Sensitivity Enhancement by Field-Amplified Sample Injection in Interfacing Microchip Electrophoresis with Inductively Coupled Plasma Mass Spectrometry for Bromine Speciation in Bread

In this study, we reported bromine speciation analysis using a microchip electrophoresis-inductively coupled plasma-mass spectrometry (MCE-ICP-MS)-hyphenated system with sensitivity enhancement by the field-amplified sample injection technique. Satisfactory separation of bromide and bromate within 35 s was achieved in the 1.5-cm separation channel under an electric field of approximately -260 V cm(-1) in the buffer environment of 65 mM NaAc-HAc (pH 8.0). The sensitivities were improved by 12.8 for bromide and 12.0 for bromate by preparing the standards or samples in 3 mM sodium acetate instead of the background electrolyte. The detection limits for Br- and BrO3- were 0.18 and 0.22 mu g L-1, respectively, and the precisions of the migration time and reproducibilities of peak height and area were all lower than 4 %. Under the optimized conditions, the proposed method was successfully applied for speciation analysis of bromine in bread samples. Recoveries of BrO3 and Br- in six bread samples were between 97.2 and 105.2 %. The good agreement between the determined values by the proposed MCE-ICP-MS method and the high-performance liquid chromatography (HPLC)-ICP-MS method was obtained. All results prove its advantages including high sensitivity, high efficiency, and low operation cost, which are beneficial to routine analysis of bromine speciation in environmental, biological, and food fields.