Sensitive determination of parabens in soy sauces by capillary zone electrophoresis with amperometric detection

A high-performance capillary zone electrophoresis with amperometric detection (CZE-AD) method has been developed for the separation and sensitive determination of the preservatives methylparaben (MP), ethylparaben (EP), propylparaben (PP) and butylparaben (BP) in soy sauce samples. The effects of several factors such as the pH and concentration of running buffer, the separation voltage, the applied potential and the injection time on CZE-AD were investigated. Under the optimum conditions, four preservatives can be well separated within 16 min at the separation voltage of 16 kV in a 80 mmol/L borax running buffer (pH 9.94), and adequate extraction was obtained with ethanol for the determination of the above four parabens. Satisfactory recovery (95.0–102.0%), repeatability of the peak current (≤2.4%) and migration time (≤0.5%) of four analytes, as well as detection limits (5.7 × 10⁻⁸–4.4 × 10⁻⁸ g/mL) for the method, were achieved. This proposed procedure has been successfully used for the analysis of paraben preservatives in soy sauce samples, and the content of EP was from 0.08 to 0.14 mg/mL in the tested samples.