Evaluation of new high-frequency discharge lamps for atomic absorption and atomic fluorescence spectrometry of cadmium,lead and zinc

High-frequency discharge lamps with a hollow electrode are successfully utilized as the spectral line sources for atomic absorption and atomic fluorescence spectrometry of cadmium, lead and zinc. The sensitivities for atomic absorption spectrometry are superior to those obtained with commercially available hollow-cathode lamps by factors of 1.5 (Cd), 1.4 (Pb) and l.6 (Zn). Detection limits for non-dispersive atomic fluorescence spectrometry with graphite furnace atomization are 1 × 10^-13 g (Cd), 3 × 10^-11 g (Pb) and 2 × 10^-13 g (Zn). The linear analytical range covers over four (Cd, Zn) and three (Pb) decades of concentration above the detection limits.     

Disposable Bismuth Oxide Screen Printed Electrodes for the High Throughput Screening of Heavy Metals

We present a simplified approach for the trace screening of toxic heavy metals utilizing bismuth oxide screen printed electrodes. The use of bismuth oxide instead of toxic mercury films facilitates the reliable sensing of lead(II), cadmium(II) and zinc(II). A linear range over 5 to 150 μg L^?1 with detection limits of 2.5 and 5 μg L^?1 are readily observed for cadmium and lead in 0.1 M HCl, respectively. Conducting a simultaneous multi‐elemental voltammetric detection of zinc, cadmium and lead in a higher pH medium (0.1 M sodium acetate solution) exhibited a linear range between 10 and 150 μg L^?1 with detection limits of 5, 10 and 30 μg L^?1 for cadmium, lead and zinc respectively. The sensor is greatly simplified over those recently reported such as bismuth nanoparticle modified electrodes and bismuth film coated screen printed electrodes. The scope of applications of this sensor with the inherent advances in electroanalysis coupled with the negliable toxicity of bismuth is extensive allowing high throughput electroanalysis.     

A Study of Nafion‐Coated Bismuth‐Film Electrode for the Determination of Zinc,Lead, and Cadmium in Blood Samples

In this article a sensitive differential pulse stripping voltammetry technique on Nafion‐coated bismuth‐film electrode (NCBFE) was studied for the simultaneous determination of zinc, cadmium, and lead ions in blood samples at ultra trace levels. The measurement results were in excellent agreement with those obtained from atomic absorption spectroscopy. Various operational parameters were investigated and discussed in terms of their effect on the measurement signals. Under optimal conditions, calibration curves for the simultaneous determination of zinc, cadmium, and lead ions were achieved, based on three times the standard deviation of the baseline, the limits of detection were 0.09 μg L^?1 for Cd(II), 0.13 μg L^?1 for Pb(II), and 0.97 μg L^?1 for Zn(II) respectively.     

Screen-printed electrodes incorporated in a flow system for the decentralized monitoring of lead,cadmium and copper in natural and wastewater samples

Mercury-based screen-printed electrodes (SPE) combined with square-wave anodic stripping voltammetry (SWASV) techniques for the analysis of copper, cadmium, lead, and zinc in different water samples have been applied. The detection system has been implemented in a flow cell and different experimental conditions have been tested in view of its application for in-situ monitoring. In particular, an acetate buffer together with a low chloride concentration (0.025?M NaCl) provided best performance and reproducible results. Additionally, the flow system was validated for the first time in terms of limits of detection, linearity, repeatability and recovery. Limits of detection of 2.8?µg?L^?1, 4.1?µg?L^?1, and 7.5?µg?L^?1 for cadmium, lead and copper respectively and repeatabilities lower than 10% (as RSD) were found. Good recoveries have been obtained for the three cations and in particular for copper, even in the presence of zinc. Finally, the method has shown its efficiency for the rapid screening of lead, cadmium and copper contained in both natural waters and wastewater samples.     

