2,3,7-Trihydroxyfluorones immobilized on cellulose matrices in test methods for determining rare elements

It was shown that 2,3,7-trihydroxyfluorones immobilized by adsorption on cellulose matrices can be used as reagents for the test determination of Mo(VI), Ti(IV), Ge(IV), Hf(IV), Nb(V), Ta(V), W(VI), Bi(III), V(IV), and Zr(IV). The change of the protolytic and complexing properties of trihydroxyfluorones immobilized on cellulose matrices was considered in comparison to corresponding properties in a solution. It was found that the reactions of trihydroxyfluorones with rare elements on cellulose matrices and in a solution exhibit similar effects upon the addition of cetylpyridinium. These effects are the bathochromic shift of the absorption maxima of the reagents and their complexes with analytes and the extension of the range of optimum acidity for complex formation. The complexation of salicylfluorones with the titanium(IV) in solution and on cellulose paper was studied by IR spectrometry. Phenylfluorone immobilized on a mixed-fiber cloth as used in test determinations of (mg/L) 0.05–5 Ti(IV), V(IV), Hf(IV), Nb(V), and Mo(VI); 0.01–5 Ge(IV) and Zr(IV); 0.05–1 Bi(III) and W(VI); and 0.1–5 Ta(V) by the color intensity of the indicator matrix after passing through 20 mL of a test solution. It was shown that phenylfluorone immobilized on cellulose paper can be used to determine (mg/L) 0.05–50 Ti(IV), 0.5–1000 Ge(IV), 0.5–500 Zr(IV), 5–200 Bi(III), 0.1–50 Mo(VI), 0.1–1000 V(IV), 0.1–100 Nb(V), 0.1–800 Hf(IV), 1–100 Ta(V), and 1–800 W(VI) by the length of the colored zone of a test strip after it was brought into contact with a test solution.     

Fabrics and papers modified with analytical reagents for the test determination of selenium(IV) and tellurium(IV)

It is shown that Malachite Green and Crystal Violet immobilized on viscose fabrics can be used as reagents for the rapid determination of selenium(IV) and tellurium(IV). Selenium is determine by the color intensity of ion associates formed by the reagents with the triiodide ion formed upon the reduction of selenium(IV) with potassium iodide and tellurium, by the color intensity of reagent ion associates with telluromolybdic heteropoly acid. The analytical ranges for selenium and tellurium(IV) were 0.005–0.5 and 0.01–0.1 mg/L upon passing 20 and 100 mL of a test solution through the indicator matrix, respectively. The duration of analysis does not exceed 15–20 min. The relative standard deviation is 50%. Test strips were proposed for determining 0.1–100 mg/L selenium(IV) and 1–1000 mg/L tellurium(IV) by the length of the colored zone. The determination of selenium(IV) is based on the oxidation of 4-nitrophenylgydrazine to its diazonium salt and salt interaction with naphthylamine chemically immobilized on paper with the formation of a red azo compound. The determination of tellurium(IV) is based on its reaction with Bismuthol II immobilized on a paper.     

Test determination of molybdenum(VI) with the use of phenylfluorone immobilized on a cellulose cloth

It was demonstrated that phenylfluorone immobilized on a cellulose cloth matrix can be used as a reagent for the test determination of molybdenum(VI). Phenylfluorone was immobilized on a mixed fiber cloth (viscose with cotton), which provides high retention of the reagent (97%) and exhibits chemical stability and mechanical strength. The selectivity of the reaction was studied. A test procedure was developed for the determination of 0.05–5 mg/L molybdenum(VI) in natural waters (RSD < 40%); the time of analysis is 10–15 min.     

