Liquid-liquid extraction study of tellurium(IV) with N-n-octylaniline in halide medium and its separation from real samples

N-n-Octylaniline in xylene is used for extractive separation of tellurium(IV) from hydrochloric acid media. Tellurium(IV) is extracted quantitatively with the 3% reagent in xylene from 5.5 to 7.5 M hydrochloric acid. It is stripped from organic phase with 1:1 ammonia and estimated spectrophotometrically with pyrimidine-2-thiol (4'-bromoPTPT). The effects of metal ion, acids, reagent concentration, diluents and various foreign ions have been investigated. The log-log plots of distribution ratio (D(Te(IV))) versus N-n-octylaniline concentration indicate that the nature of extracted species is [(RR'NH(2)(+))(2) TeCl(6)(2-)](org). The method affords binary separation of tellurium(IV) from gold(III), selenium(IV), bismuth(III), copper(II), lead(II), antimony(III), germanium(IV) and is applicable to the analyses of synthetic mixture containing associated metal ions and alloy samples. The method is simple, selective, rapid and accurate.     

Coprecipitation with lanthanum phosphate as a technique for separation and preconcentration of iron(III) and lead

The usefulness of coprecipitation with lanthanum phosphate for separation and preconcentration of some heavy metals has been investigated. Although lanthanum phosphate coprecipitates iron(III) and lead quantitatively at pH 2.3, iron(II) can barely be collected at this pH. This coprecipitation technique was applicable to the separation and preconcentration of iron(III) before inductively coupled plasma atomic-emission spectrometric (ICP-AES) determination; the recoveries of iron(III) and iron(II) from spiked water samples were 103-105% and 0.2-0.7%, respectively. The coprecipitation was also useful for separation of 20 microg lead from 100 mL of an aqueous solution that also contained 1-100 mg iron. Coprecipitation of iron was substantially suppressed by addition of ascorbic acid, which enabled recovery of 97-103% of lead added to the solution, bringing the recovery to within 1.6-5.0% of the relative standard deviations. Lanthanum phosphate can also coprecipitate cadmium and indium quantitatively, although chromium(III), cobalt, and nickel and large amounts of sodium, potassium, magnesium, and calcium are barely coprecipitated at pH approximately/= 3.     

Liquid-liquid extraction of palladium(II) with N-n-octylaniline from hydrochloric acid media

N-n-Octylaniline in xylene is used for the extractive separation of palladium(II) from hydrochloric acid medium. Palladium(II) was extracted quantitatively with 10 ml of 2% reagent in xylene from 0.5-2 M hydrochloric acid medium. It was stripped from the organic phase with 1:1 ammonia and estimated spectrophotometrically with pyrimidine-2-thiol at 420 nm. The effects of metal ion, acids, reagent concentration and of various foreign ions have been investigated. The method affords binary separation of palladium(II) from iron(III), cobalt(II), nickel(II) and copper(II) and is applicable to the analysis of synthetic mixtures and alloys. The method is fast, accurate and precise.     

Determination of lead by selective chelatometric titration with HEDTA after separation as its sulphate by an improved method of precipitation

A selective titrimetric determination of Pb after separation by a modified method of precipitation as its sulphate is proposed. Pb(II), present as the perchlorate, is precipitated by gentle boiling in 3.6M H(2)SO(4) presaturated with PbSO(4) and free from any extraneous anions. The customary time-consuming evaporation to fumes of sulphuric acid is dispensed with. The precipitate is collected, and dissolved in excess of HEDTA, the surplus of which is back-titrated with Zn(II) at pH 5.0-5.5. Use of Catechol Violet and Xylenol Orange as a mixed indicator gives a sharper end-point. The standard deviation of the proposed method for 60 mg of lead is 0.35 mg. The method has been successfully used to determine Pb in non-ferrous alloys.     

