Determination of Amino Acids in Plasma and Nutritional Supplements by Capillary Electrophoresis with Copper(II) Coordination

Abstract

A capillary zone electrophoresis (CZE) method was developed using interactions between amino acids and copper(II) without derivatization. The optimized separation buffer included 10% isopropanol, 50 mmol L−1 CuSO4, 50 mmol L−1 acetic acid, and 50 mmol L−1 sodium acetate at pH = 3.98 at a detection wavelength of 233 nm. This method allowed baseline separation and determination of ten amino acids in less than 21 min. Quality parameters such as linearity (r > 0.99), precision (relative standard deviation <2.51%), limits of detection (0.05 µg mL−1), and recovery (82.25% to 117.6%) were measured. The separation of amino acids in high salt solutions was explored. The method was used to directly determine amino acids in human plasma and nutritional supplements.