Bismuth-dispersed xerogel-based composite films for trace Pb(II) and Cd(II) voltammetric determination

We report for the first time the synthesis of bismuth-modified (3-mercaptopropyl) trimethoxysilane (MPTMS) and its application for the determination of lead and cadmium by anodic stripping voltammetry. Xerogels made from bismuth-modified MPTMS and mixtures of it with tetraethoxysilane, under basic conditions (NH₃·H₂O), were characterized with scanning electron microscopy, energy dispersive spectroscopy, infrared spectroscopy and electrochemical methods. Bismuth-modified xerogels were mixed with 1.5% (v/v) Nafion in ethanol and applied on glassy carbon electrodes. During the electrolytic reductive deposition step, the bismuth compound on the electrode surface was reduced to metallic bismuth. The target metal cations were simultaneously reduced to the respective metals and were preconcentrated on the electrode surface by forming an alloy with bismuth. Then, an anodic voltammetric scan was applied in which the metals were oxidized and stripped back into the solution; the voltammogram was recorded and the stripping peak heights were related to the concentration of Cd(II) and Pb(II) ions in the sample. Various key parameters were investigated in detail and optimized. The effect of potential interferences was also examined. Under optimum conditions and for preconcentration period of 4 min, the 3σ limit of detection was 1.3 μg L⁻¹ for Pb(II) and 0.37 μg L⁻¹ for Cd(II), while the reproducibility of the method was 4.2% for lead (n = 5, 10.36 μg L⁻¹ Pb(II)) and 3.9% for cadmium (n = 5, 5.62 μg L⁻¹ Cd(II)). Finally, the sensors were applied to the determination of Cd(II) and Pb(II) ions in water samples.     

Sequential injection anodic stripping voltammetry with monosegmented flow and in-line UV digestion for determination of Zn(II), Cd(II), Pb(II) and Cu(II) in water samples

A cost-effective sequential injection system incorporating with an in-line UV digestion for breakdown of organic matter prior to voltammetric determination of Zn(II), Cd(II), Pb(II) and Cu(II) by anodic stripping voltammetry (ASV) on a hanging mercury drop electrode (HMDE) of a small scale voltammetric cell was developed. A low-cost small scale voltammetric cell was fabricated from disposable pipet tip and microcentrifuge tube with volume of about 3 mL for conveniently incorporated with the SI system. A home-made UV digestion unit was fabricated employing a small size and low wattage UV lamps and flow reactor made from PTFE tubing coiled around the UV lamp. An in-line single standard calibration or a standard addition procedure was developed employing a monosegmented flow technique. Performance of the proposed system was tested for in-line digestion of model water samples containing metal ions and some organic ligands such as strong organic ligand (EDTA) or intermediate organic ligand (humic acid). The wet acid digestion method (USEPA 3010a) was used as a standard digestion method for comparison. Under the optimum conditions, with deposition time of 180 s, linear calibration graphs in range of 10-300 μg L⁻¹ Zn(II), 5-200 μg L⁻¹ Cd(II), 10-200 μg L⁻¹ Pb(II), 20-400 μg L⁻¹ Cu(II) were obtained with detection limit of 3.6, 0.1, 0.7 and 4.3 μg L⁻¹, respectively. Relative standard deviation were 4.2, 2.6, 3.1 and 4.7% for seven replicate analyses of 27 μg L⁻¹ Zn(II), 13 μg L⁻¹ Cd(II), 13 μg L⁻¹ Pb(II) and 27 μg L⁻¹ Cu(II), respectively. The system was validated by certified reference material of trace metals in natural water (SRM 1640 NIST). The developed system was successfully applied for speciation of Cd(II) Pb(II) and Cu(II) in ground water samples collected from nearby zinc mining area.     

Determination of trace heavy metals in herbs by sequential injection analysis-anodic stripping voltammetry using screen-printed carbon nanotubes electrodes

