Anionic Lead Complexes on the Solid Phase of Fibrous Filled Materials in the Reaction with 4(2-Pyridylazo)resorcinol

The influence of the nature of anions (iodide, bromide, thiosulfate, pyrophosphate, tartrate, and acetate) in the anionic lead complex adsorbed on a solid phase of a fibrous sorbent filled with the AV-17 anion exchanger on the color reaction between lead and 4-(2-pyridylazo)resorcinol (PAR) was studied by diffuse reflectance spectrometry. The influence of anions on the complexation of lead with PAR on the solid phase was discussed for different types of the color reaction. It was demonstrated that the reactions with iodide at pH 5–10 and with thiosulfate at pH 10 are significant in the determination of lead as three-component complexes on the support. In the presence of other anions, lead ions do not react with PAR on the AV-17 solid phase.     

A test method for determining palladium in chloride solutions on the solid phase of a fibrous anion exchanger

The sorption of palladium(II) from chloride solutions on polyacrylonitrile fiber filled with the AV-17 anion exchanger (PANF-AV-17) and its subsequent determination with p-nitrosodiethylaniline on the solid phase were studied. The results of determining palladium with this reagent on the solid phase of polyacrylonitrile fiber filled with the KU-2 cation exchanger and the AV-17 anion exchanger were compared. A test method was developed for determining palladium on the PANF-AV-17 solid phase. Sorption was performed in the batch mode; the analytical signal was estimated by measuring the diffuse reflection coefficient or visually using a color scale. The detection limit was 0.005 µg/mL; the range of the calibration scale was 0–0.2 µg/mL at the volume of the test solution 10–20 mL. The accuracy of the procedure was verified by the added-found method in the analysis of tap water and a standard reference sample of natural sodium chloride water. The relative standard deviation was no more than 25%; the time of the analysis of 5 or 6 samples was 25–30 min.Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 1, 2005, pp. 85–90.Original Russian Text Copyright © 2005 by Dedkova, Shvoeva, Savvin.     

Test Method for the Determination of Mercury(II) with Dithizone on the Solid Phase of a Fibrous Anion Exchanger

The sorption and determination of mercury(II) on the solid phase of a fibrous polyacrylonitrile material filled with the AV-17 anion exchanger is studied. Mercury is adsorbed in the form of the chloride complex from a solution with pH 5–7.5; it is determined on the solid phase by the reaction with dithizone either visually or by the measuring the color hue. A procedure for the test determination of mercury(II) has been developed and tested in the analysis of fresh natural waters by the added–found method. The detection limit is 0.02 mg/L. The time of analysis of 5 or 6 samples is no more than 15–20 min.     

Effect of Anions on the Development of Color Reactions of Cadmium, Lead, and Mercury with Dithizone and 4-(2-Pyridylazo)resorcinol on a Fibrous Material Filled with the Anion Exchanger AV-17

The effect of nitrates, chlorides, iodides, sulfates, thiosulfates, thiocyanates, acetates, tartrates, nitrilotriacetates, and ethylenediaminetetraacetates in the sorption of Cd(II), Pb(II), and Hg(II) and their subsequent determination with dithizone and 4-(2-pyridylazo)resorcinol (PAR) on the solid phase of a fibrous anion-exchange sorbent filled with AV-17 was studied. The dependences of the analytical signals of complexes adsorbed on the solid phase on the concentration of anions in the solution and on the stability of anionic complexes were revealed. The analytical signals in the sorption and determination of Cd, Pb, and Hg with dithizone and PAR on the solid phase were maximum for iodide and thiosulfate complexes. Conditions of the sorption of Cd(II), Pb(II), and Hg(II) were found for their subsequent total and separate determination with PAR and dithizone.     

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.     

