Liquid Chromatography-Electrochemical Detection of Inorganic Arsenic Using a Wall Jet Cell with Conventional and Microsized Platinum Disk Electrodes

A critical evaluation of a highly sensitive and specific liquid chromatography amperometric detection method (wall jet cell) for the determination of arsenic has been undertaken with platinum disk electrodes of variable size. The limit of detection is considerably tower with platinum disk electrodes of conventional size (millimeter radius) than is the case with microelectrodes (radius in micrometer range) because of a more favorable signal to noise ratio. Thus, the determination of arsenic is readily achieved in a bottled mineral water sample with a conventional size electrode, whereas the arsenic levels are too low to be detected precisely with a microelectrode. However, with respect to the desirable properties of a lower dependence on flow rate and a shorter time taken to achieve a stable baseline, and in cases where sensitivity is not a problem, the microelectrode method is advantageous. The method for detection of arsenic Involves a surface-based oxidation process In which As(III) is converted to As(V). This work suggests that advantages and disadvantages offered by using microelectrodes as an alternative to conventionally sized electrodes are critically dependent on the mechanism of the electrode process.