Determination of cadmium,copper and lead in mineral coal using solid sampling graphite furnace atomic absorption spectrometry

Solid sampling graphite furnace atomic absorption spectrometry (SS-GF AAS) was investigated as a potential technique for the routine determination of trace elements in mineral coal and cadmium, copper and lead were chosen as the model elements. Cadmium and lead could be determined at their main resonance lines at 228.8 nm and 283.3 nm, respectively, but an alternate, less sensitive line had to be used for the determination of copper because of the high copper content in coal. No modifier was necessary for the determination of copper and calibration against aqueous standards provided sufficient accuracy of the results. For the determination of cadmium and lead two different modifiers were investigated, palladium and magnesium nitrates in solution, added on top of each sample aliquot before introduction into the atomizer tube, and ruthenium as a ‘permanent’ modifier. Both approaches gave comparable results, and it is believed that this is the first report about the successful use of a permanent chemical modifier in SS-GF AAS. Calibration against solid standards had to be used for the determination of cadmium and lead in order to obtain accurate values. The agreement between the values found by the proposed procedure and the certificate values for a number of coal reference materials was more than acceptable for routine purposes. The detection limits calculated for 1 mg of coal sample using the ‘zero mass response’ were 0.003 and 0.007 μg g⁻¹ for cadmium with the permanent modifier and the modifier solution, respectively, approximately 0.04 μg g⁻¹ for lead, and 0.014 μg g⁻¹ for copper.     

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.     

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,Copper, and Cadmium by Adsorptive Stripping Voltammetry in the Presence of Thymolphthalexone

A novel, sensitive and selective adsorptive stripping procedure for simultaneous determination of iron, copper and cadmium is presented. The method is based on the adsorptive accumulation of thymolphthalexone (TPN) complexes of these elements onto a hanging mercury drop electrode, followed by reduction of adsorbed species by voltammetric scan using differential pulse modulation. The influences of control variables on the sensitivity of the proposed method for the simultaneous determination of iron, copper and cadmium were studied using the Derringer desirability function. The optimum analytical conditions were found to be TPN concentration of 2.0 μM, pH of 9.5, and accumulation potential at ?0.4 V vs. Ag/AgCl with an accumulation time of 60 s. The peak currents are proportional to the concentration of iron, copper and cadmium over the 1–80, 0.5–100 and 1–100 ng mL^?1 ranges with detection limits of 0.5, 0.4 and 0.9 ng mL^?1_, respectively. The R.S.D. at a concentration level of 20 ng mL^?1 of iron, copper and cadmium were 2.5%, 0.9% and 1.5% (n=6), respectively. The procedure was applied to the simultaneous determination of iron, copper and cadmium in the tap water and some synthetic samples with satisfactory results.     

Determination of Ultratrace Amounts of Copper and Cadmium in Seawater by Graphite Furnace Atomic Absorption Spectrometry with Flow-Injection Semi On-line Preconcentration

Methods are described for the determination of ultratrace amounts of copper and cadmium in seawater by graphite furnace atomic absorption spectrometry with flow-injection, microcolumn preconcentration. A new type of C₁₈ column loaded with sodium diethyldithiocarbamate (sodium-DDC) was used to extract copper and cadmium from seawater as the DDC chelates. The analytical effects of the pH of the mixture of the sample and sodium-DDC solutions and the concentration of the chelating reagent were studied. Sodium-DDC-loaded columns and unloaded C₁₈ columns with different shapes and volumes were compared. To determine copper in seawater, a simple aqueous calibration was made with a mixture of palladium and magnesium nitrate as a matrix modifier, while for cadmium no matrix modifier was necessary. This method required only small seawater volumes, 600 and 400 μl for the determination of copper and cadmium respectively, with preconcentration factors of 15-fold for copper and 10-fold for cadmium. Detection limits for the preconcentration of aqueous solutions of copper and cadmium were 0.024 and 0.004 μg liter⁻¹ (3σ), respectively. Results for determinations of copper and cadmium in National Research Council of Canada, CASS-2, Nearshore Seawater Reference Material showed no significant differences between the certified values and the measured values, based on Student′s t test at the 95% confidence level. The relative standard deviations of the various measurements varied between 2 and 8%.     

