Studies on the potentiometric thallium(III)-selective carbon paste electrode and its possible applications

Construction, performance characteristics and applications of a carbon paste thallium(III) ion-selective electrode are described. The electrode, which is based on ion-associate compounds formed between cetylpyridinium and chlorothallate(III) complexes dissolved in tricresyl phosphate as pasting liquid, showed near-Nernstian response over the concentration range of 5.8 × 10^–6– 2.9 × 10^–3 mol/L. Potentiometric titrations of thallium(III) with cetylpyridinium chloride were affected by higher concentrations of excess halides, probably due to the formation of higher halogenothallates.     

Investigation of the extraction equilibrium of ternary ion-association complex of thallium(III) with iodo-nitro-tetrazolium chlorid

The extraction equilibrium of the ternary ion-association complex of iodo-nitro-tetrazolium [3-(4-iodophenyl)-2-(4-nitrophenyl)-5-phenyltetrazolium chloride] with the chlorocomplex of thallium(III) is investigated radiochemically. The molar ratio of the ion-associate is found to be 1∶1, the association constant has a value of β=3.2·10³ in aqueous solution and the distribution constant is K_D=8.9. The extraction constant which gives a quantitative characterization of the equilibrium has a relative high value, E=2.3·10⁴. This enables a convenient application of the investigated system for analytical purposes.     

Voltammetric behavior of neptunium(vi) in glutamic acid media at the rotating glassy carbon electrode

The voltammetry of neptunium(VI) glutamate was investigated over the pH range 3.8–10.0. A reversible, one-electron wave was obtained for glutamate concentrations above 0.1 M in the pH range 3.8–6.1, or above 0.3 M in the pH range 6.1–10.0. At pH 3.8–6.1, the half-wave potential was independent of pH, but at pH 6.1–10.0, it was a function of pH. The metal-ligand ratio was found to be 1:2 by conductometric titration. The limiting current was proportional to the concentration of the neptunium(VI) from 7.83·10^-5 to 1.96·10^-3M. The diffusion coefficient was 0.35·10^-5 cm² sec^-1 at pH 4.5 and 0.30·10^-5 cm² sec^-1 at pH 9.4.     

Solid Membranes of Copper Hriacyanoferrats (III) as Thallium (I) Sensitive Electrode

Abstract

Solid membranes of copper hexacyanoferrate (III) in Areldite are evaluated as thallium (I) sensitive electrode. The membrane electrode gave a linear near Normstian response to thallium (I) ions in the concentration range 10^?1 - 5 × 10^?4 M and can be used to estimate T1 (I) down to 10^?4 M. The responses of the electrode is fast and steady potentials are obtained in less than a minute. The same membrane has been used over a period of six months without any appreciable drift in potential. The electrode can also be used satisfactory in partially non-aqueous media and in presence of a number of interfering ions. It is superior to the existing T1(I) solid membrane electrodes as it can function in alkaline range also.     

Separation of Tl(I)-Pb(II) by liquid-liquid extraction with diethyldithiocarbamic acid isolation of201Tl

The production of²⁰¹ Tl is described. Natural thallium is irradiated with protons and the induced²⁰¹Pb is separated from the target by liquid-liquid extraction with diethyldithiocarbamic acid in chloroform.²⁰¹Tl is separated from the mother activity (²⁰¹Pb) by liquid-liquid extraction with the same reagent. The decontamination of the final product (carrier free²⁰¹TlCl) is ≥5·10⁶ from the thallium of the target and>5×10⁴ from lead isotopes.     

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.     

Coated-wire ion-selective electrode for the determination of gold(III)

A coated-wire gold(III)-selective electrode based on the 1,2,4,6-tetraphenyl-pyridinium tetrachloroaurate(III) ion-pair is described. The response is Nernstian in the gold concentration range 10^?2–3 × 10^?6 (slope 59.0 mV/pAu). Of the 22 ions tested, only the interference of thallium(III) is important. The electrode is applied to the determination of gold in an Ag-Pd-Au alloy with satisfactory results.     

