Absorption Spectrometric Determination Of Cadmium Research Articles

Investigation of thermospray flame furnace atomic absorption spectrometric determination of cadmium combined with ultrasound-assisted dispersive liquid-liquid microextraction

ABSTRACT Ultrasound-assisted dispersive liquid-liquid microextraction (UA-DLLME) was combined with thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) for the first time to develop a highly sensitive method for the determination of cadmium. Ultrasound was used to assist the liquid phase extraction, replacing the traditional disperser solvent. A self-assembled TS-FF-AAS instrument was adopted to improve the analytical performance of traditional flame atomic absorption spectrometry (FAAS), and the characteristic of micro-injection is fully suitable to be coupled with UA-DLLME. The developed combination significantly improved the analytical performance of TS-FF-AAS and traditional FAAS, while overcoming problems of nebulisation associated with the coupling of FAAS and liquid phase extraction methods. Some environmental water samples were collected and analysed by the developed coupling with satisfactory results.

An experimental design for the optimization of the extraction methods of metallic mobile fractions from environmental solid samples.

The evaluation of the cadmium and lead mobile forms from environmental solid samples provides information about their mobility and bioavailability. In the present study, the Cd and Pb mobile fractions were obtained by two modified extraction methods applied to industrial and acidic pH soils or to polluted sediments. In order to highlight that the extraction procedure does not significantly influence the quantitative atomic absorption spectrometric determination of cadmium and lead, the robustness of the extraction methods was evaluated and proven applying a Youden and Steiner factorial design. Within this experimental design, the shaking rate, the shaking time, and the solid/liquid extraction ratio were modified. The measurement uncertainty of the whole analytical procedure was assessed, the contribution of the factors involved in the extraction process being insignificant compared to the other uncertainty sources. The importance of the study is related to the fact that it proves the applicability in the routine laboratory practice of the modified extraction methods by increasing the extraction ratio following thorough optimization and robustness studies.

Flame Atomic Absorption Spectrometric Determination of Cadmium in Vegetable and Water Samples After Preconcentration Using Magnetic Solid-Phase Extraction

ABSTRACTAccurate and reliable determination of cadmium (Cd) in vegetables is often difficult due to low concentrations and matrix effects. Magnetic solid-phase extraction (MSPE) was developed for preconcentration and determination of trace amounts of Cd in vegetables and water samples prior to flame atomic absorption spectrometry (FAAS) analysis. Cobalt magnetic nanoparticles were synthesized and modified by sodium dodecyl sulfate (SDS) and 2-(5-bromo-2-pyridylazo)-5-diethyl aminophenol ligand (5-Br-PADAP) through a chemical precipitation method so that the nanoparticles (NPs) could be used as a new sorbent. The NPs bearing the Cd ions were easily separated from the aqueous solution by applying an external magnetic field and the complexed metals were desorbed using dilute HNO3. Extraction conditions including pH, amount of sorbent, contact time, desorption solvent, breakthrough volume, and sorption capacity were optimized. Under optimal conditions, the calibration curve was linear from 1.0–500 ng·mL−1 of Cd, R2 = 0.997. The detection limit was 0.6 ng·mL−1 in the original solution (3 Sb·m−1) and the relative standard deviation for eight replicates determination of 0.1 μg·mL−1 Cd was ±2.2%. Cadmium is easily aggregated in edible parts of leafy vegetables. Heavy metals analysis of vegetables is essential for protection of human health and to comply with regulatory controls.

Ion-pair-based surfactant-assisted dispersive liquid–liquid microextraction for the determination of cadmium in water samples: Optimization using response surface methodology

A sensitive, simple, and rapid method is developed for ion-pair-based surfactant-assisted dispersive liquid–liquid microextraction (IPSA-DLLME) and flame atomic absorption spectrometric determination of cadmium in water samples. In this procedure, trace amounts of Cd2+ were converted to CdI42–, and after addition of a tetrabutylammonium bromide (TBAB) solution as cationic surfactant the analyte was transformed to the ion-pair state. This cadmium species was extracted by fast injection of a solution containing 200 μL of chloroform and 800 μL of methanol as extraction and disperser solvents, respectively. The pH of the sample solution, concentration of iodide, TBAB amount, and the extractant volume were optimized using a 27-run Box–Behnken design with a triplicate central point. Under the optimized conditions, the calibration curve was linear in the range 1–200 μg L–1 (R2 = 0.9959); with the detection limit (signal/noise = 3) of 0.28 μg L–1. The relative standard deviations (RSD) for eight runs (Cd2+ = 10 μg L–1) and enrichment factor were found to be 3.04 % and 50, respectively.

