Preconcentration Of Trace Metals Research Articles

Supramolecular deep eutectic solvent: a powerful tool for pre-concentration of trace metals in edible oil.

The utilization of supramolecular deep eutectic solvent eddy-assisted liquid-liquid microextraction utilizing 2-hydroxypropyl β-cyclodextrin (SUPRADES) has been identified as a successful method for pre-enriching Cu, Zn, and Mn in vegetable oil samples. Determination of each element was conducted by inductively coupled plasma optical emission spectrometry (ICP-OES) after digestion of metal-enriched phases. Various parameters were examined, including the composition of SUPRADES species [2HP-β-CD: DL-lactic acid], a cyclodextrin mass ratio of 20wt%, a water bath temperature of 75 °C, an extractor volume of 800 μL, a dispersant volume of 50μL, and an eddy current time of 5min. Optimal conditions resulted in extraction rates of 99.6% for Cu, 105.2% for Zn, and 101.5% for Mn. The method exhibits a broad linear range spanning from 10 to 20,000μg L-1, with determination coefficients exceeding 0.99 for all analytes. Enrichment coefficients of 24, 21, and 35 were observed. Limits of detection ranged from 0.89 to 1.30μg L-1, while limits of quantification ranged from 3.23 to 4.29 μg L-1. The unique structural characteristics of the method enablethe successful determination of trace elements in a variety of edible vegetable oils.

Patricia Smichowski, a researcher who works hard to contribute to science, kindly granted BrJAC an interview

Patricia Smichowski is a Licentiate in Chemistry (equivalent to a Master in Science) of the University of Buenos Aires. She obtained an MS in Nuclear Engineering from the Engineering School of the University of Buenos Aires in 1981 and received her Ph.D. in chemistry in 1995 from the Complutense University, Madrid, Spain. In 1982, she joined the Argentine Atomic Energy Commission (CNEA) where she is currently Head of the Analytical Developments Division. She is also Principal Researcher at the National Council of Scientific and Technical Research (CONICET). She specializes in the development and application of atomic spectrometric techniques to environmental and biological analysis. Her interests lie in the preconcentration, speciation, and determination of trace metals and metalloids in a variety of matrices by employing plasma-based techniques, atomic fluorescence spectrometry, and other coupled techniques. She has conducted national and international projects aimed at characterizing the presence of metals, metalloids, ions, and organic compounds in airborne particulate matter, as well as elucidating their origin. She holds a patent, with other researchers, relating to the development of a sorbent for arsenic retention. Patricia Smichowski has published 130 peer reviewed articles and 12 book chapters, given 45 invited lectures at international meetings, and has co-organized several international conferences. She is a member of the advisory board of four international analytical chemistry journals, as well as the European Virtual Institute for Speciation Analysis.

Simultaneous preconcentration and determination of trace metals in edible plants and water samples by a novel solvent bar microextraction using a meltblown layer of facemask as the extractant phase holder combined with FAAS

A new microextraction method as a facile, efficient, and safe intermediate sample preparation procedure was developed for simultaneous extraction and preconcentration of nickel (II), cobalt (II), and lead (II) in some vegetables and water samples. The new method uses a novel deep eutectic solvent as an extractant on the surface of a meltblown layer of a facemask with an iron wire inside of it. 2-(5-Bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) was used as a chelating reagent. The concentrations of the enriched ions were measured using a flame atomic absorption spectrophotometer (FAAS). The introduced method underwent significant parameter optimization, which may influence the extraction process efficiency. Under the best situations, the calibration curve of the method showed excellent linearity over the concentration range 2–150 μg L−1, 3–150 μg L−1, and 7–500 μg L−1 have satisfactory coefficients of determination (R2 ≥ 0.998) for nickel (II), cobalt (II), and lead (II), respectively. Detection limits were within 0.61 – 2.30 μg L−1, and the relative standard deviation values were fewer than 2.6 % (n = 10). Experimental results indicated that the presented method has a high ability to cleanly and enrich metal ions in several samples, including natural water, dill, coriander, and spinach leaves, with limited solvent consumption and low operating costs.

