[Rapid determination of 18 amino acids in soy sauce by ultra-performance liquid chromatography with pre-column...

A rapid ultra-performance liquid chromatographic (UPLC) method was developed for the separation and determination of 18 amino acids in soy sauce by using 6-aminoquinolyl-N-hydroxyl-succinimidyl-carbamate (AQC) as pre-column derivatization reagent. The 18 amino acids were separated within 12 min using a BEH C18 column, ultraviolet (UV) detection at 260 nm, ammonium acetate-acetic acid-acetonitrile-water and acetonitrile-acetic acid as the mobile phases with combined gradient elution and gradient flow-rate. A linear relationship between the UV absorbance and the concentration of each amino acid was obtained with the correlation coefficient (r2) above 0.999. The detection limits were ranged from 0.032 mg/L to 0.12 mg/L for different amino acids, and the overall relative standard deviations from 0.72% to 4.05%. The recoveries of 18 analytes in a spiked soy sauce were from 90.2% to 103.7%. With simple pretreatment of the samples and shorter analysis time, the proposed method can be applied to determine amino acids in soy sauce.