Electrothermal atomic absorption spectrometric determination of cadmium in environmental samples with niobium wire preconcentration method

A preconcentration method by adsorption of cadmium on a niobium wire was developed for the environmental waters, followed by electrothermal atomic absorption spectrometry with a tungsten tube atomizer. After the preconcentration, the niobium wire was directly inserted into the tungsten tube atomizer. In the preconcentration (adsorption) process of cadmium, the optimal immersing time was 60 s. The effects of large amounts of concomitants on the preconcentration of cadmium were evaluated. When 103–104 fold excess of matrix elements existed in aqueous solution at pH 4 and 9, the cadmium response was profoundly affected by the matrix elements. However, the cadmium absorption signal was not significantly influenced at pH 7. Therefore, pH 7 was selected for the application into the real environmental samples. Under the optimal conditions, the detection limit (3S/N) for cadmium by the niobium wire preconcentration method was 7.0 pg mL−1 and the relative standard deviation was 6.8%. The method with preconcentration on a niobium wire was applied to the determination of cadmium in water and proved to be sensitive, simple and convenient. Because this preconcentration method can be utilized in the in situ treatment of trace cadmium in environmental water samples, it was unnecessary to carry the water samples to the analytical work place. The technique was shown to be useful for the determination of cadmium in environmental water samples at 0.1–1 µg L−1 levels.

Cloud Point Extraction and Flame Atomic Absorption Spectrometric Determination of Cadmium and Nickel in Drinking and Wastewater Samples

A simple method for the preconcentration of cadmium (Cd) and nickel (Ni) in drinking and wastewater samples was developed. Cloud point extraction has been used for the preconcentration of both metals, after formation of complexes with 8-hydroxyquinoline (8-HQ) and extraction with the surfactant octylphenoxypolyethoxyethanol (Triton X-114). Dilution of the surfactant-rich phase with acidified ethanol was performed after phase separation, and the Cd and Ni contents were measured by flame atomic absorption spectrometry. The experimental variables, such as pH, amounts of reagents (8-HQ and Triton X-114), temperature, incubation time, and sample volume, were optimized. After optimization of the complexation and extraction conditions, enhancement factors of 80 and 61, with LOD values of 0.22 and 0.52 microg/L, were obtained for Cd and Ni, respectively. The proposed method was applied satisfactorily for the determination of both elements in drinking and wastewater samples.

Atomic absorption spectrometric determination of cadmium and lead in soil after total digestion

ABSTRACTTo establish the baseline levels of cadmium (Cd) and lead (Pb) in Pakistani soil, samples were collected from various ecological areas of the country. A total digestion procedure using an acid mixture of HFHClO4 was investigated for heavy metal analysis of soil samples. Concentrations of these elements were measured using flame and graphite furnace atomic absorption spectrometry. Measured elemental contents of Cd and Pb varied from 0.41–1.18 and 22.47–95.75 µg/g with geometric mean 0.73 and 47.99 and geometric standard deviation concentrations of 1.36 and 1.65 µg/g, respectively. Two certified reference materials (IAEA Soil‐7 and IAEA‐405 estuarine sediment) were introduced for the validation of analytical data. The estimated values were compared with other regions of the world and found lower than the world average values, Cd 27% and Pb 13%, and therefore considered comparatively safe and may not be a cause of concern for environmental pollution. Copyright © 2010 Curtin University of Technology and John Wiley & Sons, Ltd.

Electrothermal atomic absorption spectrometric determination of cadmium and lead in traces in aquatic systems following flotation by two chromium(III) collectors

A fast flotation method for determination of cadmium and lead in aquatic systems by two chromium(III) collectors is described. The first collector is a colloid precipitate of hydrated chromium(III) oxide, Cr2O3· xH2O, while the second is a bulk chromium(III) pentamethylenedithiocarbamate, Cr(PMDTC)3. Cadmium and lead present in water are incorporated into the collector mass at pH 7.5 by addition of 20 mg of Cr(III) and 0.4 mmol of pentamethyleneammonium pentamethylenedithiocarbamate, PMA-PMDTC, to 0.5 L water sample. A solid precipitate was separated from the processed water system by air bubbles. After dissolving with strong acid, the solution is tested by electrothermal atomic absorption spectrometry (ETAAS). The limit of detection for Cd by flotation/ETAAS method is 0.002 μg L− 1, while for Pb is 0.04 μg L− 1. The precision of the method is expressed as relative standard deviations ranging of 5.0% for Cd (concentration range from 0.1 to 0.5 μg L− 1) and 4.25% for Pb (concentration range from 0.5 to 5 μg L− 1). The characteristic mass (mass that gives an integrated absorbance of 0.0044 s) of 1.06 pg for Cd and 16.7 pg for Pb were obtained. The method was validated by the standard additions and by its application to the reference materials (Surface water-SPS-SW-1, River Thames Water-LGC-6019).