BISMUTH-ANTIMONY FILM ELECTRODE FOR STRIPPING VOLTAMMETRIC DETERMINATION OF TRACE CADMIUM AND LEAD IN THAI RICE WINE

Stripping analysis was proposed for the voltammetric determination of trace cadmium and lead in local rice wine alcoholic beverages. A bismuth-antimony film electrode (Bi-SbFE) was employed for accumulative preconcentration of trace metals by adding 4 mg L-1 of bismuth and 1 mg L-1 of antimony directly to the sample solution and simultaneously depositing bismuth, antimony, and trace cadmium and lead target metals on the glassy carbon electrode by applying a fixed potential of –1.1 V versus the Ag/AgCl reference electrode for 300 s. Pre-treatment parameters for mineralization of the sample were optimized using the wet acid digestion procedure. Under the optimum conditions, linear calibration graphs ranging 20-200 µg L-1 for Cd and Pb were obtained with detection limits of 0.22 and 0.62 µg L-1 and limits of quantitation 0.73 and 2.07 µg L-1, respectively. Reproducibility values for seven replicate analyses of 50 µg L-1 Cd and Pb were 3.6 and 3.3%, respectively. The developed method was successful for Cd and Pb analyses in Thai rice wine samples and results were validated by the flame atomic absorption spectrometric method. Most samples were not contaminated with Cd and Pb. The amount of Cd contaminants in only one of rice wine sample was still lower than the maximum permitted level of Cd in wine.

Ultrasonic assisted dispersive-solid phase extraction for preconcentration of trace metals in wastewater samples

In this work, MgO-SnO-Zeolite composites material has been synthesized, characterized, and, used as a sorbent material in the determination of Cd, Cr, Mn, Ni, and Zn in water samples using the ultrasonic-assisted dispersive-solid phase extraction. The synthesized MgO-SnO-Zeolite composite was prepared by the co-precipitation method and the results show the crystallinity phase of the material that exhibits most of the zeolite structure. Scanning electron microscopy with energy-dispersive X-ray spectroscopy was conducted on the composite material. The structure of the scanning electron microscopy images shows the cubic material with the energy-dispersive X-ray spectroscopy peaks that confirms the presence of the elements that form part of MgO-SnO-Zeolite. Furthermore, they were no impurities observed on the prepared composite material. The central composite design was used to optimize the adsorption and desorption of the developed ultrasonic-assisted dispersive-solid phase extraction method. The optimum conditions were: pH 7.5, extraction time 17.5 min, adsorbent mass 75 mg, desorption time 5 min, eluate concentration 2 M nitric acid, and desorption volume 7 mL. Under optimum conditions, the limit of detection was found to be 0.13, 0.45, 0.21, 0.34, and 0.08 μgL−1 for Cd, Cr, Mn, Ni, and Zn, with a preconcentration factor of 4.3. The intra-day (n = 15) and inter-day (n = 5) precision expressed as relative standard deviations ranged from 0.4 to 1.3 and 1.34–2.4, respectively. The developed ultrasonic-assisted dispersive-solid phase extraction method was found to be applicable for the determination of Cd, Cr, Mn, Ni, and Zn in wastewater samples.

Magnetic Fe3O4@Mg/Al-layered double hydroxide adsorbent for preconcentration of trace metals in water matrices

A magnetic Fe3O4@MgAl-layered double hydroxide (MLDH) nanocomposite was successfully synthesized and applied as an effective adsorbent for preconcentration of trace As(III), Cd(II), Cr(III), Co(II), Ni(II), and Pb(II) ions from complex matrices. The quantification of the analytes was achieved using the inductively coupled plasma optical emission spectrometry (ICP-OES) technique. The nanocomposite was then characterized using BET, FTIR, SEM, and EDS. Due to its high adsorption surface area, compared to traditional metal oxide-based adsorbents, MLDH nanocomposite exhibited high extraction efficiency. Several experimental parameters controlling the preconcentration of the trace metals were optimized using response surface methodology based on central composite design. Under optimum conditions, the linearity ranged from 0.1 to 500 µg L−1 and the correlation of coefficients (R2) were higher than 0.999. The limits of detection (LODs) and quantification (LOQs) were 0.11–0.22 µg L−1 and 0.35–0.73 µg L−1, respectively. The intra-day (n = 10) and inter-day precisions (n = 5 working days) expressed in the form of percent relative standard deviations (%RSDs) were below 5%. The proposed method was successfully applied for the analysis of the As(III), Cd(II), Cr(III), Co(II), Ni(II), and Pb(II) ions in different environmental water samples.