Artificial and natural fiber fabrics with immobilized di-and triaminotriarylmethane reagents in chemical test methods

The potentials of fabrics made of artificial and natural fibers as supports for the di-and triaminotriarylmethane reagents were shown for their possible use in chemical test methods. Malachite Green, Brilliant Green, Methyl Violet, Crystal Violet, and Parafuchsine were immobilized on viscose, calico, coarse calico, and a mixed fabric. The reagent retention was 70–90%. The indicator fabrics are resistant to strong acids and alkalies and can be used for the test determination of 0.01–10 mg/L of phosphates, 1–80 mg/L of silicates, 0.01–8 mg/L of dissolved oxygen, biological oxygen demand for 5 days (BOD₅), 0.5–10 mg/L of formaldehyde, and 0.1–10 mg/L of anionic surfactants. The analysis time was 10–15 min. The relative standard deviation did not exceed 30%.     

Test determination of aluminum, beryllium, and cationic surfactants using phenolcarboxylic acids of the triphenylmethane series immobilized on cloths from synthetic and natural fibers

We consider the use of cloth matrices from viscose and cotton fibers bearing phenolcarboxylic acids of the triphenylmethane series immobilized by adsorption in chemical test methods of analysis. Chrome Azurol S, Sulfochrome, and Eriochrome Cyanine R were used for immobilization. It was found that the reagents are weakly retained on cellulose matrices. The degree of retention varied from 10 to 60%. It was observed that the reagent complexes of metal ions exhibited enhanced adsorbability on the matrices. Cloths with immobilized Chrome Azurol S were used in the test determination of 0.0005–0.5 mg/L beryllium and 0.0005–1.0 mg/L aluminum. When the reaction products were preconcentrated on the cloth from 100 mL of a test solution, the detection limit was 0.0001 mg/L. Procedures were developed for determining 0.1–100 mg/L aluminum and 0.02–0.6 mg/L beryllium in solutions using cloth test strips encapsulated into a polymeric film. It was demonstrated that Sulfochrome and Eriochrome Cyanine R immobilized on cloths can be used to determine 0.01–1 and 1–1000 mg/L cationic surfactants.     

Artificial and natural fiber fabrics with immobilized reagents in chemical test methods of analysis

Fabric matrices made of viscose and cotton fiber with adsorption-immobilized organic reagents are considered with respect to their possible use for chemical test methods of analysis. Triarylmethane, thiazine, eurhodine, acridine, azo, and diazo compounds are used for immobilization. It is found that the degree of reagent retention (R, %) depends on the pH and the type of the matrix used. R varies within 12–99%. The absorption spectra of the reagents immobilized on fabric matrices exhibit hypsochromic or bathochromic shifts of absorption bands (2–45 nm as compared to their absorption spectra in solution). As a rule, the degree of retention is higher for the reagents that exhibit a shift of the absorption band on the support. The adsorption isotherms of the reagents on various cellulose supports are analyzed. Test procedures are developed for the determination of antimony and mercury using modified fabric matrices. The rapidity, precision, and sensitivity of previously developed procedures for the test determination of Cu(II), Cd, and S^2? are improved. The relative standard deviations of the determinations are no more than 0.1; the analysis time is 5–10 min.     

Test analysis method using ion pairs of pyrocatechol azo derivatives and trihydroxyfluorones with cetylpyridinium and their chelates with metal ions immobilized on paper

A two-stage procedure is proposed for the immobilization of ion pairs of pyrocatechol azo derivatives and trihydroxyfluorones and their chelates with metal ions on paper. It is demonstrated that ion pairs of phenylfluorone and thiazolylazopyrocatechol with cetylpyridinium can be used for the test determination of 0.01-10 mg/L Ti(IV), 0.05-20 mg/L Mo(VI), and 0.1–20 mg/L W(VI) and V(V) by the length of the colored zone of test strips after their contact with a test solution and for the determination of 0.01-0.5 mg/L Al and Mo(VI) and 0.001-0.1 mg/L Ti(IV) by the color intensity of reactive papers after passing a test solution. Chelates of Mo(VI) with tiazolylazopyrocatechol and of Sb(III) with phenylfluorone are used for the test determination of 0.01-1000 mg/L cationic surfactants. The selectivity of reactions is studied, and procedures are proposed for the determination of the above elements in different materials. The relative standard deviation of the results of analysis is no higher than 50%.     

