Determination of 3-chloro-1,2-propanediol in soy sauces by capillary electrophoresis with electrochemical detection

A capillary electrophoresis technique with electrochemical detection (CE-ED) for determination of 3-chloro-1,2-propanediol (3-MCPD) in soy sauces was described. Effects of several factors, such as the pH value and the concentration of the running buffer, separation voltage, injection time and the potential applied to the working electrode, were investigated to find the optimum conditions. With a 50 cm length of 25 μm diameter fused-silica capillary, well-defined separation of 3-chloro-1,2-propanediol from propanediol and glycerol was achieved in 30 mmol/L borate (pH 9.24) within 13 min. Operated in a wall-jet configuration, a 0.45 mm copper-disk electrode used as the working electrode exhibits good response at 0.65 V (vs. SCE) for the analyte in 0.05 mol/L sodium hydroxide solution. The linear range for 3-MCPD was from 2 × 10−4 g/mL to 6.6 × 10−6 g/mL. Notably, the detection limit (S/N = 3) of 1.3 × 10−7 g/mL for 3-chloro-1,2-propanediol coincides with the criterion of food safety. This method was successfully used in the rapid analysis of 3-MCPD in soy samples. The average recoveries of 93.8–106.8% indicated that the experimental results were satisfactory.