A method for the simultaneous determination of Pb(II), Cd(II), and Zn(II) at low μg L⁻¹ concentration levels by sequential injection analysis-anodic stripping voltammetry (SIA-ASV) using screen-printed carbon nanotubes electrodes (SPCNTE) was developed. A bismuth film was prepared by in situ plating of bismuth on the screen-printed carbon nanotubes electrode. Operational parameters such as ratio of carbon nanotubes to carbon ink, bismuth concentration, deposition time and flow rate during preconcentration step were optimized. Under the optimal conditions, the linear ranges were found to be 2-100 μg L⁻¹ for Pb(II) and Cd(II), and 12-100 μg L⁻¹ for Zn(II). The limits of detection (S_bl/S = 3) were 0.2 μg L⁻¹ for Pb(II), 0.8 μg L⁻¹ for Cd(II) and 11 μg L⁻¹ for Zn(II). The measurement frequency was found to be 10-15 stripping cycle h⁻¹. The present method offers high sensitivity and high throughput for on-line monitoring of trace heavy metals. The practical utility of our method was also demonstrated with the determination of Pb(II), Cd(II), and Zn(II) by spiking procedure in herb samples. Our methodology produced results that were correlated with ICP-AES data. Therefore, we propose a method that can be used for the automatic and sensitive evaluation of heavy metals contaminated in herb items.     

Antimony-film electrode for the determination of trace metals by sequential-injection analysis/anodic stripping voltammetry

The possibility of applying antimony-film modified glassy carbon electrode in sequential-injection analysis (SIA) was investigated with the objective of determining Pb(II) and Cd(II) by anodic stripping voltammetry (ASV). The conditions of antimony-film deposition concerning composition of the plating/carrier solutions, concentrations of Sb(III) and hydrochloric acid, effects of different supporting electrolyte salts, and plating potential were optimized. It was found that the antimony-film deposition on glassy carbon substrate in a sample solution consisting of 750 μg L⁻¹ Sb(III), 0.5 mol L⁻¹ HCl at −1.5 V (vs. Ag/AgCl/3 mol L⁻¹ KCl) yielded a modified electrode suitable for the determination of Pb(II) and Cd(II) at the μg L⁻¹ level. The reproducibility of the analytical signals was characterized by a relative standard deviation lower than 2.8%, and the calculated values of detection limits were 1.2 μg L⁻¹ for Pb(II) and 1.4 μg L⁻¹ for Cd(II). The presence of KSCN in the sample solution offers the possibility of detecting ions with more negative oxidation potentials like Zn(II), Mn(II) or Cr(III). The developed SIA-ASV procedure was compared with the commonly used batch method, and its applicability was tested on a spiked tap water sample.     

Simultaneous determination of Cd(II) and Pb(II) by differential pulse anodic stripping voltammetry based on graphite nanofibers-Nafion composite modified bismuth film electrode

A bismuth-film modified graphite nanofibers-Nafion glassy carbon electrode (BiF/GNFs-NA/GCE) was constructed for the simultaneous determination of trace Cd(II) and Pb(II). The electrochemical properties and applications of the modified electrode were studied. Operational parameters such as deposition potential, deposition time, and bismuth ion concentration were optimized for the purpose of determination of trace metal ions in 0.10 M acetate buffer solution (pH 4.5). Under optimal conditions, based on three times the standard deviation of the baseline, the limits of detection were 0.09 μg L⁻¹ for Cd(II) and 0.02 μg L⁻¹ for Pb(II) with a 10 min preconcentration. In addition, the BiF/GNFs-NA/GCE displayed good reproducibility and selectivity, making it suitable for the simultaneous determination of Cd(II) and Pb(II) in real sample such as river water and human blood samples.     

Sequential injection monosegmented flow voltammetric determination of cadmium and lead using a bismuth film working electrode

A cost-effective sequential injection monosegmented flow analysis (SI-MSFA) with anodic stripping voltammetric (ASV) detection has been developed for determination of Cd(II) and Pb(II). The bismuth film working electrode (BiFE) was employed for accumulative preconcentration of the metals by applying a fixed potential of −1.10 V versus Ag/AgCl electrode for 90 s. The SI-MSFA provides a convenient means for preparation of a homogeneous solution zone containing sample in an acetate buffer electrolyte solution and Bi(III) solution for in situ plating of BiFE, ready for ASV measurement at a flow through thin layer electrochemical cell. Under the optimum conditions, linear calibration graphs in range of 10-100 μg L⁻¹ of both Cd(II) and Pb(II) were obtained with detection limits of 1.4 and 6.9 μg L⁻¹ of Cd(II) and Pb(II), respectively. Relative standard deviations were 2.7 and 3.1%, for 11 replicate analyses of 25 μg L⁻¹ Cd(II) and 25 μg L⁻¹ Pb(II), respectively. A sample throughput of 12 h⁻¹ was achieved with low consumption of reagent and sample solutions. The system was successfully applied for analysis of water samples collected from a draining pond of zinc mining, validating by inductively coupled plasma-optical emission spectroscopy (ICP-OES) method.     

