Abstract: HPLC was applied to monitor the dehydration reaction,in the production process of L-pyroglutamic acid from L-glutamic acid.The chromatography is operated by adopting a YMC-Pack Pro C₁₈ RP column (4.6 mm×250 mm×5 μm) and mobile phase composed of aqueous solution of 5 mmol·L^-1 potassium dihydro phosphate and 0.05 mmol·L^-1 ammonium dihydro phosphate in combination of acetonitrile with volume ratio of 9:1.The content of L-pyroglutamic acid in reaction solution was determined by the standard spiking method.The results showed that the plot of the content and the peak area displays good linearity in the range of 0.017 8~0.065 3 g·L^-1 with r=0.998 7;the average recovery is 99.31%,while the relative standard deviation for repetitions is 0.45%.Based upon this monitoring method,it showed that the dehydration reaction achieves the best condition at reaction time of 1 h.

Key words: material of cosmetics, L-pyroglutamic acid, dehydration reaction, HPLC