Sorption-spectrometric determination of lanthanum in the presence of uranium and thorium with the reagent Arsenazo M on the solid phase of fibrous filled sorbents

The possibility of the determination of La(III) in the presence of U(VI) and Th(IV), a solid phase with the reagent Arsenazo M, was examined. It was demonstrated that the determination of lanthanum with Arsenazo M in 0.05 M HCl in the presence of 3-, 2-, 1-, and 10-fold amounts of U(VI), Th(IV), Zr(IV), and Ti(IV) is possible after sorption on polyacrylonitrile fiber filled an ion exchanger with iminodiacetate groups (PANV-ANKB-50). For sorption under the optimum conditions at pH 5, the detection limit of lanthanum is 0.01 μg/mL. The method for the determination of lanthanum was verified by the added-found method in the analysis of tap water. To decrease the matrix effect, it is recommended to perform sorption in the analysis of water at pH 2.5. In this case, the detection limit of La(III) is 0.02 μg/mL, RSD < 20%. The time of the analysis of 5 or 6 samples is no longer than 20 min.     

Effect of complexants on the adsorption and color reactions of lanthanum(III), uranium(VI), thorium(IV), and zirconium(IV) with Arsenazo M in the solid phase of an ANKB-50 fibrous ion-exchanger

The effect of complexants—acetic, aminoacetic, tartaric, malonic, and oxalic acids; EDTA; and Na₂CO₃—on the adsorption and subsequent determination of thorium(IV), lanthanum(III), uranium(VI), and zirconium(IV) with Arsenazo M in the solid phase of polyacrylonitrile fiber filled with an ANKB-50 anion exchanger was studied. Complexing agents were introduced into the solution at the step of metal ion adsorption. It was shown that zirconium and uranium interacted with the iminodiacetate groups of the adsorbent in the course of adsorption; the adsorption of elements from 10^?3 to 10^?2 M complexant solutions (except for tartaric and oxalic acids and EDTA) under the optimum conditions was enhanced as compared to their adsorption from pure solutions; complexation with Arsenazo M in the solid phase proceeded at a higher acidity than in the solution. When the elements were present simultaneously, their total concentration and individual thorium could be determined from malonic acid solutions with Arsenazo M by varying the concentration of acid and the adsorption pH.     

Effect of arsenate and phosphate ions on the adsorption and complexation of uranium(VI) with Arsenazo III on the solid phase of the ion exchanger PAN-EDE-10p fibrous anion exchanger

The effect of arsenate and phosphate ions on the adsorption and color reaction of uranium(VI) with Arsenazo III on the solid phase of a fibrous material filled with the EDE-10p anion exchanger was studied in different adsorption processes. We selected the optimum conditions for the system of U(VI)-AsO ₄ ^3? (H₂PO ₄ ^? )-PANV-EDE-10p-Arsenazo III and used this system for the adsorption-spectrophotometric determination of (0.03–0.3) 10^?3 M arsenate, (0.004–0.06) 10^?3 M phosphate, and 0.01–0.1 μg/mL uranyl ions.     

New metallochromic indicator for barium: Determination of sulfate in water and soil extracts

A new metallochromic indicator for barium, Orthanilic NM, is synthesized and proposed. The color reaction of Orthanilic NM with barium ions is compared with the reactions of carboxyarsenazo and other orthanilic group reagents, such as Orthanilic K, nitchromazo, etc. The quantitative characteristics of the reactions are determined. It is shown that Orthanilic NM can be used for the titrimetric (down to 20 mg/L) and photometric (down to 0.2 mg/L) determinations of sulfate. Substantial amounts of conventional anions, alkali, alkaline-earth, and nonferrous metals do not interfere with the titrimetric determination (at pH 2.5). For the photometric determination, a 1:1 Ba²⁺-Orthanilic NM complex is used at pH 2. In these conditions, sulfite and phosphate do not interfere with the determination either. Procedures are developed for the determination of sulfate in various types of water and soil extracts. Examples of their practical application are given.     

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.     

