S. B. Savvin

Sorption-spectrometric determination of thorium(IV) and uranium(VI) with the reagent Arsenazo III on the solid phase of a fibrous material filled with a cation exchanger

The possibility of the use of organic reagents of the Arsenazo III group for the sorption-spectrometric determination of elements on fibrous cation-exchange materials was examined. The conditions of the sorption of Arsenazo III with the use of diphenylguanidinium chloride on the strongly acidic fibrous cation exchanger PANV-KU-2 were found. Procedures for the determination on the solid phase were developed for thorium in 7 M HNO3 in the presence of 30-fold amounts of uranium with the detection limit of thorium of 0.005 μg/mL and for uranium in 0.05 M HCl in the presence of fivefold amounts of thorium with a detection limit of uranium of 0.05 μg/mL. The conditions were found for the selective preconcentration of thorium and uranium in the presence of each other, and a procedure was developed for their separate sorption-spectrometric determination.

Determination of Lead with 4-(2-Pyridylazo)resorcinol after the Sorption of Lead as its Thiosulfate Complex on a Fibrous Sorbent Filled with AV-17

The sorption of lead from a thiosulfate solution on a fibrous material filled with AV-17 (PANF-AV-17) was studied. Lead was determined by the color reaction with 4-(2-pyridylazo)resorcinol (PAR) on the solid phase by diffuse reflectance spectrometry. Optimal conditions were selected for lead sorption (pH 4.5 ± 0.5) and determination (pH 10); the selectivity of the determination was studied. A new system Pb–thiosulfate–(PANF-AV-17)–PAR was proposed for the determination of lead on the solid phase. A procedure was developed for the determination of lead in fresh water with the detection limit 0.01 mg/L and RSD < 25%.

Test Determination of Cu(II), Ni(II), and Cr(VI) in a Single Sample

It was shown that Cr(VI), Ni(II), and Cu(II) can be simultaneously adsorbed on a solid phase consisting of two filled fibrous disks and then determined visually using organic reagents. One sorbent disk, a fibrous material filled with an AB-17 anion exchanger, was used to determine chromium by its reaction with 1,5-diphenylcarbazide. Another disk filled with an KU-2 cation exchanger was used for the simultaneous sorption of copper and nickel followed by the consecutive determination of nickel with dimethylglyoxime and copper with sodium diethyldithiocarbamate. The conditions were optimized for the determination of nickel in the presence of copper and of copper in the presence of nickel after decomposing its dimethylglyoxime complex with 1 M HCl. The detection limits were 0.02, 0.1, and 0.05 mg/L for Cr, Ni, and Cu, respectively. The time of analysis was no longer that 20 min.

Determination of Arsenic(V) as a Heteropoly Acid after Its Adsorption on a Fibrous Anion Exchanger

The conditions were found for determining arsenic(V) as a heteropoly acid after its adsorption on a fibrous anion exchanger. A blue form of a molybdoarsenic heteropoly acid formed on the adsorbent at any order of the adsorption of the reactants; however, the sensitivity of determination was higher if arsenic was adsorbed first. A detection limit of 4 ng/mL was attained using adsorption from a 100-mL portion of a test solution. The sensitivity and selectivity of the proposed method are significantly higher than those of known methods because of the preconcentration of arsenate ions on an anion exchanger as a heteropoly acid followed by the direct determination of the heteropoly acid in the solid phase.

Spectrophotometric methods for determining noble metals

The main trends of the development of spectrophotometric methods for determining noble metals (NMs) are considered. One of these trends is the synthesis and study of new, highly sensitive and selective organic reagents for determining NMs in solutions and in solid phase. Another trend is the search for and development of new methodological approaches (techniques) and color reactions, including those that involve modified and immobilized reagents. The third trend includes the improvement of equipment and automation in FIA, CFA, derivative, rapid-scanning, and multiwavelength spectrophotometry. It also implies a new generation of instruments measuring the absorbance and reflectance of solid materials modified with organic reagents and with their NM complexes; microwave energy sources for the dissolution of samples, preparation of test solutions, and activation of photometric reactions; and multioperational analytical moduli for autoclave sample preparation with resistive heating. The present-day spectrophotometry can provide the determination of NMs in samples with concentrations from several to 10–4% (photometry and differential photometry) and down to 10–7% (test and sorption–spectroscopic methods based on photometry and diffuse-reflectance spectroscopy, including the use of chromaticity functions).

