Spectrophotometric determination of mercury(II) by solvent extraction with 2, 2'-bipyridyliron(II) chelate

YAMAMOTO Yuroku, KIKUCHI Sumiyoshi, HAYASHI Yasuhisa, KUMAMARU Takahiro

doi:10.2116/bunsekikagaku.16.931

A spectrophotometric method for the determination of mercury(II), based on a solvent extraction of the associated ion pairs formed between 2, 2'-bipyridyliron(II) chelate cations and bromo-mercury(II) complex anions, is described. The best extractant is 1, 2-dichloroethane, whereas other organic solvents are useless in this system. The absorbance maximum of 2, 2'-bipyridyl-iron (II) chelate in the organic phase is at 526 mμ. The recommended procedure for the calibration curve is as follows. Five milliliters of potassium bromide (1 M ), varying amounts of standard mercury(II) solution (25 μg Hg²⁺ /ml, 010 ml), 1 ml of acetate buffer solution (1 M, pH 4.5) and 5 ml of 2, 2'-bipyridyl-iron(II) solution (5 × 10^-3 M) are mixed. This solution is diluted to 25 ml with distilled water, and shaken for 3 min. with 10.0 ml of 1, 2-dichloroethane. The absorbance of the organic phase is measured at 526 mμ against the solvent. The percentage of the extraction is determined to be 82% (19°C) by radiochemical technique using Hg197. Beer's law is obeyed over the range of 110 μg/ml of mercury(II). Several features of the proposed method are as follows: A good extraction is obtained in the wide range of pH (210), the reagent employed is readily available in pure form, and the solution remains stable over a long period of storage. The method is convenient, accurate and highly selective for the determination of a small amount of mercury(II).

Spectrophotometric determination of mercury(II) by solvent extraction with 2, 2'-bipyridyliron(II) chelate

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