Solid-phase fluorescence in chemical test methods of analysis based on the principles of planar chromatography

Morin immobilized on cellulose matrices was used as a reagent for determining Al, Be, and Zr(IV) by the length of the fluorescent zone on a test strip after its contact with the test solution and by the fluorescence intensity of the reaction zone of the indicator matrix after passing the test solution through it. A test procedure was developed for determining 0.2–200 mg/L Al in potable water using paper test strips sealed in a polymer film. Test procedures were developed for determining 0.0001–1 mg/L Al and 0.00001–0.1 mg/L Be in river water by the intensity of the fluorescent zone on the indicator viscose fabric after passing 100 mL of the test solution through it, using a test facility. The time of analysis was 15–20 min. The relative standard deviation did not exceed 40% in the former case and 60% in the latter case.     

Catalytic Adsorptive Stripping Voltammetry of Germanium(IV) in the Presence of Gallic Acid and Vanadium(IV)‐EDTA

A highly sensitive and selective catalytic adsorptive cathodic striping procedure for the determination of trace germanium is presented. The method is based on adsorptive accumulation of the Ge(IV)‐gallic acid (GA) complex onto a hanging mercury drop electrode, followed by reduction of the adsorbed species. The reduction current is enhanced catalytically by addition of vanadium(IV)‐EDTA. The optimal experimental conditions include the use of 0.03 mol/L HClO₄ (pH1.6), 6.0×10^?3 mol/L GA, 3.0×10^?3 mol/L V(IV), 4.0×10^?3 mol/L EDTA, an accumulation potential of ?0.10 V(vs. Ag/AgCl), an accumulation time of 120 s and a differential pulse potential scan mode. The peak current is proportional to the concentration of Ge(IV) over the range of 3.0×10^?11 to 1.0×10^?8 mol/L and the detection limit is 2×10^?11 mol/L for a 120 s adsorption time. The relative standard deviation at 5.0×10^?10 mol/L level is 3.1%. No serious interferences were found. The method was applied to the determination of germanium in ore, mineral water and vegetable samples with satisfactory results.     

Sorption preconcentration and separation of Palladium(II) and Platinum(IV) for visual test and densitometric determination

We have demonstrated the advantages of the dynamic preconcentration and separation of Pd(II) and Pt(IV) on paper carriers modified with 3-methyl-2,6-dimercapto-1,4-thiopyrone. The optimal conditions of the solid-phase reaction have been determined in Pd(II) sorption; after its separation Pt(IV), has been preconcentrated by sorption as its dimercaptides. Test scales have been produced for the visual determination of 0.5–40 μg Pd(II) and 1–195 μg Pt(IV) in 10- and 100 mL-samples, respectively. In addition, a procedure of their sorption-chromaticity densitometry determination from a single aliquot portion has been developed with detection limits of 5 and 1 ng/mL, respectively, and a procedure of Pd(II) determination using a test strip (c _min = 0.40 mg/L) has been proposed. The procedures have been applied to the determination of palladium and platinum in electrolytes, sludges, and alloys.     

Solid-phase spectrophotometric iodometric determination of nitrite and selenium(IV) using a polymethacrylate matrix

Procedures for the iodometric solid-phase spectrophotometric determination of nitrite and selenium( IV) using a polymethacrylate matrix are proposed. The procedures are based on the reaction of nitrite and selenium(IV) with iodine in an acidic medium with the release of free iodine in amounts equivalent to those of the substances to be determined, extraction of the iodine formed with a polymethacrylate matrix, and measurement of absorbance of the matrix at 370 nm. The developed procedures ensure the determination of 0.01–0.12 mg/L of nitrite and 0.05–0.40 mg/L of selenium(IV) with limits of detection of 0.005 and 0.03 mg/L, respectively. It was shown that the proposed procedures can be applied to the determination of selenium(IV) in mineral water and nitrites in vegetables and soil.     