Determination of Poisonous Trace Element Thallium(I) by Kinetic Catalytic Reaction

Abstract

A effective and simple determination of poisonous trace element thallium(I) by means of kinetic catalytic reaction is proposed. The method is based on a catalytic effect of thallium(I) on a luminol-hydrogen peroxide system. Three different kinds of surfactants, cetrimonium bromide (CTMAB), sodium dodecyl sulphate (SDS), and Tween-80, are also investigated to improve the detection sensitivity. In optimum conditions, a highly selective and sensitive method for detecting trace thallium(I) has been established. The detection limit is 0.0073 µg · mL^?1, the relative standard deviation for six determinations of 0.04 µg · mL^?1 thallium(I) is less than 4.0%, and the linear range of determination is 0.02–0.1 µg · mL^?1.     

Distribution behavior of U(VI), Am(III) and Eu(III) on diglycolamide based extraction chromatographic resin in perchloric acid medium

An attempt has been made in the present work to investigate the role of anion for the uptake of Am(III)/Eu(III)/U(VI) by extraction chromatography (EXC) resin incorporating tetra-n-octyl-3-oxapentanediamide, commonly referred to as tetra-octyl diglycolamide (TODGA). In contrast to the nitric acid, perchloric acid medium favors extraction of trivalent metal ions even at low acidity (pH 2) and is almost insensitive to the acidity up to 5 M. Exceptionally large distribution coefficients (10⁵–10⁶) in the wide range of perchlorate concentration (10^?2–5 M) is quite unusual and is by far the largest reported in the literature for Am(III)/Eu(III). Thermodynamic data suggests the possibility of inner sphere/cation exchange mechanism involving TODGA aggregates at higher acidity but outer sphere/cation exchange mechanism at low acidity for Eu(III). There is a possibility of employing TODGA based EXC resin for the remediation of liquid waste (contaminated with long lived transuranics like ^241/243Am and ²⁴⁵Cm) in the wide range of acidity.     

Bis[2-(5-bromo-2-pyridylazo)-5-(N-propyl-N-sulpho propylamino)phenolato]cobaltate(III) as a counter ion for the extraction and spectrophotometric determination of long-chain quaternary ammonium salts and tertiary alkylamines in the presence of each other

The singly charged complex anion bis[2-(5-bromo-2-pyridylazo)-5-(N-propyl-N-sulphopropylamino)phenolato]cobaltate(III) is intensely purple-violet and is stable over the pH range 1–13. Its absorption spectrum remains the same over this pH range. At pH2, it forms extractable ion pairs with long-chain quaternary ammonium ions and protonated alkylamines. Only the quaternary ammonium ions are extracted into chloroform at pH 11, hence separate extractions allow both types to be determined. The absorbance of the organic phase is measured at 594 nm. The apparent molar absorptivity is 7.0 × 10⁴ l mol^?1 cm^?1. Calibration graphs for zephiramine, benzethonium and hexadecylpyridinium ions are linear over the range 0.1–2 × 10^?6 M. The only interference found was from anionic surfactants. The method is applied to hair and fabric conditioners.     

The solvent extraction of the ternary complexes of iron(II)-rhodamine b with various nitrosophenols: Determination of iron in waters

Twenty nitrosophenols and nitrosonaphthols were examined as reagents for ternary complex formation with iron(II) and rhodamine B. Only reagents containing electron-attracting substituents were satisfactory, and of these, 2-nitroso-4-chlorophenol was best. The ternary complex contains 2-nitroso-4-chlorophenol, iron(II) and rhodamine B in the ratio 3:1:1, and can be readily extracted into benzene. The red extracted complex shows maximal absorbance at 558 nm with a molar absorptivity of9.0·10⁴. Beer's law is obeyed over the range 0-1· 10^?5M iron (II); the pH range for extraction is 4.3–5.3, and the color is stable for at least 1 week. The application of'the method to the determination of iron in potable and river waters is described.     

