Determination of lead in water samples by graphite furnace atomic absorption spectrometry after cloud point extraction

Cloud point extraction (CPE) has been used for the pre-concentration of lead, after the formation of a complex with 2-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol (5-Br-PADAP), and later analysis by graphite furnace atomic absorption spectrometry (GFAAS) using octylphenoxypolyethoxyethanol (TritonX-114) as surfactant. The chemical variables affecting the separation phase were optimized. Separation of the two phases was accomplished by centrifugation for 15 min at 4000 rpm. Under the optimum conditions i.e., pH 8.0, cloud point temperature 40 °C, [5-Br-PADAP] = 2.5 × 10⁻⁵ mol l⁻¹, [Triton X-114] = 0.05%, added methanol volume = 0.15 ml, pre-concentration of only 10 ml sample permitted an enhancement factor of 50-fold. The lower limit of detection (LOD) obtained under the optimal conditions was 0.08 μg l⁻¹. The precision for 10 replicate determinations at 5 μg l⁻¹ Pb was 2.8% relative standard deviation (R.S.D.). The calibration graph using the pre-concentration system for lead was linear with a correlation coefficient of 0.9984 at levels near the detection limits up to at least 30 μg l⁻¹. The method was successfully applied to the determination of lead in water samples.     

ICP-AES determination of small amounts of zinc in copper-base alloys after separation by adsorption of the zinc-TAN complex on Sep Pak C18 cartridges

The use of ICP/AES for the determination of zinc, in low concentration levels, in matrices containing high levels of copper is difficult because copper interferes in the zinc main emission wavelength (213.856 nm). In the present work, a separation of zinc from copper matrices was possible, using the reaction of zinc(II) cation with 1-(2-tiazolylazo)-2-naphthol (TAN), in the pH range of 6.5–8.0, resulting in a stable red complex. Copper also reacts with TAN but its interference was avoided by the addition of ascorbic acid and thiosulphate in the reaction medium. In this way, the aqueous solution was passed through a SEP PAK C18 cartridge, in which the zinc(II)–TAN complex was quantitatively retained, but it did not occur with copper which passes through the cartridge, as [Cu₂(S₂O₃)₂]²⁻, with the aqueous solution. The cartridge was washed with water and the complex eluted with ethanol. Then, the alcohol was evaporated and the complex decomposed by nitric acid. It results in both zinc pre-concentration and separation from copper. The zinc quantification was carried out by ICP/AES at 213.856 nm. The relative standard deviations, for ten different aliquots, were 5.7% and the average recovery found for zinc was 96%, even when the concentration ratio Cu/Zn was up to 500/1 (mg l⁻¹:mg l⁻¹). Other metals, like nickel, for example, can react with TAN in the same way as zinc but they do not interfere in the emission wavelength 213.856 nm.     

Spectrophotometric determination of manganese with 1-(2-pyridylazo)-2-naphthol and a non-ionic surfactant

A spectrophotometric method for the determination of trace amounts of manganese with 1-(2-pyridylazo)-2-naphthol (PAN) is described. The method is based on the measurement of absorbance of the manganese—PAN chelate solubilized with a non-ionic surfactant, Triton X-100. No extraction procedure is required in the method proposed. High concentrations of calcium, aluminium and magnesium do not interfere. The presence of up to 10 ppm of lead can be tolerated. Iron, cadmium, zinc, cobalt and nickel can be effectively masked with potassium cyanide. Beer's law is obeyed up to 2 ppm of manganese. The molar absorptivity of the manganese—PAN chelate found was 4.4 × 10⁴ l. mole ⁻¹. cm⁻¹ at 562 nm. The overall stability constant of Mn(PAN)₂ in 0.4% Triton X-100 medium is 10^16.8.     

Cloud point preconcentration and flame atomic absorption spectrometric determination of Cd and Pb in human hair

Cloud point methodology has been successfully used for the preconcentration of trace amounts of Cd and Pb as a prior step to their determination by flame atomic absorption spectrometry. O,O-Diethyldithiophosphate and Triton X-114 are used as hydrophobic ligand and non-ionic surfactant, respectively. After phase separation at 40 °C based on cloud point of the mixture, the surfactant-rich phase is diluted with methanol. The enriched analyte in the final solution is determined by flame atomic absorption spectrometry using conventional nebulization. After optimization of the complexation and extraction conditions, enhancement factors of 22 and 43 were obtained for Cd and Pb, respectively. Under the experimental conditions used, preconcentration of only 10 ml of sample in the presence of 0.05% (v/v) Triton X-114 permitted the detection of 0.62 μg l⁻¹ of Cd and 2.86 μg l⁻¹of Pb. The proposed method was applied to the determination of Cd and Pb in human hair samples.     

