Speciation analysis of thallium in water samples after separation/preconcentration with the Empore™ chelating disk

A simple, reliable and novel solid phase extraction procedure using the Empore? chelating disk has been developed for determination of Tl(I) and Tl(III) in environmental water samples by electrothermal atomic absorption spectrometry (ETAAS). The influence of humic acids on separation/preconcentration of thallium species with the Empore? chelating disk is investigated. The preconcentration factor and detection limit are 500 and 5?ng?L^?1, respectively. The recoveries are in the range 93–103% for mineral, pond, sea, snowmelt, waste waters at 28–500?ng?L^?1 Tl and in the range 82–112% for river waters at 18–28?ng?L^?1 Tl.     

Determination of Thallium in Soil

Abstract

A new spectrophotometric method is described for the determination of thallium in soil by extraction of Tl(III) with a toluene solution of N,N′-diphenylbenzamidine after acidification with 0.2–4.0 M HCl, and reaction of the extract with Crystal violet in the presence of 0.01–0.8 M HCl. The value of molar absorptivity of Tl(III)-X-CV complex (where X = Cl or Br; CV = Crystal violet) in toluene is 7.00 × 10⁴ 1 mole^?1 cm^?1 at the absorption maximum of 610 nm. The detection limit of the method is 20 ng ml^?1. The present method is free from interference of almost metal ions commonly associated with Tl. The method has been applied for analysis of the metal to soils.     

Determination trace amounts of thallium after separation and preconcentration onto nanoclay loaded with 1-(2-pyridylazo)-2-naphthol as a new sorbent

A procedure has been proposed for the separation and preconcentration of trace amounts of thallium. It is based on the adsorption of thallium ions onto organo nanoclay loaded with 1-(2-pyridylazo)-2-naphthol (PAN). Thallium ions were quantitatively retained on the column in the pH range of 3.5–6.0, whereas quantitative desorption occurs with 5.0?mL of 5% ascorbic acid and thallium was determined by flame atomic absorption spectrometry. Linearity was maintained between 0.66?ng?mL^?1–15.0?µg?mL^?1?in initial solution. Detection limit was 0.2?ng?mL^?1?in initial solution and preconcentration factor was 150. Eight replicate determinations of 2.0?µg?mL^?1 of thallium in final solution gave a relative standard deviation of ±1.48%. Various parameters have been studied, such as the effect of pH, breakthrough volume and interference of a large number of anions and cations and the proposed method was used to determine thallium ions in water and standard samples. Determination of thallium ions in standard sample showed that the proposed method has good accuracy.     

A new sensitive optical bulk test-system for thallium based on pyridylazo resorcinol

A color changeable optode for thallium(III) ions in aqueous solutions was prepared by physical inclusion of 4-(2-pyridylazo)-resorcinol into a plasticized PVC film. The increase in the absorbance of the optode at 524 nm is proportional to thallium(III) concentration. Different parameters effecting the sensitivity such as sample parameters and composition of the membrane were optimized. The response times of the prepared test-system are found to be 230, 210, and 180 s for 4.8 × 10^?6, 4.8 × 10^?5, and 4.8 × 10^?4 M Tl(III), respectively. The analytical performance of the optode was evaluated, obtaining a linear concentration range of two decades of concentration, 3.1 × 10^?6 ? 4.7 × 10^?4 M Tl(III), with a limit of detection of 1.8 × 10^?6 M Tl(III). Selectivity of the optode is also studied. Application of the optode to the determination of Tl(III) in some aqueous samples yields good results.     

The determination of thallium in sediments and natural waters

Thallium is determined in natural waters (including sea water) by first preconcentrating it by adsorption from oxidizing medium onto a strongly basic anion exchanger as the tetrachlorothallate(III) ion. After elution with sulphur dioxide and evaporation, thallium is estimated either by graphite-furnace atomic absorption spectrometry or by differential-pulse anodic stripping voltammetry. Relative standard deviations of 4% were found for both endpoints at thallium concentrations of 15 ng l^?1. There was good agreement between the results obtained by the two techniques. The technique is also applied to digests from deep-sea sediments.     