Extraction—spectrophotometric and fluorimetric determination of thallium with 2-(4-methoxyphenyl)-5,7-diphenyl-4h-l,3,4-thiadiazolo[3,2-α] pyridinium chloride

The synthesis, characteristics and applications of 2-(4-methoxyphenyl)-5,7-diphenyl-4H⁺-1, 3,4-thiadiazolo[3,2-α]pyridinium chloride (TDZP) as a reagent for the formation of ion-pair complexes is described. Tetrachlorothatllate(III) can be extracted into isoamyl acetate as an ion-pair with TDZP. Thallium can be determined spectrophotometrically and fluorimetrically in the range 1–25 and 0.1–2 μg of thallium per 5 ml of organic layer, respectively. The molar absorptivity is 3.9 × 10⁴ l mol^-1 cm^-1. The quantum efficiency of the reagent is 0.42. The method is applicable to the determination of thallium in sphalerites and zinc or cadmium concentrates.     

A calcium-sensitive microelectrode suitable for intracellular measurement of calcium(II) activity

A calcium-selective microelectrode with a l-μm diameter tip suitable for impaling single neurons has been developed. The electroactive material is di[p-(1,1,3,3-tetramethyl-butyl) phenyl] phosphoric acid (t-HDOPP). The selectivity coefficients are about 5 · 10^-7 for k_Ca,K, 1–4·10^-7 for k_Ca,Na, and 10^-3 for k_Ca,Mg. Values reported previously for other calcium-selective electrodes based on long-chain phenylphosphoric acids are given for comparison. The calcium-selective microelectrodes have a linear response in 0.2 M KCl solutions over the range 10^-2–10^-XXX M CaCl₂; 10^-7 and 10^-8 M CaCl₂ solutions containing 0.2 M KCl can be detected but the response is not linear.     

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.     

The spectrophotometric determination of anions by solvent extraction with metal chelate cations. part XX : Trichloroacetic acid with tris(1,10-phenanthroline)iron(ii) chelate

Trichloroacetic acid can be extracted from an aqueous solution by nitrobenzene with tris(1,10-phenanthroline)iron(II) chelate, and can be determined spectrophotometrically by measuring the extract at 516 nm. The extracted species is probably [Fe(phen)₃].(CCl₃COO)₂. Beer's law is obeyed over the concentration range 1.0·10^-5–1.0·10^-4M trichloroacetic acid in aqueous solution. Large amounts of phosphate and sulfate and moderate amounts of chloride, acetic acid, and monochloroacetic acid do not interfere, equal amounts of dichloroacetic acid give a slight positive error     

“Palladiazo” a new selective metallochromic reagent for palladium: Part I the main characteristics of the pure reagent and its reaction with palladium(II)

The synthesis and purification of 2,7-bis(4-azophenylarsono)-1,8-dihydroxy-naphthalene 3,6-disulphonic acid is reported. Because of its selectivity for palladium-(II), the name palladiazo is suggested for the reagent. Aqueous solutions of palladiazo are very stable and exhibit 2 absorption maxima located at 540 and 625 nm, the molar absorptivities being 3.3 · 10⁴ and 1.7 · 10⁴, respectively. Palladiazo changes color stepwise and reversibly with increase in hydrochloric acid concentration from 0 to 13 M. A negatively charged complex of type M₂L₃ is formed with Pd(II) at pH 2.5–3.5, and shows an absorption maximum at 640 nm with a molar absorptivity of (5.7 ± 0.1) ·10⁴; the complex can be readily extracted with diphenylguanidine chloride or quaternary ammonium salts dissolved in n-butanol or higher alcohols. The complex obeys Beer's law at 675 nm in the concentration range 10–250 μg Pd(II)/50 ml. Pb(II), Bi(III), Ce(III) and the rare-earth elements are the only expected cationic interferences.     

