Spectrophotometric Determination of Trace Amounts of Mercury With Phenanthroline and Eosin

Owing to the toxicity of mercury in the environment, the determination of trace amounts of mercury has attracted great attention. I 32 The conventional technique of dithizone extraction is not always favoured because the procedure is cumbersome, sensitive to light and is subject to interferences from other metal ions.3 Analytical methods based on ternary complex formation seem to offer superior sensitivity and selectivity. A number of ternary systemsG-7 have been proposed for the determination of mercury, among which the tetrabromomercurate(I1) methylene blue system is the most sensitive. However, most of the ternary systems involve an additional extraction step. Colour development and measurement in aqueous solution itself would alleviate this difficulty, leading to a rapid, more accurate and precise analytical method. A survey of the various ternary systems proposed for mercury revealed that anionic mercury complexes are coupled with cationic dyes to form the ternary complex. On the other hand, the reaction of mercury with neutral ligands and anionic dyes can be utilised to form ternary complexes. A detailed examination of the reaction of mercury with phenanthroline-type compounds and anionic dyes showed that the colour reaction of mercury, phenanthroline and eosin could be used to advantage with an aqueous finish. This paper describes studies conducted on this system.