Thallium In Environmental Samples Research Articles

Sequential determination of gallium, indium, and thallium in environmental samples after preconcentration on halloysite nanotubes using ultrasound-assisted dispersive micro solid-phase extraction

A preconcentration procedure for gallium, indium, and thallium using HNTs was developed prior to their sequential determination by HR-CS GFAAS.

Determination of thallium in environmental samples by surfactant assisted dispersive liquid-liquid microextraction combined with first order derivative spectrophotometry

A surfactant assisted dispersive liquid-liquid microextraction (SA-DLLME) combined with derivative spectrophotometric method has been proposed for the determination of thallium(III) using a chelating agent diacetylmonoxime- p -hydroxybenzoylhydrazone. Disperser solvent was substituted by surfactant, which made the emulsification more effective and extraction, quite environment friendly. Carbon tetrachloride was employed as the extractant. The developed SA-DLLME technique was coupled with first order derivative spectrophotometric method to improve the analytical performance. Optimum conditions relevant to SA-DLLME and instrumental parameters were studied in detail. The enrichment factor of the method was found to be 23. The limit of detection and quantitation limit of first order derivative spectrophotometric method were found to be 0.22 and 0.67 µg/L, respectively. The relative standard deviation (RSD) for five replicates of 50.0 µg/L of thallium(III) was found to be 1.12%. The applicability of the method was evaluated by the trace level determination of thallium in different environmental samples.

Development of surfactant assisted kinetic method for trace determination of thallium in environmental samples

A simple and highly selective surfactant assisted kinetic spectrophotometric method for the determination of thallium has been developed. The method is based on the quantitative oxidation of Tl(I) to Tl(III) using bromine water where the resulting Tl(III) liberated iodine from potassium iodide in acidic medium. The liberated iodine was subsequently reacted with I− ion to form tri-iodide ions (I3−). The tri-iodide ions formed were further reacted with cetylpyridinium cation (CP+) which produced a violet ion associate species having a λmax of 512nm at which reaction was monitored. The reaction variables such as time, temperature, reagent concentration and acidity were optimized for the indicator reaction to achieve maximum sensitivity. The linear regression calibration concentration range of 0.007–0.1μgmL−1 Tl(I) was established as the Beer's law was obeyed in this range. Sandell's sensitivity and molar absorptivity of the ion associate species in terms of thallium were determined to be 0.000133μgcm−2 and 1.99×106Lmol−1cm−1 respectively. The limit of detection was determined as 0.0029μgmL−1. The developed method has successfully been applied for the determination of thallium in different environmental samples with satisfactory results.

Thallium (III) determination in the Baltic seawater samples by ICP MS after preconcentration on SGX C18 modified with DDTC

The main difficulty of speciation analysis of thallium lies in extremely low concentrations of Tl(III) in comparison to Tl(I), which is the dominating form of thallium in environmental samples. In this study, a sensitive method is presented for separation of trace amounts of Tl(III) from Tl(I) and preconcentration of Tl(III) using octadecyl silica gel modified with diethyldithiocarbamate (DDTC). Under optimal conditions, only Tl(III) is retained on the sorbent, and then eluted with 96% ethanol. After chemical decomposition of Tl(III)–DDTC complex, thallium is determined by inductively coupled plasma mass spectrometry. High performance liquid chromatography with ICP MS detection was used to control the correctness of the obtained results. Parameters affecting solid phase extraction (SPE) such as pH, type, concentration and volume of eluent, breakthrough volume, and the impact of sample salinity (chlorides) and other interfering ions (Cd(II), Zn(II), Pb(II), Cu(II), Sn(II)) were investigated. The limit of detection (LOD), evaluated for 2mL of sample solution, was 0.10ng for Tl(I) and 0.43ng for Tl(III). The method was applied to the determination of Tl(I) and Tl(III) in the Baltic seawater samples enriched in both thallium species.

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

AbstractAn 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.

Determination of thallium in environmental samples by inductively coupled plasma mass spectrometry: comparison and validation of isotope dilution and external calibration methods

Two methods of thallium quantification by inductively coupled plasma mass spectrometry were validated: isotope dilution (ID) after spiking by 203Tl and external calibration (EC) where the sum of 205Tl + 203Tl was measured. Both methods are almost specific. The results are significantly influenced only by 1000-fold excess of tungsten due to the interference of 186W17O. The limits of detection of both techniques are 0.15 ng g−1 and 0.20 ng g−1 for ID and EC, respectively. The ID technique is robust with respect to instrument parameters settings (rf power, nebulizer Ar flow and lens voltage). The results of EC analysis can be slightly affected by alteration of rf power. For the verification of accuracy of results, three approaches were applied. (1) The analysis of samples prepared from standard thallium solution gave results in agreement with theoretical values. (2) The analysis of spiked plant samples with a very low (wheat flour) and high (defatted rape-seed meal) thallium content proved the accuracy of the ID method (recovery values of 99.5 and 99.8%, respectively do not differ significantly from 100%). On the other hand, EC analysis gave recovery values of 99.2 and 101.6%, respectively, which are more than satisfactory for routine trace analysis, but owing to high precision of measurement these values are statistically different from 100%. (3) Analysis of several CRMs by ID gave results in agreement with certified values except for SRM NIST 2709 San Joaquin Soil. Results of EC analysis can be affected by the choice of internal standard. The usage of rhodium was the best choice. The repeatabilities of both analytical procedures are comparable; relative standard deviations ranged from 0.4 to 1.0%.

