An amperometric detector with a platinum tubular electrode for high performance liquid chromatography

An amperometric detector based on a platinum tubular electrode was construc ted from a long narrow-bored platinum tube which was directly connected to the column outlet. The tube is immersed in a vessel containing an electroly te solution in which a common reference and counter electrodes are also imm ersed. Only the internal platinum wall is exposed to the electrolyte soluti on. At this geometrical arrangement, the platinum tube internal wall is non uniformly polarized so that only a certain length of the tube from its outl et attains a potential suitable for the detection. As a result, the detecto r effective volume is substantially lower than the platinum tube total geom etric volume. The detector was tested both in conventional and micro-HPLC s ystems. The peak parameters obtained with the test detector are comparable with those obtained with a standard spectrophotometric detector. However, t he detector dynamic range from 2 x 10 (- 8) to 5 x 10 (- 3) mol L (- 1), li near dynamic range from 2 x 10 (- 8) to 2 x 10 (- 5) mol L (- 1) and a limi t of detection 2 x 10 (- 5) mol L (- 1) were obtained for a test compound ( 1-aminonaphthalene).