Reversed Flow Injection Chemiluminescence Determination of Pyridoxine Hydrochloride Based on the Cerium(IV)-Sodium Sulfite System

A rapid chemiluminescence (CL) reaction was observed when Ce(IV) was injected into the mixed solution of pyridoxine hydrochloride and sodium sulfite. A new flow-injection CL method for the determination of pyridoxine hydrochloride was established. The detection limit (3σ) was 0.5 mg/L pyridoxine hydrochloride and the relative standard deviation (RSD) was 3.3% (n = 11, γ = 5 mg/L). The CL intensity responded linearly to the concentration of pyridoxine hydrochloride in the ranges 1.0–10.0 mg/L and 10.0–100.0 mg/L with linear correlation coefficients of 0.9994 and 0.9991, respectively. The method had been applied to the determination of pyridoxine hydrochloride in tablets and injections successfully.     

Indicator Tubes and Indicator Powders for Determining Fluoride and Chloride Ions

Noncovalent immobilization of Arsenazo I, Alizarin Red, Xylenol Orange, and diphenylcarbazone by incorporation into silicic acid xerogels and modification of silica gels was studied, and procedures for determining fluoride and chloride ions by solid-phase spectrophotometry and test methods were developed. Reactions of immobilized reagents with aluminum(III), zirconium(IV), and mercury(II) were studied. The possibility of using immobilized reagent–metal ion–halide ion systems for the determination of halide ions was assessed. Indicator powders were proposed for determining 0.5–10 mg/L fluoride ions and 1–30 mg/L chloride ions, and indicator tubes were developed for determining 20–200 mg/L chloride ions. The determination of fluoride and chloride ions is based on exchange complexation reactions proceeding in the systems immobilized Xylenol Orange–zirconium(IV) and immobilized diphenylcarbazone–mercury(II), respectively. Performance characteristics of the developed procedures were estimated. The procedures were verified by determining halide ions in Narzan mineral water.     

Adsorptive stripping measurements of germanium(IV) in the presence of pyrogallol

The adsorptive stripping voltammetric determination of germanium(IV) based on the adsorptive accumulation of the germanium(IV)-pyrogallol complex on a hanging mercury drop electrode is reported. The reduction current of the adsorbed germanium complex is measured by differential-pulse cathodic stripping voltammetry. The peak potential is at -0.42 V vs. Ag AgCl (saturated KCL). The effects of various parameters (ligand concentration, supporting electrolytic composition and concentration, accumulation potential and collection time) on the response are discussed. With controlled accumulation for 3 min, the detection limit is 1.2 x 10(-9) M germanium. The relative standard deviation (at 1.2 x 10(-8) M germanium) is 3.6%. Possible interferences are evaluated. The applicability of the method to the determination of germanium(IV) in ore samples was also successfully carried out.     

Reversed phase HPLC determination of titanium(IV) and iron(III) with sodium 1,2-dihydroxybenzene-3,5-disulfonic acid

A highly sensitive method has been developed for the determination of titanium(IV) and iron(III) by ion-pair reversed phase liquid chromatography using sodium 1,2-dihydroxybenzene-3,5-disulfonic acid (Tiron) as a precolumn chelating reagent. The metal - Tiron chelates were separated on a C₁₈ (ODS) column; the mobile phase was a 2:8 (v/v) mixture of acetonitrile and acetate buffer (0.04 mol/L, pH 6.2) containing 2.0 × 10^?3 mol/L Tiron, 0.04 mol/L tetrabutylammonium bromide, and 0.1 mol/L potassium nitrate. The detection limits for titanium(IV) and iron(III) are 0.5 and 2.0 μg/L, respectively. The method has been applied to the simultaneous determination of titanium(IV) and iron(III) in river water samples and has furnished highly precise results.     

Solid-phase fluorescence determination of gallium(III) with morin and lumogallion immobilized on cellulose matrices

It has been demonstrated that the fluorometric test determination of gallium(III) can be performed with morin and lumogallion immobilized on thin-layer cellulose matrices. Test procedures have been developed for the determination of Ga(III) in the range 0.5–90 mg/L by the length of fluorescence zone on a test strip sealed into a polymer film (after its contact with the test solution) in the ranges 0.001–1 and 0.01–1 mg/L with the visual detection of the fluorescence of the indicator matrix with morin and lumogallion, respectively (after passing 100 and 20 mL of a test solution through it), and in the range 0.0001–0.1 mg/L by detecting the fluorescence with a portable fluorimeter.     

