The Establishment Of Amino Acids HPLC Detection Methods In Milk Powder

This article has systematically researchsed four derivatization reagents of amino acids,compared the diffent conditions of amino acids detection and estblished essential and semi-essential amino acids'HPLC detection methods in the milk powder through the four derivatization methods which are validated by different ways.The article has also analysed the essential and semi-essential amino acids of the bulk raw materials and infant formula milk powder in the market.Derivatization reagent phenylisothiocyanate (PITC):Reagent amount is200μ;Derivatization temperature is room temperature; Derivatization time is60min;Recovery mean is90%～110%; Detection limit is10-100μg/g;Precision is within10%;Relative error is within10%as compared with the data of third party laboratory.Derivatization reagent dansyl chloride:Reagent amount is1ml;Derivatization temperature is room temperature; Derivatization time is15min;Recovery mean is90%～110%;Detection limit is10～100μg/g;Precision is within10%;Relative error of methionine and cystine is within20%and the others are within10%as compared with the data of third party laboratory.Derivatization reagent chloride dimethylamine azobenzene:Reagent amount is100μl;Derivatization temperature is55℃; Derivatization time is15min;Recovery mean is about80%;Detection limit is30～200μg/g;Precision is within20%;Relative error is within40%as compared with the data of third party laboratory.Derivatization reagent o-nitrophenyl chloride:Reagent amount is150μl;Derivatization temperature is room temperature; Derivatization time is10min;Recovery mean is below80%;Detection limit is50～400μg/g;Precision exceeds20%;Relative error is within60%as compared with the data of third party laboratory.The derivatization method of phenylisothiocyanate (PITC) is accurate;The derivatization method of dansyl chloride needs to be validated;The derivatization method of chloride dimethylamine azobenzene and o-nitrophenyl chloride has low accuracy.We only compared the four derivatization methods with one third party laboratory, there may be contingency, so it is necessary to expand the amount of validation labs,then validate the accuracy of the derivatization methods,in the end,make them applied in the mational standards.The article analysed the amino acids of the bulk raw materials of infant formula milk powder and infant formula milk powder in the market.The essential and semi-essential amino acids of70#whey powder are significant different from the other raw materials.No matter the imported products or the domestic products didn't individually add monomer amino acids.The prescription design of infant formula products needs to be upgraded and we should consider the essential and semi-essential amino acids content of the products.