Cadmium Species Research Articles

Thermodynamic and Kinetic Aspects on the Biosorption of Cadmium by Low Cost Materials: A Review

Environmental Context. The toxicity of cadmium in waters can be decreased by using a wide variety of low-cost biomaterials. A number of such investigations are reviewed here and the models used to describe the process of biosorption discussed. Fundamental investigations that probe the thermodynamics and kinetics of the biosorption process are essential for a strong understanding of all biosorption processes. Areas that still need addressing are highlighted, in particular with regard to cadmium biosorption, some models for which are ready to be tested in pilot plants. Abstract. Cadmium is internationally recognized as an important pollutant in the environment, and different methods for its removal from wastewaters (chemical precipitation being the most commonly used) have been reported in the literature. Those methods are in most cases oriented to situations with high concentrations of the pollutant. Thus, alternative removal and recovery methods are being considered for removing very low concentrations of cadmium. These methods are all based on biosorption, the passive adsorption and sequestration of metals by several natural materials of biological origin. In this review we have considered the biosorption of cadmium onto biomaterials from a physicochemical, thermodynamic, and kinetic perspective. The thermodynamic perspective is based on the characterization of the interactions of the binding sites of the biosorbents with cadmium species in aqueous solution. Traditionally, this approach has been quantified using different kinds of isotherms. In addition, the description is completed by taking into account electrostatic effects, and the influence of pH and ionic strength, which are associated with the negative charge developed, in most cases, by the biomaterial. The other point of view in this review is the kinetic one, which is necessary for a full physicochemical description of the sorbate–biosorbent system. Consequently, an updated description of the various approaches commonly employed in kinetic studies in biosorption has been carried out.

Enhanced electrokinetic remediation of Cd and Pb spiked soil coupled with cation exchange membrane

Electrokinetic (EK) remediation is one of the popular and promising in situ remediation techniques for metal-contaminated soils, but the remediation effect is strongly affected by soil type and chemical species of contaminants; moreover, pH is very difficult to control. This paper investigates the species of cadmium (Cd) and lead (Pb) in simulating contaminated soil before and after EK remediation, and the soil is a typical silt loam soil from Shanghai. Heavy metal speciation in the soil sample was analysed through a sequential extraction procedure. Cation-exchange membrane (CEM) and conductive solution were applied to improve the remediation efficiency. Both methods help to keep acid conditions and CEM can prevent anions in the cathodic compartment from penetrating into the soil sample system. The pH of the soil specimen was acidic during the test, and Cd was quickly removed from the soil while Pb was removed more slowly. The average removal efficiencies of Cd and Pb were 68.7 and 38.7%, respectively, after 60 h of remediation.

Nanostructured Sorbents for Capture of Cadmium Species in Combustion Environments

The pathways of cadmium species to form a submicrometer-sized aerosol in a combustion system exhaust were established. Cadmium oxide was the predominant species formed in the experiments and resulted in particles of a mean size of 26-63 nm with number concentrations in the range of 2-8 x 10(6) cm(-3). Two different nanostructured sorbents, a solid montmorillonite (MMT) and an in situ generated agglomerated silica, were used for capture of the cadmium species. The MMT sorbent was not stable at 1000 degrees C, and structural changes resulted. MMT did not suppress nucleation of cadmium species and partially captured it by weak physisorption as established by the leachability tests. In contrast, the in situ generated silica nanostructured agglomerates had a high surface area, suppressed nucleation of cadmium species vapors, and chemisorbed them effectively resulting in a firm binding, as compared to the MMT sorbent. There is an optimal temperature-time relationship at which the capture process is expected to be most effective. The leaching efficiency under these conditions was less than 3.2%. The nanostructured silica agglomerate size can be tuned for effective capture in existing particle control devices.