Activated carbon cloth filled pipette tip for solid phase extraction of nickel(II), lead(II), cadmium(II), copper(II) and cobalt(II) as 1,3,4-thiadiazole-2,5-dithiol chelates for ultra-trace detection by FAAS

A solid phase extraction method is established for preconcentration of nickel, lead, cadmium, copper and cobalt using pipette tip solid phase extraction. The presented process was dependent on chelation of analytes with 1,3,4-thiadiazole-2,5-dithiol, then allowing the solution to flow through an activated carbon cloth packed pipette tip. The adsorbed metal chelates on the surface of activated carbon cloth were eluted by 5 mL of 3 M HNO₃. The concentrations of nickel, lead, cadmium, copper and cobalt were detected using a flame atomic absorption spectrometer (FAAS). The pipette tip solid phase extraction exhibit a preconcentration factor of 120. The limit of detection values were 2.7, 1.7, 1.3, 2.0 and 2.9 µg L^?1 for Ni(II), Pb(II), Cd(II), Cu(II) and Co(II), respectively. Validation of the method was checked by the analysis of TMDA-53.3 and TMDA-64.2 certified reference materials. The method was successfully applied for water and fertiliser samples.     

Use of Nb(2)O(5)-SiO(2) in an automated on-line preconcentration system for determination of copper and cadmium by FAAS

A procedure for the determination of trace level of copper(II) and cadmium(II) by FAAS using an on-line preconcentration system has been proposed. In this system, copper and cadmium ions were adsorbed onto a minicolumn packed with silica gel modified with niobium(V) oxide (Nb₂O₅-SiO₂), followed by nitric acid elution in reverse mode and determination on-line by flame atomic absorption spectrometry (AAS) without interference of the matrix. Chemical and flow variables as well as concomitant ions were studied in the developed procedure. The enrichment factor for copper(II) and cadmium(II) was 34.2 and 33.0, respectively, using a preconcentration time of 2 min. The limit of detection for copper(II) and cadmium(II) was 0.4, and 0.1 μg l⁻¹, respectively. The precision of the method, evaluated as the relative standard deviation in solutions containing 15 μg l⁻¹ of copper and 10 μg l⁻¹ of cadmium, by analyzing a series of seven replicates, was 1.8 and 1.6%, respectively. The accuracy was assessed through recovery experiments of certified material and water samples.     

Use of a nitrate-form anion exchange resin for the determination of traces of gold in copper and cadmium by neutron activation analysis

A method is described for the determination of traces of gold in copper and cadmium by neutron activation analysis, using anion exchange resin as a preconcentration agent: gold was separated from large amount of copper or cadmium with Cl-form Dowex 1X8 AG, 100–200 mesh, resin. To reduce the interfering activities, the resin was irradiated in NO ₃ ⁻ -form and washed with dilute hydrochloric acid after irradiation.¹⁹⁸Au in the resin was then counted with a Ge(Li) or NaI(Tl) detector. The chemical yields were more than 99%. The concentration factors of gold for copper and cadmium samples were 1.1×10⁸ and 2.7×10⁶, respectively. The analytical results of gold in 99.99% copper and 99.999% cadmium were 65 and 0.15 ppb, respectively. The blank was 0.05 ng Au per 200 mg of wet resin.     

Biosorption of Copper and Cadmium in Packed Bed Columns with Live Immobilized Fungal Biomass of <Emphasis Type="Italic">Phanerochaete chrysosporium</Emphasis>

Biosorption of copper (II) and cadmium (II) by live Phanerochaete chrysosporium immobilized by growing onto polyurethane foam material in individual packed bed columns over two successive cycles of sorption–desorption were investigated in this study. Initial pH and concentrations of the metals in their respective solutions were set optimum to each of those: 4.6 and 35 mg·l⁻¹ in case of copper and 5.3 and 11 mg·l⁻¹ for cadmium. The breakthrough curves obtained for the two metals during sorption in both the cycles exhibited a constant pattern at various bed depths in the columns. The maximum yield of the columns in removing these metals were found to be, respectively, 57% and 43% for copper and cadmium indicating that copper biosorption by the immobilized fungus in its column was better than for cadmium. Recovery values of the sorbed copper and cadmium metals from the respective loaded columns by using 0.1 N HCl as eluant was observed to be quite high at more than 65% and 75%, respectively, at the end of desorption in both the cycles. Breakthrough models of bed-depth service time, Adams–Bohart, Wolborska, and Clark were fitted to the experimental data on sorption of copper and cadmium in the columns, and only the Clark model could fit the sorption performance of the columns well over the entire range of ratios of concentrations of effluent to influent, i.e., C/C ₀ for both copper and cadmium biosorption. The kinetic coefficients of mass transfer and other suitable parameters in the system were determined by applying the experimental data at C/C ₀ ratios lower than 0.5 to the other three models.     