Bestimmung der freien Säure in wäßrigen Uran(IV)-nitrat- und Uran(IV)-perchloratlösungen

Methods described in literature for the determination of free acid in solutions containing plutonium(IV), uranium(VI) and aluminium(III) were investigated for their applicability in the presence of uranium(IV). Most methods turned out to work in the presence of uranium(IV). The simplest procedure was the suppression of the uranium(IV) hydrolysis by complexation with excess of fluoride. No bias was observed in the presence of 0–30 mg of uranium(IV). A variance of 1.4% resulted from the determination of 0.4 millimole of acid in the presence of 26 mg of uranium(IV) and a variance of 0.26% was obtained when 2 millimoles of acid were determined in the presence of 130 mg of uranium(IV). Uranium(IV) from 30–260 mg in 250 ml caused a negative bias, which can be corrected for. — A concentration of potassium fluoride in the titration medium of 10 g/l turned out to be optimum. In 11/2 years more than 750 determinations were carried out with the same glass electrode and no destruction of the electrode was observed. The influence of uranium(VI), iron(III) and aluminium (III) on the determination of the free acid was also investigated.     

Ceramic composite electrode for the determination of selenium(IV) by stripping voltammetry

A ceramic composite electrode for the determination of selenium(IV) was manufactured using solgel and screen-printing technologies. This electrode exhibits a higher sensitivity and selectivity in comparison with the other studied carbon-containing electrodes. The effect of the type and amount of graphite powder, modifier, catalyst, and pore-forming agent on the properties of the ceramic composite electrode was investigated. It was found that an increase in the pore size in the electrode reduced the selectivity of selenium(IV) determination. The calibration plot was linear over the range 0.1–20 μg/L at an accumulation time of 10 s. The relative standard deviation for the determination of 1.0 and 0.05 μg/L of selenium(IV) (n = 5) was 3% and 8%, respectively. The detection limit of selenium(IV) was 0.02 μg/L at an accumulation time of 90 s. The results of selenium(IV) determination in natural and mineral waters are presented.     

Preconcentration of Ti(IV) in Ore and Water by Cloud Point Extraction and Determination by UV-Vis Spectrophotometry

Trace amounts of titanium(IV) were determined with a simple and selective method based on cloud point extraction. Preconcentration of titanium from aqueous solution was performed using Triton X-114 surfactant and 4-(2-pyridylazo) resorcinol as complexing agent. After centrifugation, the surfactant- rich phase was removed, diluted with water and ethanol, transferred into a 500 μL quartz cell, and its absorbance was measured at 520 nm. The effect of experimental conditions influencing the extraction process was considered. In the optimum conditions, linearity ranges was 0.01–0.1 with the correlation coefficients (R²) of 0.9903. The limits of detection was 0.005. The method was successfully used for the determination of titanium(IV) in the samples of ore and river water with relative recovery of 98?99%.     

Rapid and Sensitive Spectrophotometric Determination of Hafuium(IV) With 2-(5-Bromo-2-Pyridylazo)-5-Diethylaminophenol

Abstract

Hafnium(IV) reacts with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol in the pH range 3.3–11.0 to yield a sparingly soluble red-coloured chelate that can be dissolved with Triton X-100. Effect of initial pH of metal ion and order of addition of reagents was studied in detail. The 1:3 complex adheres to Beer's law over the concentration range 0.02–1.12 μg/ml of Hf(IV), has a molar absorptivity 1.33x10⁵ 1 mol^?1cm^?1, Sandell sensitivity 1.3 ng cm^?2, formation constant (log K) 11.94 and the method had a relative standard deviation of ± 1.5%. Effect of 60 diverse ions on the determination of hafnium(IV) was studied. This fairly selective method is the most sensitive so far reported for the spectrophotometric determination of hafnium(IV).