Sample pretreatment for voltammetric analysis

In applications of voltammetry to biological samples, it is often the sample rather than the sensitive voltammetric analyzer that is the limiting factor. Getting the sample into a form that can take full advantage of the instrument capability may be the hardest part of the analysis. For this reason, the sample is usually treated prior to analysis. Such treatment releases the trace metals bound to sample components, and minimizes fouling of electrode (by adsorption of certain sample components) or background currents (from other electroactive constituents). The precision and bias of the data obtained by voltammetric analysis of biological samples will be more dependent on how well the sample is decomposed than with many other analytical techniques (e.g., atomic absorption spectroscopy which relies on atomization of the metal from the solution). 

Eriksen (1979) compared different wet digestion procedures for voltammetric stripping analysis of urine and preferred the use of a mixture of nitric, sulfuric, and perchloric acids. Satisfactory recovery (92-100%) of lead and cadmium from spiked samples was obtained. An effective procedure based on a rapid (20 min.) digestion of freeze-dried urine samples coupled with voltammetric analysis was reported (Golimowski et al., 1979). 

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