Determination of Mercury(II) with Dithizone by Diffuse Reflectance Spectrometry on a Fibrous Anion Exchanger

The possibility of the determination of mercury(II) with dithizone on the solid phase of a fibrous ion-exchange material filled with the AV-17 anion exchanger was studied. Mercury is adsorbed as an anionic complex. The sorption of mercury as chloride, iodide, sulfate, thiosulfate, nitrate, and EDTA complexes was studied. A procedure was proposed for the sorption–spectrometric determination of mercury with dithizone on a solid phase after sorption as the chloride complex. For improving the selectivity of the method, EDTA is added to the solution. The determination is affected only by Pd(II). The time of analysis is 15 min. The procedure was tested in the analysis of tap and river water and a solution modeling natural water.     

Test method for the separate determination of mercury(II), cadmium, and lead in one sample on the fibrous sorbent PANV-AV-17

The sorption of Hg(II), Cd(II), and Pb(II) as anionic complexes on the solid phase of polyacrylonitrile fiber filled with the AV-17 anion exchanger from NaCl and KI solutions and their complexation with 4-(2-pyridylazo)resorcinol (PAR) and dithizone were studied. A test method was developed for the individual determination of Hg(II), Cd(II), and Pb(II) from one sample on three support disks. From the same solution, by the successive sorption on two disks from a 0.2 M NaCl solution, mercury was determined with dithizone and cadmium was determined with PAR. After the addition of a KI solution and sorption on the third disk, lead was determined with PAR. Using the added-found method, the procedure was approved in the analysis of natural sodium chloride water. The detection limit was 0.01 mg/L for Hg(II) and 0.02 mg/L for Cd(II) and Pb(II) for a volume of the analyzed sample of 25 mL. The time of the analysis of five or six samples (determination of three elements) is no longer than 50 min.     

Differential Pulse Polarographic Determination of Trace Amounts of Lead in Alloys and Biological Samples after Column Preconcentration Using Nitroso-S and TDBA

A highly selective, sensitive, rapid, and economical differential pulse polarographic method has been developed for the determination of trace amounts of lead in various standard alloys and biological samples after the adsorption of its 2-nitroso-l-naphthol-4-sulfonic acid (nitroso-S)—tetradecyldimethylbenzylammonium (TDBA) chloride on microcrystalline naphthalene in the pH range of 8.0–10.5. After filtration, the solid mass is shaken with 9.0 mL of 1 M hydrochloric acid, and lead is determined by differential pulse polarography (DPP). Lead can alternatively be quantitatively adsorbed on 2-nitroso-l-naphthol-4-sulfonic acid-tetradecyldimethylbenzylammonium-naphthalene adsorbent packed in a column and determined similarly. In this case, 1.0 g of lead can be concentrated in a column from 500 mL of an aqueous sample in which its concentration is as low as 2 ng/mL. Characterization of the electroactive process included an examination of the degree of reversibility. Various parameters, such as the pH effect, volume of aqueous phase, HCl concentration, reagent concentration, naphthalene concentration, shaking time, and the interference of a number of metal ions on the determination of lead were studied in detail to optimize the conditions for determination in standard alloys and standard biological samples.     

Determination of trace amounts of vanadium by UV-vis spectrophotometric after separation and preconcentration with modified natural clinoptilolite as a new sorbent

Natural clinoptilolite was used as a sorbent material for solid phase extraction and preconcentration of vanadium. The clinoptilolite was first saturated with a cation such as nickel(II) and then modified with benzyldimethyltetradecyleammonium chloride (BDTA) for increasing sorption of 4-(2-pyridylazo)resorcinol (PAR). Vanadium–PAR complex was quantitatively retained on the sorbent by the column method at the pH range 6.2–7.0 at a flow rate of 1 mL min⁻¹. It was removed from the column with 5.0 mL of dimethylformamide solution at a flow rate of 0.8 mL min⁻¹ and determined by UV–vis spectrophotometry at λ_max = 550 nm. 0.031 μg of vanadium can be concentrated from 450 mL of aqueous sample (where detection limit as 0.07 ng mL⁻¹ with preconcentration factor of 90). Relative standard deviation for eight replicate determination of 5.0 μg of vanadium in final solution is 2.1%. The interference of number of anions and cations has been studied in detail to optimize the conditions and method was successfully applied for determination of all vanadium as V(IV) form in standard samples.     

