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

Luo, Tian, Dong, Yue, He, Shujuan, Yang, Jing, Dong, Yuming
Electrophoresis 2018 v.39 no.11 pp. 1410-1416
United Nations, acetates, amino acids, capillary electrophoresis, copper, copper sulfate, detection limit, electric power, models, pH, principal component analysis, vinegars, wavelengths
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 50 mM CuSO₄ and adjusted pH 4.40 with 8 mM acetate, 70 s injection time, 22.5 kV separation voltage, and 254 nm detected wavelength. Method validation, indicating good linearity (R² > 0.9989), precision with an RSD less than 8.0% (n = 5), LOD (0.13–0.25 μg/mL), LOQ (0.43–0.83 μg/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.