Determination of traces of thallium by fluorimetric titration

Summary Thallium(I) shows strong fluorescence in a solution which is 3.3 M in HCl and 0.8 M in KCl. The excitation wavelength is 253 nm and the wavelength selected for the fluorescence 438 nm. Due to the strong absorption at 253 nm by thallium(III) a reductometric rather than an oxidimetric titration will lead to a correct fluorimetric end-point indication. The precision and the selectivity of the titrimetric method are better than those of the corresponding methods based on the use of calibration curves. Traces of thallium down to 1 g can be determined with good precision. The method can be used for the determination of thallium in urine at the ppm level.

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Bestimmung von Spuren Thallium durch fluorimetrische Titration

Zusammenfassung Thallium(I) zeigt starke Fluorescenz in einer Lösung, die 3,3 M an HCl und 0,8 M an KCl ist. Diese Erscheinung wurde zur Endpunktsanzeige der Redoxtitration Tl(III)-Tl(I) verwendet (Excitationswellenlänge 253 nm, Fluorescenzwellenlänge 438 nm). Wegen der starken Lichtabsorption von Thallium(III) bei 253 nm kann nur ein reduktometrisch durchgeführtes Titrationsverfahren benutzt werden. Genauigkeit und Selektivität sind beim titrimetrischen Verfahren besser als beim Eichlinienverfahren. Spuren Thallium (bis einige Mikrogramm) können mit guter Genauigkeit bestimmt werden. Die Anwendung der Methode für die Bestimmung von Thallium in Urin im ppm-Bereich wird beschrieben.

     

Complexometric determination of thallium(III) in pure solution,alloys, and complexes using semicarbazide hydrochloride as a releasing agent

A simple and accurate complexometric method is proposed for the determination of Tl(III) using semicarbazide hydrochloride as a releasing agent. In the presence of diverse metal ions, thallium is complexed first with a known excess of EDTA, and the surplus EDTA is then titrated with standard zinc sulfate at pH 5.0–6.0 (hexamine) using xylenol orange indicator. An excess of 5% aqueous neutral solution of semicarbazide hydrochloride is then added and the released EDTA is titrated against standard zinc sulfate solution. The method works well in the range 2–50 mg of Tl(III) with relative errors < 0.5%, standard deviations 0.05mg and coefficient of variation 0.4%. The method is applied for the determination of thallium content in complexes and alloy compositions     

Spectrofluorometric trace determination of cerium(III) in sodium hexametaphosphate solutions

The use of sodium hexametaphosphate in the spectrofluorometric determination of trace amounts of cerium(III) ions is described. Sodium hexametaphosphate acts as a specific reagent for enhancing the fluorescence intensity of cerium(III) in aqueous solutions. The apparent excitation and fluorescence wavelength used are 304 and 344 nm, respectively. Maximum fluorescence intensity is obtained by irradiating Ce(III) dissolved in 5.346 g/l sodium hexametaphosphate solution at room temperature. The fluorescence varies linearly with the concentration of cerium(III) in the range of 0.001–60 g/ml. The coefficient of variation for 45 g/ml Ce(III) in 5.346 g/l sodium hexametaphosphate solution is 1. The quenching effects of other lanthanides and some inorganic anions are given. This technique permits a direct and rapid determination of cerium(III) in rare earth mixtures and cerium concentrates.     

About the microdetermination of thallium with rhodamine B

Summary The spectrophotometric determination of thallium with Rhodamine B as Rhodamine B-thallium(III) tetrabromide using extraction of the complex into benzene was investigated. For the oxidation of thallium(I) ceric sulphate was used. The optimum conditions and interferences of some ions for the determination of microgram amounts of Tl are described. The sensitivity is 0.0028 g of Tl per 1 ml of benzene. 5 g of Tl can be determined with a precision of ±2.4%. The method described may be applied in trace analyses of thallium, where sulphuric-nitric acid is used for the decomposition of the sample.

