Mixture design of an electrolyte system for the simultaneous separation of Cl - , SO 4 2- , NO 3 - , NO 2 - , and HCO 3 - in shrimp-farming water by CZE-UV.

Shrimp is one of the most traded fishery products in the world. The shrimp-farming water ionic composition is fundamental to the growth and survival of these specimens. Therefore, this study is aimed to develop a method for the simultaneous separation of Cl - , SO 4 2- , NO 3 - , NO 2 - , and HCO 3 - in this sample by capillary zone electrophoresis with UV indirect detection, without any prior sample treatment, besides dilution. The background electrolyte (BGE) was composed of CrO 4 2- (60 mmol L -1 ), cetyltrimethylammonium bromide (CTAB, 2.5 mmol L -1 ), acetonitrile (0.875% (v/v)), and methanol (2.625% (v/v)). The mixture design optimized the BGE composition. Acetonitrile and methanol changed the degree of solvation of the anions, which decreased the radius, a phenomenon proven by calculating the radius of anions in all the conditions of the mixture design. The optimized and validated method allowed the simultaneous determination of the five above-mentioned anions in 10 min.