Simultaneous determination of iron,cadmium and lead in zinc by proton activation analysis

Iron, cadmium and lead are determined in zinc by proton activation followed by chemical separation of the indicator radionuclides. The method provides detection limits of 0.03, 0.008 ad 0.1 μg g^?1 for iron, cadmium and lead, respectively. The BCR Unalloyed Zinc reference material 321 was analysed. Concentrations of 2.23, 0.215 and 4.641 μg g^? with 1–7% relative standard deviation were obtained for iron, cadmium and lead, respectively. These results contributed to the provisional certification of the reference material.     

Cloud point extraction for the determination of cadmium and lead employing sequential multi-element flame atomic absorption spectrometry

A cloud point extraction procedure for pre-concentration and determination of cadmium and lead in drinking water using sequential multi-element flame atomic absorption spectrometry is described. 4-(2-thiazolylazo)-orcinol (TAO) has been used as complexing agent and the micellar phase was obtained using the non-ionic surfactant octylphenoxypolyethoxyethanol (Triton X-114) and centrifugation. The conditions for reaction and extraction (surfactant concentration, reagent concentration, effect of incubation time, etc) were studied and the analytical characteristics of the method were determined. The method allows the determination of cadmium and lead with quantification limits of 0.30?µg?L^?1 and 2.6?µg?L^?1, respectively. A precision expressed as relative standard deviation (RSD, n?=?10) of 2.3% and 2.6% has been obtained for cadmium concentrations of 10?µg?L^?1 and 30?µg?L^?1, respectively, and RSD of 1.3% and 1.7% for lead concentrations of 10?µg?L^?1 and 30?µg?L^?1, respectively. The accuracy was confirmed by analysis of a natural water certified reference material. The method has been applied for the determination of cadmium and lead in drinking water samples collected in the cities of Ilhéus and Itabuna, Brazil. Recovery tests have also been performed for some samples, and results varied from 96 to 105% for cadmium and 97 to 106% for lead. The cadmium and lead concentrations found in these samples were always lower than the permissible maximum levels stipulated by World Health Organization and the Brazilian Government.     

Glucose oxidase inhibition in poly(neutral red) mediated enzyme biosensors for heavy metal determination

A biosensor for the determination of heavy metal cations based on glucose oxidase enzymatic inhibition has been developed. The biosensor was assembled on carbon film electrode supports with glucose oxidase immobilised by cross-linking with glutaraldehyde on top of a film of poly(neutral red) as redox mediator, prepared by electropolymerisation. The biosensor was used to determine the metallic cations, cadmium, copper, lead and zinc in the presence of chosen amounts of glucose. The detection limits were found to be 1 μg L^?1 for cadmium, 6 μg L^?1 for copper, 3 μg L^?1 for lead and 9 μg L^?1 for zinc. Inhibition constants were determined by using the Dixon plot, and the type of inhibition induced by the metallic cations was evaluated from Cornish-Bowden plots plus Dixon plots, it being found that the inhibition is reversible and competitive for cadmium, mixed for copper and lead and uncompetitive for zinc. Copper-inhibited glucose oxidase to a greater extent followed by cadmium, lead and zinc. Regeneration of the glucose oxidase response was studied by using Ethylene diamine tetracetic acid metal-chelating agent and the nonionic surfactant Triton X-100. The suitability of the biosensor for determination in foodstuffs or beverages which contain trace concentrations of metals was investigated by performing recovery tests in commercial milk samples.     

Solid-phase preconcentration of cadmium(II) using amino-functionalized magnetic-core silica-shell nanoparticles, and its determination by hydride generation atomic fluorescence spectrometry

We report on the synthesis and evaluation of aminated-CoFe₂O₄/SiO₂ nanoparticles that can serve as a selective solid-phase sorbent for the extraction of cadmium ion. The nanoparticles consist of a magnetic CoFe₂O₄ core and an amino-modified silica shell. They can efficiently extract cadmium(II) ion and then can be isolated from the sample solution due to the magnetic nature of the core. The effects of the experimental conditions on the extraction process were optimized. Cadmium was then quantified by hydride generation atomic fluorescence spectrometry. The resulting calibration curve is linear in the concentration range of 0.01–10 μg?L^?1, the instrumental detection limits (3σ) is 3.15 ng?L^?1 and the relative standard deviation is 4.9 % at the 1.0 μg?L^?1 level (for n?=?11). The enrichment factor is 50 (for 50 mL samples), and the adsorbent can be used for at least 45 cycles of preconcentration and elution. The method was applied to the determination of cadmium in environmental water samples, and successfully validated by analyzing two certified reference materials.