Preconcentration of noble metals on a polymer support as complexes of organic reagents and their subsequent determination in the solid phase

Conditions of the sorption preconcentration of Pt, Pd, Au, Ag, and Hg as colored complexes of azorhodanines, tyrodine, and sulfonitrophenol M from acidic solutions (pH 0–2) on a polyamide membrane in the flow mode are determined. At a flow rate of 10–20 mL/min, concentrations of determined elements of 10-9-10-7 M, and pressure of 10–20 mm Hg, the complexes are nearly quantitatively sorbed on a polyamide membrane disk (d = 1 cm,m = 2.7 mg, andl = 0.1 mm). The influence of the composition of the test solutions on the formation of the analytical signal in the solid phase is studied. Rapid sorption-spectrometric procedures are developed for the determination of Pt, Pd, Au, Ag, and Hg with the detection limit 5–30 ng of the element in the sorbent zone

Sorption and complexation of uranium(VI) and thorium(IV) with reagents Arsenazo III and Arsenazo M on fibrous filled sorbents

The possibility of the highly sensitive sorption-spectrometric determination of Th(IV) and U(VI) in the presence of each other on the solid phase of fibrous anion-exchange materials with Arsenazo M and Arsenazo III was examined. Polyacrylonitrile fiber filled with an exchanger AN-31, ANKB-50, or EDE-10p was used as the solid phase. It was demonstrated that the studied systems allow the selective determination of thorium in the presence of one-to twofold amounts of uranium. On PANV-EDE-10p with immobilized Arsenazo III, the detection limit of thorium in 2–10 M HCl is 0.002 μg/mL, and in 10 M HCl the presence of up to twofold amounts of uranium is permissible. A high sensitivity of the determination of uranium in 2–7 M HCl of 0.005 μg/mL, which has not been reported before, was attained. The time of the analysis of five or six samples is no longer than 20 min.

Adsorption and determination of bismuth with 4-(2-pyridylazo)resorcinol on a fibrous ion exchanger

The adsorption of bismuth was studied on a fibrous material filled with a Chelex 100 ion exchanger with iminodiacetic groups and a KU-2 cation exchanger, and as thiosulfate and iodide complexes on a fibrous AV-17 (PANV-AV-17) anion exchanger. Bismuth adsorbed on the solid phase was determined with 4-(2-pyridylazo)resorcinol (PAR). The optimal conditions for adsorption and determination were selected and selectivity was studied. The system bismuth-iodide-PANV-AV-17-PAR was proposed for the determination of bismuth in the solid phase. A procedure was developed for the adsorption-spectroscopic determination of 0.04–0.4 mg/L of bismuth in fresh water and urine with a detection limit of 0.03 mg/L and RSD < 20%.

Determination of vanadium(V) and chromium(VI) in a single sample on a fibrous ion exchanger disk

The determination of vanadium(V) and chromium(VI) in a single sample on a support disk was studied. Polyacrylonitrile fiber filled with an AV-17 anion exchanger was used as a solid phase. After adsorption, the elements were successively detected in the solid phase by color complexation reactions of vanadium with 8-hydroxyquinoline-5-sulfonic acid and chromium with 1.5-diphenylcarbazide. A procedure was developed for the adsorption-spectroscopic determination of 0.04–0.4 μg/mL vanadium(V) and 0.01–0.05 μm/mL chromium(VI) at V: Cr ratios of 1: 1 to 10: 1 in the dynamic mode. The limits of detections for vanadium and chromium were 0.04 and 0.005 μg/mL, respectively. It was shown that the background salt content of potable water had no appreciable effect; no preliminary sample preparation was required.

A Test Method for the Determination of Mercury(I, II) on a Polymer Surface

It was found that mercury(I, II) reacts with 5-chloro-2-hydroxy-3-[(tetrahydro-2,4-dithioxo-1,3-thiazin-5-yl)azo]benzenesulphonic acid (tyrodine) in weakly acid solutions in the presence of acetates, formates, and some organic solvents (ethanol and acetone) to give an intensely colored insoluble compound (λmax = 600 nm, ε > 3 × 104). The composition of the solution affected the sensitivity of the color reaction between mercury and tyrodine. A test procedure was developed for the determination of mercury(I, II) on the surface of a polycaproamide membrane with a detection limit of <50 ng in the adsorbent zone. The procedure involves the quantitative and selective adsorption of the mercury complex of tyrodine on the support surface from 0.5 M acetate solutions of pH 3–4 in the dynamic mode; the sample volume was 5–25 mL. Mercury was then determined by the change in the support color using a color scale or by the change in diffuse reflectance at 600 nm. The adsorption of the mercury complex was accompanied by an abrupt change in the color of the support surface from pale crimson (reagent) to stable blue-violet. The test procedure was used in the analysis of an industrial sample of complex composition with a mercury concentration of lower than 0.05%. The determination error (relative standard deviation) was 20%.