Analysis of some micro pollutants

Ubiquitous environmental pollutants from anthropogenic sources have put a challenge to analytical chemists. For many of the compounds there are no safe levels from an environmental point of view. Toxicologists will rarely be able to cover the intricate impact of all possible combinations of chemicals and their decomposition products that the contaminants might appear in. Also, since many of the compounds induce immune systems it has become necessary to analyse at lower and lower levels. Chlorinated hydrocarbons have been known since the 1830s and the chemical properties of these compounds have made them useful for numerous industrial applications. Many organo chlorine compounds (OC) have insecticidal properties and were developed to protect man and standing crops. During the 1960s the environmental problem with OC, mainly aromatic OCs, as ubiquitous contaminants were recognized, and major scientific efforts were made to attend that field of chemistry. As these subjects came to be permanent items on agendas of several international bodies, the difficulties in assessing spatial differences and temporal trends were illustrated. To evaluate discrepancies among laboratories at reported environmental levels, intercomparison studies have been conducted both nationally and internationally. Although the problem remains, there have been improvements in the analytical techniques which led to decreased coefficients of variation in some exercises. Many of the conducted intercalibration exercises have also been less successful, mainly due to systematic errors. This could be in part dependent upon the quality of standards and lack of certified reference materials for the laboratories quality assurance work. The time identified for such work may consume as much as 20% of the analytical work.