Determination of 4 Tea Polyphenols in Hairtail by High Performance Liquid Chromatography-Tadem Mass Spectrometry

An aliquot (2 g) of the edible part of hairtail was taken, and 20 mL of ethyl acetate was added. The mixture was oscillated for 1 min, shaken for 30 min, and centrifuged for 5 min. The ethyl acetate phase was taken, and spin evaporated to near dryness under reduced pressure, and 2 mL of 10% (volume fraction, the same below) acetonitrile solution was added to dissolve the residue. After shaking, the mixed solution obtained was placed into a 10 mL-volumetric flask, and 2 mL of 10% acetonitrile solution was used for repeated washing. The washing solutions were combined, and its volume was made up with 10% acetonitrile solution. After centrifugation for 5 min, the supernatant was passed through a 0.22 μm filter membrane, and the filtrate was determined by high performance liquid chromatography-tandem mass spectrometry. The chromatographic column of Waters Atlantis dC₁₈ was used as the stationary phase, and the mixed solution composed of acetonitrile and 0.1% (volume fraction) formic acid solution at different volume ratios was used as the mobile phase for gradient elution. The separated epigallocatechin gallate, epigallocatechin, epicatechin gallate and epicatechin were ionized by the electric spray ion source with negative ion mode, detected by the multiple reaction monitoring mode, and quantified by the matrix matching method. It was shown that linear relationships between the mass concentration of the 4 tea polyphenols and the corresponding peak area were kept in the same range of 10-200 μg·L^-1, with detection limit of 0.03 mg·kg^-1. The spiked recovery test was made on blank hairtail sample at three concentration levels, giving results of recovery in the range of 81.2%-92.0%, and RSDs (n=6) of the determined values were less than 7.0%.