Seasonal variations of cadmium speciation in the Penzé estuary, NW France

The study reported here was carried out in the macrotidal estuary of Penzé (Brittany, Western Channel, France). Ten field stations along the freshwater–seawater mixing zone were sampled each month in order to examine the speciation of dissolved and particulate cadmium. Different biogeochemical parameters (suspended particulate matter, Chlorophyll- a, pH and dissolved organic carbon) were also measured. Levels of total dissolved and total particulate metal ranged from 0.06 to 0.46 nM and from 0.4 to 2.4 μg g −1, respectively. Our data showed a non-conservative behaviour for cadmium as a result of desorption from particles. The rise in total dissolved cadmium in the salinity range 0–20 was about 0.2 nM. Incidentally, a decrease of total particulate concentrations of about 0.5 μg g −1, which corresponds approximately to 0.2 nM, was observed. The study of the various cadmium species led us to identify desorption of cadmium occurred from the iron/manganese oxide-associated fraction. This desorption process leads to the formation of labile complexes, i.e. chlorocomplexes in spring and summer. However, in winter and autumn, a large part of the dissolved fraction was constituted by organic complexes. These complexes can be formed from suspended particles desorption or could be a released from sediment. Analysis of flux indicated that most of the metal inputs to the estuary (usually more than 80%) corresponded to organic cadmium. Spring and summer outputs were mainly constituted of chlorocomplexes whereas cadmium organic complexes were predominant in winter and autumn output fluxes.

A Novel Kinetic Method for the Speciation of Cadmium in River Water by Micro Solvent Extraction with Dithizone

Cadmium species in river water were kinetically extracted with dithizone by varying the extraction time. The obtained extraction curve showed a three-stage stepwise profile that reflected the rate of the ligand substitution reaction between the dithizone and cadmium species. Corresponding to each stage, we divided these extracted cadmium species into three groups: "highly labile", "moderately labile" and "slowly labile" species.

Cold vapour generation and on-line trapping of cadmium species on quartz surface prior to detection by atomic absorption spectrometry

A quartz trap for on-line preconcentration of Cd species was designed. The cold vapour generation technique was used for the generation of Cd species. The trapping medium was formed by external heating of the inlet arm of a quartz T-tube. The generated analyte species were trapped on a quartz surface heated to the collection temperature, 350 °C, and the collected species were revolatilized when the trap was heated further to revolatilization temperature, 1000 °C, and hydrogen gas was introduced in the trapping medium. Two-level fractional factorial design and central composite design were used to optimize generation conditions in the flow injection mode. The results of the fractional factorial design demonstrated that the factors and their interactions were statistically significant. Three factors, length of reaction coil, carrier HCl concentration and NaBH4 concentration, were considered to be the most significant parameters in the optimization and their optimum values were found to be 30 cm, 0.3 M and 3% (m/v), respectively. Sea-water (BCR), tomato leaves (NIST 1573a) and oyster tissue (NIST 1566b) standard reference materials were analyzed to assess the accuracy of the proposed method. For a collection period of 3.0 min, i.e., 6.0 ml sample volume, the 3σ limit of detection was 1.8 pg ml−1; the enhancement factor for LOD was found to be 90 as compared with FI-HGAAS. The sample throughput rate was 12 h−1.

High-temperature removal of cadmium from a gasification flue gas using solid sorbents

In this work, the retention capacity of solid sorbents for cadmium species present in coal gasification flue gases at high temperature was investigated. The influence of HCl(g) on the gas atmosphere was also evaluated. The study was carried out in a laboratory scale reactor, using synthetic gas mixtures with the sorbent as fixed bed. The sorbents tested were kaolin, limestone, alumina and fly ashes. The results obtained were compared with data from the works of other authors, who used similar solid sorbents in typical coal combustion flue gases. Whereas in the combustion atmospheres described in the literature, kaolin, limestone and alumina showed high retention capacities for cadmium compounds (0.5–40 mg g −1), in the coal gasification atmospheres studied in the present work, the amount of cadmium captured by these solid sorbents was negligible. Fly ashes were found to be the most efficient for retaining cadmium in gasification atmospheres, their maximum retention capacity in the conditions studied being approx 0.75 mg g −1.

Syntheses and spectroscopy of diamine complexes of Zn(II) and Cd(II) ethylxanthates and the molecular structures of [M(S 2COEt) 2TMEDA]: formation of CdS nanoparticles from [Cd(S 2COEt) 2] and [Cd(S 2COEt) 2TMEDA

The zinc and cadmium ethylxanthate complexes of N, N, N′, N′-tetramethylethylenediamine (TMEDA), [M(S 2COEt) 2TMEDA], were synthesized and characterized with infrared, 1H and 13C NMR spectroscopy, mass spectrometry and X-ray crystallography. Whereas the cadmium complex has a six-coordinate {CdS 4N 2} centre with bidentate xanthate ligands, the zinc complex contains four coordinate {ZnS 2N 2} zinc with two monodentate xanthate groups. The cadmium species [Cd(S 2COEt) 2(diamine)] (where diamine = N, N-dimethylethylenediamine or N, N′-diisopropylethylenediamine) were also synthesized. The surfactant-assisted formation of nanoparticles from [Cd(S 2COEt) 2] and [Cd(S 2COEt) 2TMEDA] was studied with TEM, XRD and XRF techniques. From [Cd(S 2COEt) 2], spherical nanoparticle aggregates 140–200 nm in diameter were obtained but from [Cd(S 2COEt) 2TMEDA], single nanoparticles were produced with estimated diameters in the range of 4–7 nm and almost no aggregation.

