Trace Metal Preconcentration Using A Thioglycolate Chelating Resin

Abstract

A styrene-divinyl benzene copolymer resin (Amberlite XAD-4), modified with thioglycolate complexing groups, has been employed for the preconcentration of cadmium, zinc, lead and nickel fron natural waters. the resin exhibits its strongest affinity for cadmium and lead but can be used to quantitatively remove all four metals from non-saline waters. With seawater samples, the resin is best only employed for the enrichment of cadmium and lead as the recovery of nickel and zinc from this medium is poor.     

Flow injection determination of Pb and Cd traces with graphite furnace atomic absorption spectrometry

The preconcentration and recovery of lead and cadmium traces at ng l(-1) level were evaluated in standard solutions and natural aqueous samples using a FIAS (Flow Injection Atomic Spectrometry) apparatus. The method is based on retention of the complex formed between Pb or Cd and 1,2-dihydroxy-3,5-benzendisulphonic acid (Tiron) on a macroporous anion-exchange resin. The recovery of the analytes was obtained by elution with 0.1 M HCl and their determination was performed by Graphite Furnace Atomic Absorption Spectrometry (GFAAS). The detection limits were 9 and 7 ng l(-1) for Pb and Cd respectively. The effects of sample solution pH and composition and of interfering agents as well as reagent purity are discussed. The technique was applied to the analysis of natural waters.     

Application of a poly(dithiocarbamate) resin to the determination of trace copper,iron and zinc in natural waters

A chelating poly(dithiocarbamate) resin with macroreticular support is shown to be effective for the preconcentration of copper, iron and zinc in natural waters. The retained ions can be eluted efficiently in 5 ml of 8M nitric acid from 1–20-cm columns of resin.This poly(dithiocarbamate) resin is used for the preconcentration and determination of copper, iron and zinc by flame atomic absorption spectrophoto-metry. Common ions present in natural waters do not interfere. The detection limits were 0.50, 0.21 and 0.04 g 1^–1 for Cu, Fe and Zn respectively.     

Determination of lead and cadmium in tap water and apple leaves after preconcentration on a new acetylacetone bonded polyurethane foam sorbent

The present work describes a rapid, cost-effective analytical procedure for the determination of lead and cadmium in environmental samples by off-line preconcentration with polyurethane foam (PUF) functionalised with acetylacetone by covalent coupling through the–N=N–group. The optimum pH ranges for quantitative uptake were 5–7, 6–7 for lead and cadmium, respectively. The kinetics of metal uptake by the new foam was found to be fast, reaching equilibrium in a few minutes. Metal ions were sorbed in the minicolumn, eluted with acid solutions and determined by flame atomic absorption spectrometer (FAAS). Under the optimum conditions, the preconcentration factors obtained were 288 for Cd and 224 for Pb. The limits of detection of the proposed procedure were 0.09 and 0.07 µg L^?1 for Pb and Cd, respectively. The relative standard deviation (RSD) was less than 10%. The accuracy of the method was estimated by using environmental samples that were spiked with Cd and Pb ions. The capacity of the acetylacetone bonded PUF (AA-BPUF) sorbent at optimum conditions has been found to be 4.5, 6.9 µmol g^?1 of sorbent for Pb and Cd, respectively.     

The uses of 1-(2-pyridylazo) 2-naphtol (PAN) impregnated Ambersorb 563 resin on the solid phase extraction of traces heavy metal ions and their determinations by atomic absorption spectrometry

1-(2-pyridylazo) 2-naphtol (PAN) impregnated Ambersorb 563 resin was used as solid phase extractor of copper, nickel, cadmium, lead, chromium and cobalt ions in aqueous solutions prior to their atomic absorption spectrometric determinations. The parameters including pH, sample volume, matrix effects were also investigated. The relative standard deviation (R.S.D.) of the combined method of sample treatment, preconcentration and determination with atomic absorption spectrometry is generally lower than 10%. The limit of detection was between 0.21 and 1.4 μg l⁻¹. The results were used for preconcentration of analyte ions from natural water samples. The method was also applied to a stream sediment standard reference material (GBW7309) for the determination of Cu, Ni, Cd, Pb, Cr and Co.     

