Rapid Detection of D-amino Acids in Cheese with a Chiral Ligand- Exchange Chromatography System

Abstract

Due to the well established difference in the pharmaco/toxicological profile of many amino acid enantiomers, and also for typifying the food quality and origin, the exact knowledge of their presence and relative ratio in foodstuffs, is a matter of growing interest. In this setting, with an interest in identifying the presence of D-amino acids in a selected set of cheese samples, and with the aim to introduce a fast and easily accessible chromatographic procedure, we analyzed six cheese extracts with a CLEC-based chiral stationary phase (CLEC-CSP). The CLEC analyses were run without any preor post-column derivatization of the amino acidic mixture. The successful chemo- and enantioseparation were contemporarily achieved with the use of a dynamically coated CSP (C-CSP) based on the S-trityl-L-cysteine (L-STC) as the chiral selector. With the applied CLEC procedure, the presence of D-Ala, D-Asp and D-Glu was diagnosed in all the analyzed samples and then confirmed via conventional chiral gas chromatographic (CGC) analysis. A certain degree of peak overlapping was found to be the main drawback of the simplified sample analysis, which is nevertheless balanced by the advantages of the rapid detection. Keywords: D-Amino acids, Cheese, Chiral gas chromatography (CGC), Chiral ligand-exchange chromatography (CLEC), Coated-chiral stationary phase (C-CSP), Food analysis, Mass spectrometry (MS) detection, Thin layer chromatography (TLC)