On the mechanism of trace-element uptake during the hydrothermal growth of sulfide mineral crystals

The stable species of cadmium and mercury are formed in iron and lead sulfides at elevated temperatures and pressures under hydrothermal conditions. Their formation proceeds through different mechanisms. The most general mechanism involves the uptake of trace elements in the form of structural species due to isomorphous exchange. The results obtained for cadmium in pyrrhotite indicate that structural defects substantially affect the incorporation of impurities into the crystal structure. It is found that trace elements are accumulated on the surface in the absence of defects and are incorporated into the crystal bulk in the form of structural impurities in the presence of defects. Moreover, at elevated temperatures and pressures, trace elements can form their own (surface nonautonomous) phases. These phases are formed not only at trace-element concentrations close to saturation (Cd in Fe1.0S) but also under conditions far from saturation as a result of the interaction of trace elements with the oxidized surface of the mineral (the cadmium uptake by galena with the formation of either a sulfate surface phase or a sulfate-chloride surface phase). An important mechanism of trace-element uptake by sulfides during the hydrothermal growth of crystals is associated with external and internal adsorption of impurities by defects. This adsorption manifests itself both in an increase in the content of sorbed mercury in galena at a high sulfur activity due to the interaction of mercury with lead vacancies and in the formation of dislocation cadmium species, which results in an increase in the coefficient of cadmium distribution in the crystal-solution system.

Determination of cadmium in polyethylene by analytical atomic spectrometry with gas-phase sample introduction technique

Cadmium in polyethylene was determined by both inductively coupled plasma atomic emission spectrometry (ICP-AES) and atomic absorption spectrometry (AAS) with continuous-flow gas-phase sample introduction in a reaction medium of ascorbic acid. In the presence of mixture of cobalt and thiourea in the ascorbic acid solution, the sensitivities by both ICP-AES and AAS for cadmium were greatly enhanced. The gaseous cadmium species was phase-separated in a gas–liquid separator and directed via a stream of argon carrier gas to an inductively coupled plasma and an electrically heated quartz tube atomizer (QTA) for atomic spectrometry. Under the optimized experimental conditions, the best attainable detection limits at Cd I 228.802 nm line were 1.3 and 0.017 ng/ml with linear dynamic ranges of 10–500 ng/ml and 0.1–1 ng/ml in concentrations by ICP-AES and QTA-AAS, respectively. The instrumental precisions expressed as the relative standard deviation (R.S.D.) from ten replicate measurements of 50 and 1 ng/ml cadmium by ICP-AES and QTA-AAS were 5.6% and 3.2%, respectively. With the use of ICP-AES and QTA-AAS with gas-phase sample introduction method, six- and 200-fold improvements in detection limits for cadmium were obtained in comparison with their conventional solution nebulization methods, respectively. After the effects of several diverse elements on the determination of cadmium by ICP-AES and QTA-AAS with the present gas-phase sample introduction systems were examined, these methods were applied to the determination of low concentrations of cadmium in polyethylene. The results obtained by the present method were in good agreement with the certified values.

Determination of cadmium in polyethylene by analytical atomic spectrometry with gas-phase sample introduction technique

