Thallium determination

Thus excess of Mn(IV) hydroxide represents itself as a collector of thallium which practically completely passes into a deposit, and interfering metal ions (Cu, Cd, Pb, Ni, etc.) remain in a solution and are separated providing high selectivity of thallium determination. Effect of some factors on the value of analytical signal of thallium has been investigated at the stages of water pretreatment. Based on of these data the unified technique for thallium determination has been developed and tested on natural waters. The method proposed allows to determine content of thallium in waters which is 10 times lower than it is required by maximum allowable concentration limits. 

For thallium, determinations at the 276.78 nm line with an acetylene/air flame are used throughout. Matrix problems are very low, but the sensitivity with regard to the low level of occurrence is poor. The sensitivity can be increased by mounting a slotted quartz tube on the burner head STAT = "slotted tube atom trap") (Milner, 1983), which leads to a detection limit of about 20 mg/kg in the solid sample, which is insufficient for the analysis of biological matrices. In MIBK extracts, determination of thallium is much more sensitive in flame AAS than in aqueous solutions (till about 7-fold). This can be used for solvent extraction of thallium from 0.1M HBr (Hubert and Chao, 1985), as xanthate at pH 8 (Aihara and Kiboku, 1980), or as iodide with tri-n-octylphosphinoxide into MIBK, and direct aspiration of the organic phase into the flame. 

In the most sensitive eiectroanaiytical methods, exclusively treated within this context, the analyte ion is electrodeposited on an electrode from an electrically conducting sample solution. Current and potential of subsequent redissolution are due to the concentration and the kind of ion to be determined. For thallium, the reversible redox couple TI /TI° at about -0.5 V versus saturated calomel electrode is used (Bellavance and Miller, 1975). Infinite tolerance towards alkali, alkaline earths and halogenides are great merits for the analysis of biological materials. Because of the preconcentration step included, thallium determination is more sensitive than atomic spectrometric methods. For thallium, the multielement capabilities of the method can hardly be used, because lead and frequently cadmium have to be masked with excess of complexants, leaving just Tl in the potential... 

Thallium determination with the graphite tube technique (Furnace method)... 

Differential pulse polarography is used to determine the concentrations of lead, thallium, and indium in a mixture. ... 

The aim of this work is the development of pyrene determination in gasoline and contaminated soils. For this purpose we used room temperature phosphorescence (RTP) in micellar solutions of sodium dodecylsulphate (SDS). For pyrene extraction from contaminated soils hexane was used. Then exttacts earned in glass and dried. After that remains was dissolved in SDS solution in the presence of sodium sulphite as deoxygenation agent and thallium (I) nitrate as heavy atom . For pyrene RTP excitation 337 nm wavelength was used. To check the accuracy of the procedures proposed for pyrene determining by RTP, the pyrene concentrations in the same gasoline samples were also measured by GC-MS. 

PRECONCENTRATION AND DETERMINATION OF THALLIUM TRACES IN WATER BY STRIPPING VOLTAMMETRY... 

The method of stripping voltammetry (SV) is one of the most perspective methods in concentration range of thallium(I) determination of 10 -10 M. Achievement of high sensitivity of thallium(I) determination needs carrying out its additional concentration and sepai ation from other metals which ai e close by electrochemical properties. For these purposes it is offered to use a method of coprecipitation with collector. The combination of SV and a method of coprecipitation on a collector have shown that minimum detectable concentration can be decreased by 2-3 orders of magnitude. 

Stripping voltammetry procedure has been developed for determination of thallium(I) traces in aqueous medium on a mercury film electrode with application of thallium preconcentration by coprecipitation with manganese (IV) hydroxide. More than 90% of thallium present in water sample is uptaken by a deposit depending on conditions of prepai ation of precipitant. Direct determination of thallium was carried out by stripping voltammetry in AC mode with anodic polarization of potential in 0,06 M ascorbic acid in presence of 5T0 M of mercury(II) on PU-1 polarograph. 

The amount of oxygen dissolved in a sample of water can be determined by using thallium metal containing a small amount of the isotope Tl-204. When excess thallium is added to oxygen-containing water, the following reaction occurs. 

Determination of silver as chloride Discussion. The theory of the process is given under Chloride (Section 11.57). Lead, copper(I), palladium)II), mercury)I), and thallium)I) ions interfere, as do cyanides and thiosulphates. If a mercury(I) [or copper(I) or thallium(I)] salt is present, it must be oxidised with concentrated nitric acid before the precipitation of silver this process also destroys cyanides and thiosulphates. If lead is present, the solution must be diluted so that it contains not more than 0.25 g of the substance in 200 mL, and the hydrochloric acid must be added very slowly. Compounds of bismuth and antimony that hydrolyse in the dilute acid medium used for the complete precipitation of silver must be absent. For possible errors in the weight of silver chloride due to the action of light, see Section 11.57. 

Determination of thallium as chromate Discussion. The thallium must be present in the thallium(I) state. If present as a thallium(III) salt, reduction must be effected (before precipitation) with sulphur dioxide the excess of sulphur dioxide is boiled off. 