Preconcentration of trace amounts of manganese from natural waters by means of a macroreticular poly(dithiocarbamate) resin

A chelating poly(dithiocarbamate) resin (PDTC) with macroreticular support is characterized as effective collector for traces of manganese from natural waters. Using small PDTC columns preconcentration of manganese can be achieved even at high flow-rates (5-6 ml/min) and sample volumes (1500 ml). Accordingly, PDTC resin is used for the preconcentration of manganese from water samples prior to its determination by flame atomic-absorption spectrometry. A series of ions abundant in natural waters do not interfere. The sensitivity and detection limit were 2.5 and 0.5 mug/l., respectively. The relative standard deviations of the results for a manganese concentration of 40-400 mug/l. are in the range 1.1-6.2%. In mineral and tap waters analysed, the manganese concentration range was between 2.9 and 30.8 mug/l.     

A new method of microvolume back-extraction procedure for enrichment of Pb and Cd and determination by flame atomic absorption spectrometry

The need for highly reliable methods for the determination of trace elements has been recognised in analytical chemistry and environmental science. A method for the trace analysis of Pb and Cd in natural waters is described. In a preconcentration step, 500 ml of an aqueous sample containing lead and cadmium were extracted into 3.5 ml of a solution containing a complexing agent (dithizone) in xylene. Subsequently, the dithizonate complexes were back-extracted into 600 mul of nitric acid solution for direct determination by flame atomic absorption spectrometry. Important microextraction parameters were optimised using spiked deionised water. The 3sigma detection limits, relative standard deviations and linear calibration graphs were, respectively, 0.39 mugl(-1), 6.3% and 1.0-20.0 mugl(-1) for lead and 8.2 ngl(-1), 4.0% and 0.05-1.0 mugl(-1) for cadmium for solvent microextraction times of 4 min and microvolume back-extraction times of 1 min. The preconcentration factors were 543- and 331-fold for lead and cadmium, respectively.     

Supported hydrophobic ionic liquid on magnetic nanoparticles as a new sorbent for separation and preconcentration of lead and cadmium in milk and water samples

We have prepared a highly selective and efficient sorbent for the simultaneous separation and preconcentration of lead and cadmium ions from milk and water samples. An ionic liquid was deposited on the surface of magnetic nanoparticles (IL-MNPs) and used for solid phase extraction of these ions. The IL-MNPs carrying the target metals were then separated from the sample solution by applying an external magnetic field. Lead and cadmium were almost quantitatively retained by the IL-MNPs, and then eluted with nitric acid. The effect of different variables on solid phase extraction was investigated. The calibration curve is linear in the range from 0.3 to 20?ng mL^?1 of Cd(II), and from 5 to 330?ng mL^?1 of Pb(II) in the initial solution. Under optimum conditions, the detection limits are 1.61 and 0.122?μg?L-1 for Pb(II) and Cd(II) respectively. Relative standard deviations (n?=?10) were 2.87?% and 1.45?% for 0.05?μg?mL^-1 and 0.2?μg?mL^-1 of Cd (II) and Pb (II) respectively. The preconcentration factor is 200 for both of ions.

The efficiency of cellix-p for the preconcentration of lead and other trace metals from waters

The cheating ion-exchanger Cellex-P, a cellulose phosphate ester, is shown to be effective for the preconcentration of Cu, Ni, Mn, Cd, Zn and Pb from water. The pH of the sample is not critical within the approximate range 5–8. The collected ions can be eluted efficiently in 10–25 ml of 1 M nitric acid from 2–16.5-cm columns of resin. Common salts present in natural waters do not interfere. Cellex-P is used for the preconcentration and determination of the metal ions in potable water by graphite-furnace atomic absorption spectrometry.     

Thiosalicylic acid-immobilized Amberlite XAD-2: metal sorption behaviour and applications in estimation of metal ions by flame atomic absorption spectrometry

