Simultaneous separation and determination of thallium in water samples by high‐performance liquid chromatography with inductively coupled plasma mass spectrometry

An analytical method for separation and determination of thallium species in water using high‐performance liquid chromatography with inductively coupled plasma mass spectrometry was developed. The composition and concentration of mobile phase, injection volume, and pH value were optimized respectively with an anion or cation exchange column. The results showed that Tl(I) and Tl(III) were effectively separated using anion exchange column Hamilton PRP‐X100, with the mobile phase consisting of 200 mmol/L ammonium acetate and 10 mmol/L diethylenetriaminepentaacetic acid (pH = 4.2). When using a Dionex cation exchange guard column, CS12A, 15 mmol/L HNO₃, and 3 mmol/L diethylenetriaminepentaacetic acid as the mobile phase, Tl(I) and Tl(III) could be effectively separated. The detection limits of the methods were 3–6 and 9–12 ng/L, respectively. In a solution containing Fe ions and oxalic acid, a significant quantity of Tl(I) was oxidized. Fe ions and oxalic acid in the water samples did not interfere with high‐performance liquid chromatography‐inductively coupled plasma mass spectrometry measurement results.     

Thallium(II) in the chemically induced thallium(I)-Thallium(III) exchange

The rate of the electron exchange between thallium(I) and thallium(III) induced by iron(II) has been measured at various concentrations of Tl(I), Tl(III), and Fe(II).²⁰⁴Tl tracer, initially in the Tl(I) state, was used. Exchange induced by the separation method was less than 0.01%. The mechanism earlier discussed is $$\begin{gathered} Tl^{III} + Fe^{II} \rightleftharpoons Tl^{II} + Fe^{III} \left( {k_1 ,k_{ - 1} } \right) \hfill \\ Tl^{II} + Fe^{II} \rightharpoonup Tl^I + Fe^{III} \left( {k_2 } \right) \hfill \\ *Tl^I + Tl^{II} \rightleftharpoons *Tl^{II} + Tl^I \left( {k_I } \right) \hfill \\ *Tl^{II} + Tl^{III} \rightleftharpoons *Tl^{III} + Tl^{II} \left( {k_{III} } \right), \hfill \\ \end{gathered} $$ which provides an exchange path in addition to the two-electron reaction^*Tl^I+Tl^III?^*Tl^III+Tl^I (k_ex). The rate law deduced from this mechanism agrees with experiment over a limited range of conditions but fails to account for the observed effect at low concentrations of Tl(I). The additional rate can be represented by inclusion of a term in which the rate of the induced exchange is independent of the concentration of Tl(I). When treated according to the resulting complete rate law the data are consistent with earlier photochemical studies. The present results in combination with other data give k₂=3·10⁶ M^?1·sec^?1 in 1M perchloric acid at 25°C. This is in satisfactory agreement with a recent pulse radiolysis measurement as well as with independent flash photolysis studies.     

Selective solid-phase extraction of trace thallium with nano-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> from environmental samples

A novel sorbent, nano-Al₂O₃ was employed for the separation and preconcentration of thallium from aqueous solution in batch equilibrium experiments. It was found that the adsorption percentage of thallium ions was close to 100% at pH 4.5, and the desorption by 1.0 mL of 0.25 M HCl reached 99%. The adsorption equilibrium was well described by the Langmuir isotherm model with maximum adsorption capacity of 5.78 mg/g (20 ± 0.1°C). The enrichment factor values of Tl(III) was 25 for 25 mL sample. Detection limit of thallium (3σ, n = 11) equal to 0.8 μg/mL and relative standard deviation (2.4%) were obtained. The method has been successfully applied to the determination of trace thallium in some environmental samples and the certified reference material polymetallic nodule (GBW07296) with satisfactory results.     