Validation of an inductively coupled plasma mass spectrometry (ICP-MS) method for the determination of cerium, strontium, and titanium in ceramic materials used in radiological dispersal devices (RDDs)

This work describes the optimization of a cloud point extraction (CPE) method for casein proteins from cow milk samples. To promote phase separation, polyoxyethylene(8) isooctylphenyl ether (Triton^® X-114) and sodium chloride (NaCl) were used as nonionic surfactant and electrolyte, respectively. Using multivariate studies, four major CPE variables were evaluated: Triton^® X-114 concentration, sample volume, NaCl concentration, and pH. The results show that surfactant concentration and sample volume were the main variable affecting the CPE process, with the following optimized parameters: 1% (w/v) Triton^® X-114 concentration, 50 μL of sample volume, 6% (w/v) NaCl concentration and extractions carried out at pH 7.0. At these conditions, 923 ± 66 and 67 ± 2 μg mL⁻¹ of total protein were found in the surfactant-rich and surfactant-poor phases, respectively. Finally, matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) was then used to evaluate those target proteins (_s1-casein, _s2-casein and β-casein) separation as well as to check the efficiency of the extraction procedure, making a fingerprint of those target proteins possible.     

Flow injection sorbent extraction with dialkyldithiophosphates as chelating agent for the determination of cadmium, copper and lead by flame atomic absorption spectrometry

Using octadecyl functional groups (C₁₈) bonded to silica gel as sorbent and methanol as eluent, the flow injection sorbent extraction features of dialkyldithiophosphates (RO)₂P(S)S⁻ as the chelating agent for cadmium, copper and lead was investigated in respect of the effects of pH, alkyl substituent group, reagent concentration and masking agent, with flame atomic absorption spectrometric detection. The elements are quantitatively extracted with the short-alkyl-chain reagents (R up to propyl) in acidic medium. The extractability decreases with the number of carbon atoms in the alkyl groups of the reagents and with the reagent concentration when the alkyl groups are larger than butyl, but masking agents increase the extractability. An explanation proposed for this effect is the formation of polynuclear chelates. Diethyldithiophosphate can be used for the selective determination of cadmium, copper and lead in digested solid environmental samples. With 20 s sample loading at 8.7 ml min⁻¹, the enhancement factors are 35 for cadmium and copper or 26 for lead; the detection limits (3σ) are 0.8, 1.4 and 10.0 μg 1⁻¹ for cadmium, copper and lead, respectively.     

Atomic absorption spectrophotometric determination of trace copper in waters, aluminium foil and tea samples after preconcentration with 1-nitroso-2-naphthol-3,6-disulfonic acid on Ambersorb 572

An atomic absorption spectrophotometric method for the determination of trace copper after adsorption of its 1-nitroso-2-naphthol-3,6-disulfonic acid chelate on Ambersorb 572 has been developed. This chelate is adsorbed on the adsorbent in the pH range 1–8. The copper chelate is eluted with 5 ml of 0.1 mol l⁻¹ potassium cyanide and determined by flame atomic absorption spectrometry (FAAS). The selectivity of the proposed procedure was also evaluated. Results show that iron(III), zinc(II), manganese(II) and cobalt(II) at the 50 μg l⁻¹ level and sodium(I), potassium(I), magnesium(II), calcium(II) and aluminium(III) at the 1000 μg l⁻¹ level did not interfere. A high enrichment factor, 200, was obtained. The detection limit (3σ) of copper was 0.34 μg l⁻¹. The precision of the method, evaluated by seven replicate analyses of solutions containing 5 μg of copper was satisfactory and the relative standard deviation was 1.7%. The adsorption of copper onto Ambersorb 572 can formally be described by a Langmuir equation with a maximum adsorption capacity of 14.3 mg g⁻¹ and a binding constant of 0.00444 l mg⁻¹. The accuracy of the method is confirmed by analysing tomatoes leaves (NIST 1573a) and lead base alloy (NBS 53e). The results demonstrated good agreement with the certified values. This procedure was applied to the determination of copper in waters (tap, river and thermal waters), aluminium foil and tea samples.     

