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A fast and simple preconcentration procedure for recovering various cation impurities from potassium dihydrogenphosphate (KDP) single crystals and raw materials, followed by energy-dispersive X-ray fluorescence analysis (EDXRF), is described. The technique is based on the adsorption of metal 8hydroxyquinoline complexes from aqueous solutions of KDP on activated carbon, separation of the concentrate on a Nuclepore filter and subsequent determination by EDXRF. To fix activated carbon powder on a filter surface, an amount of 1-hexadecanol is added to the KDP solution during the preconcentration procedure. The optimum conditions for the best recovery of the impurities were established. It was shown that a preconcentration factor of 100 can be achieved and the detection limit for a number of elements was down to 0.01 µg g −1 . The relative standard deviations were 6-17% for element concentrations of 0.2 µg g −1 .The method was successfully applied to the determination of Fe, Co, Cu, Ni, Zn, Mn, Ti and Bi in KDP single crystals and raw materials.

Catalymetry belongs to nonspecific analytical methods; however, it can be used as a method for multicomponent analysis. It is expected that catalysts can be determined simultaneously based on the differences in the rates of catalytic reactions. This approach excludes separation, which makes an additional contribution to the error of the determination. Catalymetric multicomponent analysis based on the additive action of anions in complexation reactions is used rather rarely. The mathematical fundamentals of multicomponent kinetic analysis reported in the literature mostly deal with noncatalytic reactions [1]. There are only a few analytical applications of the method for the determination of metal catalysts in the presence of each other under the conditions when the sensitivity coefficients of the components are significantly (by 1-2 orders of magnitude) different [2].In this work, we demonstrate that the reproducible simultaneous catalymetric determination of two anions with similar sensitivity coefficients is possible with the use of the mathematical apparatus of two-component spectrophotometry. Taking into account the features of catalymetry, we developed an algorithm for two-component analysis and the processing of its results. The use of the optimality î test common in nonselective multicomponent spectrophotometry allows the selection of the conditions of the separate simultaneous determination of two anions with a permissible error.The previously studied reactions of aluminum(III) with Xylenol Orange [3] (hereafter reaction (1)) and cobalt(III) with nitroso-R salt [4] (hereafter reaction (2)) were used for the selective determination C and P , respectively; masking of interfering anions was used. If masking agents are not used, the rate of reaction (1) depends not only on the concentration of carbonate ions, but also on the concentration of borate ions. The rate of reaction (2) also depends on the con-O 3 2-O 4 3-centration of carbonate ions. This was the reason for examining the possibility of the simultaneous catalymetric determination of carbonate and borate ions by the reaction of aluminum(III) with Xylenol Orange and of carbonate and phosphate ions by the reaction of cobalt(III) with nitroso-R salt. In reaction (2), borate ions were masked with D -mannite.If the principle of the additivity of catalytic reaction rates is fulfilled, the equation relating the concentrations of the two anions with the analytical signal (total rate of the catalytic reaction v ) is as follows:(1)The known techniques for calculating concentrations in multicomponent systems are frequently based on the different versions of the least squares method [5,6].Calibration was performed by measuring the total rate of the catalytic reaction in the presence of the two anions at i different conditions under which the partial sensitivities ( k ) of ions are changed. Among the conditions of the reaction, the concentrations of the reagents, temperature, pH, etc., were varied. The values of k were determined with the use of calibration mixtur...