Determination of 20 Free Amino Acids in Asparagus Tin by High-Performance Liquid Chromatographic Method after Pre-Column Derivatization

A novel method was studied for determination of 20 free amino acids in asparagus tin by high-performance liquid chromatography with pre-column derivatization. Derivatization of the samples was performed with 4-chloro-3,5-dinitrobenzotrifluoride (CNBF), and the SPE cartridge was used for purification and enrichment of the analytes. The derivatization conditions and the influence of elution composition on the separation were investigated. The reaction of amino acids with CNBF was completed in pH 9.0 borate buffer. The separation of amino acids was achieved at room temperature within 60 min by gradient elution mode with triethylamine in mobile phase, and the flow rate is 0.32 mL min−1 constantly. The method correlation coefficient was from 0.9975 to 1.0000 in concentrations ranging from 20 to 2000 μmol L−1, except asparagine (from 100 to 10000 μmol L−1). The detection limits of amino acids were from 1.2 to 6.0 μmol L−1, with a signal-to-noise ratio of three times. The calculated recoveries of the proposed method were from 81.4% to 109.4%, and relative standard deviations were 0.48–3.94% in application to the quantitative determination of free amino acids in asparagus tin samples. The present method is reliable and sensitive that allows fast analysis of free amino acids in asparagus tin, which makes it suitable for further study of free amino acids in other asparagus foods.