On-line simultaneous pre-concentration procedure for the determination of cadmium and lead in drinking water employing sequential multi-element flame atomic absorption spectrometry

An on-line pre-concentration system for the sequential determination of cadmium and lead in drinking water by using fast sequential flame atomic absorption spectrometry (FS-FAAS) is proposed in this paper. Two minicolums of polyurethane foam loaded with 2-(6-methyl-2-benzothiazolylazo)-orcinol (Me-BTAO) were used as sorptive pre-concentration media for cadmium and lead. The analytical procedure involves the quantitative uptake of both analyte species by on-column chelation with Me-BTAO during sample loading followed by sequential elution of the analytes with 1.0?mol?L^?1 hydrochloric acid and determination by FS-FAAS. The optimisation of the entire analytical procedure was performed using a Box–Behnken multivariate design utilising the sampling flow rate, sample pH and buffer concentration as experimental variables.

The proposed flow-based method featured detection limits (3σ) of 0.08 and 0.51?µg?L^?1 for cadmium and lead, respectively, precision expressed as relative standard deviation (RSD) of 1.63% and 3.87% (n?=?7) for cadmium at the 2.0?µg?L^?1 and 10.0?µg?L^?1 levels, respectively, and RSD of 6.34% and 3.26% (n?=?7) for lead at the 5.0?µg?L^?1 and 30.0?µg?L^?1 levels, respectively. The enrichment factors achieved were 38.6 and 30.0 for cadmium and lead, respectively, using a sample volume of 10.0?mL. The sampling frequency was 45 samples per hour. The accuracy was confirmed by analysis of a certified reference material, namely, SRM 1643d (Trace elements in natural water). The optimised method was applied to the determination of cadmium and lead in drinking water samples collected in Santo Amaro da Purificação City, Bahia, Brazil.     

The determination of lead and nickel by atomic-absorption spectrometry with a flameless wire loop atomizer

In an extension of studies of flameless atomizers for atomic-absorption spectrometry, an electrically heated tungsten-rhenium alloy wire loop was examined. Reduction of metallic salts to ground-state metal atoms was accomplished with the high temperature produced by the loop. Lead and nickel were investigated. Experimental parameters such as wavelength, slit width, atomization temperature and sheathing gas flow rate were optimized. Absolute detection limits of 6.6·10^?10 and 1.2·10^?10, and absolute sensitivities of 7·10^?10 and 8·10^?11 g of lead, were established for unenclosed and enclosed cells, respectively. The interferences of twenty cations and sixteen anions were studied; foreign cations generally enhanced the lead absorption by retarding its vaporization, allowing the slow detection system to respond more efficiently. Nickel was investigated as a representative less volatile metal; an absolute detection limit of 1.6·10^?9 and an absolute sensitivity of 9·10^?10 g of nickel were established.     

Determination of cadmium,copper and lead in urine by flame atomic absorption spectrometry after extraction of the iodide complexes as ion-pairs with tri-n-octylamine

A simple, rapid sensitive atomic absorption spectrometric method is described for the determination of cadmium, copper and lead in urine. The metals are extracted as their iodide complexes with tri-n-octylamine in n-butyl acetate, without elaborate pretreatment, and measured by direct nebulization of the extract into an air/ acetylene flame. Detection limits for cadmium, copper and lead in urine were 0.008, 0.05 and 0.02 × 10^?6 mol l^?1, respectively.     