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Zusammenfassung Ein spektrophotometrisches Verfahren zur Thalliumbestimmung mit Rhodamin B wird beschrieben, bei dem der gebildete Thallium(III)-komplex mit Benzol extrahiert wird. Zur Oxydation von einwertigem Thallium wird Cer(IV)-sulfat verwendet. Die optimalen Bedingungen sowie Störungen durch Fremdionen bei der Bestimmung von g-Mengen Thallium werden beschrieben. Die Empfindlichkeit betrÄgt 0,0028 g Tl/1 ml Benzol. 5 g Tl können mit einer Genauigkeit von±2,4% bestimmt werden. Das beschriebene Verfahren kann bei der Spurenanalyse von Thallium in solchen Proben benutzt werden, die mit Schwefel- und SalpetersÄure aufgeschlossen worden sind.

     

Substoichiometric radiochemical determination of thallium with sodium isopropyl xanthate

A rapid radiochemical method for the determination of thallium(III) has been developed based on the substoichiometric extraction of its 13 complex with sodium isopropyl xanthate into chloroform from pH 9 ammonia buffer. The effect of foreign ions on the extraction was also studied. 10 g amounts of thallium were determined with an average error of 1.9%. The method has been successfully applied for the determination of thallium content present in sphalarite ores collected from Jawar Mines, Rajasthan (India).     

Solvent Extraction with Two Immiscible Organic Solvents Separation of Thallium(iii)

Abstract

A methylisobutyl ketone/formamide two-phase organic solvent system was utilized for the separation of thallium(III) from the elements Ga, In, Fe(III), Sn(II) and Sn(IV). The procedure involves a semi-selective extraction of the elements from an aqueous 2M HBr solution with methylisobutyl ketone followed by the complete separation of thallium from the other elements enumerated by stripping the ketone phase with a 1.5M HBr-formamide solution. Thallium was determined at 3776 Å by flame emission spectrometry.     

Kinetics of the oxidation of cyclohexene by thallium(III) acetate

The kinetics of the reaction by which thallium(III) acetate oxidizes cyclohexene in glacial acetic acid medium, has been studied by UV spectrophotometric observation at 30°C. The consumption of thallium(III) acetate follows a second-order rate law exhibiting first-order dependence on each of thallium(III) acetate and cyclohexene; however, the first-order dependence on cyclohexene disappears at high cyclohexene concentrations as pseudo-first-order conditions prevail above 0.2 M cyclohexene. A steady-state model of the following form is proposed: where Tl, Cy, and Com are units of Thallium(III) acetate, cyclohexene, and a reaction complex. The value of k₂ has been evaluated as 0.00027 and (k_?1 + k₂) as 0.0385k₁. For low thallium(III) acetate concentrations the reaction kinetics follow the rate law: where α = the excess concentration of cyclohexene over thallium(III) triacetate. For thallium(III) acetate concentrations above 0.02 M, double salt formation of thallium(III) acetate with product thallium(I) acetate removes thallium(III) acetate from the reaction and a modified rate law is observed. Runge–Kutta numerical solutions to the differential equations provide confirmation that the rate expressions are valid in predicting the observed concentrations of thallium(III) acetate.     

Spectrofluorimetric determination of trace amounts of Tb(III) using acetylacetone in ethanol solution

Summary The spectrofluorimetric determination of terbium(III) in ethanol (95%) solution of acetylacetone (3×10^–4 mol/l) was studied. Intensive fluorescence of terbium(III) (=545 nm) was observed after excitation of the system (=310 nm). The method proposed is satisfactory for the determination of terbium(III) in the range of 4 to 40 ng/ml (2.5×10^–8 to 2.5×10^–7 mol/l). The effect of other rare earths, common metal ions and anions upon the intensity of the fluorescence emitted by terbium(III) is discussed.

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Spektrofluorimetrische Bestimmung von Tb(III)-Spuren mit Acetylaceton in Ethanollösung

     

Quantification of gold(III) in solution and with a test stripe via the quenching of the fluorescence of molybdenum disulfide quantum dots

The paper describes a fluorescent method for determination of Au(III) using molybdenum disulfide quantum dots (MoS₂ QDs) that were prepared by a hydrothermal route using glutathione as a reductant. The photoluminescence of MoS₂ QDs peaks at 416 nm if excited at 340 nm and is temporally stable even in presence of NaCl or when stored in the refrigerator for one year. Its quantum yield is 12.7 %. The blue-green fluorescence of MoS₂ QDs is fairly specifically quenched by Au(III) ions and therefore presents a useful nanoprobe for this ion. Fluorescence intensity drops linearly with the concentration of Au(III) in the range from 0.5 to 1000 μM, and the lower detection limit is 64 nM. The quenching mechanism was investigated and it is concluded that the process is due to the reduction of Au(III) and the deposition of Au(0) on the surface of the MoS₂ QDs. The nanoprobe was successfully applied to the determination of Au(III) in (spiked) environmental samples. A test stripe for Au(III) was obtained by soaking a piece of paper with a colloidal solution of the MoS₂ QDs, and it was found that this stripe, after drying, can also be used to quantify Au(III) via fluorescence.