Stripping Potentiometry of Lead,Cadmium and Copper at a Nafion Coated Glassy Carbon Electrode with Encapsulated Mercury Acetate

Abstract

The stripping potentiometric determination of lead, cadmium and copper with mercury film glassy-carbon electrodes coated with a Nafion membrane was investigated. The mercury film was plated using either mercury(II) acetate encapsulated within the Nafion membrane or a mercury(II) solution. Dissolved dioxygen was used as the stripping agent. The electrodes showed promising properties, particularly robustness and response repeatability. A linear dependence of the stripping time on concentration was found in the μg l^?1 concentration range (s.d. of intercept ≤ 0.3 μg l^?1, r.s.d. of slope ≤ 1%, for both lead and cadmium).     

In-Situ Investigation of Discolouration Processes Between Historic Oil Paint Pigments

Discolouring interactions between paint pigments have been observed since the mid 19^th century. The source of some of these discolourations is the production of copper sulfides from an interaction between cadmium sulfide pigments and copper containing pigments. In this work, the discolouring interaction between cadmium yellow and malachite pigments was observed dynamically using the environmental scanning electron microscope (ESEM).     

Chronopotentiometric and controlled-potential electrolytic studies of the formation of intermetallic compounds in copper-zinc,platinum-zinc,and other amalgams

The behaviors of amalgams containing: copper and zinc; platinum and zinc; platinum and cadmium; silver and zinc; silver and cadmium; cadmium and copper; cadmium, copper and platinum; and silver, nickel and zinc were investigated by controlled-potential electrolysis and chronopotentiometry. Copper-zinc amalgams contain the compound CuZn, for which the solubility product at 25°C is equal to (3.8±0.6)×10^?6M², and also a soluble but sparingly dissociated compound that is richer in zinc. Platinum-zinc amalgams contain PtZn₂, PtZn₃ and PtZn₄ in metastable equilibrium. Gold-cadmium amalgams contain the compound AuCd, whose solubility product at 25°C is equal to (1.7±0.1)×10^?5M². Compound formation could not be detected in silver-zinc, silver-cadmium, cadmium-copper, platinum-copper or cadmium-copper-platinum amalgams, but there was an uncertain indication that silver-nickel-zinc amalgams might contain the first ternary intermetallic compound found in amalgams.     

Electrochemical Detection of Trace Concentrations of Cadmium and Lead with a Boron‐Doped Diamond Electrode: Effect of KCl and KNO3 Electrolytes,Interferences and Measurement in River Water

Parts‐per‐billion levels of cadmium and lead were detected using square‐wave anodic stripping voltammetry with a boron‐doped diamond electrode. Calibration plots (10‐minute deposition time) in KCl and KNO₃ were non‐linear at low concentrations (1–5 ppb) due to the deposition mechanism of these metals. The preferred electrolyte for cadmium was KCl, while lead could be measured in either electrolyte. The lowest concentrations included in the linear portion of the calibration plot (5 minute deposition time) for cadmium were 10 ppb and 50 ppb in KCl and KNO₃, respectively, and 10 ppb for lead in KNO₃. The presence of either lead or copper suppressed the cadmium stripping peak, but the lead stripping peak was unaffected by cadmium, and enhanced by the addition of copper. A river water sample was analyzed for cadmium and lead, and the cadmium results were confirmed using ICP‐AES spectrometry. It was determined electrochemically that a fraction of lead in the river sample was bound by complexing material in the sample.     

Removal of Cu(II), Cd(II) and Cr(III) ions from aqueous solution by dam silt

The removal of heavy metals, such as Cu(II), Cd(II) and Cr(III) from aqueous solution was studied using Chorfa silt material (Mascara, Algeria). The main constituents of silt sediment are quartz, calcite and mixture of clays. The experimental data were described using Freundlich, Langmuir, Dubinin–Radushkevich (D–R) and Langmuir–Freundlich models. The adsorbed amounts of chromium and copper ions were very high (95% and 94% of the total concentration of the metal ions), whereas cadmium ion was adsorbed in smaller (55%) amounts. The Langmuir–Freundlich isotherm model was the best to describe the experimental data. The maximum sorption capacity was found to be 26.30, 11.76 and 0.35 mg/g for Cr³⁺, Cu²⁺ and Cd²⁺, respectively. The results of mean sorption energy, E (kJ/mol) calculated from D–R equation, confirmed that the adsorption of copper, chromium and cadmium on silt is physical in nature.     