Determination of thallium in environmental samples using potentiometric stripping analysis. Method development

AbstractA method employing computerized potentiometric stripping analysis has been developed in order to determine trace levels of thallium in various environmental samples. The method is based on the preconcentration of T1 onto a mercury film electrode (formed in situ) with a subsequent reoxidation of amalgamated T1. A deaeration of the solution as well as the use of EDTA have resulted in a significant improvement of the sensitivity. In a supporting electrolyte containing 0.02–0.07 M HNO3 + 0.02 M CH3COONa + 0.001 M EDTA + 6 × 10−5 M HgCl2, the analytical signal versus concentration dependence is linear from 9 × 10−11 to 2.5 × 10−8 M T1 (preconcentration time from 5 to 30 min). A detection limit of about 5 × 10−11 M T1 (0.01 μg/L) is achieved when using preconcentration for 30 min. Despite a relatively high acidity of the supporting electrolyte used (pH 1.0–2.5), EDTA is capable to suppress the interferences from PbII ions up to a 500‐fold excess in concentration and from CdII and CuII up to their 100‐fold excess, respectively. Nitric acid has been incorporated into the supporting electrolyte as its constituent in order to determine T1 directly in the samples decomposed by means of high pressure ashing. The applicability of the method is demonstrated on various samples such as tap water (spiked), rain water, river sediment or sewage sludge. The results agree well with those obtained by isotope dilution‐mass spectrometry. The method has also been tested to determine T1 in digested biological samples (e.g., pine needles, poplar leaves and mussel tissues).

Suitability of open system digestions for the determination of thallium in environmental samples

Abstract The determination of thallium (T1) content in environmental samples is important because of the high toxicity of this metal. Fast and accurate analytical methods are required. Therefore, various open system digestion methods were investigated for the rapid determination of T1 in plant and soil samples. For soils, all procedures were tested by analysis of two National Institute of Standards and Technology (NIST) standard reference materials. For plant samples, the accuracy of the methods was evaluated using three digested materials, with and without a standard addition of 1 μg T1 on each one before digestion. Thallium was determined directly on digested solutions, without separation or preconcentration procedures and with two electrothermal atomic absorption spectrophotometers (ETAAS). Results showed that only one procedure was suitable. The method is based on the solubuization of sample by heating a solution made from 30% hydrogen peroxide (H2O2) and 65% nitric acid (HNO3). The procedure gave good agreement with the NIST certified concentration for soils and adequate recoveries for plant samples. No further hydrofluoric acid (HF) digestion was required on soils samples. Thallium concentrations numerically were higher but the increase was not significant. Volatility of T1 compounds was a drawback with the other digestion methods (aqua regia digestion, HNO3‐H2SO4 digestion and sample dry‐ashing at 480°C) where Tl losses occurred. After volumation in flasks, changes in Tl concentration in digested solutions were not detected during 10 days. The detection limit for the wet digestion method in 10% HNO3 is 60 ng TI/L which is adequate with other investigations.

Preconcentration of thallium(I) with the ion pair of 1,10-phenanthroline-tetraphenylborate-naphthalene adsorbent

A solid ion-pair material produced from 1,10-phenanthroline and tetraphenylborate on naphthalene provides a simple, rapid, economical, and fairly selective method for the preconcentration of Tl(I) from a larger volume of aqueous solutions (about 200-fold concentration can be easily achieved). Tl(I) is quantitatively adsorbed on this material in the pH ranges 0–11 and 1–8 N in HNO 3 aqueous media and at a flow rate of 1 ml/min. The solid mass in the column is dissolved out with 5 ml of dimethylformamide (DMF), and metal is determined by atomic absorption spectrophotometry at 276.8 nm. A calibration curve is linear over the concentration range 1.0–100 μg of thallium in 5 ml of the DMF solution. Seven replicate analyses of a sample solution containing 10 μg of thallium gave a mean absorbance of 0.115 with a relative standard deviation of 0.8%. The sensitivity for 1% absorption is 0.077 μg Tl/ml (0.090 μg Tl/ml for the direct absorption spectrophotometric method from the aqueous solution). The method is highly sensitive and various parameters have been evaluated. The method has been employed for the trace determination of thallium in various standard materials and can be employed safely for the determination of thallium in environmental samples.

Determination of thallium in environmental samples by activation analysis with fast reactors neutrons

A procedure is described for the determination of thallium in coal fly ash by fast neutron activation analysis using the reaction203Tl/n, 2n/202Tl. A 31 h reactor irradiatioon under cadmium cover at a fast neutron flux of 3.05×1012 n.cm−2.s−1 is applied. The simple radiochemical separation involves a wet attack in acids followed by an extraction of Tl/III/into diisopropylether from 0.5M HBr. The radiochemical purity is sufficient for immediate γ-spectrometry. A value of 5.7±0.7 ppm is found in the NBS 1633a coal fly ash.