Antimony film screen-printed carbon electrode for stripping analysis of Cd(II), Pb(II), and Cu(II) in natural samples

An in-situ antimony film screen-printed carbon electrode (in-situ SbSPCE) was successfully used for the determination of Cu(II) simultaneously with Cd(II) and Pb(II) ions, by means of differential pulse anodic stripping voltammetry (DPASV), in a certified reference groundwater sample with a very high reproducibility and good trueness. This electrode is proposed as a valuable alternative to in-situ bismuth film electrodes, since no competition between the electrodeposited copper and antimony for surface sites was noticed. In-situ SbSPCE was microscopically characterized and experimental parameters such as deposition potential, accumulation time and pH were optimized. The best voltammetric response for the simultaneous determination of Cd(II), Pb(II) and Cu(II) ions was achieved when deposition potential was −1.2 V, accumulation time 120 s and pH 4.5. The detection and quantification limits at levels of μg L⁻¹ suggest that the in-situ SbSPCE could be fully suitable for the determination of Cd(II), Pb(II) and Cu(II) ions in natural samples.     

Anodic Stripping Voltammetry Determination of Pb(II) and Cd(II) at a Bismuth/Poly(aniline) Film Electrode

Abstract

A novel voltammetric method—anodic—using a bismuth/poly(aniline) film electrode has been developed for simultaneous measurement of Pb(II) and Cd(II) at low µg L^?1 concentration levels by stripping voltammetry. The results confirmed that the bismuth/poly(aniline) film electrode offered high‐quality stripping performance compared with the bismuth film electrode. Well‐defined sharp stripping peaks were observed for Pb(II) and Cd(II), along with an extremely low baseline. The detection limits of Pb(II) and Cd(II) are 1.03 µg L^?1 and 1.48 µg L^?1, respectively. The bismuth/poly (aniline) electrode has been applied to the determination of Pb(II) in tap water samples with satisfactory results.     

Sensitive and stable monitoring of lead and cadmium in seawater using screen-printed electrode and electrochemical stripping analysis

Sensitive and stable monitoring of heavy metals in seawater using screen-printed electrodes (SPE) is presented. The analytical performance of SPE coupled with square wave anodic stripping voltammetry (SWASV) for the simultaneous determination of Pb and Cd in seawater samples, in the low μg L⁻¹ range, is evaluated. The stripping response for the heavy metals following 2 min deposition was linear over the concentration range examined (10-2000 μg L⁻¹) with detection limits of 1.8 and 2.9 μg L⁻¹ for Pb and Cd, respectively. The accuracy of the method was validated by analyzing metal contents in different spiked seawater samples and comparing these results to those obtained with the well-established anodic stripping voltammetry using the hanging mercury drop electrode. Moreover, a certified reference material was also used and the results obtained were satisfactory.     

Disposable Nafion-modified micro-fabricated bismuth-film sensors for voltammetric stripping analysis of trace metals in the presence of surfactants

This work is a study of the analytical utility of Nafion-modified microfabricated bismuth film electrodes (BiFEs) for the determination of Pb(II) and Cd(II) by anodic stripping voltammetry (ASV) in the presence of surfactants. Micro-fabricated BiFEs were prepared by depositing a thin film of bismuth on the surface of a silicon substrate by sputtering while the two-dimensional geometry of the final sensors was defined by photolithography. The BiFEs were further drop-coated with a Nafion film. These devices were applied to the determination of Pb(II) and Cd(II) by square wave ASV (SWASV) in the presence of Triton X-100 (a non-ionic surfactant), cetyltrimethylammonium bromide (CTAB) (a cationic surfactant) and sodium dodecyl sulphate (SDS) (an anionic surfactant). It was found that the presence of Nafion afforded an increase in sensitivity and the tolerance against surfactants but these properties were severely influenced by both the thickness of the Nafion film and the nature of the interfering surfactant. Using a Nafion of 0.4 μm thickness and 120 s of preconcentration, the repeatability (expressed as the % relative standard deviation on the same sensor (n = 8)) at the 20 μg l⁻¹ level was 3.8% for Pb(II) and 3.1% for Cd(II) and the limits of detection were 0.5 μg l⁻¹ for Cd(II) and Pb(II). The sensors were applied to Cd(II) and Pb(II) determination in a certified lake-water sample.     