Cadmium in polyethylene was determined by both inductively coupled plasma atomic emission spectrometry (ICP-AES) and atomic absorption spectrometry (AAS) with continuous-flow gas-phase sample introduction in a reaction medium of ascorbic acid. In the presence of mixture of cobalt and thiourea in the ascorbic acid solution, the sensitivities by both ICP-AES and AAS for cadmium were greatly enhanced. The gaseous cadmium species was phase-separated in a gas–liquid separator and directed via a stream of argon carrier gas to an inductively coupled plasma and an electrically heated quartz tube atomizer (QTA) for atomic spectrometry. Under the optimized experimental conditions, the best attainable detection limits at Cd I 228.802 nm line were 1.3 and 0.017 ng/ml with linear dynamic ranges of 10–500 ng/ml and 0.1–1 ng/ml in concentrations by ICP-AES and QTA-AAS, respectively. The instrumental precisions expressed as the relative standard deviation (R.S.D.) from ten replicate measurements of 50 and 1 ng/ml cadmium by ICP-AES and QTA-AAS were 5.6% and 3.2%, respectively. With the use of ICP-AES and QTA-AAS with gas-phase sample introduction method, six- and 200-fold improvements in detection limits for cadmium were obtained in comparison with their conventional solution nebulization methods, respectively. After the effects of several diverse elements on the determination of cadmium by ICP-AES and QTA-AAS with the present gas-phase sample introduction systems were examined, these methods were applied to the determination of low concentrations of cadmium in polyethylene. The results obtained by the present method were in good agreement with the certified values.

Chemical vapor generation by reaction of cadmium with potassium tetrahydroborate and sodium iodate in acidic aqueous solution for atomic fluorescence spectrometric application

In the traditional chemical vapor generation system of KBH4 (or NaBH4)–Cd2+–HCl in aqueous solution, volatile components containing cadmium species can be generated but with low efficiency. In this work, it was found for the first time that the efficiency for the generation of the cadmium-containing vapor was greatly improved when halogenate, i.e., NaBrO3 or NaIO3, was added. The chemically generated vapor was separated from the reaction medium, and introduced into an atomic fluorescence spectrometer (AFS) with argon as the carrier gas, for the atomization and detection of cadmium. The experimental conditions for the efficient generation of the cadmium-containing vapor were optimized and the limit of detection (LOD, 3σ) was then found to be 10 pg mL−1. This modified chemical vapor generation system is potentially cleaner, and could have wide applications for sample introduction and/or matrix separation in analytical atomic spectrometries, such as flame atomic absorption spectrometry (FAAS), electrothermal atomic absorption spectrometry (ETAAS), inductively coupled plasma atomic emission spectrometry (ICP-AES), ICP-MS (mass spectrometry), microwave induced plasma atomic emission spectrometry (MIP-AES) and MIP-MS for the determination of ultratrace cadmium or some other elements.

Simultaneous determination of trace mercury and cadmium in tobacco samples by cold vapor generation-atomic fluorescence spectrometry

A highly sensitive and simple method was developed for the simultaneous determination of trace cadmium and mercury in tobacco samples by cold vapor generation-atomic fluorescence spectrometry equipped with an intermittent flow reactor. The reaction was accomplished with potassium tetrahydroborate(III) in aqueous solutions. A newly modified atomizer was presented on the basis of the present atomic fluorescence system, which effectively improved the stability of the signals. Special accent was put on the study of the conditions for the generation of volatile cadmium and mercury species were investigated in detail. Some transition metal ions that could be used as sensitivity enhancers, including iron(III), cobalt(II), nickel(II), zinc(II) and molybdenum(VI) in the presence of thiourea. The tolerance to the interference of coexisting ions was carefully examined in this system. Under optimal conditions, the detection limits (3σ) were evaluated to be 2.8 ng l−1 for cadmium and 4.3 ng l−1 for mercury, respectively. The relative standard deviations for 10 replicate determinations of 0.8 µg l−1 mercury and 1 µg l−1 cadmium were 3.2% and 2.9%, respectively. The proposed method was successfully applied to the simultaneous determination of mercury and cadmium in tobacco leaf samples.

Distribution and chemical speciation of dissolved cadmium and copper in the Loire estuary and North Biscay continental shelf, France