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.     

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.     

The X-ray fluorescence determination of Cd, Ni, and Zn electrodeposited from aqueous solutions

The concentrations of cadmium, nickel, and zinc in standard solutions were determined by energy-dispersive X-ray fluorescence analysis of deposits prepared by flow electrolysis on graphite cloth electrodes. Reduction of the metal species in solution was complete only if cadmium or zinc was the major constituent (80 or 90 mole%, respectively). Deposits of cadmium and zinc, and cadmium-rich Cd---Ni, Cd---Zn, and Cd---Ni---Zn deposits were analysed. For pure metals the detected X-ray intensity displayed a power-law relationship, Rn^p, for up to 10⁻⁴ moles. The enhancement effect of the cadmium on the nickel and zinc signals, and the absorption and enhancement effects between nickel and zinc, were corrected empirically. The absorption of cadmium X-rays by nickel and zinc was insignificant. Deposits of pure copper on heavier electrodes displayed similar fluorescent intensities.     

The atomic absorption determination of antimony,arsenic, bismuth, cadmium, lead, and tin in iron, copper,and zinc alloys with the graphite furnace

Antimony, arsenic, bismuth, cadmium, lead, and tin can be determined in metallurgical samples by flame atomic absorption spectrometry at levels of 0.005 wt%, but lower concentrations frequently necessitate preconcentration. The graphite furnace allows determination of these elements at concentrations 1–2 orders of magnitude lower than is possible with flame techniques. All six elements have detection limits at or below 1μg g⁻¹ in a variety of alloys. Calibration for antimony and load was done with standards containing the principal component of the alloy as a synthetic matrix. Bismuth, cadmium, and tin could be determined accurately only by the standard addition method. Arsenic could be determined in iron alloys with synthetic standards, but standard additions were required for copper alloys.     

Biosorption of Lead,Copper, and Cadmium by <Emphasis Type="Italic">Phanerochaete chrysosporium</Emphasis> in Ternary Metal Mixtures: Statistical Analysis of Individual and Interaction Effects

Biosorption of three divalent metals, viz., lead, copper, and cadmium in ternary aqueous mixtures was studied using Phanerochaete chrysosporium in batch shake flasks. The mixtures were prepared containing the metals at their either varying optimum or equal initial concentration combinations in aqueous solution of pH optimum to each of the metals. Following were the optimum initial concentration ranges of the metals in mixture: lead, 60–100 mg/L; copper, 20–60 mg/L; and cadmium, 5–15 mg/L. And, for varying these optimum concentration levels of the metals, a 2³ full factorial design of experiments was employed. The results revealed that an increase in lead and cadmium concentrations helped in their better biosorption by the fungus, but an increase in initial copper concentration slightly diminished its removal. Statistical analysis of the results in the form of analysis of variance and Student t test gave a clear interpretation on the roles of both the individual metals and their interactions in the uptake of metals from mixture. Compared to the uptake of metals when presented individually, lead biosorption in mixture was found to be enhanced to a degree as high as 99%; on the other hand, copper and cadmium removals from mixtures were inhibited to the extent of 100% and 98%, respectively. However, this extent of inhibition or enhancement in the metal removals compared to the individual removals was less in mixtures containing all equal concentrations of the metals.     

Determination of heavy metals in real samples by anodic stripping voltammetry with mercury microelectrodes : Part 1. Application to Wine

Differential-pulse anodic stripping voltammetry with a mercury microelectrode is used for the determination of zinc, cadmium, lead and copper in wine at its natural pH without pretreatment. The effects of the matrix on the stripping peaks are studied in detail by varying the concentration of the metals. Intermetallic (CuZn) interferences and the effects of oxygen are described. The results obtained for the labile metal contents varied from 2 μg l^?1 for cadmium to 148 μg l^?1 for zinc; standard addition plots were linear over about two orders of magnitude above these levels, demonstrating the negligible effect of organic matter. Acidification of the sample with hydrochloric acid to pH 1 allowed the total metal contents to be determined. The reliability of the method was tested by comparison with the results obtained with atomic absorption spectrometry; the differences were within 10–20%.