Ultra-Performance Liquid Chromatographic Determination of L-Ergothioneine in Commercially Available Classes of Cow Milk

A new efficient and sensitive precolumn hydrophilic interaction ultra-performance liquid chromatography (HILIC-UPLC) method was established for the quantitative determination of L-ergothioneine (ERT) in milk. After derivatization of ERT with 7-diethylamino-3-[4-(iodoacetamido) phenyl]-4-methylcoumarin, chromatographic separation was achieved in a fairly short time, less than 5min, on a 100x2.1 mm Waters Cortecs UPLC HILIC 1.6-mu m column, by using a mixture of 30 mmol/L ammonium acetate/acetonitrile (10: 90, v/v) as a mobile phase flowing isocratically at 0.9 mL/min. Limit of detection and the limit of quantification were 0.03 and 0.10 mu mol/L, respectively. The method exhibited linearity in a concentration range of 0.16 and 5.08 mu mol/L. Mean recovery was 106.66%, whereas intra-and interassay precisions were determined to be within 6 RSD%. On average, ERT concentration in different commercially available classes of cow milk was found to be 0.442 +/- 0.191 mu mol/L, with the highest levels in the ultra-high temperature milks and low values in the unprocessed and HTST whole milks. In this light, our experiments suggest that ERT could be used as a marker for the heat treatment of milk.