Ultratrace determination of lead,cadmium and copper in environmental and biological samples by atomic absorption spectrometry after their separation and preconcentration using octadecyl silica membrane disks modified with a new n–s schiff base

Pb(II), Cd(II) and Cu(II) ions were separated and preconcentrated by solid-phase extraction on octadecyl-bonded silica membrane disks modified with a new S–N-containing Schiff base (bis-2-thiophenal propandiamine) (BTPD) followed by elution and atomic absorption spectrometric detection. The method was applied as a separation and detection method for lead(II), cadmium(II) and copper(II) in environmental and biological samples. Extraction efficiency and the influence of sample matrix, flow rate, pH, and type and minimum amount of stripping acid were investigated. The maximum capacity of the membrane disks modified by 4?mg of BTPD was found to be 668 ± 10, 480 ± 8 and 454 ± 7?µg of lead, cadmium and copper, respectively. The limit of detection of the proposed method is 0.25, 0.01 and 0.02?ng/mL for lead, cadmium and copper, respectively.     

Extraction of lead(II) and copper(II) from salicylate media by tributylphosphine oxide.

Tributylphosphine oxide (TBPO) is proposed as an extractant for the extraction of lead(II) and copper(II) from salicylate media. The optimum conditions were evaluated by varying the experimental parameters, such as the pH, sodium salicylate concentration, tributylphosphine oxide (TBPO) concentration, shaking period and various diluents. The probable extracted species, deduced from log-log plots were Pb(HSal)2.2TBPO and Cu(HSal)2.2TBPO. The extraction took place through a solvation mechanism. The method permits the binary separation of lead(II) and copper(II) from commonly associated elements as well as the mutual separation of lead(II) and copper(II). The method is applicable to the determination of lead(II) and copper(II) in various alloys as well as environmental and pharmaceutical samples.     

Spectrophotometric determination of lead in foods with dibromo-p-methyl-bromosulfonazo

The synthesis and purification of a new chromogenic reagent dibromo-p-methyl-bromosulfonazo (DBMBSA) are described. A method is proposed for the spectrophotometric determination of lead with DBMBSA. In 0.24 M phosphoric acid medium, which greatly increases the selectivity, lead reacts with DBMBSA to form a 1:2 blue complex, having a sensitive absorption peak at 638 nm. Under the optimal conditions, Beer's law is obeyed over the range from 0 to 1 mug ml(-1) Pb(II) and the apparent molar absorptivity is 8.44x10(4) l mol(-1)cm(-1). The detection limit and the variation coefficient were found to be 2.45 ng ml(-1) and 1.3%, respectively. It is found that, except for Ca(II) and Ba(II), all foreign ions studied do not interfere with determination. The interference caused by Ca(II) and Ba(II) can be easily eliminated by prior extraction with potassium iodide-methylisobutylketone (KI-MIBK). The method has been applied to the determination of lead in foods with satisfactory results.     

Capillary electrophoretic separation between Fe(II) and Ni(II) precomplexed with 1,10-phenanthroline in a high concentration buffer of n-butyric acid/ n-butyrate and its application

The capillary electrophoretic separation was accomplished for Fe(II) and Ni(II) precomplexed with 1,10-phenanthroline (phen) in 2 M n-butyric acid/ n-butyrate buffer at pH 4.5 with direct UV detection at 260 nm. The applied voltage was 5 kV. The high concentration buffer of the n-butyrate resulted in a similar separation mechanism to that of ion-pair reversed-phase high-performance liquid chromatography. The separation would be due to the hydrophobic interaction between the ionic associates, [Fe(phen)(3)]( n-butyrate)(+) and [Ni(phen)(3)]( n-butyrate)(+), with the n-butyrate ion and n-butyric acid as background electrolyte. Linear calibration ranges were obtained for Fe(II) and Ni(II) from 100 to 500 ng ml(-1). The relative standard deviations ( n=10) for 3 g mL(-1) Fe(II) and Ni(II) were 0.090 and 0.086, respectively. Detection limits ( S/ N=3) for Fe(II) and Ni(II) were 20 ng mL(-1). The method was applied to the determination of nickel in aluminium and duralumin alloys.     

Solvent extraction separation of cobalt(II) with hexaacetatocalix(6)arene

A new method is proposed for the solvent extraction separation of cobalt(II) with hexaacetatocalix(6)arene in toluene. Cobalt(II) was extracted at pH 7.4 with 10 x 10(-4) M hexaacetocalix(6)arene, stripped with 2 M nitric acid, and determined spectrophotometrically at 500 nm as its complex with nitroso-R-salt. Cobalt was separated from any associated elements. The method was extended to the analysis of cobalt(II) in real samples such as vitamin B-12.     