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Graphical abstract Molybdenum disulfide quantum dots (MoS₂ QDs) have a high quantum yield and show good stability. MoS₂ QDs are shown to be a sensitive fluorescent probe for the determination of Au³⁺ ions in solution and with a test stripe via fluorescence quenching.

     

Analytical separation of antimony(III) from bismuth(III), lead(II), gallium(III), thallium(III), tellurium(IV) and tin(IV) with cyanex 302

A method is proposed for the separation of antimony(III) (100–400 g) from bismuth(III), lead(II), gallium(III), thallium(III), tellurium(IV) and tin(IV) from an aqueous solution of pH 0.5–1.5 using 8×10^–3–1×10^–2 mol dm^–3 cyanex 302 dissolved in toluene as an extractant. The antimony is stripped from the cyanex phase with water and determined spectrophotometrically with iodide. Various experimental parameters are optimized and the probable 13 stoichiometry of the extracted species is evaluated. The method is applicable to the analysis of alloys and pharmaceutical samples. The separation and determination take only 20 min.     

Determination of Iron(III), Cobalt(II) and Chromium(III) in Various Water Samples by Flame Atomic Absorption Spectrometry After Preconcentration by Means of Saccharomyces Carlsbergensis Immobilized on Amberlite XAD-4

A method for the determination of Fe(III), Co(II) and Cr(III) by flame atomic absorption spectrophotometry (FAAS) after preconcentrating on a column containing S. carlsbergensis immobilized on Amberlite XAD-4 has been developed. The optimum values of pH, amount of adsorbent, elution solution and flow rate of the sample solution were determined for the quantitative recovery of the analytes. The effect of interfering ions on the recovery of the analytes was also investigated. Under the optimum conditions, recoveries of Fe(III), Co(II) and Cr(III) by S. carlsbergensis immobilized on Amberlite XAD-4 were 99±2, 100±2 and 98±2% at 95% confidence level, respectively. The limit of detections for Fe(III), Co(II) and Cr(III) were 2.8, 3.9 and 7.4ngmL^–1, respectively. The proposed method was applied to the determination of the analytes in various water samples. The validity of the method was checked with spiked water samples. Fe(III), Co(II) and Cr(III) was determined with a relative error of less than 5%.     

Determination of thallium(III) by use of a mercury reductor

A convenient method has been developed for the determination of thallium(III) by using a mercury reductor. Thallium(III) is reduced to thallium(I) in 0.5–4N hydrochloric or sulphuric acid medium and the determination is completed by oxidative titration with potassium bromate. The method is extended to analysis of thallium(III)-thallium(I) and thallium(III)-iron(III) mixtures.     

Nachweisstarke,hochselektive extraktions-spektral-photometrische Thalliumbestimmung mit Rhodamin B

Zusammenfassung Zur zuverlässigen Erfassung von Thalliumspuren (20 ng Tl absolut) in wäßrigen, silikatischen und biologischen Proben wurden die herkömmlichen spektralphotometrischen Bestimmungsmethoden kritisch diskutiert und die besonders nachweisstarke und selektive, extraktionsphotometrische Methode über den Tl(III)-Bromo-Rhod-amin-B-Komplex eingehend auf Fehler untersucht. Durch Schütteln der thalliumhaltigen organischen Phase mit 0,5 M HBr-Lösung, die 0,2% Hydroxylamin enthält, konnten Störungen von Elementen (Au, Hg, J), die ebenfalls mit Rhodamin B intensive Farbkomplexe bilden, wesentlich vermindert werden. Die zulässigen Höchstkonzentrationen für Störelemente wurden tabelliert.Die ausgearbeitete Vorschrift erlaubt es, Thalliumgehalte 20 ng neben praktisch allen in umweltrelevanten Proben vorkommenden Elementen mit hoher Genauigkeit zu bestimmen. Die Standardabweichung beträgt bei der Bestimmung von 100 ng Tl/ml±2,5% (20 Bestimmungen).