Thiosalicylic acid (TSA)-modified Amberlite XAD-2 (AXAD-2) was synthesized by coupling TSA with the support matrix AXAD-2 through an azo spacer. The resulting chelating resin was characterized by elemental analyses, thermogravimetric analysis (TGA) and infrared spectra. The newly designed resin quantitatively sorbs CdII, CoII, CuII, FeIII, NiII and ZnII at pH 3.5-7.0 when the flow rate is maintained between 2 and 4 ml min-1. The HCl or HNO3 (2 mol l-1) instantaneously elutes all the metal ions. The sorption capacity is 197.5, 106.9, 214.0, 66.2, 309.9 and 47.4 mumol g-1 of the resin for cadmium, cobalt, copper, iron, nickel and zinc, respectively, whereas their preconcentration factor is between 180-400. The breakthrough volume of HCl or HNO3 for elution of these metal ions was found to be 4-8 ml. The limit of detection (LOD) for CdII, CoII, CuII, FeIII, NiII and ZnII was 0.48, 0.20, 4.05, 0.98, 1.28 and 3.94 micrograms l-1, respectively, and the limit of quantification (LOQ) was found to be 0.51, 0.29, 4.49, 1.43, 1.58 and 4.46 micrograms l-1, respectively. The loading half time, t1/2, for the cations was found to be less than 2.0 min, except for nickel for which the value was 13.1 min. The determination of each of these six cations is possible in the presence of other five, if their concentration is up to 4 times. All six metals were determined in river water (RSD approximately 0.7-7.7%) and tap water samples (RSD approximately 0.3-5.7%). The estimation of Co was made in the samples of multivitamin tablets (RSD < 2.3%). The results agree with those quoted by manufacturers.     

Column solid-phase extraction with Chromosorb-102 resin and determination of trace elements in water and sediment samples by flame atomic absorption spectrometry

A column, solid-phase extraction (SPE), preconcentration method was developed for determination of Bi, Cd, Co, Cu, Fe, Ni and Pb ions in drinking water, sea water and sediment samples by flame atomic absorption spectrometry. The procedure is based on retention of analytes in the form of pyrrolidine dithiocarbamate complexes on a short column of Chromosorb-102 resin from buffered sample solution and then their elution from the resin column with acetone. Several parameters, such as pH of the sample solution, amount of Chromosorb-102 resin, amount of ligand, volume of sample and eluent, type of eluent, flow rates of sample and eluent, governing the efficiency and throughput of the method were evaluated. The effects of divers ions on the preconcentration were also investigated. The recoveries were >95%. The developed method was applied to the determination of trace metal ions in drinking water, sea water and sediment samples, with satisfactory results. The 3σ detection limits for Cd, Cu, Fe, Ni and Pb and were found to be as 0.10, 0.44, 11, 3.6, and 10 μg l⁻¹, respectively. The relative standard deviation of the determination was <10%. The procedure was validated by the analysis of a standard reference material sediment (GBW 07309) and by use of a method based on coprecipitation.     

Preconcentration and determination of lead, cadmium and nickel from water samples using a polyethylene glycol dye immobilized on poly(hydroxyethylmethacrylate) microspheres.

A simple and sensitive preconcentration analysis-atomic absorption spectrometric procedure is described for the determination of lead, cadmium and nickel. The method is based upon on-line preconcentration of metal ions on a minicolumn of Cibacron Blue F3-GA immobilized on poly(hydroxyethylmethacrylate), poly(HEMA). The enrichment factors obtained were 42 for lead, 52 for cadmium and 63 for nickel (sample volume 10 mL and sample flow rate 5 mL/min). The relative standard deviations (n = 10), in 10 mL sample solutions containing 100 microg/L Pb(2+), 10 microg/L Cd(2+) and 100 microg/L Ni(2+) were 8.9, 3.7 and 3.5%, respectively. The limits of detection (blank + 3s) (n = 10), were found to be 12.01 microg/L for Pb(2+), 1.34 microg/L for Cd(2+) and 28.73 microg/L for Ni(2+). The accuracy of the system was checked with certified and tap water samples spiked with known amounts of metal ions. No significant difference was found between the achieved results and the certified values.     

Preconcentration and separation with Amberlite XAD-4 resin; determination of Cu, Fe, Pb, Ni, Cd and Bi at trace levels in waste water samples by flame atomic absorption spectrometry

A method for the preconcentration of Cu, Fe, Pb, Ni, Cd and Bi as their diethyldithiocarbamate chelates was proposed using a column filled with Amberlite XAD-4 resin. The retained analytes on the resin were recovered with a small volume of acetone. The metal ions in the effluent were determined by a flame atomic absorption spectrometer. Different factors including pH of sample solution, sample volume, amount of XAD-4 resin, amount of ligand, eluent volume and matrix effects for preconcentration were examined. The recoveries for the analytes under the optimum working conditions were higher than 95%. The relative standard deviations of the determinations were below 9%. The limits of detection (3 s, n=20) for analytes were found to be between 4 and 23 mug l(-1). The proposed method was applied to the analysis of some waste waters from the organized industrial region of Kayseri.     