Graphite furnace atomic absorption spectrometric determination of cadmium after solid-liquid extraction with dithizone

A method for the determination of trace amount of cadmium ion after preconcentration by extracting its dithizone complex into molten naphthalene was developed. Several experimental conditions such as pH of the solution, stirring time, the amounts of naphthalene, standing time and volume of the solution were optimized. Trace amount of cadmium ion in aqueous solution of sample was chelated with 5 mL of 0.001 M dithizone at pH 8. After addition of 0.15 g naphthalene, the solution was heated to about 85 oC and stirred (800 rpm) for 2 min to reproduce the microcrystalline naphthalene. Cadmium ion was determined by a graphite furnace atomic absorption spectrometer. The interfering effects of diverse concomitant ions (cations and anions) were investigated. Artificial sea water and a standard reference material (SRM) were analyzed by this method. The sensitivity and detection limit of 1.2 ngL -1 and 1.5 ng L -1 were found, respectively.

Vapor Generation Atomic Absorption Spectrometric Determination of Cadmium in Environmental Samples with In-Line Anion Exchange Separation

A novel in-line anion exchange separation method is described for the removal of Mn(2+), Fe(3+), Ni(2+), Co(2+), Cu(2+), Zn(2+), and Pb(2+) from Cd(2+) and for its subsequent determination by vapor generation atomic absorption spectrometry. High Cd(2+) retention efficiency and maximum exclusion of other metal ions were achieved by using Cl(-), Br(-), or I(-) loaded strong base anion exchange resin and fiber in chloride medium. SO(4)(2-) and NO(3)(-) affected the retention of Cd(2+) on Cl(-) or Br(-) loaded exchangers but were beneficial for elution from I(-) loaded exchangers. Fast and efficient elution from the exchangers was achieved by using ethylenediamine solution. The removal of Zn(2+) was unnecessary as it prevents a decline in the sensitivity of cadmium response when ethylenediamine and high acid concentration were used. Under optimum conditions, the achievable detection limits (3sigma) with sample loadings of 0.48 and 9.6 mL were 40 ng L(-1) and 3 ng L(-1), respectively. Interference of residual organic matrix, in sample digests, with the separation and retention of cadmium were eliminated by use of microwave assisted digestion. The method was successfully applied to the determination of Cd in river sediment, fish liver, and water samples.

Cloud point extraction and flame atomic absorption spectrometric determination of cadmium(II), lead(II), palladium(II) and silver(I) in environmental samples

The phase-separation phenomenon of non-ionic surfactants occurring in aqueous solution was used for the extraction of cadmium(II), lead(II), palladium(II) and silver(I). The analytical procedure involved the formation of understudy metals complex with bis((1H-benzo [d] imidazol-2yl)ethyl) sulfane (BIES), and quantitatively extracted to the phase rich in octylphenoxypolyethoxyethanol (Triton X-114) after centrifugation. Methanol acidified with 1 mol L −1 HNO 3 was added to the surfactant-rich phase prior to its analysis by flame atomic absorption spectrometry (FAAS). The concentration of BIES, pH and amount of surfactant (Triton X-114) was optimized. At optimum conditions, the detection limits of (3 sdb/m) of 1.4, 2.8, 1.6 and 1.4 ng mL −1 for Cd 2+, Pb 2+, Pd 2+ and Ag + along with preconcentration factors of 30 and enrichment factors of 48, 39, 32 and 42 for Cd 2+, Pb 2+, Pd 2+ and Ag +, respectively, were obtained. The proposed cloud point extraction has been successfully applied for the determination of metal ions in real samples with complicated matrix such as radiology waste, vegetable, blood and urine samples.

Flow injection wetting-film extraction system for flame atomic absorption spectrometric determination of cadmium in environmental waters

A newly simple flow injection wetting-film extraction system coupled to flame atomic absorption spectrometry (FAAS) has been developed for trace amount of cadmium determination. The sample was mixed on-line with sodium diethyl dithiocarbamate and the produced non-charged Cd(II)–diethyl dithiocarbamate (DDTC) chelate complex was extracted on the thin film of diisobutyl ketone (DIBK) on the inner wall of the PTFE extraction coil. The wetting-film with the extracted analyte was then eluted by a segment of the cover solvent, and transported directly to the FAAS for evaluation. All the important chemical and flow parameters were optimized. Under the optimized conditions an enhancement factor of 35, a sample frequency of 22 h −1 and a detection limit of c L = 0.7 μg l −1 Cd(II) were obtained for 60 s preconcentration time. The calibration curve was linear over the concentration range 1.5–45.0 μg l −1 Cd(II) and the relative standard deviation, R.S.D. ( n = 10) was 3.9%, at 10.0 μg l −1 concentration level. The developed method was successfully applied to cadmium determination in a variety of environmental water samples as well as waste-water sample.