Extraction and separation of uranium and lead with liquid anion-exchangers

A method is proposed for the extraction and separation of microgram amounts of uranium(VI) and lead(II) from sodium salicylate solution with high molecular-weight amines such as Aliquat 336, TOA, TIOA, Amberlite LA-1 or Amberlite LA-2 dissolved in xylene. From a critical study of pH, salicylate concentration, amine concentration, diluent and period of equilibration, the optimum conditions were identified. The method permits separation of uranium and lead from binary mixtures with metal ions commonly associated with them, the determination of uranium, and of lead in air samples.     

Determination of aluminium in molybdenum and tungsten metals, iron, steel and ferrous and non-ferrous alloys with pyrocatechol violet

A method for determining 0.001-0.10% of aluminium in molybdenum and tungsten metals is described. After sample dissolution, aluminium is separated from the matrix materials by chloroform extraction of its acetylacetone complex, at pH 6.5, from an ammonium acetate-hydrogen peroxide medium, then back-extracted into 12M hydrochloric add. Following separation of most co-extracted elements, except for beryllium and small amounts of chroinium(III) and copper(II), by a combined ammonium pyrrolidincdithiocarbamate-cupfen-on-chlorofonn extraction, aluminium is determined spectrophotometrically with Pyrocatechol Violet at 578 nm. Chromium interferes during colour development but beryllium, in amounts equivalent to the aluminium concentration, does not cause significant error in the results. Interference from copper(II) is eliminated by reduction with ascorbic acid. The proposed method is also applicable to iron, steel, ferrovanadium, and copper-base alloys after preliminary removal of the matrix elements by a mercury cathode separation.     

Spectrophotometric flow-injection determination of nickel in biological materials

A flow injection method has been developed for the direct determination of free available Pb(II) and total Pb content in wine samples. The method is based on the chemical sorption of Pb(II), from pH 7 buffered solutions, on a packed polyurethane foam column, modified by addition of 2-(2-benzothiazolylazo)-p-cresol (BTAC). After this step, lead was directly eluted with a stream of 0.1 mol l(-1) HCl into an air C(2)H(2) flame in which lead was determined by atomic absorption spectrometry. Total lead was analyzed after sample digestion with nitric acid and hydrogen peroxide, being free available lead determined by direct sample on-line preconcentration and elution. The method provides a limit of detection (3sigma) of 1 mug l(-1) lead and relative standard deviation, which varies from 6 to 0.7% for lead concentration of 10 and 500 mug l(-1). Total content of lead in wine samples analyzed varied from 8 to 42 mug l(-1) being obtained free available values of Pb(II) under the limit of detection of the method. Recovery studies on natural wine samples, spicked with inorganic lead, evidenced the remaining capability of ligands, present in the wine, to avoid lead retention on the polyurethane foam loaded with BTAC.     

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).     

Determination of cadmium, zinc, nickel and cobalt in tobacco by reversed-phase high-performance liquid chromatography with 2-(8-quinolylazo)-4,5-diphenylimidazole as a chelating reagent.

A sensitive and selective method has been developed for the simultaneous determination of cadmium, zinc, nickel and cobalt. The method is based on the chelation of metal ions with 2-(8-quinolylazo)-4,5-diphenylimidazole (QAI) and the subsequent reversed-phase (RP) high-performance liquid chromatographic separation and spectrophotometric detection of the metal chelates. The chelates were separated on an RP column with acetonitrile-water containing ethylenediamine tetraacetic acid and sodium acetate (pH 7.5). Though Zn(II) and Cd(II) chelates with azo compounds were generally labile in the RP column, these chelates with QAI were successfully detected. When analyses were carried out at 575 nm and at 0.001 absorbance unit full scale, the peak height calibration curves were linear up to 2.0 ng for Cd(II), 2.4 ng for Zn(II), 0.14 ng for Ni(II) and 0.72 ng for Co(II) in 100-microL injections, respectively; the detection limits (3sigma, three times of the standard deviation for the blank signal) for Cd(II), Zn(II), Ni(II) and Co(II) were 4.8, 24, 2.4 and 7.2 pg in 100 microL of injected solution, respectively. The proposed method was successfully applied to the analysis of tobacco without any preliminary concentration or separation.     