Simultaneous determination of nickel(II) and cobalt(II) by square wave adsorptive stripping voltammetry on a rotating-disc bismuth-film electrode

This works reports the use of square-wave adsorptive stripping voltammetry (SWAdSV) for the simultaneous determination of Ni(II) and Co(II) on a rotating-disc bismuth-film electrode (BFE). The metal ions in the non-deoxygenated sample were complexed with dimethylglyoxime (DMG) and the complexes were accumulated by adsorption on the surface of the BFE. The stripping step was carried out by using a square-wave potential-time voltammetric excitation signal. Electrochemical cleaning of the bismuth film was employed, enabling the same bismuth film to be used for a series of measurements. The experimental variables (choice of the working electrode substrate, the presence of oxygen, the DMG concentration, the buffer concentration, the preconcentration potential, the accumulation time, the rotation speed and the SW parameters) as well as potential interferences were investigated and the figures of merit of the methods were established. Using the selected conditions, the 3σ limits of detection were 70 ng l⁻¹ for Co(II) and 100 ng l⁻¹ for Ni(II) (for 300 s of preconcentration) and the relative standard deviations were 2.3% for Co(II) and 3.9% for Ni(II) at the 2 μg l⁻¹ level (n = 8). Finally, the method was applied to the determination of nickel and cobalt in real samples with satisfactory results.     

Individual and simultaneous determination of lead, cadmium, and zinc by anodic stripping voltammetry at a bismuth bulk electrode

A bismuth bulk electrode (BiBE) has been investigated as an alternative electrode for the anodic stripping voltammetric (ASV) analysis of Pb(II), Cd(II), and Zn(II). The BiBE, which is fabricated in-house, shows results comparable to those of similar analyses at other Bi-based electrodes. Metal accumulation is achieved by holding the electrode potential at −1.4 V (vs. Ag/AgCl) for 180 s followed by a square wave voltammetric stripping scan from −1.4 to −0.35 V. Calibration plots are obtained for all three metals, individually and simultaneously, in the10-100 μg L⁻¹ range, with a detection limit of 93, 54, and 396 ng L⁻¹ for Pb(II), Cd(II), Zn(II), respectively. A slight reduction in slope is observed for Cd(II) and Pb(II) when the three metals are calibrated simultaneously vs. individually. Comparing the sensitivities of the metals when calibrated individually vs. in a mixture reveals that Zn(II) is not affected by stripping in a mixture. However, Pb(II) and Cd(II) have decreasing sensitivities in a mixture. The optimized method has been successfully used to test contaminated river water by standard addition. The results demonstrate the ability of the BiBE as an alternative electrode material in heavy metal analysis.     

A novel flow injection chemiluminescence determination of Cr(VI) with Dichlorotris(1,10-phenanthroline)ruthenium(II)

A selective novel reverse flow injection system with chemiluminescence detection (rFI-CL) for the determination of Cr(VI) in presence of Cr(III) with Dichlorotris (1,10-phenanthroline)ruthenium(II), (Ru(phen)₃Cl₂), is described in this work. This new method is based on the oxidation capacity of Cr(VI) in H₂SO₄ media. First, the Ruthenium(II) complex is oxidized to Ruthenium(III) complex by Cr(VI) and afterwards it is reduced to the excited state of the Ruthenium(II) complex by a sodium oxalate solution, emitting light inside the detector. The intensity of chemiluminescence (CL) is proportional to the concentration of Cr(VI) and, under optimum conditions, it can be determined over the range of 3-300 μg L⁻¹ with a detection limit of 0.9 μg L⁻¹. The RSD was 8.4% and 1.5% at 5 and 50 μg L⁻¹, respectively. For the rFI-CL method various analytical parameters were optimized: flow rate (1 mL min⁻¹), H₂SO₄ carrier concentration (20% w/V), Ru(phen)₃Cl₂ concentration (5 mM) and sodium oxalate concentration (0.1 M). The effect of Cr(III), Fe(III), Al(III), Cd(II), Zn(II), Hg(II), Pb(II), Ca(II) and Mg(II), was studied. The method is highly sensitive and selective, allowing a fast, on-line determination of Cr(VI) in the presence of Cr(III). Finally, the method was tested in four different water samples (tap, reservoir, well and mineral), with good recovery percentage.     