Graphite furnace and hydride generation atomic absorption spectrometric determination of cadmium, lead, and tin traces in natural surface waters: Study of preconcentration technique performance

In this study three major types of preconcentration methods based upon different principles (cation exchange, physical absorption and hydrophobic extraction) were evaluated and optimized for the extraction and determination of three highly toxic heavy metals namely Cd, Pb and Sn by graphite furnace and hybrid generation atomic absorption spectrometry in real samples. The optimum analytical conditions were examined and the analytical features of each method were revealed and compared. Detection limits as low as 0.003–0.025 μg L −1 for Cd 2+, 0.05–0.10 μg L −1 for Pb 2+ and 0.1–0.25 μg L −1 for Sn 4+ depending on the extraction method were obtained with RSD values between 3.08% and 6.11%. A preliminary assessment of the pollution status of three important natural ecosystems in Epirus region (NW Greece) was performed and some early conclusions were drawn and discussed.

Flow injection on-line hydrophobic sorbent extraction for flame atomic absorption spectrometric determination of cadmium in water samples

A flow injection system was developed for on-line sorbent extraction preconcentration and flame atomic absorption spectrometric determination of cadmium in natural water samples. The non-charged cadmium complex with diethyl-dithiophosphate (DDPA) was formed on-line in 0.1 mol L−1 HNO3 and retained on the hydrophobic poly-chlorotrifluoroethylene (PCTFE) sorbent material. The adsorbed complex was eluted with isobutyl methylketone (IBMK) and injected directly into the nebulizer via a flow compensation unit. All major chemical and flow parameters affecting the complex formation adsorption and elution as well as interference were studied and optimized. By processing 2.4 mL of sample, the enhancement factor was 39 and the sampling frequency was 50 h−1. For 30 s preconcentration time the detection limit was 0.3 µg L−1 and the relative standard deviation at 5.0 µg L−1 Cd concentration level was 2.9%. The calibration curve was linear in the range 0.8–40.0 µg L−1. The accuracy of the method was estimated by analyzing a certified reference material NIST-CRM 1643d (Trace elements in water). Good recoveries were obtained for spiked natural-water and waste-water samples.

Flame atomic absorption spectrometric determination of cadmium(II) and lead(II) after their solid phase extraction as dibenzyldithiocarbamate chelates on Dowex Optipore V-493

An enrichment procedure for cadmium and lead after their solid phase extraction as dibenzyldithiocarbamate chelates on Dowex Optipore V-493 has been established prior to their flame atomic absorption spectrometric determinations. The analytical parameters including pH, amounts of dibenzyldithiocarbamate, sample volume, etc., were investigated. The effects of alkaline and earth alkaline ions and some metal ions on the retentions of analytes on Dowex Optipore V-493 resin were examined. Under the optimized conditions, the detection limits (3s, n = 21) for cadmium and lead were 0.43 μg L −1 and 0.65 μg L −1, respectively. The relative standard deviation (R.S.D.), and the recoveries of standard addition for this method were lower than 5% ( n = 11) and 95–102%, respectively. Three standard reference samples (LGC 6010 Hard drinking water, NIST SRM 2711 Montana soil and GBW 07605 Tea) were introduced for accuracy and precision of analytical data. The proposed solid phase extraction system was successfully applied to the analysis of environmental samples.

Minicolumn field preconcentration and flow-injection flame atomic absorption spectrometric determination of cadmium in seawater

A simple method for the continuous field preconcentration of trace dissolved cadmium in seawater samples has been developed based on the minicolumn field sampling technique. For this purpose, minicolumns containing Chelite P (aminomethylphosphonic groups) were connected to a field flow preconcentration system (FFPS). Once in the laboratory, these minicolumns are sequentially inserted into a flow-injection system for on-line cadmium elution and detection by flame atomic absorption spectrometry. Factorial designs have been used to optimise the FFPS and the flow-injection elution process. Six experimental variables were optimised: sample pH, sample flow-rate, eluent concentration, eluent volume, eluent flow-rate and minicolumn diameter. The detection limit (3 F ) of the procedure was 2.7 ng l −1 for a sample volume of 300 ml. The precision (expressed as relative standard deviation) for 11 independent determinations was 0.5–9.4% for cadmium solutions of 10–300 ng l −1. Analysis of certified reference materials (SLEW-3 and NASS-5) showed good agreement with the certified values. This procedure has been successfully applied to the determination of cadmium in seawater samples from Galicia (Spain).

