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Dissolved oxygen can be reduced on platinum and gold electrodes, although the presence of adsorbing species can attenuate the amount of cathodic current observed. By monitoring the degree that the current is suppressed, one can indirectly monitor the concentration of the adsorbate. This type of quantitative procedure can be done on both metals, with platinum giving a larger residual reduction signal and greater sensitivity to the presence of adsorbate. Amines, halides, and sulfur compounds were all demonstrated to be detectable in this manner. This indirect detection was incorporated into a Pulsed Electrochemical Detection (PED) waveform that was named the Indirect Adsorption Detection (IAD) waveform. IAD was utilized successfully following flow injection analysis and HPLC, yielding similar detection limits to those seen with other forms of PED. Application of IAD was hampered by inconsistent performance resulting from gas evolution at the negative potentials necessary for sensitive detection. |
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