Microfabricated disposable lab-on-a-chip sensors with integrated bismuth microelectrode arrays for voltammetric determination of trace metals

This work reports the fabrication of disposable three-electrode cells with integrated metal-film electrodes. The devices were fabricated by a multi-step micro-fabrication approach combining sputtering for the deposition of metals and the dielectric material (SiO₂) on the surface of a silicon wafer and photolithography for the definition of the geometry of the sensors. The working electrode was a microelectrode array consisting of bismuth microdisks while the reference and counter electrode strips were made of Ag and Pt, respectively. The utility of these devices was tested for the trace determination of Pb(II) and Cd(II) by anodic stripping voltammetry and Ni(II) by adsorptive stripping voltammetry. The detection of these trace metals was carried out in unstirred and undeoxygenated solutions exhibiting sub-μg L⁻¹ limits of detection and enhanced analytical characteristics compared to conventional bismuth-film electrodes.     

Voltammetric determination of Cu(II) in natural waters and human hair at a meso-2,3-dimercaptosuccinic acid self-assembled gold electrode

An electrochemical sensor for the detection of copper(II) ions is described using a meso-2,3-dimercaptosuccinic acid (DMSA) self-assembled gold electrode. First in ammonia buffer pH 8, copper(II) ions complex with self-assembled monolayer (SAM) via the free carboxyl groups on immobilized meso-2,3-dimercaptosuccinic acid (accumulation step). Then, the medium is exchanged to acetate buffer pH 4.6 and the complexed Cu(II) ions are reduced in negative potential of −0.3 V (reduction step). Following this, reduced coppers are oxidized and detected by differential pulse (DP) voltammetric scans from −0.3 to +0.7 V (stripping step). The effective parameters in sensor response were examined. The detection limit of copper(II) was 1.29 μg L⁻¹ and R.S.D. for 200 μg L⁻¹ was 1.06%. The calibration curve was linear for 3-225 μg L⁻¹ copper(II). The procedure was applied for determination of Cu(II) to natural waters and human hairs. The accuracy and precision of results were comparable to those obtained by flame atomic absorption spectroscopy (FAAS).     

Sensitive electrochemical sensor using a graphene–polyaniline nanocomposite for simultaneous detection of Zn(II), Cd(II), and Pb(II)

This work describes the development of an electrochemical sensor for simultaneous detection of Zn(II), Cd(II), and Pb(II) using a graphene–polyaniline (G/PANI) nanocomposite electrode prepared by reverse-phase polymerization in the presence of polyvinylpyrrolidone (PVP). Two substrate materials (plastic film and filter paper) and two nanocomposite deposition methods (drop-casting and electrospraying) were investigated. Square-wave anodic stripping voltammetry currents were higher for plastic vs. paper substrates. Performance of the G/PANI nanocomposites was characterized by scanning electron microscopy (SEM) and cyclic voltammetry. The G/PANI-modified electrode exhibited high electrochemical conductivity, producing a three-fold increase in anodic peak current (vs. the unmodified electrode). The G/PANI-modified electrode also showed evidence of increased surface area under SEM. Square-wave anodic stripping voltammetry was used to measure Zn(II), Cd(II), and Pb(II) in the presence of Bi(III). A linear working range of 1–300 μg L⁻¹ was established between anodic current and metal ion concentration with detection limits (S/N = 3) of 1.0 μg L⁻¹ for Zn(II), and 0.1 μg L⁻¹ for both Cd(II) and Pb(II). The G/PANI-modified electrode allowed selective determination of the target metals in the presence of common metal interferences including Mn(II), Cu(II), Fe(III), Fe(II), Co(III), and Ni(II). Repeat assays on the same device demonstrated good reproducibility (%RSD < 11) over 10 serial runs. Finally, this system was utilized for determining Zn(II), Cd(II), and Pb(II) in human serum using the standard addition method.     

Determination of Pb in natural waters with 2-mercaptobenzimidazole-5-sulfonate (MBIS)chemically modified gold electrode

The preparation, characterization and analytical applications of gold electrodes modified with ω-mercapto alkyl/aryl sulfonates are described. The devices resulted effective for the determination of free and labile Pb(II) in water samples by anodic stripping voltammetry (E_dep = −600 mV) and in particular 2-mercaptobenzimidazole-5-sulfonate (MBIS) offered the best performances with detection limit of 0.4 μg L⁻¹.Quantitative stripping of Pb from the electrode surface during the anodic scan, is obtained using sodium citrate buffer (pH = 9.0) as supporting electrolyte. Natural waters were analysed by standard addition method with good recoveries (mean percentage = 97%); no fouling effects due to humic acids or other organic constituents were observed in the reported conditions.     

