6. Contamination control

Controlling the risk of contamination is essential at all stages of the analytical process, as the risk increases as concentrations decrease. In the confined space of the (clean) laboratory, this control is relatively easy to achieve, but the precautions needed to avoid contamination tend to be neglected, or even forgotten, during the sample collection and processing stages in the field.

Trace metal concentrations in the marine environment tend to be lower than in most freshwater aquatic systems, and it has taken marine chemists many years to develop effective measures to minimize the risk of contamination. The author is convinced that at least part of the drop in trace metal concentration observed, for example, in river waters after 1985, is linked to the introduction of quality assurance and quality control procedures for analytical steps, resulting in better...