Determination of mercury in biological samples by cold vapor atomic absorption spectrometry following cloud point extraction with salt-induced phase separation

Method development for the pre-concentration of mercury in human hair, dogfish liver and dogfish muscle samples using cloud-point extraction and cold vapor atomic absorption spectrometry is demonstrated. Before the extraction, the samples were submitted to microwave-assisted digestion in a mixture of H₂O₂ and HNO₃. Cloud point extraction was carried out using 0.5% (m/v) ammonium O,O-diethyldithiophosphate (DDTP) as the chelating agent and 0.3% (m/v) Triton X-114 as the non-ionic surfactant. Phase separation was induced after the addition of Na₂SO₄ to a final concentration of 0.2 mol L⁻¹. Aliquots of the final extract were transferred to PTFE tubes and NaBH₄ and HCl were added. The mercury vapor was driven to a non-heated quartz tube for measuring the absorbance. The results obtained with salt-induced phase separation were in good agreement with the certified values at a 95% confidence level. An enrichment factor of 10 allowed a detection limit of 0.4 ng g⁻¹ to be obtained, which demonstrates the high sensitivity of the proposed procedure for the determination of mercury at trace levels.     

Biosorption of heavy metals on Aspergillus fumigatus immobilized Diaion HP-2MG resin for their atomic absorption spectrometric determinations

A solid phase extraction procedure based on biosorption of copper(II), lead(II), zinc(II), iron(III), nickel(II) and cobalt(II) ions on Aspergillus fumigatus immobilized Diaion HP-2MG has been investigated. The analytical conditions including amounts of A. fumigatus, eluent type, flow rates of sample and eluent solutions were examined. Good recoveries were obtained to the spiked natural waters. The influences of the concomitant ions on the retentions of the analytes were also examined. The detection limits (3sigma, N = 11) were 0.30 μg l⁻¹ for copper, 0.32 μg l⁻¹ for iron, 0.41 μg l⁻¹ for zinc, 0.52 μg l⁻¹ for lead, 0.59 μg l⁻¹ for nickel and 0.72 μg l⁻¹ for cobalt. The relative standard deviations of the procedure were below 7%. The validation of the presented procedure is performed by the analysis of three standard reference materials (NRCC-SLRS 4 Riverine Water, SRM 1515 Apple leaves and GBW 07605 Tea). The procedure was successfully applied for the determination of analyte ions in natural waters microwave digested samples including street dust, tomato paste, black tea, etc.     

Sequential injection spectrophotometric determination of zinc(II) in pharmaceuticals based on zinc(II)–PAN in non-ionic surfactant medium

A sequential injection analysis (SIA) spectrophotometric method for the determination of trace amounts of zinc(II) with 1-(2-pyridylazo)-2-naphthol (PAN) is described. The method is based on the measurement of absorbance of the zinc(II)–PAN chelate solubilized with a non-ionic surfactant, Triton X-100, no extraction procedure is required in the proposed method, yielding a pink colored complex at pH 9.5 with absorption maximum at 553 nm. The SIA parameters that affect the signal response have been optimized in order to get the better sensitivity and minimum reagent consumption. A linear relationship between the relative peak height and concentration was obtained in the concentration range of 0.1–1.0 μg ml⁻¹. The limit of detection (LOD, defined as 3σ) and limit of quantification (LOQ, defined as 10σ) were 0.02 and 0.06 μg ml⁻¹, respectively. The sample throughput about 40 samples/h was obtained. The repeatability were 1.32 and 1.24% (n = 10) for 0.1 and 0.5 μg ml⁻¹, respectively. The proposed method was successfully applied to the assay of zinc(II) in three samples of multivitamin tablets. The results were found to be in good agreement with those obtained by flame atomic absorption spectrophotometric method and with the claimed values by the manufactures. The t-test showed no significant difference at 95% confidence level.     

Determination of manganese in water samples by flame atomic absorption spectrometry after cloud point extraction

Cloud point extraction has been used for the preconcentration of manganese, after the formation of a complex with 1-(2-thiazolylazo)-2-naphthol (TAN), and later analysis by flame atomic absorption spectrometry using octylphenoxypolyethoxyethanol (Triton X-114) as surfactant. The chemical variables affecting the separation phase and the viscosity affecting the detection process were optimized. Under the optimum conditions (i.e., pH = 9.2, [TAN] = 2.0 x 10(-5) mol l-1, [Triton X-114] = 0.05%, added methanol volume = 0.2 ml), preconcentration of 50 ml of sample solution permitted the detection of 0.28 ppb for manganese. The enhancement factor was 57.6. The proposed method has been applied to the determination of manganese in water samples.     