Determination of Metals in Natural Waters by Inductively Coupled Plasma Optical Emission Spectroscopy after Preconcentration on Silica Sequentially Coated with Layers of Polyhexamethylene Guanidinium and Sulphonated Nitrosonaphthols.

A series of complexing adsorbents is prepared by coating silica particles with linear polyhexamethylene guanidinium (PHMG) chloride followed by saturation with a number of sulphonated nitrosonaphthols reagents electrostatically retained by positively charged polymer layer. PHMG coated silica is hydrolytically stable even during treatment with 6 M HCl heated up to 50 °C. The adsorption of 1-nitroso-2-naphthol-3,6-disulfonic acid (nitroso-R-salt), 2-nitroso-1-naphthol-4-sulfonic acid (nitroso-N-salt), and 2-nitroso-1-naphthol-3,6-disulfonic acid (nitroso-K-salt) on PHMG modified silica was studied. The effective immobilisation of sulphonated nitrosonaphthols was achieved in the range of pH of 3 - 8, while the adsorption of the monosulphonated reagent (nitroso-N-salt) is twice as high as the disulphonated analogues (nitroso-R-salt and nitroso-K-salt). The adsorption of Cu(II), Fe(III), Co(II), Ni(II), Al(III), Zn(II), Pb(II), Mn(II), and Cr(III) on prepared complexing adsorbents under static and dynamic conditions was studied as a function of time, pH, sample volume, and presence of interfering ions. Metal ions can be desorbed by using 1 M HCl or 1 M HNO3. The preconcentration factors of metals under optimized conditions are varied from 20 to 80. The developed method was used for the preconcentration of trace metals from natural waters followed by ICP-OES determination. The sub-ppb limits of detection of metals are achieved.

Synthesis, characterization and application of a new chelating resin for solid phase extraction, preconcentration and determination of trace metals in some dairy samples by flame atomic absorption spectrometry

In this study, a simple and rapid solid phase extraction/preconcentration procedure was developed for determination of Cd(II), Co(II), Cr(III), Cu(II), Fe(III), Mn(II), Pb(II), and Zn(II) trace metals by flame atomic absorption spectrometry (FAAS). A new chelating resin, poly(N-cyclohexylacrylamide-co-divinylbenzene-co-2-acrylamido-2-methyl-1-propanesulfonic acid) (NCA-co-DVB-co-AMPS) (hereafter CDAP) was synthesized and characterized. The influences of the analytical parameters such as pH of the sample solution, type and concentration of eluent, flow rates of the sample and eluent, volume of the sample and eluent, amount of chelating resin, and interference of ions were examined. The limit of detection (LOD) of analytes were found (3s) to be in the range of 0.65–1.90μgL−1. Preconcentration factor (PF) of 200 and the relative standard deviation (RSD) of ⩽2% were achieved (n=11). The developed method was applied for determination of analytes in some dairy samples and certified reference materials.

New Approaches to the Cloud Point Extraction: Utilizable for Separation and Preconcentration of Trace Metals

New Approaches to the Cloud Point Extraction: Utilizable for Separation and Preconcentration of Trace Metals

Synthesis and chelation properties of a new polymeric ligand derived from 1-amino-2-naphthol-4-sulfonic Acid.

A novel chelating resin for preconcentration of heavy metals from various seawater samples has been developed by condensing 1-amino-2-hydroxy-7-[(4-hydroxyphenyl)diazenyl] naphthalene-4-sulfonic acid (AHDNS) with formaldehyde (1:2 mole ratio) in the presence of oxalic acid as the catalyst. The resin thus obtained was used as a solid sorbent for the separation of divalent metal ions present at trace levels in seawater. The functionalized phenol (AHDNS) was characterized by spectral studies. The polymeric resin AHDNS-formaldehyde (AHDNS-F) obtained by condensing the functionalized phenol and formaldehyde was characterized by IR and NMR spectral studies. The chelating property of the AHDNS-F resin towards divalent metal ions was studied as a function of pH and in the presence of electrolyte. The metal uptake properties of the resin were determined by using an atomic absorption spectrophotometer. This procedure was validated for recovery of divalent metal ions from seawater samples. The recoveries of cadmium, cobalt, copper, manganese, lead, and zinc were above 92% under the optimum preconcentration conditions. The LOD was <0.73 μg/L and the RSDs were <2%. Thus, the AHDNS-F resin can be widely used as a solid sorbent for the preconcentration of trace metals at ppm levels in seawater samples.