Electrothermal atomic absorption spectrometric determination of cadmium and lead in environmental, botanic and biological samples by different permanent modifiersElectronic supplementary information (ESI) available: Temperature program for modifier coating; optimization of mass and mass ratio of permanent modifiers and cadmium peak profiles; pyrolysis temperatures; characteristic masses and detection limits of cadmium and lead; and contents and recoveries of cadmium and lead

Permanent modifiers (Zr, W, Ru, Zr–Ru and Zr–W) thermally deposited on platforms inserted in pyrolytic graphite tubes and Pd + Mg(NO3)2 conventional modifier mixture have been employed for the determination of cadmium and lead in dissolved environmental, botanic and biological samples by electrothermal atomic absorption spectrometry (ETAAS). Optimum masses and mass ratios of permanent modifiers for Cd and Pb have been investigated. 240 µg Zr + 240 µg W or 240 µg Zr + 200 µg Ru has been found as efficient as 5 µg Pd + 3 µg Mg(NO3)2 for obtaining thermal stabilization and for avoiding most serious interferences. Comparison has been made in terms of pyrolysis and atomization temperatures, atomization and background signal shapes, characteristic masses and detection limits. Long-term stability curves for analytes in samples with Zr, Zr–Ru, Zr–W and Pd + Mg(NO3)2 have been obtained. Cadmium and lead contents determined in certified and standard reference materials by using optimum conditions studied were in agreement with the certified reference materials.

Electrothermal atomic absorption spectrometric determination of cadmium in bangladeshi vegetables with a metal tube atomizer and slurry sampling technique

Ultrasonic slurry sampling electrothermal atomic absorption spectrometry with a molybdenum tube atomizer has been applied for the determination of cadmium in vegetable samples in Bangladesh. The suspension-stabilizing medium was 10% glycerol solution. The optimum pyrolysis temperature was 300°C. The detection limit was 13 fg (3S/N). Matrix element interference was studied and it was found that thiourea as a chemical modifier eliminated the interference. The results for the determination of cadmium in vegetable samples by the proposed method were in good agreement with those measured in dissolved acid-digested samples. The method enables rapid calibration, and simple and rapid analysis of cadmium in vegetable samples at low cost.

Nickel as a chemical modifier for sensitivity enhancement and fast atomization processes in electrothermal atomic absorption spectrometric determination of cadmium in biological and environmental samples.

A systematic study of the efficiency of protons, Ni, Pd and Th as chemical modifiers for the determination of cadmium by electrothermal atomic absorption spectrometry (ETAAS) using fast temperature programs was made for platform atomization. A comparison was made in terms of the salt type, absorbance-time profiles and elimination of the sodium chloride interference. The results were adapted to develop a method for the ETAAS determination of cadmium in biological and environmental samples. The highest sensitivity to determine cadmium in biological and environmental samples was obtained using nickel (together with protons) as a chemical modifier. The accuracy of the method was tested by the determination of cadmium in different certified reference materials. The best detection limit and the characteristic mass of Cd were found to be 0.03 ng mL(-1) and 0.35 pg, respectively.

Electrothermal atomic absorption spectrometric determination of cadmium and lead with stabilized phosphate deposited on permanently modified platforms

Some drawbacks of the phosphate modifier such as reagent blank contribution and background absorption in electrothermal atomic absorption spectrometric determination of cadmium and lead are substantially alleviated by application of small amounts of phosphate, approximately 0.2 μmol (25 μg of NH 4H 2PO 4 or (NH 4) 2HPO 4), on the integrated platform of transversely heated graphite atomizer pre-treated with 2.7 μmol of Zr (250 μg) or W (500 μg) and 0.1 μmol of Ir (20 μg). Pyrolysis temperatures for Cd and Pb are up to 900 and 1100 °C for aqueous solutions and within 400–600 °C (Cd) and 750–850 °C (Pb) for biological fluids (urine, blood) and tissues (hair, liver, muscle) solubilized with tetraethylammonium hydroxide. The thermally stabilized phosphate on Zr–Ir or W–Ir treated platforms serves as a permanent modifier in analyses of environmental waters by multiple hot injections of large sample aliquots. Applications to water and biological certified reference materials are tabulated and show good agreement with certified values. Characteristic masses are 0.7–1.0 pg for Cd and 26–31 pg for Pb.