Preconcentration of trace metals on Amberlite XAD-4 resin coated with dithiocarbamates and determination by inductively coupled plasma-atomic emission spectrometry in saline matrices

Preconcentration of Cd(II), Cu(II), Mn(II), Ni(II), Pb(II) and Zn(II) in saline matrices on Amberlite XAD-4 resins coated with ammonium pyrrolidine dithiocarbamate (APDC) and piperidine dithiocarbamate (pipDTC) and subsequent determination by inductively coupled plasma atomic emission spectrometry were studied. Parameters such as effect of pH, effect of HNO(3) concentration on elution of metals from resin were studied. The results show that Amberlite XAD-4 coated with APDC was more efficient in the recovery of metal ions compared with Amberlite XAD-4 coated with pipDTC, in the concentration range of 0.1-200 mug l(-1), for 1 g of Amberlite XAD-4 coated resin. The detection limits for Cd(II), Cu(II), Mn(II), Ni(II), Pb(II), Zn(II) are 0.1, 0.4, 0.3, 0.4, 0.6, 0.5 mug l(-1), respectively, for resin coated with APDC and 0.7, 1.0, 0.8, 0.9, 1.7 and 1.2 mug l(-1) for resin coated with pipDTC. The effect of diverse ions on the determination of aforesaid metals was studied. The method was applied for the determination of trace metal ions in artificial sea water and natural water samples. The results were compared with extraction AAS method.     

Thioacetamide chemically immobilized on silica gel as a solid phase extractant for the extraction and preconcentration of copper(II), lead(II), and cadmium(II)

Thioacetamide immobilized on silica gel was prepared via the Mannich reaction. The extraction and enrichment of copper(II), lead(II), and cadmium(II) ions from aqueous solutions has been investigated. Conditions for effective extraction are optimized with respect to different experimental parameters in both batch and column processes prior to their determination by flame atomic absorption spectrometry (FAAS). The optimum pH ranges for quantitative adsorption are 4.0-8.0, 2.0-7.0, and 5.0-10.0 for Pb(II), Cu(II), and Cd(II), respectively. Pb(II) and Cd(II) can be desorbed with 3 mol/L and 0.1 mol/L HCl/HNO3, and Cu(II) can be desorbed with 2.5% thiourea. The adsorption capacity of the matrix has been found to be 19.76, 16.35, and 12.50 mg/g for Pb(II), Cu(II), and Cd(II), respectively, with the preconcentration factor of approximately equal to 300 for Pb(II) and approximately equal to 200 for Cu(II) and Cd(II). Analytical utility is illustrated in real aqueous samples generated from distilled water, tap water, and river water samples.     

Determination of cadmium and lead in aqueous environmental samples after complexation and microextraction onto the surface of an empty solvent-impregnated polypropylene fibre coupled with electrothermal AAS

A procedure based on polypropylene hollow-fibre preconcentration coupled with electrothermal atomic absorption spectrometry (ETAAS) was developed for the determination of cadmium and lead in seawater, wastewater, tap water and lake water samples. The n-octanol was immobilised in the pores of the polypropylene hollow fibre, which was used as the liquid sorption membrane negating the need for acceptor liquid phase in the lumen. The metal ions were extracted from water samples onto the impregnated fibre, as ammonium pyrrolydine dithiocarbamate (APDC) complexes, and then back-extracted into a small volume of 0.1?mol?L^?1 HNO₃. The main extraction-related parameters were properly evaluated and an interference study was carried out. Linear regression lines were plotted and replicate analyses of real samples revealed that the proposed method is precise and accurate, able to be applied in routine analysis with detection limits of 4?ng?L^?1 and 12?ng?L^?1 for Cd and Pb, respectively.     