A highly selective thallium(I) electrode based on a thia substituted macrocyclic ionophore

A new highly Tl(I)-selective PVC membrane electrode based on tetrathia macrocycle 6,7: 14,15-dibenzo-5,8,13,16-tetraoxo-1,4,9,12-tetrathiacyclohexadecane [Bz₂O₄(16)aneS₄] (I) as membrane carrier, o-nitrophenyloctyl ether (o-NPOE) as solvent mediator and potassium tetrakis(p-chlorophenyl)borate (KTpClPB) as lipophilic additive has been developed. The best performance was given by the membrane of macrocycle (I) with composition 3:120:1.5:50 (I:o-NPOE:KTpClPB:PVC). This electrode exhibits a Nernstian response to Tl(I) ions in the concentration range 1.0 × 10⁻¹-2.23 × 10⁻⁶ M with a slope of 58.2 mV/decade of concentration and a detection limit of 1.58 × 10⁻⁶ M. The response time of the sensor is 12 s and can be used over a period of 4 months with good reproducibility. The proposed electrode revealed good selectivity over a wide variety of other cations including alkali, alkaline earth, heavy and transition metals. The electrode works well over a pH range of 3.2-11.5 and in partially non-aqueous medium with up to 30% organic content. The sensor was also used as an indicator electrode in potentiometric titration of Tl(I) ions with KI solution.     

Highly polyhapto-aromatic interactions in thallium(I) coordination

In the solid state, the Tl(I) complex of 4-hydroxybenzoate (HB⁻), [Tl(HB)]_n (1), can be regarded as containing polymeric chains linked through 2 × η⁶ interactions of the Tl atoms with phenyl groups from adjacent units. The thallium atoms contain close Tl^I ? π (aromatic) contacts, thus attaining a total hapticity of 16 with environments TlO₄C₁₂. The unusually high coordination number in the this compound may reflect the capacity of Tl(I) to act as both a Lewis acid and a Lewis base.     

Extraction separation of thallium (III) from thallium (I) with n-octylaniline

A novel method is developed for the extraction separation of thallium(III) from salicylate medium with n-octylaniline dissolved in toluene as an extractant. The optimum conditions have been determined by making a critical study of weak acid concentration, extractant concentration, period of equilibration and effect of solvent on the equilibria. The thallium (III) from the pregnant organic phase is stripped with acetate buffer solution (pH 4.7) and determined complexometrically with EDTA. The method affords the sequential separation of thallium(III) from thallium(I) and also commonly associated metal ions such as Al(III), Ga(III), In(III), Fe(III), Bi(III), Sb(III) and Pb(II). It is used for analysis of synthetic mixtures of associated metal ions and alloys. The method is highly selective, simple and reproducible. The reaction takes place at room temperature and requires 15-20 min for extraction and determination of thallium(III).     

The application of redox and induced reactions to the determination of thallium(III) in the presence of thallium(I)

Summary A new method of the determination of thallic ions [Tl(III)] in the presence of thallous [Tl(I)] ones, based on the oxidizing properties of Tl(III) towards cysteine was proposed. Cysteine was employed as an initiator in the iodineazide reaction and the oxidized part of the initiator was eliminated from the induced reaction medium by the respective redox reaction; the reaction products do not affect the above reaction. The contents of thallic ions (50–500 ng) in the sample can be determined from the progress in the induced reaction by measuring the unreacted iodine. The relative experimental error of the determination does not exceed 6%.     

A novel tetrachlorothallate (III)-PVC membrane sensor for the potentiometric determination of thallium (III)

A novel tetrachlorothallate (III) (TCT)-selective membrane sensor consisting of tetrachlorothallate (III)-2,3,5-triphenyl-2-H-tetrazolium ion pair dispersed in a PVC matrix plasticized with dioctylphthalate is described. The electrode shows a stable, near-Nernstian response for 1×10⁻³-4×10⁻⁶ M thallium (III) at 25 °C with an anionic slope of 56.5±0.5 over the pH range 3-6. The lower detection limit and the response time are 2×10⁻⁶ M and 30-60 s, respectively. Selectivity coefficients for Tl(III) relative to a number of interfering substances were investigated. There is negligible interference from many cations and anions; however, iodide and bromide are significantly interfere. The determination of 0.5-200 μg ml⁻¹ of Tl(III) in aqueous solutions shows an average recovery of 99.0% and a mean relative standard deviation of 1.4% at 50.0 μg ml⁻¹. The direct determination of Tl(III) in spiked wastewater gave results that compare favorably with those obtained by the atomic absorption spectrometric method. The electrode was successfully applied for the determination of thallium in zinc concentrate. Also the tetrachlorothallate electrode has been utilized as an end point indicator electrode for the determination of thallium using potentiometric titration.     

