Liquid-Chromatography Quantitative Analysis of 20 Amino Acids after Derivatization with FMOC-Cl and Its Application to Different Origin Radix isatidis

We developed a simple, rapid and reliable method for determination of 20 common amino acids based on derivatization with 9-fluorenylmethyl chloroformate (FMOC-Cl) and RP-LC/UV, this method was first introduced into quantitative analysis of amino acids. The amino groups of amino acids were trapped with FMOC-Cl to form amino acid-FMOC-Cl adducts which can be suitable for LC-UV. Chromatographic separation was performed on a C-18 column with a mobile phase gradient consisting of acetonitrile and sodium acetate solution. This method was shown to be sensitive for 20 common amino acids. In the intra-day precisions assay, the range of RSDs was 3.21-7.67% with accuracies of 92.34-102.51%; for the inter-day precisions assay, the range of RSDs was 5.82-9.19% with accuracies of 90.25-100.63%. The results also indicated that solutions of amino acids-FMOC-Cl can be kept at room temperature for at least 24 h without showing significant losses in the quantified values. The validated method was successfully applied to the determination of major four kinds of amino acids in R. isatidis samples (Arg, Pro, Met and Val). The total content of amino acids in different origin R. isatidis was 13.32-19.16 mg/g. The differences between R. isatidis samples were large using HCA.