Determination of 21 amino acids in grass carp, clam and shrimp by enzymatic hydrolysis coupled with high-performance liquid chromatography and tandem mass spectrometry

A simple and sensitive method was developed and validated for the simultaneous determination of 21 amino acids in three aquatic products including grass carp ( Ctenopharyngodon idella ), clam ( paphia undulata ) and shrimp ( Metapenaeus ensis ) with high-performance liquid chromatography coupled with ionization tandem mass spectrometry (HPLC-MS/MS). Firstly, aquatic products samples were pretreated by enzymatic hydrolysis and the efficiencies of different hydrolysis conditions were investigated. Then both chromatographic and mass spectrometric conditions were optimized to improve sensitivity and accuracy for the analytes. Under the optimized conditions, the limits of detection (LODs) for 21 amino acids were in the range from 0.02 μg/g to 1.78 μg/g. The correlation coefficients and recoveries were ranged from 0.997 to 0.999 and 80–115 %, respectively, and the relative standard deviation was within the range of 0.6–8.7 %. The results showed that 21 amino acids were all detected in samples. Except for asparagine, glutamine, tryptophan, cystine, cysteine, aspartic acid and glutamic acid, there is no significant difference in the measurement of amino acids by HPLC-MS/MS and amino acid analyzer.