Determination of thallium in soils by flame atomic absorption spectrometry

A method is described for the determination of Tl in soils by FAAS, involving extraction of Tl from 5 g of soil by digestion with HClO₄/HNO₃ followed by separation of the extracted Tl into 5 mL of diisopropylether from HBr solution, including Ce(SO₄)₂. Tl in the organic phase is determined by direct aspiration into the spectrophotometer. The percentage relative standard deviation (% RSD) for 5 replicate samples is about 1%. The detection limits (S/N = 3) of this method are 0.001 mg/L for aqueous solution and 0.02 mg/kg DW for soil, when 50 mL of soil solution corresponding to 2.5 g soil are used. The Tl concentration even of unpolluted soils can be determined. The method was shown to be unaffected by the presence of various ions in soil and was able to recover nearly 100% Tl added to soils. The arithmetic mean (range) of 18 Japanese unpolluted surface soils was 0.33 (0.10–0.56)mgTl/kg DW.     

Determination of total thallium in fresh water by electrothermal atomic absorption spectrometry after colloid precipitate flotation

Tl(I) and Tl(III) are preconcentrated simultaneously from aqueous solutions by colloid precipitate flotation using two collectors: hydrated iron(III) oxide (Fe₂O₃·xH₂O) and iron(III) tetramethylenedithiocarbamate (Fe(TMDTC)₃). After the coprecipitation step and the addition of foaming agents, Tl(I) and Tl(III) were separated from the water by a stream of air bubbles. Various factors affecting Tl(I) and Tl(III) recoveries during the separation from water, including the collector mass, the nature of the supporting electrolyte, pH, ζ potential of the collector particle surfaces, type of tenside, etc., were investigated. Within the optimal pH range (6–6.5), establishing by a recommended procedure, Tl(I) and Tl(III) were separated quantitatively (94.9–100.0%) with 30 mg Fe(III). Both Tl ions were simultaneously separated without any previous conversion of one type of Tl ion to the other. Total Tl determination was performed by electrothermal atomic absorption spectrometry by previous matrix modification of the concentrated samples. The determination limit of Tl by this method is 0.108 μg l⁻¹.     

Synthesis and characterization of four new thallium(I) tetrazole supramolecular compounds with various secondary interactions; new precursors for thallium(III) oxide nano-particles

Four new thallium(I) coordination polymers, [TlBt](n) (1) (Hbt = 5-phenyltetrazole), [TlBbt] (2) (Hbbt = 5-(4-bromobenzyl)tetrazole), [Tl(2)Bdt](n) (3) (H(2)bdt = 5,5'-benzene-1,4-diylbistetrazole), [Tl(2)Pht·H(2)O](n) and [TlBet] (4), (Hbet = 5-(benzyl)tetrazole) have been synthesized and characterized. The single-crystal X-ray data shows that, in compounds 1-3, the coordination sphere of the Tl(I) ion is the same and it is surrounded with six tetrazolate rings. In compound 4, one thallium atom has three interactions with tetrazolate groups and close Tl(I)···π (aromatic) contacts with the phenyl ring. Furthermore, in all cases the single-crystal X-ray data show the same stereo-chemical activity of the valence shell electron lone pair of Tl(I). There is a strong Tl(I)···Tl(I) interaction in one dimension in compounds 1 and 3. All these four compounds have been used as new precursors for the preparation of thallium(III) oxide nano-particles through a simple calcination method. Thallium(III) oxide was characterized by powder XRD diffraction and the morphology of nano particles characterized by scanning electron microscope (SEM).     

Studies with dithizone : Part 26. The interaction of thallium(III) with solutions of dithizone in organic solvents

The strong oxidising capacity of thallium(III) dominates its reaction with solutions of dithizone (H₂Dz) in organic solvents. When carbon tetrachloride is used as solvent, the unstable thallium(III) complex Tl(HDz)³ is found in the organic phase but it very quickly disproportionates to the thallium(I) complex [Tl(HDz)], and bis-1,5-diphenylformazan-3-yl-disulphide. This reaction is notably faster in chloroform, in which thallium(I) dithizonate is the first identifiable product. In contact with an acidic aqueous phase, thallium(I) dithizonate is reverted to regenerate dithizone in the organic phase and Tl⁺ ions appear in the aqueous phase. Organic solutions of the disulphide disproportionate spontaneously by first-order kinetics to give an equimolar mixture of dithizone and the mesoionic compound, 2,3-diphenyl-2,3-dihydrotetrazolium-5-thiolate: this change is much slower in carbon tetrachloride than in the more polar chloroform and is catalysed by both Tl⁺ and Tl³⁺. If thallium(III) is present in excess, the mesoionic compound is the principal oxidation product of the dithizone although a dication may also be formed. The mesoionic compound does not react with thallium(I) but forms a water-soluble 2:1 complex with thallium(III); partition of this complex into the organic phase is uninfluenced by chloride ions. Because of the large number of competing reactions, the composition of the reaction mixture at any stage of the reaction between thallium(III) and dithizone depends on the relative concentrations of the components, the order in which they are brought together, the time elapsed after mixing, the pH of the aqueous phase, and the nature of the organic solvent.     

