ABSTRACT
The term chemical method refers to the qualitative and quantitative determination of pollutants at trace concentrations in environmental matrices by their chemical reactions by selectively carrying out such reactions. The precipitation reactions involve the formation of solid products that precipitate out from the solution which may be determined by gravimetry. Several chemical methods for the environmental analysis are based on the formation of coordination complexes or chelates as the reaction products which can be analyzed by a spectrophotometer or a filter photometer or by titrations. Oxidation/reduction, also known as redox reactions are common in analytical chemistry, and so are they in trace environmental analysis. Derivatization reactions are widely used in many chromatographic and spectrophotometric analyses. The sylilation reactions involve replacement of active hydrogen from acids, alcohols, thiols, amines, and amides with trimethylsilyl groups. An example is the reaction of nitrite ion with sulfanilamide to produce a diazonium salt which then reacts with N-(1-naphthyl)ethylenediamine forming an intense colored azoderivative.
