Substoichiometric radioisotope dilution analysis for traces of mercury by solvent extraction with silver diethyldithiocarbamate
✍ Scribed by J.M. Lo; J.C. Wei; S.J. Yeh
- Publisher
- Elsevier Science
- Year
- 1977
- Tongue
- English
- Weight
- 350 KB
- Volume
- 93
- Category
- Article
- ISSN
- 0003-2670
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✦ Synopsis
hIany metal ions form complexes with the diethyldithiocarbamate anion, (CtHs)&CSz-(DDC), and can be extracted into organic solvents. Extraction coefficients for metal ions with DDC under some conditions have been reported by several authors [l--6 J _ For analytical extractions, some complexes, Me(DDC),, in the organic solvent are often preferred as reagents to HDDC and NaDDC, which are less stable and easily decomposed in acidic solution [l, 2, 'i-91 . Moreover, a certain Me(DDC), in a suitable organic solvent can be chosen to extract metal ions selectively, in accordance with the order of the extraction coefficients [ 11. For example, in 0-W M H,SO, media, the _. _. order suggested by Wyttenbach and Bajo [l] is Hg'*, Ag', Ni'+, Cuz+, Bi'+, Sb3', Ted*, hIo6', Se", I.n3+, _A,s3+, Cd2+, and Zn'+. The extraction coefficient for _4g' is higher than those for other metals except HgZ+, hence none of these metal ions should be extracted if XgDDC is used as the reagent. The extraction coefficient for Ag', lo*=, is 3 orders of magnitude less than that for Hg"+, 10n [Z, 63 _ ..4ccordingly, mercury in water should be readily and selectively extracted into a solution of AgDDC in an organic solvent. In this study, substoichiometric isotope dilution analysis, as developed by Suzuki and Kudo [lo. 111 and R"uZi&a and Stary [12], was applied for the determination of traces of mercury in aqueous solution, by solvent extraction of Hg" with AgDDC in chloroform. The same quantities of AgDDC in chloroform are used to extract the same quantities of mercury to be partly separated in the standard and test solutions. The standard solution contains only the mercury radioisotope and the test solution is a mixture of test sample and a known amount of standard solution. Theoretically, the radioactivity of each extract should be inversely proportional to the initial total mass of mercury. in both solutions; and the general formula for the calculation of substbichiomeiric isotope dilution analysis is Mx 2 M[(AL~')-l] (1) where A and A' are the activities extracted from the standard and test solutions, respe&veIy, and..42 and MS are the masses of mercury in the standard and sample, respectively.