Preparation of a new Cd(II)-imprinted polymer and its application to determination of cadmium(II) via flow-injection-flame atomic absorption spectrometry

A new cadmium(II)-imprinted polymer based on cadmium(II) 2,2′-{ethane-1,2-diylbis[nitrilo(E)methylylidene]} diphenolate-4-vinylpyridine complex was obtained via suspension polymerization. The beads were used as a minicolumn packing for flow-injection-flame atomic absorption spectrometry (FI-FAAS) determination of cadmium(II) in water samples. Sorption effectiveness was optimal within pH range of 6.6-7.7. Nitric acid, 0.5% (v/v) was used as eluent. Fast cadmium(II) sorption by the proposed material enabled to apply sample flow rates up to 10 mL min⁻¹ without loss in sorption effectiveness. Enrichment factor (EF), concentration efficiency (CE) and limit of detection (LOD, 3σ) found for 120-s sorption time were 117, 39.1 min⁻¹ and 0.11 μg L⁻¹, respectively. Sorbent stability was proved for at least 100 preconcentration cycles (RSD = 2.9%). When compared to non-imprinted polymer the new Cd(II)-imprinted polymer exhibited improved selectivity towards cadmium(II) against other heavy metal ions, especially Cu(II) and Pb(II), as well as light metal ions. Accuracy of the method was tested for ground water and waste water certified reference materials and fortified water. The method was applied to Cd(II) determination in natural water samples.     

Hg(II) immobilized MWCNT graphite electrode for the anodic stripping voltammetric determination of lead and cadmium

The preparation of Hg(II)-modified multi walled carbon nanotube (MWCNT) by reaction of oxidized MWCNT with aqueous HgCl₂ was carried out. The Hg(II)-modified multi walled carbon nanotube (Hg(II)/MWCNT) dispersed in Nafion solution was used to coat the polished graphite electrode surface. The Hg(II)/MWCNT modified graphite electrode was held at a cathodic potential (−1.0 V) to reduce the coordinated Hg(II) to Hg forming nanodroplets of Hg. The modified electrode was characterized by FESEM/EDAX which provided useful insights on the morphology of the electrode. The SEM images showed droplets of Hg in the size of around 260 nm uniformly distributed on the MWCNT. Differential pulse anodic stripping voltammetry (DPASV) and electrochemical impedance spectroscopy were used to study the Hg(II) binding with MWCNT. Differential pulse anodic stripping voltammetry of ppb levels of cadmium and lead using the modified electrode yielded well-defined peaks with low background current under a short deposition time. Detection limit of 0.94 and 1.8 ng L⁻¹ were obtained following a 3 min deposition for Pb(II) and Cd(II), respectively. Various experimental parameters were characterized and optimized. High reproducibility was observed from the RSD values for 20 repetitive measurements of Pb(II) and Cd(II) (1.7 and 1.9%, respectively). The determination of Pb(II) and Cd(II) in tap water and Pb(II) in human hair samples was carried out. The above method of fabrication of Hg(II)/MWCNT modified graphite electrode clearly suggests a safe route for preparing Hg immobilized electrode for stripping analysis.     

Determination of cadmium, lead and thallium in highly saline hemodialysis solutions by potentiometric stripping analysis (PSA)

Potentiometric stripping analysis (PSA) was investigated to assay simultaneously cadmium, lead and thallium present as contaminants in highly saline solutions used in hemodialysis. The saline matrices were sodium, potassium, magnesium and calcium chlorides, sodium acetate, sodium bicarbonate and glucose, which constitute concentrates for hemodialysis. A 1000 μg mL⁻¹ Hg(II) solution was used to prepare the mercury film electrode (MFE) and to carry out the stripping step. After a 30 s accumulation interval the analytes were simultaneously detected in the saline matrices without using masking agents. Determination limits of 80 ng L⁻¹ for cadmium and thallium, and 50 ng L⁻¹ for lead were calculated and a R.S.D. ranging from 0.5 to 2.2% (n = 3) was obtained measuring the analytes directly in commercial hemodialysis saline solutions. Recoveries from spiked samples ranging from 94.6 to 102.0% were obtained. The investigated metals were found in concentrations ranging from 2.7 to 5.7 μg L⁻¹ for cadmium, 27.7 to 75.8 μ L⁻¹ for lead and 9.6 to 18.7 μg L⁻¹ for thallium in commercial hemodialysis solutions. The PSA method showed to be adequate to the quality control of saline concentrates for hemodialysis.