Determination of cadmium,indium and zinc in nickel—base alloys by atomic absorption spectrometry with introduction of solid samples into furnaces

Atomic absorption spectrometry with an induction furnace is used for the determination of cadmium (0.002–2 μg g^-1), indium (0.6–350 μg g^-1) and zinc (0.05–26 μg g^-1) in 0.8–35 mg samples of nickel—base alloys dropped into the furnace. A resistively-heated furnace is employed for the determination of lower concentrations of indium (<0.6 μg g^-1). Standardised alloys were used for calibration. Accuracy, precision and detection limits are described for numerous nickel—base alloys. With alloys containing zinc, > 0.1 μg Cd g^-1 and >0.6 &,mu;g In g^-1, the relative standard deviations are 12%, 8% and 7%, respectively. Calculated detection limits for cadmium, indium and zinc are 2 ng g^-1, 10 ng g^-1 and 10 ng g^-1, respectively.     

Enzymatic determination of cadmium,zinc, and lead in plant materials

Prospects are outlined for using the following enzymes (native and immobilized on polyurethane foam) in the rapid and highly sensitive determination of cadmium, zinc, and lead ions in plant materials (wild grass, fresh pea, and grape): horseradish peroxidase and alkaline phosphatases isolated from chicken intestine and Greenland seal small intestine. The analytical ranges of the above metals are 1 × 10^–3?25, 7 × 10^?3?250, and 3 × 10^?2?67 mg/kg dry matter, respectively. The enzymatic determination procedures developed are based on the inhibiting effect of metal ions on the catalytic activity of peroxidase in the oxidation of o-dianisidine with hydrogen peroxide and alkaline phosphatases in the hydrolysis of p-nitrophenyl phosphate. The rates of enzymatic reactions were monitored spectrophotometrically or visually. In the analysis of plant extracts, their high acidity was diminished by choosing optimum dilution factors and pH values for test samples and the nature and concentration of a buffer solution. The interference of iron(III) was removed by introducing a 0.1 M tartaric acid solution into the indicator reaction. The accuracy of the results of the enzymatic determination of cadmium, zinc, and lead in plant materials was supported by atomic absorption spectrometry and anodic stripping voltammetry.     

A New Highly Sensitive Preconcentrating Sampling Technique for Flameless Atomatic Absorption Spectroscopy

Abstract

A new technique for sampling metal ions in solution for flameless atomic absorption has been developed. A tungsten alloy wire loop is soaked in the sample solution for a specified period of time. Metal ions are concentrated on the surface of the wire loop apparently by an ion exchange mechanism. The wire loop is then used as an electrically heated atomizer for atomic absorption spectroscopy. Detection limits of 4 × 10^?14 grams for cadmium and 2 × 10^?11 grams for lead have been achieved.     

Sequential Voltammetric Determination of Uranium,Cadmium and Lead by Using the ex situ Bismuth Film Electrode: Application to Phosphate Fertilizers

A sequential voltammetric procedure for the determination of uranium, cadmium and lead was investigated at an ex situ bismuth film electrode (BiFE). First, the adsorptive stripping voltammetry was applied to assay the U(VI)‐cupferron complex in the differential pulse mode (detection limit of 1.0 µg L^?1, 200 s accumulation time). Through the manipulation of the same aliquot of the sample, efforts were made to quantify cadmium and lead by square wave anodic stripping voltammetry. Detection limits of 2.03 µg L^?1 for Cd (II) and 2.43 µg L^?1 for Pb (II) were calculated (100 s accumulation time). The methodology was successfully applied to phosphate fertilizer samples after open vessel wet decomposition (HNO₃/H₂O₂). The following value ranges were evaluated: U (VI) 37.2–150 mg kg^?1, Pb (II) 78.3–204 mg kg^?1 and Cd (II) 44.1–71.6 mg kg^?1. Validation was performed by using the standard reference materials SRM‐695 – phosphate fertilizer – and SRM‐1643e – water.     