The investigations reported here focused on the amounts of various dissolved cadmium and copper species in the whole salinity gradient of the system composed of the Loire estuary and the Biscay Bay continental shelf (France). Electrochemical labile cadmium, extractable C 18 organic copper and total dissolved species of these two metals were analysed. Within the estuary, levels of total dissolved cadmium and copper ranged from 0.08 to 0.29 nM and 8.0 to 21.2 nM, respectively. These values are higher than those currently reported in metal input-free estuarine waters, but remain lower than those found in heavily industrialised environments. At the sampling stations located on the continental shelf, concentrations of total dissolved cadmium varied within 0.11 and 0.26 nM, whereas those of copper were in the range 1.7–8.0 nM. Both these series of data are higher than those reported in the literature for areas in the close vicinity of the continental shelf and in the open Atlantic Ocean. Our experimental values highlighted a non-conservative behaviour on estuarine mixing for both metals, indicative of additional metal inputs. For cadmium, the rise in concentration was particularly strong: 360%. Further to the study of labile cadmium and non-polar hydrophobic organic copper fractions, the observed elevations in concentrations were related to particle desorption phenomena or to inputs from sediments. Discharges in dissolved cadmium and copper species to the continental shelf by the Loire river were assessed as 14 and 343 kg day −1, respectively. Among them 22% of cadmium flux corresponded to labile complexes, 36% of copper constituted of non-polar hydrophobic complexes. Concerning both metals a large area of the continental shelf was affected by waters from the Loire river. No change in the partition between hydrophobic and non-hydrophobic organic copper complexes was observed in this area, contrary to the cadmium one for which changes in chemical speciation were noticeable along the salinity gradient.

Modeling the adsorption of Cd(II) onto goethite in the presence of citric acid

The adsorption of cadmium onto goethite in the presence of citric acid was measured as a function of pH and cadmium concentration at 25°C. Potentiometric titrations were also performed on the system. Cadmium adsorption onto goethite was enhanced above pH 4 in the presence of 50 μM, 100 μM and 1 mM citric acid. While there was little difference between the enhancements caused by 50 and 100 μM citric acid below pH 6, above pH 6 further enhancement is seen in the presence of 100 μM citric acid. When 1 mM citric acid was present, the enhancement of cadmium adsorption was greater below pH 6, with increased Cd(II) adsorption down to pH 3.5. However, above pH 6, 1 mM of citric acid caused slightly less enhancement than the lower citric acid concentrations. ATR–FTIR spectra of soluble and adsorbed citrate–cadmium species were measured as a function of pH. At pH 4.6 there was very little difference between the ternary Cd(II)–citric acid–goethite spectrum and the binary citric acid–goethite spectrum. However, spectra of the ternary system at pH 7.0 and 8.7 indicated the presence of additional surface species. Further analysis of the spectra suggested that these were metal–ligand outer-sphere complexes. Data from the adsorption experiments and potentiometric titrations of the ternary Cd(II)–citric acid–goethite system were fitted by an extended constant-capacitance surface complexation model. The spectroscopic data were used to inform the choice of surface species. Three reactions in addition to those for the binary Cd(II)–goethite and citric acid–goethite systems were required to describe all of the data. They were 2SOH+Cd2++L3−+H+⇌(SOH)(SOH2+)--LCd−0,SOH+Cd2++L3−+2H+⇌[SLH−--Cd2+]++H2O, and SOH+2Cd2++L3−+2OH−⇌[SOCd+--LCdOH2−]−+H2O. Neither the spectroscopy nor the modeling suggested the formation of a ternary inner-sphere complex or a surface precipitate under the conditions used in this study.

Cadmium and vanadate oligomers effects on methaemoglobin reductase activity from Lusitanian toadfish: in vivo and in vitro studies

Cadmium and two vanadate solutions as ‘metavanadate’ (containing ortho and metavanadate species) and ‘decavanadate’ (containing decameric species) (5 mM) were injected intraperitoneously in Halobatrachus didactylus (Lusitanian toadfish), in order to evaluate the effects of cadmium and oligomeric vanadate species on methaemoglobin reductase activity from fish red blood cells. Following short-term exposure (1 and 7 days), different changes were observed on enzyme activity. After 7 days of exposure, ‘metavanadate’ increased methaemoglobin reductase activity by 67% ( P<0.05), whereas, minor effects were observed on enzymatic activity upon cadmium and ‘decavanadate’ administration. However, in vitro studies indicate that decameric vanadate, in concentrations as low as 50 μM, besides strongly inhibiting methaemoglobin reductase activity, promotes haemoglobin oxidation to methaemoglobin. Although decameric vanadate species showed to be unstable in the different media used in this work, the rate of decameric vanadate deoligomerization is in general slow enough, making it possible to study its effects. It is concluded that the increase in H. didactylus methaemoglobin reductase activity is more pronounced upon exposition to ‘metavanadate’ than to cadmium and decameric species. Moreover, only decameric vanadate species promoted haemoglobin oxidation, suggesting that vanadate speciation is important to evaluate in vivo and in vitro effects on methaemoglobin reductase activity.