A comparative study on the sorption and desorption of Hg,Th and U on clay

The sorption and desorption of uranium, thorium and mercury on a western Anatolian montmorillonite, obtained from the deposit located in Kula, were studied by application of a batch technique. The clay used is a tertiary clay originally found in a rather large geological formation of west Anatolia. It is nearly pure montmorillonite. Its cation exchange capacity (CEC) determination was performed for ammonium acetate by the Mehlich procedure. The mean CEC was found to be 83 meq/100 g, which, taking into account that CEC determinations were carried out on unfractionated material, is in good agreement with previously reported data. The concentration ranges were between 70–1500 ppm for mercury and 100–2000 ppm for thorium and uranium. The relative importance of test parameters, e.g., pH, clay particle size, groundwater composition, contact time and solid/water ratio, which determine the distribution coefficients was studied. The sorption coefficients varied between 2.7–6.4 ml/g for U, 0.22–1.59 ml/g for Th and 152.4–427.2 ml/g for Hg. The differences of distribution coefficients are discussed. The data could be fitted to Freundlich and Langmuir isotherms. The quantities of the sorbed and desorbed Th were much lower than its theoretical CEC's. This attitude was attributed to the blocking of montmorillonite by cation islands sorbed in the interlayer. Hg is sorbed most strongly. The experimental results indicate that the montmorillonites studied should be effective components of the buffer and backfill material and lead to eventual immobilization of these elements, which are environmentally dangerous.     

Fluorimetric determination of aluminium in water by sequential injection through column extraction

A fluorimetric procedure for the determination of aluminium with matrix removal in drinking water is proposed. The system is based both on the solid phase extraction of aluminium on a new chelating resin (XAD-4 modified by grafting salicylic acid) and the fluorimetric detection of a complex formed between 8-hydroxyquinoline-5-sulfonic acid (HQS) and Al(III), after elution of the resin by hydrochloric acid. The sorption and elution of aluminium were studied in both competitive and non-competitive conditions, varying pH, flow-rates, volume and concentration of reagents, as well as time contact. The optimised procedure allows determination of Al³⁺ at the sub-ppb level (LOD: 0.2 g L^–1 for 1 ml of sample) within a working range of 0.2–500 g L^–1. The analytical procedure was successfully employed for the determination of aluminium in drinking water during and after flocculation/coagulation treatment processes.     

Determination of lead in seawater by inductively coupled plasma optical emission spectrometry after separation and pre-concentration with cocrystallized naphthalene alizarin

An analytical method for separation and pre-concentration of lead in seawater for determination by inductively coupled plasma optical emission spectrometry has been investigated. Lead was retained in the solid phase (0.5 g) composed of co-precipitated naphthalene and alizarin red. The solid phase quantitatively sorbs Pb(II) at pH 8–9, and the metal was eluted using 5.0 ml of 2 mol l⁻¹ nitric acid. The effect of NaCl, KCl, BaCl₂, CaCl₂, Na₂SO₄, MgCl₂ and Na₃PO₄ on the sorption of Pb(II) in the solid phase was studied. A set of solutions containing varying amounts of electrolytes (0.5; 1.0; 3.0 and 5.0% m/v) with Pb (50 μg) was prepared and the recommended procedure applied. The Na₃PO₄ was found to interfere; the other electrolytes did not interfere up to 5% m/v. A pre-concentration factor of 40 was obtained in this analytical procedure. The limit of detection and limit of quantification for Pb(II) were 53 and 176 μg l⁻¹, respectively. Lead was determined in seawater samples collected in Salvador city, Bahia, Brazil. The precision, expressed as R.S.D., was 1.8–4.6%, and the recovery of lead added to seawater samples was 95–97%.     

