“…19 Cyanex 272, Cyanex 301, and Cyanex 302 were kindly donated by the Cytec Company (West Patterson, NJ), and PC-88A by Dailachi Chemical Industry Co. (Japan). Cyanex 272 is a phosphinic acid group extractant [di- (2,4,4-trimethylpentyl) phosphinic acid], Cyanex 301 and Cyanex 302 are alkylthiophosphinic extractants [bis(2,4,4-trimethylpentyl) dithiophosphinic acid and bis(2,4,4-trimethylpentyl) thiophosphinic acid, respectively], and PC-88A is a phosphonic acid group extractant (ester 2-ethylhexyl phosphonic acid). Cadmium solutions were prepared by dilution of Titrisol Merck standards, and other analytical-grade reagents were supplied by Fisher (H 3 PO 4 ), Merck [Oxalic acid, Cu(NO 3 ) 2 ], Analitika de Me ´xico, S.A. (HNO 3 ), Quimir S.A. de C.V. (industrial phosphoric acid), General Products Company S.A. (Na 2 S 2 O 4 , A grade, 85%), and J. T. Baker (ethanol, EDTA, HCl, and Fe and Zn powder).…”