Determination of platinum and palladium in environmental samples by graphite furnace atomic absorption spectrometry after separation on dithizone sorbent.

A graphite furnace atomic absorption method of platinum and palladium determination after their separation from environmental samples has been presented. The samples were digested by aqua regia and the analyte elements were separated on the dithizone sorbent. The procedure of sorbent preparation was described and their properties were established. Two various procedures of elution by thiourea and concentrated nitric acid were described and discussed. The low limit of detection was established as 1ngg(-1) for platinum and 0.2ngg(-1) for palladium. There was also investigated the behaviour of platinum and palladium introduced into the soil in various chemical forms.

The standard addition and successive dilution method for evaluation and verification of results in atomic-absorption analysis.

A simple procedure for evaluation and verification of results obtained by atomic-absorption analysis is proposed. It allows estimation of the correct results in the presence of unknown strong interferents and does not require any preliminary information about the sample to be analysed. The concept of the procedure arises from theoretical considerations of various types of interference effects on the form of calibration curves. The procedure may be considered as a combination of the standard addition and successive dilution methods. Although the procedure was developed and tested for atomic-absorption analysis it seems to be applicable to all analytical techniques in which preliminary elimination of non-specific interference signals that are independent of the analyte concentration is possible.

Computational elimination of interferent effects in flame atomic-absorption spectrometry.

Empirical formulae, which describe quantitatively the interferent effects in flame atomic-absorption analysis, have been proposed. The formulae enable calculation of the total multi-interferent effect of a complex system, on the basis of characteristic coefficients established for simple analyte-interferent pairs. The approach may be used for the computational elimination of interferent effects and for correction of analytical results. Experimental verification has confirmed that the corrected results are consistent with the actual concentrations.

The specificity characteristic of analytical methods-I Non-specificity coefficients.

Two types of non-specificity coefficients are defined. These coefficients quantitatively characterize the change caused in an analytical result by the presence of interferents. The first of these coefficients describes a parallel shift of a calibration curve and the second a shift in the slope. The properties of these coefficients and of their practical application as characteristics of a method are discussed. The approach described may be used to characterize the specificity of an analytical method when the calibration curve is linear and the presence of an interferent causes a parallel shift of the curve or changes its slope but not its shape.

The specificity characteristic of analytical methods-II Estimation and experimental verification of the non-specificity coefficients.

A procedure for estimation of non-specificity coefficients by use of small amounts of standard samples is described. This procedure enables also the simultaneous verification if the specificity of a method with respect to the investigated interferent may be characterized by means of these coefficients. Four various analytical methods were tested and a good agreement of experimentally found values of interferent effects with the values calculated by means of non-specificity coefficients have been stated.

A study of the composition and properties of the ion-association complex of Rhodamine B with silicomolybdic acid, with a view to its analytical application.

The composition of the ion-association complex of Rhodamine B with silicomolybdate has been examined by Job's method and spectrophotometric titration. The ratio of Rhodamine B to silicon in the complex is 4 : 1. The same ratio is obtained by analysis of the crystalline complex. The composition of the complex is identical in aqueous medium, an organic solvent (ethanol) and in the crystalline state (C(28)H(30)N(2)O(3))(4)SiMo(12)O(40)). The complex is stable in the organic solvent and has its absorption maximum at 555 nm and a molar absorptivity of 5 x 10(5) 1.mole(-1)cm(-1). The complex can be advantageously used for the determination of silicon.

Precise titrimetric determination of uranium in high-purity uranium compounds.

A procedure has been developed for the very precise determination of uranium in high-purity uranium compounds. Uranium(VI) is reduced in a strong hydrochloric acid solution with aluminium in the presence of cadmium ions to uranium(III). It is oxidised to uranium(IV) in the presence of excess orthophosphoric acid and then quantitatively oxidised to uranium(VI) with potassium dichromate using a potentiometric end-point detection. The coefficient of variation based on 20 analyses is -/+ 0.003%.