Flame atomic absorption spectrometric determination of trace amounts of lead, cadmium and nickel in different matrixes after solid phase extraction on modified multiwalled carbon nanotubes

The potential of modified multiwalled carbon nanotubes (a solid-phase extraction sorbent), for the simultaneous separation and preconcentration of lead, cadmium and nickel; has been investigated. Lead, cadmium and nickel, were adsorbed quantitatively; on modified multiwalled carbon nanotubes (in the pH range of 2–4). Parameters influencing, the simultaneous preconcentration of Pb(II), Ni(II) and Cd(II) ions (such as pH of the sample, sample and eluent flow rate, type and volume of elution solution and interfering ions), have been examined and optimized. Under the optimum experimental conditions, the detection limits of this method. for Pb(II), Ni(II) and Cd(II) ions, were 0.32, 0.17 and 0.04 ng mL⁻¹ in original solution, respectively. Seven replicate determinations, of a mixture of 2.0 μg mL⁻¹ lead and nickel, and 1.0 μg mL⁻¹ cadmium; gave a mean absorbance of 0.074, 0.151 and 0.310, with relative standard deviation 1.7%, 1.5% and 1.2%, respectively. The method has been applied, to the determination of trace amounts of lead, cadmium and nickel; in biological and water samples, with satisfactory results.      

Flow-injection potentiometric determination of free cadmium ions with a cadmium ion-selective electrode

The determination of free cadmium ions with solid-state cadmium ion-selective electrode can be performed in non-flow measurements in non-buffered solutions in a wide concentration range down to pCd 10. In cadmium ion buffered solutions linear Nernstian response was obtained even down to pCd 12, which is lower, that expected based on calculation of cadmium solubility from the conditional solubility product. Interferences of trace amounts of Fe(III), Cu(II) and Pb(II) commonly present in natural waters in larger concentrations than Cd(II) can be eliminated by reduction with hydroxylamine, complexation with Neocuproine and ion-exchange on anion-exchange resin in sulphate form, respectively. The developed procedure might be suitable for the determination of activity of free cadmium ions in natural water. A preliminary study on this subject is demonstrated for river water sample using stopped-flow flow-injection system.     

Cloud Point Extraction and Flame Atomic Absorption Spectrometric Determination of Cd(II) in Industrial and Environmental Samples

A micelle-mediated separation/preconcentration technique was used for the determination of trace Cd(II) in solid and liquid samples by flame atomic absorption spectrometry. Cadmium ions reacted with ammonium pyrrolidine dithiocarbamate to form a chelate that was extracted from aqueous medium by a non-ionic surfactant Tergitol NP-7 at pH 7. Values of pH, concentrations of ammonium pyrrolidine dithiocarbamate and Tergitol NP-7, temperature, incubation time, sample volume and matrix ions were optimized. The enrichment factor of the method was found to be 25, and the detection and quantitation limits were 1.5 and 3.8 μg/L, respectively. Assessment of the method was performed with a certified reference material, and the observed concentration of Cd(II) was in good agreement with the certified value. The method was also applied to the determination of Cd(II) in waters and industrial samples. Cd(II) concentrations in two industrial ZnO composite samples were determined between 59 and 69 μg/g.     

The synthesis of new polymeric sorbent and its application in preconcentration of cadmium and lead in water samples

Metal determinations at low concentration levels (≤ng mL⁻¹) comprise one of most important targets in analytical chemistry. This interest also increases in different areas such as biology, medicine, environment and food samples. In spite of inherent high sensitivities obtained for electrothermal atomic absorption spectrometry (ETAAS) and inductively coupled plasma-mass spectrometry (ICP-MS), these techniques have some limitations depending on the concomitants. As a result, interest in preconcentration techniques still continues increasingly for trace metal determinations by flame atomic absorption spectrometry (FAAS) due to the high accuracy of this method.In this work, thioureasulfonamide resin was synthesized, characterized and applied as a new sorption material for determinations of cadmium and lead in water samples. The method is based on the sorption of Cd and Pb ions on the synthesized resin without using any complexing reagent. The optimization of experimental conditions was performed using factorial design including pH, amount of resin, contact time, first sample volume and final eluent volume. Using the experimental conditions defined in the optimization, the method was applied to the determination and preconcentration of Cd and Pb at ng mL⁻¹ level in natural water. Flame AAS was used for trace metal determinations. This method exhibits the superiority in compared to the other adsorption reagents because of the fact that there is no necessity of any complexing reagent and optimum pH of solution presents in acidic media. Consequently, 600- and 360-fold improvements in the sensitivity of FAAS were achieved by combining the slotted tube atom trap-atomic absorption spectrometry (STAT-FAAS) and the purposed enrichment method for Cd and Pb, respectively.