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Powerful, highly selective extraction-spectrophotometrical determination of thallium with khodamine B

Summary Common spectrophotometric methods for the reliable determination of traces of thallium (20 ng) in aqueous and biological samples and in silicates have been discussed critically; the sources of error in the extraction-photometric method of using the thallium-bromo-rhodamine B complex, which is highly selective and sensitive, have been examined.Shaking of the thallium-containing organic layer with 0,5M HBr-solution containing 0.2% of hydroxylarnine is able to diminish the interference of elements (Au, J, Hg), which give intensively coloured complexes with rhodamine B, too. The permissible limits of concentration of foreign ions are tabulated.The elaborated procedure permits the determination of more than 20 ng thallium in presence of practically all elements occurring in environmental samples with high accuracy. The standard deviation at the 100 ng Tl/ml level is ±2.5% (20 determinations).

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Dankt der Max-Planck-Gesellschaft für ein Gastwissenschafter-Stipendium.     

Potentiometric determination of tetraphenylborate ions with silver nitrate. Determination of silver, potassium and thallium(I)

Summary The potentiometric determination of tetraphenylborate with silver nitrate solution was investigated a) at i=0 in the presence of calomel reference electrode and silver resp. silicone rubber based halide-selective indicator electrodes and b) at i0 in the presence of silver (cathode)-calomel, silver-silver, silver-platinum, platinum-silver and graphite-silver electrode couples. An indirect method is described for the determination of potassium ions with potentiometric end-point indication. Experiments were also carried out in order to develop methods for the titration of silver, potassium and thallium(I) ions with sodium tetraphenylborate solution in the presence of anodic polarized graphite and calomel reference electrodes. The relative standard deviations were 0.38–0.49% for tetraphenylborate, 1.96% for potassium and 1.07% for thallium(I).

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Potentiometrische Bestimmung von Tetraphenylborationen mit Silbernitrat. Bestimmung von Silber, Kalium und Thallium(I)

Zusammenfassung Die Möglichkeit der potentiometrischen Bestimmung von Tetraphenylborat mit Silbernitrat wurde untersucht a) in Anwesenheit von Kalomel-Bezugselektrode und Silber- bzw. haloidselektiven Silicongummi-Indicatorelektroden bei i=0 und b) in Anwesenheit von Silber (Kathode)-Kalomel-, Silber-Silber, Silber-Platin-, Platin-Silber- und Graphit-Silber-Elektrodenpaaren bei i0. Eine Methode zur indirekten potentiometrischen Bestimmung von Kalium sowie Verfahren zur Bestimmung von Silber-, Kalium- und Thallium(I)-ionen mit Natriumtetraphenylboratlösung in Anwesenheit einer anodisch polarisierten Graphitelektrode und einer Kalomel-Referenzelektrode wurden ausgearbeitet. Die relativen Standardabweichungen betragen für Tetraphenylborat 0,38–0,49%, für Kalium und Thallium 1,96 bzw. 1,07%.

     

Detection of cyanide via extended π-conjugation-induced fluorescence enhancement of a metal organic framework composed of terbium(III), bipyridyl and adenosine diphosphate

A metal-organic framework (MOF) was designed and prepared from luminescent Tb(III), adenosine diphosphate (ADP) and bipyridyl (Bipy). Its green fluorescence at 545 nm is shown to enable the fluorometric detection of cyanide ion based on the principle of π-conjugation-induced fluorescence enhancement. The fluorescence of the probe is strongly increased by cyanide due to extended π-conjugation between probe MOF and cyanide which sensitizes the fluorescence of Tb(III). This effect can be used to quantify cyanide at levels as low as 30 nM in aqueous solution. The method was applied to the determination of cyanide in saliva samples. The lack of interference by acetate and fluoride is a specific feature of this method. The method based on the principle of π-conjugation-induced fluorescence enhancement provides a new sensing way for widely used fluorescence assays.