Sorption-spectrophotometric determination of zirconium and chromium(VI) from a single sample on a two-layer support using Arsenazo III and 1,5-diphenylcarbazide

The possibility of the sorption-spectrometric determination of zirconium(IV) and chromium(VI) from a single sample using a two-layer support made of polyacrylonitrile fiber filled with a PANF-KU-2 cation exchanger and PANF-AV-17 anion exchanger is studied. After sorption zirconium is determined with Arsenazo III on PANF-KU-2 and chromium is determined with 1,5-dipehnylcarbazide on PANF-AV-17. The sorption of zirconium and chromium is studied in the dynamic mode from solutions of HCl, HNO₃, and H₂SO₄ and the optimal conditions of the simultaneous sorption of zirconium on PANF-KU-2 and chromium on PANF-AV-17 from 0.25 M HCl is chosen. Diffuse reflection spectra of zirconium and chromium complexes have are on the solid phase and the conditions of zirconium determination are optimized. Calibration curves are linear in the range of zirconium and chromium concentration 0.005–0.025 μg/mL; the detection limits are 0.002 μg/mL. The selectivity of zirconium and chromium determination is tested in the presence of interfering ions. A procedure is developed for their determination from a single sample at zirconium to chromium ratios from 3: 1 to 1: 3.     

Modified Activated Carbon as Solid Phase Extraction Adsorbent for the Preconcentration and Determination of Trace As(III) in Environmental Samples by Graphite Furnace Atomic Absorption Spectrometry

A simple and selective method was developed for the preconcentration, separation, and determination of trace amounts of As(III) in an aqueous solution by solid phase extraction combined with graphite furnace atomic absorption spectrometry. Activated carbon (AC) was modified by sodium diethyldithiocarbamate (NaDDTC) and then used as a new, stable and easily prepared solid sorbent in a mini column for the extraction of As(III) in aqueous solution. Factors influencing the sorption and desorption of As(III), such as volume and concentration of eluent, sample pH, flow rate and effect of interfering ions on the recovery of As(III) have been systemically investigated. At pH 2.0 As(III) could be adsorbed quantitatively by NaDDTC‐AC, and then eluted completely with 2 mL of 3.0 mol·L^?1 HNO₃. The amount of eluted As(III) was measured using graphite furnace atomic absorption spectrometry. The detection limit of As(III) was 0.04 ng·mL^?1 with enrichment factor of 100 and the relative standard deviation (RSD, n=8) was 1.58% at 10 ng·mL^?1 level.     

Double-walled carbon nanotubes as a solid phase extractor for separation-preconcentration of traces of gold from geological and water samples

In this work, a solid phase extraction method has been developed using a column filled with double-walled carbon nanotubes (DWNT) for preconcentration-separation of gold(III) ions prior to their flame atomic absorption spectrometric determination. Gold(III) ions were quantitatively recovered on DWNT in 1.0?mol?L^?1 HCl. The influences of the analytical conditions including eluent type, sample volume, etc. on the recoveries of gold(III) ions were examined. The effects of concomitant ions were also investigated. The detection limits for gold(III) based on 3σ was calculated as 1.5?µg?L^?1. The procedure presented in this paper was applied to the gold content of a number of water, geological and anodic slime samples with successful results.     

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.     

Use of pyrocatechol violet modified sodium dodecyl sulfate coated on alumina for separation and preconcentration of uranium(VI)

A sensitive and selective solid phase extraction procedure for the determination of trace of uranium(VI) has been developed. An alumina-sodium dodecyl sulfate coated on with pyrocatechol violet was used for preconcentration and determination of uranyl ions by spectrophotometry method using Arsenazo III reagent. Sorbed ions were quantitatively eluted using 5 mL of 0.25 mol L⁻¹ HNO₃. The effects of parameters such as pH, amount of alumina, amount of ligand, flow rate, type and concentration of elution agent were examined. The capacity of the sorbent for U(VI) was found to be 0.92 mmol g⁻¹. The relative standard deviation was 1.28% for 10 replicate determinations of U(VI) ion in a solution with a concentration of 1.0 μg mL⁻¹. The practical applicability of the developed sorbent was examined using synthetic and real samples such as standard reference material 2709 (San Joaquin Soil) and 2711 (Montana Soil).     