A new application of atomic absorption spectrophotometry : Determination of phthalic acid by solvent extraction with neocuproine-copper(I) chelate

A new application of atomic absorption spectrophotometry is reported for the determination of phthalic acid. Phthalic acid is extracted as the ion-pair formed between bis(neocuproine)-copper(I) and the univalent anion of phthalic acid with MIBK; the copper concentration in the extract is then determined by atomic ab sorption in an air-acetylene flame at the 3247 Å copper line. Optimal conditions are described. The absorbance of the extract showed a linear relationship to the concentration of phthalic acid initially present in the aqueous solution over the range of 4·10^-6 to 4·10^-5M. The effect of some analogous aromatic carboxylic acids on the phthalate extraction and the composition of the extracted species were also investigated.     

Determination of thallium(III) with novel arsenoxylphenylazo rhodanine after pre-concentration and separation

A new catalytic kinetic fluorescent method for determination of trace thallium(III) was investigated. The method was based on the catalytic effect of thallium on oxidation of 3-p-chlorophenyl-5-(2′-arsenoxylphenylazo) rhodanine (4ClRAAP) by hydrogen peroxide in potassium hydrogen phthalate-hydrochloric acid (pH?=?5.2). Under the optimum conditions the great increase of fluorescence intensity had a linear relationship against the concentration of thallium in the range of 0.43 to 10.0?µg?L^?1 with a detection limit of 2.6?×?10^?10?g?L^?1. The coexistent metal ions can be separated, and thallium can be enriched by polyamide, which greatly improved the selectivity and sensitivity of the system. The method was applied to determine trace amount of thallium in wine, water and mineral samples, with satisfactory results.     

Determination of niacin and niacinamide in pharmaceutical products by automatic discrete-sample analysis

A spectrophotometric method is proposed for the determination of small amounts of iodide. The method is based on the reduction of bis(neocuproine)-coppcr(II) to the monovalent copper chelate cation in the aqueous phase by iodide ion and subsequent solvent extraction into chlorobenzene of the ion-pair formed between bis(neocuproine)copper(I) cation and the tri-iodide anion. At least a 5-fold molar amount of the copper(II) chelate cation, relative to iodide, is needed, and the optimal pH range is 3–5. The absorbance of the extract at 370 nm is a linear function of iodide concentration in the aqueous phase over the range 5·lO^-6–4·10^-5M (ca. 0.6–5 p.p.m.). The relative standard deviation was 1.0%. Large amounts of fluoride and chloride (2000-fold molar) and bromide (50-fold) did not appreciably affect the determination of iodide. The extraction mechanism is elucidated.     

Synergistic extraction and spectrophotometric determination of palladium(II), iron(III), and tellurium(IV) at trace level by newly synthesized p-[4-(3,5-dimethylisoxazolyl)azophenylazo]calix(4)arene

A spectrophotometric method for the determination of palladium, iron and tellurium from nitric acid media after extraction of their p-[4-(3,5-dimethylisoxazolyl)azophenylazo]calix(4)arene [DMIAPAC] complexes has been developed and possible synergistic effects have been investigated. Chloroform, carbon tetrachloride, cyclohexane, 1,2-dichloroethane, toluene and xylene were used as the diluents. The maximum enhancement was obtained in the presence of 30% 1,2-dichloroethane. The trace amounts of metals were determined spectrophotometrically. Beer’s law obeyed in the concentration range of 5.0–95.0 μg, 8.0–120.0 μg and 10.0–140.0 μg/10 mL of the final solution of palladium, iron and tellurium, respectively. The molar absorptivities (l mol^?1cm^?1) and Sandell’s sensitivities (μg cm ^?1) were calculated: Pd(II) = 1.73 × 10⁴ and 0.0061; Fe(III) = 1.08 × 10⁴ and 0.0052; Te(IV) = 1.67 × 10⁴ and 0.0077. Ten replicate analyses containing 20 μg of Pd(II), 12.5 μg of Fe(III) and 32 μg of Te(IV) gave mean absorbance of 0.326, 0.242 and 0.418 with relative standard deviation of 0.36, 0.65 and 0.82% for Pd(II), Fe(III) and Te(IV), respectively. The interference of various ions was studied and optimum conditions were developed for the determination of these metals in certain alloys and synthetic mixtures.