Capillary electrophoresis method with UV-detection for analysis of free amino acids concentrations in food

Simple and inexpensive capillary electrophoresis with UV-detection method (CE-UV) was optimized and validated for determination of six amino acids namely (alanine, asparagine, glutamine, proline, serine and valine) for Sudanese food. Amino acids in the samples were derivatized with 4-chloro-7-nitro-2,1,3-benzoxadiazole (NBD-Cl) prior to CE-UV analysis. Labeling reaction conditions (100 mM borate buffer at pH 8.5, labeling reaction time 60 min, temperature 70 °C and NBD-Cl concentration 40 mM) were systematically investigated. The optimal conditions for the separation were 100 mM borate buffer at pH 9.7 and detected at 475 nm. The method was validated in terms of linearity, limit of detection (LOD), limit of quantification (LOQ), precision (repeatability) (RSD%) and accuracy (recovery). Good linearity was achieved for all amino acids (r2 > 0.9981) in the concentration range of 2.5-40 mg/L. The LODs in the range of 0.32-0.56 mg/L were obtained. Recoveries of amino acids ranging from 85% to 108%, (n = 3) were obtained. The validated method was successfully applied for the determination of amino acids for Sudanese food samples.