Field procedures to assess soils and waste disposals

The aim of this research was the development of rapid analytical test methods for arsenic, lead, cadmium, chromium(VI), copper, nickel, and zinc to classify waste materials into waste classes and assess contaminated soils for purification purposes. In order to estimate the danger potentials of contaminated soils, a rapid ecotoxicological method was developed (A. Götzl, H. Malissa, W. Riepe, FACT 3 (6) (1999) 329.). These rapid analytical and ecotoxicological tests offer an instrument to comprehensively assess soils and wastes. The developed rapid methods are suitable for the elution of different soils and wastes, the analysis of the eluates and also for waste waters with concentrations greater than 0.1 mg l⁻¹ arsenic, 0.5 mg l⁻¹ lead, 0.01 mg l⁻¹ cadmium, 0.1 mg l⁻¹ chromium(VI), 0.3 mg l⁻¹ copper, 0.5 mg l⁻¹ nickel and 0.1 mg l⁻¹ zinc in the eluate. Our developed rapid analytical test methods described below can be implemented on site, are of low cost and are not time-consuming (about 30 min). They also do not need to be carried out by highly qualified specialists only, they can also be easily applied by persons with some experience. The comparability of results obtained using the developed rapid test method and standardised methods was tested with various matrices.     

Cloud point extraction equilibrium of lanthanum(III), europium(III) and lutetium(III) using di(2-ethylhexyl)phosphoric acid and Triton X-100

The cloud point extraction behaviors of lanthanoids(III) (Ln(III) = La(III), Eu(III) and Lu(III)) with and without di(2-ethylhexyl)phosphoric acid (HDEHP) using Triton X-100 were investigated. It was suggested that the extraction of Ln(III) into the surfactant-rich phase without added chelating agent was caused by the impurities contained in Triton X-100. The extraction percentage more than 91% for all Ln(III) metals was obtained using 3.0 × 10⁻⁵ mol dm⁻³ HDEHP and 2.0% (v/v) Triton X-100. From the equilibrium analysis, it was clarified that Ln(III) was extracted as Ln(DEHP)₃ into the surfactant-rich phase. The extraction constant of Ln(III) with HDEHP and 2.0% (v/v) Triton X-100 were also obtained.     

Cloud point extraction for the determination of As(III) in water samples by electrothermal atomic absorption spectrometry

Cloud point extraction was applied as a preconcentration step for electrothermal atomic absorption spectrometry (ETAAS) determination of As(III) in aqueous solutions. After complexation with ammonium pyrrolidinedithiocarbamate, the analyte was quantitatively extracted to the surfactant-rich phase in the non-ionic surfactant octylphenoxypolyethoxyethanol (Triton X-114) after centrifugation. 0.1 mol L⁻¹ HNO₃ in methanol was added to the surfactant-rich phase before ETAAS determination. The precision (R.S.D.) for 11 replicate determinations of 5.0 μg L⁻¹ of As(III) was 3.0%. The concentration factor, which is defined as the concentration ratio of the analyte in the final diluted surfactant-rich extract ready for ETAAS determination and in the initial solution, was 36 for As(III). The linear concentration range was from 0.1 to 20 μg L⁻¹. The developed method was applied to the determination of As(III) in lake water and river water.     

Multiple square wave voltammetry for analytical determination of paraquat in natural water, food, and beverages using microelectrodes

This paper reports on the use of multiple square wave voltammetry (MSWV) for analytical determination of paraquat herbicide at gold microelectrode (Au-ME) in different samples of natural water, food, and beverages. In this work, the MSWV consisted in a sequence of four pairs of potential pulse in the same step and the interval potential evaluated was of the 0.0 V at −1.2 V versus Ag/AgCl 3.0 mol L⁻¹. The paraquat herbicide presented two reduction peaks, in −0.69 V and −0.99 V, with profile of the redox process totally reversible, and the use of multiple pulses allowed a detection of nanomolar levels after the optimization of experimental and voltammetric conditions. Analytical curves were constructed for pulse potential frequency of 250 s⁻¹, pulse amplitude of 50 mV, scan increment of 2 mV and pulse number of 8 pulses in a same step. The two reduction peaks showed that the peak currents were found to be directly proportional to the pesticide concentration in the range comprised between 5.0 × 10⁻⁷ mol L⁻¹ and 1.04 × 10⁻⁵ mol L⁻¹. With this, it was possible to determine detection limits (DL), which resulted in 0.044 μg L⁻¹ (0.044 ppb) and 0.146 μg L⁻¹ (0.146 ppb), respectively, for peak 1 and peak 2. DL results, obtained using MSWV, were 2–3 orders of magnitude lower (10⁻² to 10⁻³) less than those observed for traditional square wave voltammetry or published in literature, clearly pointing to the advantages arising from the possibility of using a MSWV for analytical purposes in contaminated matrices. In addition, the proposed methodology was applied in different samples of natural water, food and beverages without pre-treatment or pre-concentration step, where a recovery measurement indicated that the methodology could be employed to analyze paraquat in such matrices.     

