Improvement of National Standard Method for Determination of 16 Kinds of Amino Acids in Food

The national standard method GB 5009.124-2016 for determination of 16 kinds of amino acids (including of aspartic acid, threonine, serine, glutamic acid, proline, glycine, alanine, valine, methionine, isoleucine, leucine, tyrosine, phenylalanine, histidine, lysine, arginine) in food was improved. Improved conditions of acid hydrolysis were as following. Sample of 1 g was placed into a teflon tube, and 6 mol·L^-1 hydrochloric acid solution containing 0.1% (mass fraction) phenol of 10 mL was added for filling nitrogen and sealing. The acid hydrolysis tempreture was 165℃ and the acid hydrolysis time was shortened to 1 h from 22 h. Microwave digestion was proposed, and the conditions were as following. Sample of 0.1 g was placed into a quartz tank, and 6 mol·L^-1 hydrochloric acid solution of 1 mL was added. The above solution was put into a teflon tank containing 6 mol·L^-1 hydrochloric acid solution and digested at 165℃ for 12 min after filling nitrogen for deoxygenation and sealing. LCA K06/Na column was used as stationary phase, and 16 kinds of amino acids were separated according to optimized column heating program and gradient elution program. It was showed that linear relationships between concentrations of 16 kinds of amino acids and their peak areas were kept in the range of 10-200 μmol·L^-1, with detection limits in the range of 0.000 11%-0.004 2%. Recovery test was made on pig lean meat at 3 concentration levels by standard addition method, giving results in the range of 93.6%-101%, and RSDs (n=6) of the determined values were in the range of 1.2%-7.2%. The two pretreatment methods have been used for determination of substantial samples, and compared with the determination results of GB 5009.124-2016. Values of P were 0.870 for improved acid hydrolysis and 0.643 for microwave digestion, indicating that there was no significant difference between the determination results of these two pretreatment methods and GB 5009.124-2016.