAR in food samples, including three infant powdered milk samples and five supplements using nano LC/UV. The developed method was validated in terms of precision, sensitivity, linearity, recovery, and repeatability. The LOD and LOQ values were found to be in the range of 0.04–0.09 µg/kg, respectively. In short, the proposed method proved to be suitable for the routine analysis of L-CAR and Acetyl-L-CAR in food samples.