Solid phase extraction of lithium ions from water samples using K-birnessite with layer-structure material form (KBRLSM)

Layer-structure materials have attracted considerable interest for the removal, separation, and preconcentration of trace metals in analytical and environmental chemistry. In the present work, we developed a separation and preconcentration method for lithium ions from water samples using K-birnessite with layer-structure material (KBRLSM) form. The experimental parameters that affected the extraction efficiency of the method such as pH, flow rate and volume of the sample solution, concentration of eluent, amount of adsorbent, effect of common matrix ions, and capacity of adsorbent were investigated and optimized. The adsorbed Li ions on KBRLSM were eluted with 5 mL of 1 mol L−1 HCl solutions and their concentrations were determined by high resolution-continuum source flame atomic absorption spectrometry. The adsorption isotherm studies indicate that the adsorption of Li ions follows both the Langmuir and Freundlich isotherms. The Langmuir monolayer adsorption capacities (qmax) were estimated as 2.77 mg g−1. A constant of the energy (KL) for Li was calculated as 0.35 L g−1. The optimum pH value for quantitative sorption of Li ions was found between 5.0 and 7.0. The preconcentration factor was found as 40 for 200 mL aqueous solution containing 5 μg Li ions. The developed method was successfully applied to some water samples.

Preconcentration of Trace Metals in Water Using a Newly Designed Thermoresponsive Chelating Polymer for the Sensitive Determination by Graphite Furnace Atomic Absorption Spectrometry

Abstract A thermoresponsive polymer containing highly dense iminodiacetic acid segments was newly designed for the efficient preconcentration of trace metals in water. The polymer was synthesized by the water-soluble carbodiimide-mediated condensation of poly(N-isopropylacrylamide-co-acrylic acid) with polyallylamine and the subsequent conversion of amino groups to iminodiacetic acid. Metal ions in water were collected by adding the thermoresponsive polymer, sodium nitrate, dodecyltrimethylammonium chroride, and buffer components and then heating the resulting solution to form polymer deposits. The use of 0.02% (w/v) thermoresponsive polymer allowed the nearly complete (&amp;gt;99.8%) collection of seven metals (Be, Co, Ni, Cu, Cd, In, and Pb) in the pH range of 6.8–8.3. The polymer deposits were readily collected as a condensed coagulate and dissolved with a small amount of water for the analysis by graphite furnace atomic absorption spectrometry. Because of highly efficient (100-fold) concentration, these metals at pg cm−3–ng cm−3 levels were successfully determined. The precision and accuracy were evaluated by analyzing certified reference water samples.

DOWNSIZED CHELATING RESIN-PACKED MINICOLUMN PRECONCENTRATION FOR MULTIELEMENT DETERMINATION OF TRACE METALS BY ICP-MS

Chelating resin-packed minicolumn preconcentration was used for multielement determination of trace metals in seawater by inductively coupled plasma mass spectrometry (ICP-MS). The chelating resin-packed minicolumn was constructed with two syringe filters (DISMIC 13HP and Millex-LH) and an iminodiacetate chelating resin (Chelex 100, 200-400 mesh), with which trace metals in 50 mL of original seawater sample were concentrated into 0.50 mL of 2 M nitric acid, and then 100-fold preconcentration of trace metals was achieved. Then, 0.50 mL analysis solution was subjected to the multielement determination by ICP-MS equipped with a MicroMist nebulizer for micro-sampling introduction. The preconcentration and elution parameters such as the sample-loading flow rate, the amount of 1 M ammonium acetate for elimination of matrix elements and the amount of 2 M nitric acid for eluting trace metals was optimized to obtain good recoveries and analytical detection limits for trace metals. The analytical results for V, Mn, Co, Ni, Cu, Zn, Mo, Cd, Pb, and U in three kinds of seawater certified reference materials (CRMs; CASS-3, NASS-4, and NASS-5) agreed well with their certified values. The observed values of rare earth elements (REEs) in the above seawater CRMs were also consistent with the reference values. Therefore, the compiled reference values for the concentrations of REEs in CASS-3, NASS-4, and NASS-5 were proposed based on the observed values and reference data for REEs in these CRMs. Keywords: chelating resin-packed minicolumn, ICP-MS, micro-sampling introduction, seawater certified reference material, trace metals

