Cadmium analysis in soil by microwave acid digestion and graphite furnace atomic absorption spectrometry

The need to determine micronutrients and toxic elements in soils has grown in recent years and cadmium is of special interest. A method has been developed for the determination of cadmium in soils based on a prior acid digestion of the samples with nitric acid in closed Teflon vessels, into a microwave over. The cadmium determination was carried out by graphite furnace atomic absorption spectrometry (GFAAS) with L'vov platform. Optimum operating conditions, analyte modifiers and matrix interferences have been investigated. The best matrix modifier was found to be ammonium dihydrogen phosphate. The interferences are greatly reduced under these operating conditions and calibration can be performed with simple aqueous solutions of the metal standard. The method is rapid and provides accurate and precise results that agree with certified values for two reference materials: BCR 141 (calcareous loam soil) and BCR 277 (estuarine sediment).     

Comparison of procedures for correction of matrix interferences in the multi-element analysis of soils by ICP-AES with a CCD detection system

Three procedures, matrix matching, plasma optimisation and single-point standard-addition, have been evaluated to ascertain the best procedure for simultaneous multi-element analysis of industrial soils by ICP-AES with CCD detection. A standard reference material, CRM143 from the Bureau Communautaire de Réference (BCR), has been analysed for Cd, Cr, Cu, Mn, Ni and Pb using the three different matrix interference correction procedures. All three procedures give comparable results which are in good agreement with the BCR values, except for Cr. The single-point standard addition procedure was chosen, on the basis of economy and ease of implementation, to correct for matrix interferences in the determination of Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Sn and V in soil samples collected from an industrial site in England. Concentrations of some of the elements were found to vary greatly with sampling depth. For example, the concentration of Mn, determined using the atomic line at 279.920 nm, increased from 426 ± 3 g/g at a depth of 18–28 cm to 5996 ± 144 g/g at 60–85 cm.     

Cadmium Determination in Soil Extracts by Furnace Atomic Absorption

Abstract

A method for the direct determination of Cd in soil extracts by graphite furnace atomic absorption spectrosopy (GFAAS) has been developed. Optimum operating conditions, analyte modifiers and matrix interferences have been investigated. Characteristic amounts are 0.34pg for siliceous samples and 0.45 pg for calcareous soils. The precision has been based on ten replicate readings in standards, and was 1.6%. Cd has been determined by the proposed methods and the results have been compared with those obtained by ICP technique.     

Reduction des interferences sur la determination des metaux lourds dans les sediments de cours d'eau et les boues de stations d'epuration par spectrometrie d'absorption atomique en four graphite

(Reduction of interferences in the determination of trace heavy metals in river sediments and sewage sludges by electrothermal atomic absorption spectrometry.)The interferences of synthetic matrices of river sediments and sewage sludges in the determination of lead, copper, cadmium, chromium and nickel by electrothermal atomic absorption spectrometry were studied; Pb, Cd and Ni were the most sensitive to interferences. The effects of hydrochloric, nitric, perchloric and hydrofluoric acids were tested; perchloric acid was found to interfere most during the determinations. Hydrofluoric acid must be eliminated by evaporation. Techniques for reducing chemical interferences were evaluated. The best method was found to be matrix modification with ammonium dihydrogenphosphate and ascorbic acid for the determination of lead and nickel, and rapid heating (Max Power) for the determination of cadmium. Determinants of copper and chromium were less prone to interference.     

ICP emission spectrometric analysis of rare earth elements in permanent magnet alloys

An analytical method for the determination of rare earth elements (REE) in a NdFeB permanent magnet alloy by ICP emission spectrometry is described. Spectral interferences, arising from overlapping, as well as matrix effects have been studied. Considering spectral interferences, sensitivities of spectral lines, background intensities and the chemical composition of the sample investigated, optimum spectral lines for each REE have been selected. Because of an unfavourable concentration ratio in samples of a NdFeB permanent magnet alloy, a preliminary separation of matrix elements from rare earth elements by ion chromatography is necessary. Different modes of elution (isocratic and gradient) with -hydroxy-isobutyric acid and different columns (NUCLEOSIL, SULFOPROPYL SI-100, DIONEX HPIC-CS3) have been tested. Optimum separation conditions have been chosen for each element and the separation efficiency at equal or different concentrations of the selected elements have been established. Although the separation of REEs resulted in partly overlapping peaks, the ratio between analyte and interferent is improved and the spectral interferences are diminished. The results obtained are in good agreement with certified values.     