Determination of uranium using a flow system with reagent injection. Application to the determination of uranium in ore leachates

The determination of uranium by a flow system with reagent injection is based on the reaction of U(IV) with Arsenazo III in 3.6 M HCl; U(IV) is generated by reduction of uranyl ion in a lead reductor minicolumn installed in the sample channel of the manifold. The interference effect caused by several ions is studied. The calibration graph is linear up to 1.0 × 10^?5 M (2.4 mg l^?1) and the detection limit is 2.8 × 10^?8 M (6.6 μg l^?1). The modification of the manifold by including a second valve to by-pass the reducing column allows the measurement of the difference in peak heights, which makes the method specific for uranium.     

Separation,preconcentration and speciation of chromium by solid phase extraction on immobilised ferron

A sensitive and simple method for determination of chromium species after separation and preconcentration by solid phase extraction (SPE) has been developed. For the determination of the total concentration of chromium in solution, Cr(VI) was efficiently reduced to Cr(III) by addition of hydroxylamine and Cr(III) was preconcentrated on a column of immobilised ferron on alumina. The adsorbed analyte was then eluted with 5?mL of hydrochloric acid and was determined by flame atomic absorption spectrometery. The speciation of chromium was affected by first passing the solution through an acidic alumina column which retained Cr(VI) and then Cr(III) was preconcentrated by immobilised ferron column and determined by FAAS. The concentration of Cr(VI) was determined from the difference of concentration of total chromium and Cr(III). The effect of pH, concentration of eluent, flow rate of sample and eluent solution, and foreign ions on the sorption of chromium (III) by immobilised ferron column was investigated. Under the optimised conditions the calibration curve was linear over the range of 2–400?µg?L^?1 for 1000?mL preconcentration volume. The detection limit was 0.32?µg?L^?1, the preconcentration factor was 400, and the relative standard deviation (%RSD) was 1.9% (at 10?µg?L^?1; n?=?7). The method was successfully applied to the determination of chromium species in water samples and total chromium in standard alloys.     

Synthesis of nano-pore size Al(III)-imprinted polymer for the extraction and preconcentration of aluminum ions

In this study, an ion imprinted polymer (IIP) was prepared for the selective separation and preconcentration of trace levels of aluminum. Al(III) IIP was synthesized in the presence of Al(III)-8-hydroxyquinoline (oxine) complex using styrene and ethylene glycol dimethacrylate as a monomer and crosslinker, respectively. The imprinted Al(III) ions were completely removed by leaching the IIP with HCl (50 % v/v) and were characterized by FTIR and scanning electron microscopy. The maximum sorption capacity for Al(III) ions was found to be 3.1 mg g^?1 at pH 6.0. Variables affecting the IIP solid phase extraction were optimized by the univariable method. Under the optimized conditions, a sample volume of 400 mL resulted in an enhancement factor of 194. The detection limit (defined as 3 S _b/m) was found to be 1.6 μg L^?1. The method was successfully applied to the determination of aluminum in natural water, fruit juice and cow milk samples.     

Sorption of neodymium(III) ions by natural mordenite-containing tuff

Equilibrium in the system constituted by a mordenite-containing tuff and neodymium(III) was studied in a wide range of concentrations (10^?5–10^?2 M) in sorption from neodymium sulfate solutions. Isotherms of absorption of neodymium ions were constructed and kinetic parameters of the sorption process were determined.     

Highly Selective PVC‐Based Membrane Electrode Based on 2,6‐Diphenylpyrylium Fluoroborate

A highly selective PVC‐membrane electrode based on 2,6‐diphenylpyrylium fluoroborate is presented. The electrode reveals a Nernstian potentiometric response for sulfate ion over a wide concentration range (5.0 × 10^?6‐1.0 × 10^?1 M). The electrode has a response time of about 10 s and can be used for at least 2 months without any divergence. The proposed sensor revealed very good selectivities for sulfate over a wide variety of common organic and inorganic anions and could be used over a wide pH range (2.5–9.5). The detection limit of the sensor is 3.0 × 10^?6 M. It was successfully applied to the direct determination of salbutamol, paramomycin tablets, and as an indicator electrode for potentiometric titration of sulfate ions with barium ions.     