Square-Wave Anodic Stripping Voltammetry (SWASV) for the Determination of Ecotoxic Metals,Using a Bismuth-Film Electrode

This article reviews the use of square wave anodic stripping voltammetry for the simultaneous determination of ecotoxic metals (Pb, Cd, Cu, and Zn) on a bismuth-film (BiFE) electrode. The BiFE was prepared in situ on a glassy-carbon electrode (GCE) from the 0.1 mol L^?1 acetate buffer solution (pH 4.5) containing 200 µg L^?1 of bismuth (III). The addition of hydrogen peroxide to the electroanalytical cell proved beneficial for the interference-free determination of Cu (II) together with zinc, lead, and cadmium, using the BiFE. The experimental variables were investigated and optimized with the view to apply this type of voltammetric sensor to real samples containing traces of these metals. The performance characteristics, such as reproducibility, decision limit (CC_a), detection capability (CC_β), sensitivity, and accuracy indicated that the method holds promise for trace Cu²⁺, Pb²⁺, Cd²⁺, and Zn²⁺ levels by employment of Hg-free GCE with SWASV. CCa, and CCβ were calculated according to the Commission Decision of 12 August 2002 (2002/657/EC). Linearity was observed in the range 20–280 µg L^?1 for zinc, 10–100 µg L^?1 for lead, 10–80 µg L^?1 for copper, and 5–50 µg L^?1 for cadmium. Using the optimized conditions, the stripping performance of the BiFE was characterized by low limits of detection (LOD). Finally, the method was successfully applied in real as well as in certified reference water samples.     

Determination of bismuth,cadmium and lead in soil extracts by atomic absorption spectrometry with loop sample introduction

Bismuth, cadmium and lead in soil extracts with aqua regia, 2 M nitric acid, 2.5% acetic acid or ammonium acetate solution from top-soils at different locations in Turkey, were determined by atomic absorption spectrometry with loop sample introduction. Detection limits were 0.8, 0.025 and 0.5 μl^?1 for bismuth, cadmium and lead, respectively, after concentration with ammonium pyrrolidinedithiocarbamate. Use of a silica tube for atom trapping improved the detection limits.     

Cadmium and Lead Distribution in Marine Soil Sediments,Terrestrial Soil,Terrestrial Rock,and Atmospheric Particulate Matter around Split,Croatia

The distributions of cadmium and lead in marine sediments, surrounding soil, stones, and atmospheric particulate matter were determined at different locations in Split, Croatia. The determination of cadmium and lead was performed by flame atomic absorption spectrometry whereas atmospheric particulate matter samples were analyzed by inductively coupled plasma–optical emission spectrometry. Cadmium concentrations in the stones and soil were between 0.2 to 0.6 µg g^?1 and 0.2 to 0.9 µg g^?1. The concentration in the atmospheric particulate matter were <0.2 µg m^?2 d^?1(detection limit) to 1.4 µg m^?2 d^?1. Lead concentrations in marine sediments, stones, soil, and atmospheric particulate matter ranged from 31.2 to 144.4 µg g^?1, 9.3 to 29.4 µg g^?1, 11.3 to 66.1 µg g^?1, and 0.5 to 241.4 µg m^?2 d^?1, respectively. The relationship between determined parameters was established using principal component analysis and the results are in agreement with the assumption that anthropogenic sources play important roles for lead and cadmium distribution.     

Potentiometric stripping analysis for zinc,cadmium. lead and copper in sea water

Analytical procedures for the determination of zinc(II), cadmium (II), lead(II) and copper(II) in sea water by potentiometric stripping analysis are described. The results are compared with those obtained by a combined solvent extraction-atomic absorption method both in the laboratory and on-board ship. The detection limits for zinc, cadmium, lead and copper are 0.03, 0.03, 0.01 and 0.02 μg l^-1, respectively, for a total analysis time of about 75 min. A very thin mercury film is useful in the determination of lead and copper.     

Determination of trace metals in rain water by differential-pulse stripping voltammetry

Differential-pulse stripping voltammetry is applied to measure zinc, cadmium, lead and copper by anodic stripping and selenium(IV) by cathodic stripping in rain water at pH 2; subsequently, at pH 9,1, manganese is measured by anodic stripping on the same portion, and cobalt and nickel are measured in the adsorptive mode after formation of their dimethylglyoximates. The instrumental parameters are optimized. The linear ranges, mutual interferences and detection limits are studied. Excellent accuracy is demonstrated; the standard deviation is around 15% at 2.5–50 μg l^?1 levels. The method is shown to be applicable for rain water.