Mixture design of an electrolyte system for the simultaneous separation of Cl−, SO42−, NO3−, NO2−, and HCO3− in shrimp-farming water by CZE-UV

Abstract

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⁻, SO₄²⁻, NO₃⁻, NO₂⁻, and HCO₃⁻ 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 CrO₄²⁻ (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.