Application of gallium film electrode for elimination of copper interference in anodic stripping voltammetry of zinc

For elimination of copper interference in anodic stripping determinations of zinc at mercury and bismuth film electrodes gallium ions are usually added to the supporting electrolyte. In the presented studies novel ex situ formed gallium film electrode was applied for this purpose. The proposed electrode is less toxic than mercury one while the detection limit for zinc was lower than for bismuth film electrode following the same deposition time. The calibration graph for deposition time of 60 s was linear from 5 × 10⁻⁸ to 2 × 10⁻⁶ mol L⁻¹. The determinations of zinc were carried out from undeaerated solutions. The proposed procedure was applied to zinc determination in certified reference material and tap water sample.     

Study of parameters associated with the determination of cadmium in lake sediments by slurry sampling electrothermal atomic absorption spectrometry

Cadmium concentration in lake sediments is determined by suspending the solid samples in a solution containing 5% (v/v) concentrated nitric acid and 0.1% (v/v) Triton X-100. Three modifiers were tested for the direct determination. The furnace temperature programmes and appropriate amount for each modifier were optimised to get the highest signal and the best separation between the atomic and background signals. The drying stage is performed by programming a 400 °C temperature, a ramp time of 25 s and hold time of 10 s on the power supply of the atomiser. No ashing step is used and platform atomisation is carried out at 2200 °C. W–Rh permanent modifier combined with conventional modifier by delivering 10 μl of 0.50% (w/v) NH₄H₂PO₄ solution was the best chemical modifier for cadmium determination. This modifier also acts as a liquid medium for the slurry, thus simplifying the procedure. Calibration is performed using aqueous standards in the 1–5 μg l⁻¹ range. The optimised method gave a limit of detection of 0.56 ng ml⁻¹, characteristic mass of 10.1±0.8 pg for aqueous standard, 9.6±0.7 pg for slurry samples containing different Cd concentrations and good precision (7.6–5.2%). The method was validated by analysing four certified reference lake sediment materials: LKSD-1, LKSD-2, LKSD-3 and LKSD-4; satisfactory recoveries were obtained (90.0–96.3%) and no statistical differences were observed between the experimental and the certified cadmium concentration. The developed methodology was used to determine cadmium in three ‘real’ sediment samples from lakes in the area of Wielkopolski National Park, Poland.     

Flow injection determination of selenium by successive retention of Se(IV) and tetrahydroborate(III) on an anion-exchange resin and hydride generation electrothermal atomization atomic absorption spectrometry with in-atomizer trapping: Part 1. Method development and investigation of interferences

A sample solution was passed at 20 ml min⁻¹ through a column (150×4 mm²) of Amberlite IRA-410Stron anion-exchange resin for 60 s. After washing, a solution of 0.1% sodium borohydride was passed through the column for 60 s at 5.1 ml min⁻¹. Following a second wash, a solution of 8 mol l⁻¹ hydrochloric acid was passed at 5.1 ml min⁻¹ for 45 s. The hydrogen selenide was stripped from the eluent solution by the addition of an argon flow at 150 ml min⁻¹ and the bulk phases were separated by a glass gas–liquid separator containing glass beads. The gas stream was dried by passing through a Nafion® dryer and fed, via a quartz capillary tube, into the dosing hole of a transversely heated graphite cuvette containing an integrated L’vov platform which had been pretreated with 120 μg of iridium as trapping agent. The furnace was held at a temperature of 250°C during this trapping stage and then stepped to 2000°C for atomization. The calibration was performed with aqueous standards solution of selenium (selenite, SeO₃²⁻) with quantification by peak area. A number of experimental parameters, including reagent flow rates and composition., nature of the gas–liquid separator, nature of the anion-exchange resin, column dimensions, argon flow rate and sample pH, were optimized. The effects of a number of possible interferents, both anionic and cationic were studies for a solution of 500 ng 1⁻¹ of selenium. The most severe depressions were caused by iron (III) and mercury (II) for which concentrations of 20 and 10 mg  1⁻¹ caused a 5% depression on the selenium signal. For the other cations (cadmium, cobalt, copper, lead,. magnesium, and nickel) concentrations of 50–70 mg 1⁻¹ could be tolerated. Arsenate interfered at a concentration of 3 mg⁻¹, whereas concentrations of chloride, bromide, iodide, perchlorate, and sulfate of 500–900 mg l⁻¹ could be tolerated. A linear response was obtained between the detection limit of 4 ng 1⁻¹, with a characteristic mass of 130 pg. The RSDs for solutions containing 100 and 200 ng 1⁻¹ selenium were 2.3% and 1.5%, respectively.     