Xerogels Modified with 4-(2-Pyridylazo)-Resorcinol and Cetylpyridinium Chloride: Determination of Zinc in Solutions by Solid-Phase Spectrophotometry

Silicon dioxide-based xerogels modified with 4-(2-pyridylazo)-resorcinol (PAR) and cetylpyridinium chloride (CP) were synthesized. The concentration of PAR and CP in the hydrolyzed mixture in the ranges (0.6–3.10) × 10^–3 and (5–12) × 10^–3 M, respectively, does not affect the rate of gel formation as well as the specific surface area and average pore diameter of xerogels obtained upon drying in a microwave oven with a power of 600 Wt. It was found that the retention of PAR can be significantly improved in the presence of CP. Reactions of zinc with modified xerogels were studied by solid-phase spectrophotometry at different concentrations of PAR and CP, pH of the solution, and equilibrium time. A procedure was developed for determining 0.1–4.5 mg/L zinc in solutions by solid-phase spectrophotometry. Results of determining zinc in acid soil extracts and milk ash are given.     

Preconcentration of lead, cadmium and zinc on silica gel loaded with diethyldithiocarbamate prior to their determination by flame-atomic absorption spectrometry

A silica gel sorbent loaded with sodium diethyldithiocarbamate has been developed for the preconcentration of lead, cadmium and zinc prior to their determination by flameatomic absorption spectrometry (FAAS). The sorption and desorption of the metal ions was studied under both static and dynamic conditions. The metal ions were quantitatively retained on the silica gel sorbent based on an equilibrium time of less than 1 min. In case of the batch method, the effects of pH, shaking time, amount of sorbent, and desorption time were investigated. Among the desorption agents studied, only EDTA in ammonium chloride/ammonia buffer yielded quantitative recoveries. Freundlich's sorption isotherms determined for each metal show that sufficient sorption ability is obtained. The column method allows the preconcentration of metal ions from large sample volumes (e.g. 200 mL) using a flow rate of 5 mL min^–1. The influence of foreign ions present in natural waters and saline solutions was examined. The reproducibility of the total analytical method, expressed as relative standard deviation (RSD) is 1.8, 0.5 and 0.6%, for lead, cadmium and zinc, respectively.     

Coated,Wire-Based,New Schiff Base Potentiometric Sensor for Lead(II) Ion

An ion-selective electrode for lead(II) based on a dispersion of N,N"-bis(3-methyl salicylidine)-p-phenyl methane diamine particles into a polymeric membrane using coated-wire configuration is described. Membranes based on polyvinyl chloride containing different amounts of plasticizer and ionophore are studied. The best performance in terms of slope (30.3 ± 0.6 mV per decade) and response time (<15 s) is displayed. The sensor shows a Nernstian response for Pb(II) ions over a wide concentration range of 2.0 × 10^–5 to 0.10 M. The sensors can be used for more than three months without any considerable divergence in potentials. The selectivity is also good towards the most common univalent and divalent cations and the signal is constant in the pH range 1.6–6.0. An application to lead determination in mineral rocks and wastewater proved to be a success, and it was employed as an indicator electrode in potentiometric titration of CrO^2– ₄ with lead ions.     

Multivariate optimization and validation studies in on-line pre-concentration system for lead determination in drinking water and saline waste from oil refinery