The reaction is a sensitive one, but is subject to a number of interferences. The solution must be free from large amounts of lead, thallium (I), copper, tin, arsenic, antimony, gold, silver, platinum, and palladium, and from elements in sufficient quantity to colour the solution, e.g. nickel. Metals giving insoluble iodides must be absent, or present in amounts not yielding a precipitate. Substances which liberate iodine from potassium iodide interfere, for example iron(III) the latter should be reduced with sulphurous acid and the excess of gas boiled off, or by a 30 per cent solution of hypophosphorous acid. Chloride ion reduces the intensity of the bismuth colour. Separation of bismuth from copper can be effected by extraction of the bismuth as dithizonate by treatment in ammoniacal potassium cyanide solution with a 0.1 per cent solution of dithizone in chloroform if lead is present, shaking of the chloroform solution of lead and bismuth dithizonates with a buffer solution of pH 3.4 results in the lead alone passing into the aqueous phase. The bismuth complex is soluble in a pentan-l-ol-ethyl acetate mixture, and this fact can be utilised for the determination in the presence of coloured ions, such as nickel, cobalt, chromium, and uranium. 

Kubaslk, N. P. and Volosln, M. T. "A Simplified Determination of Urinary Cadmium, Lead, and Thallium, with Use of Carbon Rod Atomization and Atomic Absorption Spectrophotometry . Clin. Chem. (1973), 19, 954-958. 

Machata, G. and Binder, R. "The Determination of Lead, Thallium, Zinc and Cadmium Traces in Biological Material with Flameless Atomic Absorption". Z. Rechtsmed. (1973),... 

Kucera J, Vobecky M, Soukal L, Zakoucky D, and Venos D (1997) Low level determination of thallium in biological and environmental reference materials by RNAA using several counting methods. J Radioanal Nud Chem 217 131-137. 

From an analysis of their data, Materlik and co-workers were able to determine that for the ex situ case and in the absence of oxygen, the thallium atoms are located at twofold sites at a mean distance of 2.67 0.02 A. For the in situ case and again in the... 

Perez Ruiz et al. [26] determined penicillamine and tiopronin in pharmaceutical preparations by flow injection fluorimetry. The procedure is based on the oxidation of these drugs by thallium(III), whereupon the fluorescence of T1(T) produced in the oxidation of penicillamine is monitored using excitation at 227 nm and emission at 419 nm. A linear calibration graph for penicillamine was obtained between 3 x 10-7 and 8 x 10 5 6 M. 

H. Kahlert, S. Komorsky-Lovric, M. Hermes, and F. Scholz, Prussian blue-based reactive electrode (reactrode) for the determination of thallium ions. Fresenius J. Anal. Chem. 356, 204-208 (1996). 

J.M. Zen, H. Ho, and P.Y. Chen, Voltammetric determination of thallium on a Prussian blue/cinder paste electrode. Indian J. Chem. Sect. A Inorgan. Bio-Inorgan. Phys. Theoret. Anal. Chem. 42, 839—842 (2003). 

Polarography has also been applied to the determination of potassium in seawater [535]. The sample (1 ml) is heated to 70 °C and treated with 0.1 M sodium tetraphenylborate (1 ml). The precipitated potassium tetraphenylborate is filtered off, washed with 1% acetic acid, and dissolved in 5 ml acetone. This solution is treated with 3 ml 0.1 M thallium nitrate and 1.25 ml 2M sodium hydroxide, and the precipitate of thallium tetraphenylborate is filtered off. The filtrate is made up to 25 ml, and after de-aeration with nitrogen, unconsumed thallium is determined polarographically. There is no interference from 60 mg sodium, 0.2 mg calcium or magnesium, 20 pg barium, or 2.5 pg strontium. Standard eviations at concentrations of 375, 750, and 1125 pg potassium per ml were 26.4, 26.9, and 30.5, respectively. Results agreed with those obtained by flame photometry. 

The palladium and magnesium nitrates modifier has a substantial equalising effect on the atomisation temperature of the nine elements investigated. The optimum atomisation temperature for all but one element (thallium) is between 1900 and 2100 °C. This means that all elements can be determined at a compromise atomisation temperature of 2100 °C with a minimum sacrifice in sensitivity. Such uniform conditions for as many elements as possible are of vital importance if simultaneous multielement furnace techniques are envisaged. Moreover, in conventional graphite furnace AAS, uniform conditions for a number of elements can greatly facilitate and simplify daily routine analysis. 

Berndt et al. [740] have shown that traces of bismuth, cadmium, copper, cobalt, indium, nickel, lead, thallium, and zinc could be separated from samples of seawater, mineral water, and drinking water by complexation with the ammonium salt of pyrrolidine- 1-dithiocarboxylic acid, followed by filtration through a filter covered with a layer of active carbon. Sample volumes could range from 100 ml to 10 litres. The elements were dissolved in nitric acid and then determined by atomic absorption or inductively coupled plasma optical emission spectrometry. 

Haapakka and Kankare have studied this phenomenon and used it to determine various analytes that are active at the electrode surface [44-46], Some metal ions have been shown to catalyze ECL at oxide-covered aluminum electrodes during the reduction of hydrogen peroxide in particular. These include mercu-ry(I), mercury(II), copper(II), silver , and thallium , the latter determined to a detection limit of <10 10 M. The emission is enhanced by organic compounds that are themselves fluorescent or that form fluorescent chelates with the aluminum ion. Both salicylic acid and micelle solubilized polyaromatic hydrocarbons have been determined in this way to a limit of detection in the order of 10 8M. 

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