Abstract:

This study aimed to establish a method of micellar electrokinetic capillary chromatography for direct determination of nipagin esters in food. Effects of key factors, such as concentration and pH adjustment of running buffer, separation voltage and concentration of surface active agent (SDS) as well as organic solvent addition on separation of ethyl nipagin ester, propylparaben and butyl nipagin were investigated. The results showed that under the optimized conditions as follows: running buffer, 10 mmol/L (final concentration) sodium dihydrogen phosphate-10 mmol/L (final concentration) sodium borate (pH 8.0) solution; SDS concentration, 20 mmol/L; separation voltage, 22 kV; and UV wavelength, 256 nm, these nipagin esters were completely separated within 10 min. There were nice linear relationships between their concentrations and peak area. Butyl nipagin was not detected in two commercial soy sauces by this method. Average recoveries for ethyl nipagin ester and propylparaben in the two commercial soy sauces spiked at two levels were within the recovery of 97.2%－ 104% (n = 5).

Key words: micelle capillary electrophoresis, ethyl nipagin ester, propylparaben, butyl nipagin