Establishing a sensitive capillary electrophoresis-UV method for direct determination of amino acids to evaluate vinegar quality.

In this study, the capillary electrophoresis method with ultraviolet detection was established to directly determine amino acids in vinegar, according to the coordination interaction between amino acids (AAs) and copper ions. The online sweeping technique was combined to improve the detection sensitivity. The quality of vinegar was evaluated with AAs as parameters by United Nations Food Agriculture Organization/Word Health Organization AAs model and principal component analysis. Optimum conditions were obtained under 50mM CuSO4 and adjusted pH 4.40 with 8mM acetate, 70s injection time, 22.5kV separation voltage, and 254nm detected wavelength. Method validation, indicating good linearity (R-2>0.9989), precision with an RSD less than 8.0% (n=5), LOD (0.13-0.25g/mL), LOQ (0.43-0.83g/mL) and recovery (80.5-112.6%). Under the optimal conditions, AAs in vinegar can be directly separated which is propitious for the quality evaluation of vinegar.