Simultaneous determination of dihydroxybenzene and phenylenediamine positional isomers using capillary zone electrophoresis coupled with amperometric detection |
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Authors: | Shuqing Dong Langzhu Chi Zhiyong Yang Pingang He Qingjiang Wang Yuzhi Fang |
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Institution: | Department of Chemistry, East China Normal University, Shanghai, P. R. China. Fax: +86‐21‐62233508 |
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Abstract: | In general capillary zone electrophoresis (CZE) separation models, o‐, m‐, and p‐phenylenediamine isomers can be separated in a weak acidic running buffer for their pKa values being 4.52, 5.64, 6.04, respectively, while o‐, m‐, and p‐dihydroxybenzene isomers can be separated in a weak basic buffer for their pKa values being 9.40, 9.40 and 10.04, respectively. So, it is hard to find a suitable running buffer at a fixed pH in normal CZE for simultaneous separation of these two groups of positional isomers. In this paper, a novel method based on alternately running two different pH buffers in CZE coupled with amperometric detection (CZE‐AD) was designed to simultaneously determine these two groups of positional isomers. It is found that when two different pH running buffers were employed alternately under appropriate order and time, the six analytes could be separated perfectly in less than 20 min and the detection limits were as low as 10–7 mol/L. Furthermore, the effects of working electrode potential, pH and concentration of running buffer, separation voltage and injection time on CZE–AD were investigated. Experimental results demonstrated that the introduced method was practical to simultaneously determine two groups of positional isomers with different pKa and had some advantages of high sensitivity, good repeatability and small sample requirement. |
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Keywords: | Amperometric detection Alternate running buffers Capillary zone electrophoresis Positional isomers |
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