Speciation Analysis of Thallium by Reversed‐phase Liquid Chromatography ‐ Inductively Coupled Plasma Mass Spectrometry

An inductively coupled plasma mass spectrometer (ICP‐MS) was used as a liquid chromatographic detector for the speciation analysis of thallium in environmental samples. In this study, ionic thallium species, namely Tl(I) and Tl(III) were well separated by reversed‐phase high performance liquid chromatography (RP‐HPLC) with a C8‐HPLC column as the stationary phase and 1 mmol L^?1 tetrabutylammonium phosphate (TBAP), 2 mmol L^?1 diethylenetriamine pentaacetic acid (DTPA) in 1% v/v methanol solution (pH 6) as the mobile phase. Effluent from the HPLC column was delivered to the nebulizer of the ICP‐MS for the determination of thallium. The separation was complete in less than 3 min. Detection limit was 0.002 μg L^?1 for both Tl(I) and Tl(III) compounds based on peak height. The relative standard deviation of the peak areas for five injections of a mixture containing 1 μg Tl L^?1 was better than 3.4%. The concentrations of Tl compounds were determined in standard reference materials, including NIST SRM 1643e Trace Elements in Water and NRCC NASS‐5 Open Ocean Seawater and water samples collected in Kaohsiung area, Taiwan. The HPLC‐ICP‐MS results of the reference samples agreed with the reference values. This method has also been applied to determine Tl(I) and Tl(III) compounds in custard apple (Annona squamosa) leaves collected from Chai‐shan Mountain, Kaohsiung and Taitung City, Taiwan. The thallium species were quantitatively leached from the leaves with a 5 mmol L^?1 DTPA in 100 mmol L^?1 ammonium acetate solution in an ultrasonic bath during a period of 30 min. The HPLC‐ICP‐MS result that was obtained after the analysis of leaves sample showed a satisfactory agreement with the total thallium concentration obtained by ICP‐MS analysis of completely dissolved sample.     

A direct differential pulse anodic stripping voltammetric method for the determination of thallium in natural waters

A dual direct method for the ultratrace determination of thallium in natural waters by differential pulse anodic stripping voltamrnetry (d.p.a.s.v.) is presented. D.p.a.s.v. at the hanging mercury drop electrode and at the mercury film electrode is used in the concentration ranges 0.5–100 μg Tl l^-1, and 0.01–10 μg Tl l^-1, respectively. Quantification is aided by the technique of standard additions. The response of the method is optimized for typical natural surface water matrices. An intercomparison of thalium determinations performed by the two anodic stripping methods and electrothermal-atomization atomic absorption spectrometry on normal and thallium-spiked surface water samples demonstrates equivalent accuracy within the range where atomic absorption is applicable. The method appears free from serious interferences.     

Voltammetric sensing of thallium at a carbon paste electrode modified with a crown ether

We describe a new method for differential-pulse anodic stripping voltammetric determination of thallium(I) using a carbon paste electrode modified with dicyclohexyl-18-crown-6. The effect of supporting electrolyte (type and pH), accumulation and reduction potential, and of time and amount of modifier were investigated by differential pulse anodic stripping voltammetry. A method was then worked out for the determination of thallium at low levels. Under optimized conditions, the response to Tl(I) is linear in the range from 3.0 to 250 ng mL^?1. The detection limit is 0.86 ng mL^?1. The sensor displays good repeatability (with a relative standard deviation of ±2.70 % for n?=?7) and was applied to the determination of Tl(I) in water, hair samples, and certified reference materials.

Automated determination of total arsenic in sea water by flow constant-current stripping analysis with gold fibre electrodes

Total arsenic in sea water is determined in a fully automated flow system, by means of potentiostatic deposition for 4 min at a 25-μm gold fibre electrode and subsequent constant-current stripping in 5 M hydrochloric acid. Previously the sample is acidified with hydrochloric and arsenic(V) is reduced to arsenic(III) with iodide. During stripping, the potential vs. time transient is recorded with a real-time measurement rate of 26.5 kHz and a potential resolution of 1 mV. Cleaning and regeneration of the gold electrode are fully automated. The total arsenic concentrations in two reference sea waters (NASS-1 and CASS-1) were evaluated by single-point standard addition and found to be 1.58 and 1.14 μg l^?1 with standard deviations of 0.39 and 0.28 μg l^?1, respectively; certified values are 1.65 ± 0.19 and 1.04 ± 0.07 μg l^?1. The arsenic(III) content in these samples was below the detection limit (0.15 μg l^?1).     

Indirect Speciation Analysis of Thallium in Plant Extracts by Anodic Stripping Voltammetry

A sensitive voltammetric method (DPASV) was developed for the determination of Tl(I) and Tl(III) in plant extracts. To limit the influence of the organic matrix on the measurements, UV irradiation and addition of Amberlite XAD‐7 resin was studied. The application of 0.5 g of the resin allowed defining thallium speciation in 10.0 mL of a solution containing 0.20 mL of Sinapis alba extract. The quantification limit of 0.5 ng mL^?1 Tl(I) was found for only 10 min of preconcentration, and is low enough to allow dilution of the sample before thallium determination. The procedure was validated using the recovery study and intermethod comparison with HPLC ICP MS.     