C-H activation in bithiazole ring with thallium(III) ion

Two novel organometallic complex of 2,2′-dimethyl-4,4′-bithiazole (dm4bt) ligand (L) with formula [Tl(dm4bt)₂(NO₃)(H₂O)] (1) and [Tl(dm4bt)₂(NO₃)(DMSO)] (2) have been synthesized and structurally characterized by elemental analysis, FT-IR, ¹H NMR spectra and X-ray crystallography. These complexes also display the first transoid conformation in bithiazole ligands in which C-H bond activation in bithiazole ring is observed with Tl(III) ion.     

Anodic stripping voltammetric determination of thallium as [TlBr4]-rhodamine B complex

The anodic stripping voltammetric behaviour of the [TlBr₄]-rhodamine B complex is described and compared with that of thallium(I) and thallium(III) ions. The electrolyte composition, the best potential for the deposition of thallium from the complex in the selected electrolyte, the duration of the electrolysis, and the possibility of reduction of thallium in the [TlBr₄]-rhodamine B complex before the electrolysis with ascorbic acid were investigated. The results showed good reproducibility of the measurements of thallium as [TlBr₄]-rhodamine B complex and are similar to those obtained for thallium as Tl(I) and Tl(III) ions. As the [TlBr₄]-rhodamine B complex is strongly adsorbed on polyethylene, a previous preconcentration step on a column, packed with polyethylene powder, allowed the voltammetric determination of thallium as [TlBr₄]-rhodamine B complex in samples of KCl and NaCl as solid salts after the separation of the matrix. With this procedure it was possible to reach enrichment factors of 25 with recoveries from 96.7 to 107.9% for thallium concentrations from 5 to 40 μg L^–1 and RSD between 4.2 and 9.2%. The procedure was used to determine thallium traces in KCl and in sea salt. The results of these determinations were compared with the results obtained by graphite furnace atomic absorption spectrometry. Received: 5 February 1998 / Revised: 19 May 1998 / Accepted: 29 May 1998     

A modified method of separating Tl(I) and Tl(III) in aqueous samples using solid phase extraction

In spite of the development of new measurement techniques in recent years, the rapid and accurate speciation of thallium in environmental aqueous samples remains a challenge. In this context, a novel method of solid phase extraction (SPE), involving the anion exchange resin AG1-X8, is proposed to separate Tl(I) and Tl(III). In the presence of diethylene triamine pentacetate acid (DTPA), Tl(III) and Tl(I) can be separated by selective adsorption of Tl(III)-DTPA onto the resin, Tl(III) is then eluted by a solution of HCl with SO₂. The validity of this method was confirmed by assays of standard solutions of Tl(I) and Tl(III). The proposed method is shown to have an outstanding performance even in solutions with a high ratio of Tl(I)/Tl(III), and can be applied to aqueous samples with a high concentration of other electrolytes, which could interfere with the measurement. Portable equipment and reagents make it possible to use the proposed method routinely in the field.     

Nanometer SiO2 modified with 5-sulfosalicylic acid as selective solid-phase extractant for Fe(III) determination by ICP-AES from biological and natural water samples

