Extraction equilibrium of the ion-associate of periodate with amiloride hydrochloride and simultaneous spectrophotometric determination of periodate and iodate by liquid-liquid extraction

The extraction equilibrium of the ion-associate of periodate with amiloride hydrochloride was investigated spectrophotometrically. The ion-association constants, beta, K-D and K-ex were determined. A convenient and simple spectrophotometric method was developed for periodate determination at 354 nm after extraction into 4-methyl-2-pentanone as an 1 : 1 ion-pair with amiloride at pH 4.0-5.5. Beer's law was obeyed between 0.01-10 mu g ml(-1) periodate in aqueous solution of pH 4.0 and the optimum concentration range evaluated by Ringbom's plot was found to be 0.09-8 mu g ml(-1). The Sandell sensitivity, the molar absorptivity and the relative standard deviation (n=5) for 5 mu g of periodate were found to be 5 x 10(-4) mu g cm(-2), 4.1 +/- 0.22 x 10(-4) l mol(-1) cm(-1) and 1.1% respectively. Iodate was also determined by the proposed procedure after prior oxidation to periodate with potassium peroxodisulphate. Binary mixtures of iodate and periodate in aqueous solution were successfully determined by the proposed procedure. The effects of pH, reagent concentration and diverse ions are reported. The method was applied successfully for the determination of iodate and periodate in artificial fresh water. (C) 1997 Elsevier Science B.V.