Determination of Rh, Pd and Pt in urine samples using a pre-concentration sequential injection analysis system coupled to a quadrupole-inductively coupled plasma-mass spectrometer

The proposed flow system was developed in order to minimize the drawbacks related to the PGEs determination by quadrupole-inductively coupled plasma-mass spectrometry (Q-ICP-MS). It was intended not only to lower the limits of detection (LODs) but also to eliminate the interferences originating from some atomic and molecular ions produced in the argon plasma. This was accomplished by means of an on-line sample clean-up/pre-concentration step, using a chelating resin (Metalfix™ Chelamine™) in which Rh, Pd and Pt were preferably retained when compared with the interfering species.

The results obtained by using the developed flow system in the analysis of urine samples are presented. With a sampling rate of 9 samples h⁻¹ (i.e., 27 determinations) and a sample consumption of ca. 10 mL, the developed flow system allowed linear calibration plots up to 100 ng L⁻¹ with detection limits of 1.2 ng L⁻¹ (Rh), 0.4 ng L⁻¹ (Pd) and 0.9 ng L⁻¹ (Pt). Repeatability studies showed good precision (R.S.D.%, n = 5): 3.7% (Rh); 2.6% (Pd) and 2.4% (Pt), for 10 ng L⁻¹; 2.4% (Rh); 1.4% (Pd) and 1.9% (Pt), for 50 ng L⁻¹; and 1.3% (Rh); 0.58% (Pd) and 0.62% (Pt), for 100 ng L⁻¹. By spiking human urine samples, recovery tests were performed, and the values obtained ranged between 89% and 105% (Rh); 90% and 104% (Pd); and 93% and 105% (Pt).     

Flow injection determination of bismuth in urine by successive retention of Bi(III) and tetrahydroborate(III) on an anion-exchange resin and hydride generation atomic absorption spectrometry

Bismuth as BiCl₄⁻ and BH₄⁻ ware successively retained in a column (150 mm × 4 mm, length × i.d.) packed with Amberlite IRA-410 (strong anion-exchange resin). This was followed by passage of an injected slug of hydrochloric acid resulting in bismuthine generation (BiH₃). BiH₃ was stripped from the eluent solution by the addition of a nitrogen flow and the bulk phases were separated in a gas–liquid separator. Finally, bismutine was atomized in a quartz tube for the subsequent detection of bismuth by atomic absorption spectrometry. Different halide complexes of bismuth (namely, BiBr₄⁻, BiI₄⁻ and BiCl₄⁻) were tested for its pre-concentration, being the chloride complexes which produced the best results. Therefore, a concentration of 0.3 mol l⁻¹ of HCl was added to the samples and calibration solutions. A linear response was obtained between the detection limit (3σ) of 0.225 and 80 μg l⁻¹. The R.S.D.% (n = 10) for a solution containing 50 μg l⁻¹ of Bi was 0.85%. The tolerance of the system to interferences was evaluated by investigating the effect of the following ions: Cu²⁺, Co²⁺, Ni²⁺, Fe³⁺, Cd²⁺, Pb²⁺, Hg²⁺, Zn²⁺, and Mg²⁺. The most severe depression was caused by Hg²⁺, which at 60 mg l⁻¹ caused a 5% depression on the signal. For the other cations, concentrations between 1000 and 10,000 mg l⁻¹ could be tolerated. The system was applied to the determination of Bi in urine of patients under therapy with bismuth subcitrate. The recovery of spikes of 5 and 50 μg l⁻¹ of Bi added to the samples prior to digestion with HNO₃ and H₂O₂ was in satisfactory ranges from 95.0 to 101.0%. The concentrations of bismuth found in six selected samples using this procedure were in good agreement with those obtained by an alternative technique (ETAAS). Finally, the concentration of Bi determined in urine before and after 3 days of treatment were 1.94 ± 1.26 and 9.02 ± 5.82 μg l⁻¹, respectively.