A new modified nanometer SiO₂ using 5-sulfosalicylic acid (SSA) as a solid-phase extractant was used for separation, preconcentration and determination of Fe(III) in aqueous solutions by inductively coupled plasma atomic emission spectrometry (ICP-AES). Its adsorption and preconcentration behaviour for Fe(III) in aqueous solutions was investigated using static procedures in detail. The optimum pH value for the separation of Fe(III) on the newly designed sorbent was 3.5. Complete elution of the adsorbed Fe(III) from the nanometer SiO₂-SSA was carried out using 2.0 mL of 0.01 mol L^− 1 of HCl. The time of 90% sorption was less than 2 min for Fe(III) at pH 3.5. Common coexisting ions did not interfere with the separation and determination of Fe(III) at pH 3.5. The maximum static adsorption capacity of the sorbent at optimum conditions was found to be 44.01 mg of Fe(III) per gram of sorbent. The relative standard deviation (RSD) of the method under optimum conditions was 3% (n = 5). The procedure was validated by analyzing three certified reference materials (GBW 08301, GBW 08504, GBW 08511), the results obtained were in good agreement with standard values. The nanometer SiO₂-SSA was successfully employed in the separation and preconcentration of the investigated Fe(III) from the biological and natural water samples yielding 100-folds concentration factor.     

Nuclear field shift effect in isotope fractionation of thallium

Environmental transport of Tl is affected by redox reaction between Tl(I) and Tl(III) and ligand exchange reactions of them. In order to deepen the knowledge of Tl chemistry, we investigated fractionation of Tl stable isotopes (²⁰³Tl and ²⁰⁵Tl) in a chemical exchange system. Tl isotopes were fractionated in a liquid–liquid extraction system, in which aqueous and organic phases are hydrochloric acid solution and dichloroethane including a crown ether, respectively. After purification by ion-exchange chemistry, the isotope ratio of ²⁰⁵Tl/²⁰³Tl in equilibrated aqueous phase was measured precisely by multiple-collector–inductively-coupled-plasma–mass-spectrometry. A large isotope fractionation >1 ‰ was found. Electronic structures of possible Tl species (hydrated Tl⁺, Tl³⁺, and Tl chlorides) were calculated by ab initio methods, and the isotope fractionation factor was theoretically obtained. The isotope fractionation via intramolecular vibrations was calculated to be much smaller than the experimental result. The isotope fractionation via isotopic change in nuclear volume, named the nuclear field shift effect, was calculated to be >1 ‰ in Tl(I)–Tl(III) redox systems and/or ligand exchange systems of Tl(III). The nuclear field shift effect was found to be the major origin of Tl isotope fractionation.     

Anodic stripping voltammetric determination of thallium as [TlBr4]-rhodamine B complex

The anodic stripping voltammetric behaviour of the [TlBr₄]-rhodamine B complex is described and compared with that of thallium(I) and thallium(III) ions. The electrolyte composition, the best potential for the deposition of thallium from the complex in the selected electrolyte, the duration of the electrolysis, and the possibility of reduction of thallium in the [TlBr₄]-rhodamine B complex before the electrolysis with ascorbic acid were investigated. The results showed good reproducibility of the measurements of thallium as [TlBr₄]-rhodamine B complex and are similar to those obtained for thallium as Tl(I) and Tl(III) ions. As the [TlBr₄]-rhodamine B complex is strongly adsorbed on polyethylene, a previous preconcentration step on a column, packed with polyethylene powder, allowed the voltammetric determination of thallium as [TlBr₄]-rhodamine B complex in samples of KCl and NaCl as solid salts after the separation of the matrix. With this procedure it was possible to reach enrichment factors of 25 with recoveries from 96.7 to 107.9% for thallium concentrations from 5 to 40 μg L^–1 and RSD between 4.2 and 9.2%. The procedure was used to determine thallium traces in KCl and in sea salt. The results of these determinations were compared with the results obtained by graphite furnace atomic absorption spectrometry.     

The spectrophotometric determination of thallium(iii)by ternary complex formation

If thallium(III) is added to an aqueous solution of potassium thiocyanate containing a large amount of pyridine in the pH range 5.2–5.5, a yellow solution which is stable in diffuse light is obtained. The yellow colour can be measured at 405 nm for the colorimetric determination of thallium(III) in the range 20–300 μg Tl ml^-1. The complex is a mixed ligand complex with a metal-ligand ratio of 1:2:2. Thallium(I) does not interfere. The interference of various other metal ions and anions is discussed.     

Synthesis and Structure of Tris(8-mercaptoquinolinato)thallium and Tris(8-hydroxyquinolinato)thallium Monohydrate

Tris(8-mercaptoquinolinato)thallium Tl(C₉H₆NS)₃ and tris(8-hydroxyquinolinato)thallium monohydrate Tl(C₉H₆NO)₃·H₂O have been synthesized. Their structures have been confirmed by X-ray crystallographic analysis.