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Graphical abstract A cyanide-selective Tb-ADP-Bipy MOF was designed and synthesized for the detection of cyanide based on the principle of π-conjugation-induced fluorescence enhancement.

     

Microdetermination of fluoride by spectrophotometry of arsenazo(III)-complex of Zr back-extracted from htta in benzene

A spectrophotometric method for the determination of trace amounts of fluoride in aqueous solution is developed. It is based on the back extraction of Zr(IV) from its thenoyltrifluoroacetonate complex in benzene by aqueous F^– followed by the development of Zr-arsenazo(III) coloured complex and the measurement of the absorbance at 665 nm. Optimum conditions and effect of interfering ions are studied. The coefficients of variation obtained are 1.5% and 2.2% in 11 determination at the F^– concentration level of 10.0 g/ml and 1.6 g/ml. An excess of Al(III) is used for decomplexing Zr-fluoride prior to the colour formation if the fluoride amount is high. The method is useful for the determination of trace impurities of fluoride in nuclear fuel after separating fluoride from fuel matrix by pyrohydrolysis.     

Luminescence properties of acridine dyes in micellar sodium dodecyl sulfate solutions containing thallium ions

The effect of external heavy Tl^I ion on the luminescence properties of Trypaflavine, Acridine Yellow, and Acridine Orange solubilized in sodium dodecyl sulfate micelles was studied. An increase in the concentration of thallium ions results in a decrease in the intensity of prompt fluorescence, an increase in the intensity of delayed fluorescence, the appearance of phosphorescence at 20 °C, and a shortening of the triplet state lifetime of the dyes. The effective and micellar Stern—Volmer constants of fluorescence quenching of the dyes by thallium ions were determined. The effective and micellar quenching rate constants of triplet states of the dyes by Tl(i) ions and lifetimes of the triplet states of the dyes in the absence of thallium ions were calculated on the basis of kinetic measurements.     

Silver nanoparticles capped with 8-hydroxyquinoline-5-sulfonate for the determination of trace aluminum in water samples and for intracellular fluorescence imaging

We report on a simple method for the determination of traces of aluminum(III) in water at pH 7.4 by using silver nanoparticles (Ag-NPs) functionalized with 8-hydroxyquinoline-5-sulfonate. The modified Ag-NPs undergo (a) a distinct color change from yellow to deep orange, and (b) a strong fluorescence enhancement upon addition of Al(III). Both the ratio of absorbances at 530 and 392 nm, and the intensity of fluorescence at 492 nm can serve as the analytical information. The absorption-based calibration plot increases linearly in the 0.1 to 4.0 μM Al(III) concentration range. The detection limit is 2.0 nM which is much lower than the permissible level (7.4 μM) for drinking water as defined by the World Health Organization. The method was successfully applied to the determination of Al(III) in samples of lake water, tap water and boiler water, and the recoveries were from 98 to 105 %. The assay also was applied to the determination of Al(III) in living mouse myeloma cells via fluorescence imaging. A linear relationship was obtained between relative fluorescence intensity (F/F₀) and the concentration of Al(III) in the 0.05 μM to 4 μM concentration range. The detection limit is 15 nM.

Determination of As(III) and total inorganic arsenic by on-line pretreatment in hydride generation atomic absorption spectrometry

Summary A method for the on-line prereduction of As(V) was developed in order to determine As(III) and As(V) with the same sensitivity by continuous flow hydride generation. In this procedure, the sample is continuously mixed with concentrated hydrochloric acid and a potassium iodideascorbic acid solution, flows through a heated PTFE-tube and is determined by hydride generation atomic absorption spectrometry in a heated quartz cell. The selective analysis of As(III) is carried out by continuous mixing of the sample with acetic acid and hydride generation. The method allows the rapid determination of inorganic arsenic species at concentrations down to 1 g/l. A manual sample preparation is not required.     

Determination of Methacycline and Glucose in Biological Fluids by Europium(III)-Sensitized Luminescence

Complexation in the Eu(III)–methacycline and Eu(III)–methacycline–hydrogen peroxide systems was studied by luminescence. It was proposed to use the studied complexes as analytical forms for the luminescence determination of methacycline in blood plasma (lower determination limit 2.5 g/mL) and urine (25 g/mL) and for the indirect determination of 0.025–0.7 mM glucose in blood plasma.