Elimination of interferences in electrothermal-atomization atomic-absorption spectrometry of cadmium

The determination of cadmium by use of a molybdenum-tube atomizer and atomic-absorption spectrometry has been investigated. The absorption profiles for various cadmium compounds and the interferences caused by large amounts of concomitants were evaluated. Sulphur was tested as a matrix modifier for removal of interference and found to be effective at the interferent levels likely to be found in biological samples. A simple, precise and convenient method for determination of cadmium in biological materials has been established.     

A simple spectrophotometric determination of phorate using J-acid

Summary A new and simple spectrophotometric method for the determination of phorate, also known as Thimet, a widely used systemic insecticide is proposed. The method is based on the oxidation of phorate to sulphones by concentrated sulphuric acid and its hydrolysis under acidic conditions at 100°C to release formaldehyde which is then treated with J-acid to produce a yellow fluorescent color, which has an absorbance maximum at 470 nm. Beer's law is obeyed in the range of 1–8 ppm of phorate. The method has been applied to the determination of phorate in effluent water, rice, wheat and cabbage samples. The method is free from interferences of most of the commonly used pesticides and other common ions.     

Determination of traces of gallium and indium in ores by electrothermal-atomization atomic absorption spectrometry with matrix modifications

Methods were developed for the determination of gallium and indium in complex ores by electrothermal-atomization atomic absorption Spectrometry using matrix modifications. Nickel and nickel-ammonium sulfate as matrix modifier has enhanced the absorption signals for gallium and indium, respectively, eliminating the matrix interferences to allow their solutions in nitric acid to be used as calibration standards. No matrix separations are necessary. Results are quoted for a variety of black ore samples (Kuroko). The RSDs are 7.0% for gallium and 5.3% for indium at their 10 g/g levels, and the inverse sensitivities are 20 pg of gallium and 38 pg of indium for respective 1% absorption.     

Functionalization of cross linked chitosan with 2-aminopyridine-3-carboxylic acid for solid phase extraction of cadmium and zinc ions and their determination by atomic absorption spectrometry

We have developed a new method for solid phase extraction (SPE) and preconcentration of trace amounts of cadmium and zinc using cross linked chitosan that was functionalized with 2-aminopyridine-3-carboxy acid. Analytical parameters, sample pH, effect of flow rate, sample volume, and concentration of eluent on column SPE were investigated. The effect of matrix ions on the recovery of cadmium and zinc has been investigated and were found not to interfere with preconcentration. Under the optimum experimental conditions, the preconcentration factors for Cd(II) and Zn(II) were found to be 90. The two elements were quantified via atomic absorption spectrometry. The detection limits for cadmium and zinc are 21 and 65?ng?L^?1, respectively. The method was evaluated by analyzing a certified reference material (NIST 1643e; water) and has been successfully applied to the analysis of cadmium and zinc in environmental water samples.

Separation and determination of gold from iron rich matrices by an off/on-line preconcentration system coupled to ICP-AES

A preconcentration/separation method has been developed for the off/on-line determination by ICP-AES of gold in complex matrices, containing iron and manganese which cause severe spectral interferences on the two most sensitive Au-lines. The available automated preconcentration apparatus was modified using as absorbent the highly selective, for precious metals, chelating anion exchanger SRAFION NMRR. From the elution of this resin with 5% thiourea a nearly quantitative recovery of gold and its separation from iron, existing in percent range in the matrix, and from manganese was obtained. The validity of the developed method was tested by the determination of gold in standard reference materials from BCR, such as sewage sludge of domestic and mainly industrial origin and in a calcareous loam soil. The preconcentration procedure was synchronized with the ICP operating parameters in order to get an optimised on-line coupling of these two systems. The described process has been successfully applied to the determination of low gold contents in dissolved iron rich sediments using for the gold prospection.     