Schwermetall-π-Komplexe. X. Synthese und Kristallstruktur von {[(1,3,5-(CH3)3C6H3)2Tl][AlCl4]}2: ein arenstabilisiertes dimeres Thallium(I)-tetrachloroaluminat

π-Complexes of Heavy Metals. X. Synthesis and Crystal Structure of {[(1,3,5-(CH₃)₃C₆H₃)₂Tl][AlCl₄]}₂: an Arene Stabilized Dimeric Thallium(I) Tetrachloroaluminate From a solution of AlCl₃ and TlCl in mesitylene, the bis(arene)thallium complex {[(1,3,5-(CH₃)₃C₆H₃)₂Tl][AlCl₄]}₂ ( 1 ) (space group P2₁/c with a = 19.575(4) Å, b = 12.436(2) Å, c = 19.415(4) Å, β = 101.69(3)° at T = ?90 ± 1°C; Z = 4) will crystallize at low temperature. This compound can be described as a dimeric thallium(I) tetrachloroaluminate with a sceleton similar to that of (TeI₄)₄, shielded by four arenes, in pairs coordinated at the thallium atoms. In the solid state the complete configuration has point group symmetry 1 (C₁). Tl? Cl distances ranging from 3.292(3) to 3.679(3) Å point out an ionic bonding situation between arene₂Tl⁺ and AlCl₄^? fragments. The strengths of the η⁶ like Tl-arene interactions are characterized by distances Tl(1)–C of 3.250 Å and 3.315 Å, and Tl(2)? C of 3.285 Å and 3.328 Å and a temperature of release of all arene molecules of 61°C, which has been determined by differential thermal analysis, to yield pure thallium(I) tetrachloroaluminate.     

Ultra-trace determination of thallium(I) using a nanocomposite consisting of magnetite,halloysite nanotubes and dibenzo-18-crown-6 for preconcentration prior to its quantitation by ET-AAS

A nanocomposite modified with dibenzo-18-crown-6 was synthesized and applied as a new sorbent for the preconcentration of thallium(I) via ultrasound assisted-solid phase extraction. This extraction step was combined with electrothermal atomic absorption spectrometry to determine ultra-trace amounts of thallium(I). The nanocomposite was characterized by Fourier transform infrared spectroscopy, X-ray diffraction spectrometry, field emission scanning electron microscopy and transmission electron microscopy. Under the optimized conditions, a dynamic linear range from 7.0 to 435 ng L^?1, a detection limit of 1.8 ng L^?1 and a quantification limit of 6.0 ng L^?1 were obtained. Also, the intra- and inter-day relative standard deviations for 20.0 ng mL^?1 Tl(I) were calculated as ±4.8% and ±5.1%, respectively. The adsorbent was applied to the determination of thallium(I) in the environmental, biological and standard samples with satisfactory results.

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Graphical abstract A magnetic nanocomposite was synthesized as adsorbent from halloysite nanotubes and a crown ether. Tl(I) ions were extracted selectively and determined by electrothermal atomic absorption spectrometry.

     

Determination of Ultratrace Thallium(I) by Anodic Stripping Voltammetry at Bismuth Film Electrodes Following Double Deposition and Stripping Steps

The double deposition and stripping steps were proposed to increase the sensitivity in anodic stripping voltammetry of thallium(I). Two in situ plated bismuth film electrodes with drastically different surface areas were exploited for the measurements. Thallium was at first deposited at the electrode with a large surface area. As the deposition step at the large electrode was finished, the electrode was moved at a short distance to the small one. The thallium stripped from the large electrode was then accumulated at the second electrode. Taking into account the small volume of space between the electrodes, the concentration of Tl(I) between the electrodes was drastically higher than that in the bulk solution. The deposition step at the second electrode was performed from solution with a higher concentration of Tl(I) therefore the detection limit was lowered. The calibration graph was linear from 5×10^?11 to 5×10^?9 mol L^?1 following deposition time of 300 s at the first and the second electrode.     

Quantum yield for photosubstitution of a co group in chromium hexacarbonyl by pyridine

The quantum yield of the photosubstitution of CO by pyridine in cyclohexane has a value of 0.67 ± 0.02 for [Cr(CO)₆] = 3.10^?4 mol l^? and [pyridine] = 10^? mol l^?1.     

Determination of thallium by isotopic dilution method using substoichiometric displacement

A new analytical procedure for the determination of thallium in a wide concentration range has been developed. The method of direct isotopic dilution (IDA) using carrier-free²⁰²Tl and the formerly developed procedure of substoichiometric displacement have been used for the determination of thallium content in various types of analyzed samples e.g. minerals, sediments, ion-exchangers, hydrothermal waters, etc. in the concentration range from several percent to 10^?4%, or subsequently down to 0.01 μg/ml in waters. The results obtained are compared with those of emission spectrometry and activation analysis using (γ, n) reaction. A good agreement was found.     

