Simultaneous determination, by capillary zone electrophoresis, of multiple components of different industrial products

Summary Four parabens (esters of 4-hydroxybenzoic acid), effective preservatives against the growth of bacteria, yeast, and mold in numerous industrial products, have been used in this work as model compounds to demonstrate the resolving power of capillary electrophoresis (CE). The simultaneous determination of methyl-(MP), ethyl-(EP), propyl-(PP), and butylparaben (BP) was achieved by capillary zone electrophoresis (CZE) with UV diode-array detection at 294 nm. When run voltage, temperature, and electrolyte concentration and pH were optimized the most effective separation was achieved within 7 min by use of 50 cm (effective length) fused silica capillary tubing and operation at 25kV and 20°C. Background electrolyte comprising 35 mM tetraborate buffer adjusted to pH 10.0 gave the best results. The limits of detection of the optimized method ranged from 0.65 μg mL⁻¹ for BP to 0.81 μg mL⁻¹ for MP; the relative standard deviation was between 0.35 and 0.50%. These results showed that the method enables the determination of the four parabens in commerially available cosmetic and pharmaceutical preparations containing some of the parabens and in an unidentified canned berry fruit juice.