Preconcentration and determination of lead and cadmium in water samples with a MnO 2 coated carbon nanotubes by using ETAAS

A procedure for separation and preconcentration trace amount of Pb(II) and Cd (II) by nano-sized manganese dioxide functionalized multi-wall carbon nanotubes (MnO 2/MWCNTs) packed column has been proposed. Various influencing parameters on the separation and preconcentration of trace metals, such as pH, flow rate, concentration of eluent, sample volume and interference ions, were studied. Under the optimized conditions (pH 6, flow rate 2.5 mL min − 1 ), Pb(II) and Cd (II) were retained on the column, then quantitatively eluted by 1.5 mL 1.5 mol L − 1 nitric acid solution and determined by electrothermal atomic absorption spectroscopy (ETAAS). The detection Limits of Pb(II) and Cd(II) for an extraction of 5.0 mL water sample were 4.4 and 1.5 ng L − 1 , respectively. The relative standard deviations (R.S.D.) were 3.2% and 2.5% for Pb(II) and Cd(II), respectively. The optimized method was successfully applied to the determination of Pb(II) and Cd(II) in certified reference materials and real water samples.

Solid-phase extraction and pre-concentration of trace metals in natural waters using indigenously synthesized chelating resin and their subsequent determination by ICP-OES

A laboratory made chelating resin based on immobilization of fluorinated β-diketone group on styrene divinyl benzene was employed for the extraction and pre-concentration of trace metals in natural water samples before their determination by inductively coupled plasma optical emission spectrometry (ICP-OES). Extraction efficiency of the resin toward metal ions was examined by column procedure. Various experimental parameters consisting pH, sample loading flow rate, eluent concentration/volume and breakthrough limits were investigated for the effective uptake of metals on the resin. The resin capacity at pH (9) was found to be 10.20, 9.13, 7.47, 8.67, 3.12, 6.45 and 9.80 mg g−1 for Cd (Cadmium), Co (Cobalt), Fe (Iron), Mn (Manganese), Mo (Molybdenum), Ni (Nickel) and Zn (Zinc), respectively. The method was applied for the extraction/pre-concentration of Cd, Co, Fe, Mn, Mo, Ni and Zn in natural water samples and their subsequent determination was carried out by ICP-OES. Percentage recoveries obtained for the selected metals except Mo were ≥ 95% under similar experimental conditions with < 5% relative standard deviation. Alkali/alkaline earth metals, the major matrix ions were not retained on the resin, the resin is selective for trace metals, therefore it is suitable for the extraction of these metals in natural water samples for environmental and health-related studies. © 2011 Curtin University of Technology and John Wiley & Sons, Ltd.

Open-channel chip-based solid-phase extraction combined with inductively coupled plasma-mass spectrometry for online determination of trace elements in volume-limited saline samples

In this study, we used an automated online chip-based solid-phase extraction (SPE)–inductively coupled plasma-mass spectrometry (ICP-MS) system for analyzing trace elements in small-volume saline samples (∼15 μL). The proposed method involved the adsorption of trace metal ions in the interior of a functionalized poly(methyl methacrylate) (PMMA) channel in order to separate these ions from saline matrices. The adsorption of transition metal ions was presumably dominated by the surface complexation between the carboxylate moieties in the interior of the PMMA channel and the metal ions, which facilitated the formation of metal–carboxylate complexes. The components of the proposed online analytical system used for the simultaneous detection of multiple trace metals in saline samples involved microdialysis (MD) sampling, an established chip-based SPE procedure, and ICP-MS. The SPE–ICP-MS hyphenated system was optimized, and then, the analytical reliability of this system was further confirmed by using it to analyze the certified reference materials—SRM 2670 (human urine) and SRM 1643e (artificial saline water). The satisfactory analytical results indicated that the proposed on-chip SPE device could be readily used as an interface for coupling the MD probe with the ICP-MS system. The dramatically reduced consumption of chemicals and “hands-on” manipulations enabled the realization of a simplified and relatively clean procedure with extremely low detection limits in the range of 5.86–76.91 ng L −1 for detecting Mn, Co, Ni, Cu, and Pb in 15-μL samples by ICP-MS. The effectiveness of an online MD–chip-based SPE–ICP-MS technique for continuous monitoring of trace elements in a simulated biological system was also demonstrated. To the best of our knowledge, this is the first paper to report the direct exploitation of a PMMA chip as an SPE adsorbent for online sample pretreatment and trace metal preconcentration prior to ICP-MS measurement.