Chemically Modified Carbon Paste Electrode for Determination of Sulfate Ion by Potentiometric Method

Four Schiff base complexes of different metal ions, M=Cr(III), Mn(III), Fe(III), and Co(III), were studied to characterize their ability as sulfate ion carriers in carbon paste electrode (CPE). The modified CPE electrode with Schiff base complex of Cr(III), N,N′‐ethylenebis(5‐hydroxysalicylideneiminato) chromium(III) Chloride, showed good response characteristics to SO₄^2? ion. The proposed electrode exhibits a Nernstian slope of 28.9±0.4 mV per decade for SO₄^2? ion over a wide concentration range from 1.5×10^?6?4.8×10^?2 M, with a detection limit of 9.0×10^?7 M. The CPE electrode manifested advantages of relatively fast response time, suitable reproducibility and life time and, most important, good potentiometric selectivity relative to a wide variety of other common inorganic anions. The potentiometric response of the electrode is independent of the pH of the test solution in the pH range 4.0–9.0. The proposed electrode was used as an indicator electrode in potentiometric titration of sulfate with Ba²⁺ ion, the determination of zinc in zinc sulfate tablet and also determination of sulfate content of a mineral water sample.     

Use of diode-array detectors for the simultaneous spectrophotometric determination of calcium and magnesium by flow injection

A method for the simultaneous flow injection spectrophotometric determination of calcium and magnesium with Arsenazo III based on the use of diode-array detector and merging zones is described. The method is applicable to the resolution of mixtures in which the chromogenic reagent has a high absorbance and its spectrum strongly overlaps those of its complexes. In resolving the mixtures, the excess reagent is considered as another component. Quantitation is based on the normal absorbance and first-derivative absorbance spectra. The method is applied to 0.2–1.5 μg ml^?1 Ca and 0.1–1.0 μg ml^?1 Mg. The analysis rate is 50 h^?1.     

Complexation reactions between lanthanum,gadolinium, and ytterbium and reagents of Arsenazo III group on the surface of fibrous materials loaded with a Chelex 100 ion exchanger

The complex formation reaction between La(III), Gd(III), and Yb(III) with Arsenazo III, Arsenazo M, and Chlorophosphonazo III after adsorption on polyacrylonitrile fiber loaded with an ion exchanger with iminodiacetate groups Chelex 100 has been studied. The influence of medium acidity, duration of the contact of the solution with the adsorbent, the presence of masking agents, and the concentrations of ions on the analytical signals of complexes in the solid phase has been investigated. It has been shown that there is a possibility to perform sorption-spectroscopic determination of the total concentration of the indicated elements using Chlorophosphonazo and the sum of lanthanum and gadolinium with Arsenazo M after adsorption from malonic acid solutions.     

Removal of Zn(II) Ions from Aqueous Solution Using BPHA‐Impregnated Polyurethane Foam

Zn(II) ions sorption onto N‐Benzoyl‐N‐Phenylhydroxylamine (BPHA) impregnated polyurethane foam (PUF) has been studied extensively using radiotracer and batch techniques. Maximum sorption (～98%) of Zn(II) ions (8.9 × 10^?6 M) onto sorbent surface is achieved from a buffer of pH 8 solution in 30 minutes using 7.5 mg/mL of BPHA‐impregnated polyurethane foam at 283 K. The sorption data follow Langmuir, Freundlich and Dubinin‐Radushkevich (D‐R) isotherms. The Langmuir constants Q = 18.01 ± 0.38 μ mole g^?1 and b = (5.39 ± 0.98) × 10³ L mole^?1 have been computed. Freundlich constants 1/n = 0.29 ± 0.01 and C_m = 111.22 ± 12.3 μ mole g^?1 have been estimated. Sorption capacity 31.42 ± 1.62 μ mole g^?1, β = ?0.00269 ± 0.00012 kJ² mole^?2 and energy 13.34 ± 0.03 kJ mole^?1 have been evaluated using D‐R isotherm. The variation of sorption with temperature yields ΔH = ?77.7 ± 2.8 k J mole^?1, ΔS = ?237.7 ± 9.3 J mole^?1 K^?1 and ΔG = ?661.8 ± 117.5 k J mol^?1 at 298 K reflecting the exothermic and spontaneous nature of sorption. Cations like Fe(III), Ce(III), Al(III), Pb(II) and Hg(II) and anions, i.e., oxalate, EDTA and tartrate, reduce the sorption significantly, while iodide and thiocyanate enhanced the sorption of Zn(II) ions onto BPHA‐impregnated polyurethane foam.     

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%.