Comparison study of determination methods of free amino acid in Shuxuetong injection by HPTLC, pre-column derivation-UPLC, and ion chromatography

Free amino acids play a great role in traditional Chinese medicine in injections of animal products, as they may take part in peptide synthesis and exhibit a bioactivity in vivo. However, most of the national standards for drugs and peer-reviewed papers only focus on the total amount of amino acids after peptide hydrolysis. We compare the advantage and disadvantage among high performance thin layer chromatography (HPTLC), pre-column derivatization ultra performance liquid chromatography (UPLC) and ion chromatography. As a result, the HPTLC and pre-column derivatization UPLC are suitable for quality analysis, while there is high matrix influence for ion chromatography analysis. The verified pre-column derivatization UPLC method is utilized in quantitative analysis. 24 kinds of amino acid were detected by this method, and 8 of them were reported for the first time from the injection. The system has high repeatability and accuracy with LOD on the level of pmol·mL^-1.