Fast Fourier transform square-wave voltammetry detection of phenothiazinesin capillary electrophoresis

A new detection technique called the fast Fourier transform square-wave vol tammetry (FFT SWV) is based on measurements of ultramicroelectrode admittan ce as a function of potential. The response time of the detector (ultramicr oelectrode) is less than 1 s, which makes the method suitable for most appl ications involving flowing electrolytes. The response is generated by a var iety of processes involving the analyte, such as: reduction or oxidation, a dsorption or desorption, surface transformation, inhibition of oxygen or hy drogen adsorption and changes in the solution resistance. Proper electroche mical conditioning of the ultramicroelectrode made of a noble metal (e.g. A u or Pt) provides a stable response for several hours. The new detection te chnique was tested under capillary electrophoresis and flow-injection condi tions for the determination of ten phenothiazine derivatives. The detection limit was 2-5 x 10(-7) mol l(-1) in CE and about 1 x 10(-8) mol l(-1) in n ow injection detections.