Generation of atomic and molecular cadmium species from aqueous media.

Generation of atomic and molecular species of cadmium following reaction of acidified sample with sodium tetrahydroborate reductant using a modified parallel path Burgener nebulizer has been accomplished. Once generated, atomic species are stable in water, having a half-life of 2.2 min, and can be preconcentrated for subsequent quantitation. Although the initial products of the reduction reaction appear to be free atoms, subsequent interaction with nascent hydrogen gives rise to the molecular hydride in a transformation moderated by the chemistry of surface groups exposed to the reaction products. Use of a glass spray chamber results in a predominance of atomic vapor whereas a polymeric spray chamber releases the volatile molecular species.

Effect of pH on cadmium toxicity, speciation, and accumulation during naphthalene biodegradation

Lowering pH of a microbiological medium from 7 to 4 decreased cadmium toxicity during naphthalene biodegradation by a Burkholderia sp. Cadmium speciation and cadmium accumulation in the system were studied to explain this effect. Cadmium speciation was determined by direct measurement and by geochemical modeling. Previous studies have implicated the monovalent hydroxylated cadmium (CdOH+) species in the effect of pH on cadmium toxicity. Modeling analysis predicted CdOH+ formation only at very low concentrations (< or = 0.0128 microM), while the measured concentration of divalent ionic cadmium (Cd2+) was at least three orders of magnitude greater, suggesting that Cd2+ is the more significant metal form. With respect to cadmium accumulation, cells contained in media adjusted to pH 4 accumulated only 2.76 +/- 0.76 mg Cd/g cells, whereas cells in media adjusted to pH 7 accumulated 8.52 +/- 0.71 mg Cd/g cells. These data suggest that cadmium toxicity is correlated with increased cadmium accumulation rather than the formation of CdOH as pH is increased. At low pH, the decrease in cadmium accumulation may be caused by increased competition between hydrogen and cadmium ions for binding sites on the cell surface or by an increase in metal efflux pump activity due to an increase in the proton gradient that drives the efflux pump.

Gas quenching probe and field measurements of gaseous cadmium in a 12-MW th circulating fluidised bed combustion boiler

A probe-based technique for measurement of gas phase metal species in flue gas at high temperatures has been developed. This paper deals with work carried out to test and evaluate the technique through field measurements of cadmium species during co-combustion of sewage sludge and other solid fuels in a circulating fluidised bed combustion boiler. During the measurements of vaporous cadmium forms, solid fly ash samples were also collected at the measurement positions. Chemical composition data from these fly ash samples were used to discuss the influence that the fly ash filter cake built up on the probe tip can have on the measurements. Additionally, the solid samples were examined by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques to have a better insight into the problem. Using the data from the field measurements and/or from the integrated measurements and weighing devices of the boiler the mass balance of cadmium from the combustion process was calculated by different methods. The calculation results were fairly consistent. In one method, data from the field measurements was used. This method gave the mass balance for cadmium in the process Cd out/Cd in=113.6%, which was a very good result considering that it involved the analysis of trace amount of metals in full-scale measurements.

Simultaneous Determination of Trace Cadmium and Arsenic in Biological Samples by Hydride Generation-Double Channel Atomic Fluorescence Spectrometry

Hydride generation atomic fluorescence spectrometry (HG-AFS) has been used for determination of hydride-forming elements because of its high sensitivity, simplicity, and low costs, but most of such work has been concentrated on single element analysis, and reports dealing with multielement determination by HG-nondispersive (ND)AFS are rare. In this work, a sensitive HG-NDAFS method was developed for simultaneous determination of trace cadmium and arsenic in biological materials. The conditions for the generation of volatile cadmium and arsenic species from the reaction with KBH4 in aqueous solution were investigated using a double-channel AFS integrated with an intermittent flow reactor. Like thiourea and Co(II), ascorbic acid was found to significantly enhance the generation efficiency of volatile Cd and As species. The interferences of coexisting ions were evaluated. Under optimal conditions, the detection limits for Cd and As were determined to be 10 and 150 ng L(-1), respectively. The precision for 11 replicate determinations at the 1 microg L(-1) Cd level and the 10 microg L(-1) As level were 3.5 and 2.7% (RSD), respectively. The recoveries of spike analytes in the biological samples studied ranged from 94 to 109%. The proposed method was successfully applied to the simultaneous determination of Cd and As in a variety of biological samples.