Experimental design as an optimization approach for fabrication a new selective sensor for thallium(I) based on calix[6]arene

The performance of a new membrane sensor based on polyvinyl chloride (PVC) for Tl(I) assay was investigated using the statistical design as an optimization strategy. The Plackett-Burman and Box-Behnken designs, respectively, were utilized to find out the influencing variables and optimization of conditions. In order to evaluate the relationship between the responses of electrode (slope) and significant variables along with their interactions, a mathematical model was presented. The interactions between significant variables were intuitively illustrated according to the response surface plots. Apart from that, the optimum conditions as a result of response surface methodology for both membrane ingredients and measuring conditions such as pH, PVC, internal solution concentration, calix[6]arene, 2-nitrophenyloctylether, potassium tetrakis-(p-chlorophenyl)borate and time conditioning, respectively, were found to be: 6, 0.028 g, 0.001 M, 0.0035 g, 0.065 g, 0.0015 g and 20 h. The optimized sensor exhibits a Nernstian response for thallium(I) over a wide linear range from 2.0 × 10^?6 to 2.0 × 10^?2 M and the slope of 57.9 ± 0.1 mV/decade of the activity and limit of detection (LOD) 1.9 × 10^?5 M. The relative standard deviations (RSD) for six replicates of the measurement at 1 × 10^?5 and 1 × 10^?5 M of Tl(I) were 2.7 and 3.0%, respectively. The favorable results were given through the direct determination of Tl(I) in spiked wastewater and artificial spiked urine sample with Tl(I). The electrode was also successfully applied to the titration of a Tl(I) solution with KI.     

Ionic liquid ultrasound assisted dispersive liquid–liquid/micro-volume back extraction procedure for preconcentration and determination of ultra trace amounts of thallium in water and biological samples

A simple, highly sensitive and environment-friendly method, combined with flame atomic absorption spectroscopy (FAAS) is developed to preconcentrate and determine trace amounts of thallium in aqueous solutions. In the preconcentration step, the thallium (I) from 30?mL of an aqueous solution was extracted into 350?µL of ionic liquid, 1-hexyl-3-methylimidazolium hexa?uorophosphate [Hmim][PF₆], containing dicyclohexyl-18-crown-6 (DCH-18-crown-6) as complexing agent. Subsequently, the DCH-18-crown-6 complex was back-extracted into 300?µL of nitric acid (2?mol?L^?1) solution, and analyzed by FAAS. Several parameters in?uencing the extraction and determination of thallium, such as pH, concentration of DCH-18-crown-6, sonication and centrifugation times, sample volume, ionic liquid amounts, ionic strength, and concentration of stripping acid solution, were optimized. Under optimum conditions, the calibration graph was linear in the range of 5 to 400?ng?mL^?1, the detection limit was 0.64?ng?mL^?1 (3S_b/m, n?=?7), the enhancement factor was 98.2 and the relative standard deviation was ±1.43%. The results for preconcentration and determination of trace amount of thallium in waste water, well water, tap water, sea water, human hair and nail demonstrated the accuracy, recovery and applicability of the presented method.     

Determination of thallium in zinc by proton activation analysis

The determination of thallium in unalloyed zinc by proton activation analysis, based on the ²⁰³Tl (p,3n)²⁰¹Pb reaction, is described. Lead-201 was radiochemically separated from the matrix activities (gallium, copper and zinc) by cation exchange, anodic deposition of lead (IV) oxide and precipitation as lead thionalide. Thallium (III) oxide was used as the standard. The method was applied to the BCR reference materials 321,322,323,324 and 325 Unalloyed Zinc. The detection limit is 17 ng g^?1. The relative standard deviation obtainable is 5-1% in the 1-40 μg g^?1 concentration range.     

Separation of thallium-201 from lead-201 using N-benzylaniline

A procedure is described for the liquid extraction of ingrown²⁰¹Tl from its precursor²⁰¹Pb using N-benzylaniline. The yield for a double extraction averaged 95.9±3.2% for thallium; 2.9±4.2% for lead. Yields for back extraction into acetic acid averaged 93.7±1.5%.     

The learning machine in quantitative chemical analysis: Part I. Anodic Stripping Voltammetry of Cadmium,Lead and Thallium

The linear learning machine method was applied to the determination of cadmium, lead and thallium down to 10^-8M by anodic stripping voltammetry at a hanging mercury drop electrode. With a total of three trained multicategory classifiers, concentrations of Cd, Pb and Tl could be predicted with an accuracy of ±10%. The classifiers were trained with the use of least-squares minimization. Numerical problems in the data matrix inversion were overcome by using singular value decomposition.