The widespread pollution of water, be it in the form of rain, groundwater, rivers, lakes, coastal waters or the oceans, is one of the most important environmental challenges facing the world today. A complete solution will only come about when major changes are made to the many contributing factors, which include: mineral extraction and processing, energy conversion and use, industrial manufacturing, intensive methods of farming and sewage disposal. In the meantime many immediate problems must be faced and none, perhaps, is more urgent than the need to analyse accurately and rapidly the impurities in reservoirs, to determine if the water is fit to drink.

A recent communication from researchers at the A. N. Frumkin Institute of Electrochemistry, of the Academy of Sciences of the U.S.S.R., considers in some detail three electrochemical methods of determining impurities in water, and compares them with established methods (V. E. Kazarinov, V. S. Bagotzky, Yu. B. Vassiliev and O. A. Khazova, J. Appl. Electrochem., 1988, 18, (3), 347–356).

The most suitable of the methods tested is based upon the fact that platinum readily adsorbs organic and toxic metals. Thus the amount of such impurities can be calculated from the degree of poisoning they cause, as determined from the decrease in the hydrogen adsorption capability of a platinum micro-electrode. Measurements were made using a conventional three-electrode cell, the working electrode being 2 to 3 mm of 0.5 mm diameter platinum wire and the auxiliary electrode a 1 cm square of platinum gauze. In acid solutions a mercuric sulphate reference electrode may be used. Quantitative determination of individual substances is only possible in limited instances, but organic impurities may be differentiated according to their oxidisability into easy-, medium- and difficult-to-oxidise categories.

The proposed electrochemical method of impurity determination is highly suitable for automatic water monitoring systems, and a number of analysers have been devised.