An Amperometric Detector with a Platinum Tubular Electrode for High Performance Liquid Chromatography

An amperometric detector based on a platinum tubular electrode was constructed from a long narrow-bored platinum tube which was directly connected to the column outlet. The tube is immersed in a vessel containing an electrolyte solution in which a common reference and counter electrodes are also immersed. Only the internal platinum wall is exposed to the electrolyte solution. At this geometrical arrangement, the platinum tube internal wall is nonuniformly polarized so that only a certain length of the tube from its outlet attains a potential suitable for the detection. As a result, the detector effective volume is substantially lower than the platinum tube total geometric volume. The detector was tested both in conventional and micro-HPLC systems. The peak parameters obtained with the test detector are comparable with those obtained with a standard spectrophotometric detector. However, the detector dynamic range from 2×10–8 to 5×10–3 mol L–1, linear dynamic range from 2×10–8 to 2×10–5 mol L–1 and a limit of detection 2×10–8 mol L–1 were obtained for a test compound (1-aminonaphthalene).