Powder microelectrodes for capillary electrophoresis with amperometric detection

In this paper, we first report the use of powder microelectrodes (PMEs) as the amperometric detector for thiols, hydrazine and hydroxylamine in capill ary electrophoresis (CE). This PME, with graphite-supported metalloporphyri n powder as catalyst, offers a few advantages as an amperometric detector i n CE. Concentration limit of detection and mass limit of detection obtained for L-cysteine at the PME could reach 88 nM and 230 amol, respectively. Th e response of thiols at the PME was very reproducible since the electrode f ouling was reduced. A relative standard deviation of peak heights (n = 8) o f 1.8% and a relative standard deviation of migration time (n = 8) of 1.0% can be obtained for L-cysteine. The material packed in the PME can easily b e changed. Hence, it is very convenient to choose suitable catalysts to det ect special analytes, and this specially designed microelectrode should be applicable to many other compounds of biological interest.