Colorimetric estimation and some physicochemical properties of purified Cyanex 272

A technique for the colorimetric estimation of purified Cyanex 272 has been developed. The technique consists of the digestion of pure sample or its aqueous solution with concentrated nitric acid (70%)-perchloric acid (70%) mixture for 1 h. The oxidizing mixed acid quantitatively converts Cyanex 272 to a clear solution of orthophosphate that can be easily estimated by the molybdenum-blue colorimetric method at 830 nm. The method is sensitive with a molar extinction coefficient of similar to2.6 x 10(4) and reproducible within +/-2%. Applying this technique of analysis, the dimerization constant (K-2) distribution or partition coefficient (K-d) and ionization constant (K-a) of the purified Cyanex 272 (bis-2,4,4-trimethylpentylphosphinic acid, BTMPPA) have been estimated to be 190, 53 and 5.52 x 10(-4), respectively. (C) 2004 Elsevier B.V. All rights reserved.