Chromatographic behavior of cadmium in an ion-pair reversed-phase micro HPLC system and its application to the determination of bio-available cadmium in soil samples

A novel reversed phase ion-pair micro HPLC system with on-line fluorescence detection has been developed systematically and studied for the determination of cadmium in its bio-available fractions of soil samples. In this system, a micro ODS column of 1.0 mm i.d.×150 mm length and a mobile phase containing 6 mmol L^-1 8-hydroxyquinoline 5-sulphonic acid (HQS), 3 mmol L^-1 cetyltrimethylammonium bromide (CTMABr), 10 mmol L^-1 acetic acid-acetate buffer (pH 5.1) as well as 50% acetonitrile at 50 L min^-1 flow rate were employed to determine cadmium with a 2 L flow cell through its fluorescence at 518 nm under 338 nm excitation. Furthermore, the composition of Cd-HQS chelate formed on the column was confirmed to be [Cd(HQS)₂]^2- through a log–log plot method, and then combined with the ion-pair reagent by the electrostatic force under the chromatographic condition proposed. With such a method, the detection limit of cadmium was 8.48 ng mL^-1 (3) with 1 L sample injection, and the linear range for the determination of cadmium was 30–800 ng mL^-1 (R²=0.992). This method has been successfully applied to determination of cadmium in its bio-available fractions of BCR-483 and soil samples without interference from other coexistent metal ions. The RSD (n=6) was less than 7.3%. The results were in agreement with the indicative value for BCR-483 and those for the soil samples obtained by ICP-MS with a pretreatment of bis(1,1,3,3-tetramethylbutyl) phosphinic acid extraction.     

Direct determination of cadmium in biological material using electrothermal atomization atomic absorption spectrometry with a metal tube atomizer and a matrix modifier

A direct determination of cadmium by electrothermal atomization atomic absorption spectrometry with a molybdenum tube atomizer has been investigated. Direct calibration method with cadmium standard solutions and ultrasonic agitation method of a solution including sample powder were used. Sulfur served as a matrix modifier for removal of interferences. Though this direct analytical method for cadmium determination in biological materials had a relatively large standard deviation, the accuracy was similar or superior to those of a sample digestion method and the direct analysis without sulfur. The advantages of this method are its simplicity, low cost, high speed of analysis, and rapid calibration.     

Complexometric determination of cadmium using 2-Mercaptoethanol as masking reagent

A complexometric method for the determination of cadmium(II) in presence of other metal ions is described based on the selective masking ability of 2-mercaptoethanol towards cadmium(II). Cadmium and other ions in a given sample solution are initially complexed with excess of EDTA and the surplus EDTA is titrated with lead nitrate solution at pH 5.0–6.0 (hexamethylentetramine), using xylenol orange as indicator. A known excess of 2-mercaptoethanol solution (10% alcoholic) is then added, the mixture is shaken well and the released EDTA from the Cd-EDTA complex is titrated against standard lead nitrate solution. The interferences of various ions are studied and the method is applied to the determination of cadmium in its complexes. Reproducible and accurate results are obtained for 3.5–25mg of Cd with relative errors 0.65% and standard deviations 0.06 mg.     

Microwave treatment of biological samples for methylmercury determination by high performance liquid chromatography-cold vapour atomic fluorescence spectrometry

A simple and rapid microwave-assisted alkaline digestion procedure was developed in combination with high performance liquid chromatography-ultraviolet post-column oxidation-cold vapour atomic fluorescence spectrometric detection for methylmercury determination in biological tissues. Since the stability of methylmercury in methanolic potassium hydroxide solution under microwave irradiation was verified, the microwave-assisted extraction procedure was optimized in terms of quantitative recovery of methylmercury and minimum time required. The alkaline extracts were subjected to clean-up steps with dichloromethane and hydrochloric acid in order to reduce matrix interferences in methylmercury determination. The effects of matrix interferences were checked by comparison of the slopes corresponding to calibration and standard addition curves. The accuracy of the method was evaluated by the analysis of two biological certified reference materials, NRC TORT-2 and BCR 463. The results obtained by the proposed method were in good agreement with the certified values of methylmercury concentration in both materials. The detection limit was 10 microg kg(-1) and the relative standard deviation was < 8% for methylmercury concentrations ranging from 0.15 to 3.0 mg kg(-1).     

Determination of cadmium in biological samples by inductively coupled plasma atomic emission spectrometry after extraction with 1,5-bis[phenyl-(2-pyridyl)methylene]-thiocarbonohydrazide

A systematic study was made of the optimum conditions for cadmium determination in biological samples by ICP-AES after extraction of the metal into methyl isobutyl ketone containing 1,5-bis[phenyl-(2-pyridyl)methylene]-thiocarbonohydrazide. The maximum volume ratio of aqueous to organic phase was 30 1 for a single-stage extraction of 99–100% of the metal ion. The detection limit was 0.3 ng/ml cadmium, and the calibration was linear from 0.4 to at least 150 ng/ml. No interferences from the elements commonly found in biological materials were observed. A precision of 2.5% (P = 0.05) at the 2 ng/ml level of the metal was achieved. The accuracy of the method was demonstrated by analysis of three standard reference materials, giving concentrations of 1.90 ± 0.43, 27.1 ± 1.4 and 2.63 ± 0.38 /g of cadmium, compared with the certified values of 2.20 ± 0.10, 26.3 ± 2.1, and 2.71 ± 0.15 g/g, respectively.     