Behavior of Oil–Aqueous Solution Systems in Rotating Coil Column

Behavior of oil-aqueous solution systems used for oil analysis in rotating coil column (RCC) has been studied. An RCC can be used as effective tool for pre-concentration and isolation of trace metals from crude oil and oil products into acidic solutions. An oil sample is continuously pumped through column as a mobile phase whereas an aqueous acidic solution is retained in the column as a liquid stationary phase. The main dependences of the stationary phase retention on construction and operating parameters as well as on the physicochemical properties have been investigated. Optimal values of density and viscosity of crude oil and oil products that could be analyzed with an RCC were estimated. Theoretical dependences of the stationary phase retention on density and viscosity differences between stationary and mobile phases were obtained. These studies allow predicting the retention of the different oil/oil product-aqueous solution systems in an RCC.

Selection and design criteria of supported liquid membrane for the treatment of rad-waste

Supported Liquid Membrane (SLM) is an emerging trace metal pre-concentration technique. It has the ability to decontaminate radionuclides even from lean secondary effluent. SLM can be considered as a part of process intensification, which implies a closed loop operation. It has reduced space requirement as well as minimised secondary effluent generation and the number of unit steps. Proper selection of molecular design criteria helps in deciding performances such as selectivity, compatibility, permeability, etc., that is attributed to both feed and desired strippant characteristics, and great effort has been applied for nuclear plant waste treatment generated in the uranium metal plant of Trombay, India. This paper articulates basic views of SLM, selection of carrier by experimental verification with respect to both feed and strippant for further processing, and structural aspects with evidences (from FT-IR studies).

Development of a robust ionic liquid-based dispersive liquid–liquid microextraction against high concentration of salt for preconcentration of trace metals in saline aqueous samples: Application to the determination of Pb and Cd

A new ionic liquid-based dispersive liquid–liquid microextraction method was developed for preconcentration and determination of compounds in aqueous samples containing very high salt concentrations. This method can solve the problems associated with the limited application of the conventional IL-based DLLME in these samples. This is believed to arise from dissolving of the ionic liquids in aqueous samples with high salt content. In this method, the robustness of microextraction system against high salt concentration (up to 40%, w/v) is increased by introducing a common ion of the ionic liquid into the sample solution. The proposed method was applied satisfactorily to the preconcentration of lead and cadmium in saline samples. After preconcentration, the settled IL-phase was dissolved in 100 μL ethanol and aspirated into the flame atomic absorption spectrometer (FAAS) using a home-made microsample introduction system. Several variables affecting the microextraction efficiency were investigated and optimized. Under the optimized conditions and preconcentration of only 10 mL of sample, the enhancement factors of 273 and 311 and the detection limits of 0.6 μg L −1 and 0.03 μg L −1 were obtained for lead and cadmium, respectively. Validation of the method was performed by both an analysis of a certified reference material (CRM) and comparison of results with those obtained by ISO standard method.

Application of modified nano-alumina as a solid phase extraction sorbent for the preconcentration of Cd and Pb in water and herbal samples prior to flame atomic absorption spectrometry determination.

The first study on the high efficiency of nanometer-sized gamma-alumina coated with sodium dodecyl sulfate-1-(2-pyridylazo)-2-naphthol (SDS-PAN) as a new sorbent solid phase extraction (SPE) has been reported. A microcolumn packed with modified nanometer-sized alumina was used to preconcentrate and separate Cd and Pb in water and herbal samples. The metals were eluted with 2 mL HNO(3) directly and detected with the detection system flame atomic absorption spectrometry (FAAS). Various influencing parameters on the separation and preconcentration of trace metals, such as pH, flow rate, sample volume, amount of sorbent, and concentration of eluent, were studied. Under the optimized operating conditions, the sorption capacities of the modified nano-gamma-alumina for Cd and Pb were 11.1 and 16.4 mg g(-1) respectively. With 500.0 mL sample an enrichment factor of 250 was obtained. The detection limits of this method for Cd and Pb were 0.15 and 0.17 microg L(-1) and the R.S.D.s were 2.8 and 3.2% (n=10), respectively. The proposed method has been applied to the determination of these metal ions at trace levels in certified reference materials and real samples with satisfactory results.