The present paper proposes an on-line pre-concentration procedure for lead determination in drinking water and saline waste from oil refinery by flame atomic absorption spectrometry (FAAS). It is based on the sorption of lead (II) ions in a minicolumn of polyurethane foam loaded with 4-(2-pyridylazo)-resorcinol (PAR) reagent. The optimization step was performed using Doehlert matrix involving the variables: sampling flow rate (SR), buffer concentration (BC), pH and eluent concentration (EC). The validation process was performed considering the parameters: linearity and other characteristics of the calibration curve, analytical features of on-line system, precision, robustness, effect of other ions in the pre-concentration system and accuracy. Using the established experimental conditions, the procedure allows lead determination with detection limit (3δ/S) of 0.4 μg l⁻¹, quantification limit (10δ/S) of 1.4 μg l⁻¹, and a precision, calculated as relative standard deviation (RSD) of 5.7 (n=8) and 2.1% (n=8) for lead concentration of 5 and 50 μg l⁻¹, respectively. The pre-concentration factor (PF) considering the ratio among the slopes of the analytical curves with and without pre-concentration is 51. The achieved recovery for lead determination in presence of several cations demonstrated that this procedure could be applied for analysis of water samples. The accuracy was confirmed by analysis of the standard reference material NIST 1640 Trace elements in natural water. The sorption process was characterized by the Langmuir isotherm. The method was applied for lead determination in drinking water collected in Salvador City, Brazil and in saline effluent samples from oil refinery. The lead content for 16 samples of drinking water analyzed varied from 0.77 to 6.98 μg l⁻¹.     

Complexation of vanadium(IV) with organic reagents on the solid phase of fibrous ion exchangers according to diffuse reflectance and EPR data

Diffuse reflectance and EPR spectroscopic data are reported for the formation of vanadium complexes with the organic reagents (ORs) sulfochlorophenol S (SCP) and pyridylazoresorcinol (PAR) on the solid phase of polyacrylonitrile fiber filled with the cation exchanger KU-2 or the anion exchanger AV-17 or A-5. The effects of the order of sorption of the reaction components, sorption conditions, and the V: OR ratio on the complexation process are discussed. The characteristics of the complexes obtained on the solid phase and in solution are compares. Both M : OR = 1 : 1 and M : OR = 2 : 1 SCP complexes can form on the solid phase without involving any croups of the matrix. PAR forma a 1 : 1 complex involving groups of the A-5 matrix.     

Solid phase extraction of lead by Chelest Fiber Iry (aminopolycarboxylic acid-type cellulose)

Aminopolycarboxylic acid-type cellulose (Chelest Fiber Iry) has been studied for its sorption efficiencies with respect to lead from acidic solution. The influence pH and other properties related to sorption kinetic, isotherm, maximum capacity, stability and the mechanism of the sorption were discussed.Lead was quantitatively retained on the proposed adsorbent in the pH range of 2.5-5.5 (studied pH range 1.5-5.5). The maximum sorption capacity was found to be 0.86±0.06 mmol/g adsorbent. The decline in the efficiency of the adsorbent was not observed for repeated adsorption-desorption cycles. It was found that the preconcentration factor of 200 can be achieved. The limit of determination was found to be about 1 μg Pb/2 l. The method was applied to the determination of lead in water samples.     

A new screening procedure for the estimation of oxidizable organic compounds in water samples

Summary Immobilized lead dioxide (supported on SiO₂) has been used as the packing material in a solid phase reactor for the oxidation of organic compounds in water samples by flow injection analysis (FIA). On-line oxidation takes place in a FIA-system; this allows the detection of mobilized Pb²⁺ either photometrically, after complex formation with 4-(2-pyridylazo)-recorcinol (PAR), or directly with flame-AAS. The oxidation yield is quite different (0–100%) for a variety of organic compounds; however, calibration was possible in all cases investigated. Thus the systems can be used for the screening of polluted waters and as a post-column chemical-reaction detector (e.g. after HPLC-separation of organic compounds). After modification the FIA determination of COD equivalent values should be possible.     

The uptake of strontium by calcium phosphate phase formed at an elevated pH

The sorption of radioactive strontium by poorly crystalline hydroxyapatite (HA) obtained by the transformation of amorphous calcium phosphate (ACP) at initial pH 10.8, was investigated. Morphological analysis, performed by transmission electron microscopy, has demonstrated that the solid phase consists of nanometer size ultra-micro particles connected into spherical aggregates. A maximum sorption capacity, determined as the asymptote of the sorption isotherm was =(3.8±0.3)·10^–2mol Sr/mol P. Based on this result and the structural conditions, a possible theoretical explanation for the incorporation of a strontium ion into the apatite lattice has been proposed.