Element fingerprinting of marine organisms by dynamic reaction cell inductively coupled plasma mass spectrometry

A method for the determination of sixteen elements (Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Se, Sn, V, Zn) in seafood by dynamic reaction cell inductively coupled plasma mass spectrometry (ICP–DRC–MS) is presented. A preliminary study of polyatomic interferences was carried out in relation to the chemical composition of marine organisms belonging to different taxa. Acid effects and other matrix effects in marine organisms submitted to closed-vessel microwave digestion were investigated as well. Ammonia was the reactive gas used in the DRC to remove polyatomic ions interfering with ²⁷Al, ⁵²Cr, ⁵⁶Fe and ⁵¹V. Optimal conditions for the simultaneous determination of analytes were identified in order to develop a fast multielement method. A suite of real samples (mussels and various fish species) were used during method development along with three certified reference materials: BCR CRM 278R (mussel tissue), BCR CRM 422 (cod muscle) and DORM-2 (dogfish muscle). The proposed analytical approach can be used in conjunction with suitable chemometric procedures to address quality and safety issues in aquaculture and fisheries. As an example, a case study is described in which mussels from three farming sites in the Venice Lagoon were distinguished by multivariate analysis of element fingerprints.      

A comparison of some flame atomic absorption spectrometric methods for the determination of cadmium in fertilizers and related materials

A liquid-liquid extraction procedure for cadmium in phosphate rock and phosphate-based fertilizers is described. Extraction with tri-n-octylamine and potassium iodide into methyl isobutyl ketone is shown to be simpler and less prone to interferences than the more commonly used methods based on ammonia pyrrolidine-dithiocarbamate. Iron interest strongly in the dithiocarbamate method. Addition of ascorbic acid, and extraction at low pH allows the dithiocarbamate method to operate up to 0.15 g Fe l^?1, while the amine method tolerates at least 0.2 g Fe l^?1. Direct determination is suitable on samples with a sufficiently high cadmium content. The amine extraction method has been applied successfully at an apatite containing only 0.03 mg kg^?1 cadmium.     

Effect of ethylenediamine on the anodic stripping voltammetric determination of heavy metals in the presence of humic acid

Ligand competition coupled with differential pulse anodic stripping voltammetry has been investigated for the determination of copper, lead and cadmium. Ethylenediamine displaces humic acid in its metal complexes forming kinetically labile compounds. It also eliminates interferences associated with the oxidation of copper. This enhances the sensitivity of the determination of the metals over a wide range of humic acid concentration (up to 30 mg/l). The procedure has been applied to the determination of heavy metals in a real water sample.     

Preconcentration and Separation Procedures for the Spectrochemical Determination of Platinum and Palladium

Low concentrations of Pt and Pd in industrial (µgg^–1 level) and environmental samples (ngg^–1 level) together with the complexity of the matrix causing many interferences during the determination of noble metals often require elaboration and application of pre-concentration/matrix separation procedures before detection of the analyte. Different pre-concentration/matrix separation procedures applied prior to the determination of Pt and Pd by atomic spectrometric techniques are reviewed and critically compared taking into account potential interferences. The methods studied are divided into 5 groups including precipitation and coprecipitation, liquid–liquid extraction, solid phase extraction, electrochemical pre-concentration and biosorption. The main analytical problems occuring during sample preparation and storage are discussed.     

Liquid-liquid extraction and spectrophotometric determination of cadmium with 1,10-phenanthroline and thymol blue

A simple and highly sensitive extraction spectrophotometric method was developed for the determination of traces of cadmium. The method is based on the preconcentrative extraction of ternary-ion-association complex of cadmium—1,10-phenanthroline-thymol blue into chloroform and subsequent determination by spectrophotometry. The ternary ion associate is stable for 20 h and cadmium content as low as 0.1 g in 90 ml of sample can be determined. The method is precise and has been applied to the determination of cadmium in sea water, solder and high purity zinc and indium materials.