Motomizu S, Tôei K
Department of Chemistry, Faculty of Science, Okayama University, Tsushima-naka, Okayama-shi, Japan.
Talanta. 1982 Feb;29(2):89-94. doi: 10.1016/0039-9140(82)80026-x.
The importance of selecting the most suitable counter-cation in the solvent extraction-spectrophotometric determination of an anionic metal chelate containing a sulphonic acid group is demonstrated and discussed. In the case of cobalt and 2-nitroso-1-naphthol-4-sulphonic acid (nitroso-NW acid), the most suitable counter-cation is the tetrabutylammonium ion (Bu(4)N(+)): in this case only the ion-pair of the anionic cobalt chelate is extracted into chloroform and the excess of the nitroso-NW acid remains in the aqueous phase. The absorption maximum of the chelate in chloroform is at 307nm, at which the molar absorptivity is 6.5 x 10(4)l.mole(-1).cm(-1). The absorbance of the reagent blank at 307 nm is less than 0.010. By use of nitroso-NW acid and Bu(4)N(+), trace amounts of cobalt may be determined in nickel salts and in iron and steel samples.
本文展示并讨论了在溶剂萃取-分光光度法测定含磺酸基团的阴离子金属螯合物时，选择最合适的抗衡阳离子的重要性。对于钴和2-亚硝基-1-萘酚-4-磺酸（亚硝基-NW酸），最合适的抗衡阳离子是四丁基铵离子（Bu(4)N(+)）：在这种情况下，只有阴离子钴螯合物的离子对被萃取到氯仿中，而过量的亚硝基-NW酸则留在水相中。该螯合物在氯仿中的最大吸收波长为307nm，此时摩尔吸光系数为6.5×10(4)l·mol(-1)·cm(-1)。试剂空白在307nm处的吸光度小于0.010。使用亚硝基-NW酸和Bu(4)N(+)，可以测定镍盐以及钢铁样品中的痕量钴。