Extraction and separation studies of platinum(IV) with N-n-octylaniline

N-n-octylaniline in xylene is used for the extractive separation of platinum(IV) from acidic media. Platinum(IV) was extracted quantitatively with 10 ml of 3% reagent in xylene from 0.5 to 10 and 2.5 to 10 M hydrochloric and sulphuric acid, respectively. It was stripped from organic phase with water and estimated photometrically with stannous chloride. The effect of metal ion, acids, reagent concentration and of various foreign ions has been investigated. The method affords binary separation of platinum(IV) from iron(III), cobalt(II), nickel(II) and copper(II), and is applicable to the analysis of synthetic mixtures and alloys. The method is fast, accurate and precise.     

Indirect determination of thiocyanate with ammonium sulfate and ethanol by extraction-flotation of copper

A new method for the indirect determination of thiocyanate with ammonium sulfate and ethanol by extraction-flotation of copper in the presence of ascorbic acid is described. A small amount of Cu(II) is reduced to Cu(I) by ascorbic acid, then Cu(I) is precipitated with SCN-. In the course of phase separation of ethanol from water, the precipitated CuSCN stays in the interface of ethanol and water. A good linear relationship is observed between the flotation yield of Cu(II) and the amount of SCN-. Using 1.0 ml of 1 x 10(-3) M ascorbic acid solution, 50 micrograms of Cu(II), 3.5 g of (NH4)2SO4 and 3.0 ml of ethanol with a total volume of 10 ml, the concentration of thiocyanate could then be determined by determining the flotation yield of Cu(II). The detection limit for thiocyanate is 5 x 10(-5) M. Every parameter was optimized and the reaction mechanism was studied. The method is simple and rapid and it was successfully applied to the determination of thiocyanate in urine and saliva of smokers and non-smokers and in venous blood of patients infused with sodium nitroprusside.     

Extraktionsmethode zur Trennung kleiner Tellurmengen von Begleitelementen

Zusammenfassung Zur Trennung von Tellur aus Lösungen mit komplizierter Zusammensetzung wurde eine kombinierte Extraktionsmethode entwickelt. Die Extraktion von Eisen(III), Arsen(V), Antimon(V), Gold(III), Thallium(III), Wismut(III), Zinn(IV) und Selen(IV) erfolgt mit Diisopropyläther aus 8 M Salzsäure, wobei das gesamte Te(IV) in der wäßrigen Phase verbleibt. Diese wird dann mit Methylisobutylketon aus 4 M Salzsäure extrahiert, während in der wäßrigen Phase Kupfer(II), Aluminium(III), Silber(I), Nickel (II), Kobalt(II), Zink(II), Cadmium(II) und Blei(II) verbleiben. Die vollständige Abtrennung der Begleitelemente des Tellurs erfolgt durch zusätzliche Extraktion ihrer Kupferronate mit Methylisobutylketon bei pH 3–5. Das vorgeschlagene Extraktionsverfahren kann mit jeder bekannten Methode zur Bestimmung geringer Tellurmengen kombiniert werden.

---

Extraction method for the separation of small quantities of tellurium from accompanying elements

A new combined solvent extraction method is proposed for the separation of tellurium from solutions of complex composition. Iron(III), arsenic(V), antimony(V), gold(III), thallium(III)J bismuth(III), tin(IV) and selenium(IV) are extracted with diisopropyl ether from 8 M hydrochloric acid. Under these conditions tellurium(IV) is quantitatively retained in the aqueous phase. Subsequently tellurium(IV) is extracted from 4 M hydrochloric acid with methylisobutyl ketone, so that copper(II), aluminium(III), silver(I), nickel(II), cobalt(II), zink(II), cadmium(II) and lead(II) remain in. the aqueous phase. The complete separation of the accompanying elements is realized by an additional extraction of their cupferronates with methylisobutyl ketone at pH 3–5. The separation described can be combined with any known method for the determination of small amounts of tellurium(IV).

     

Cyclic and stripping voltammetry of tin at mercury hanging drop and film electrodes in acidic o-diphenol media in the presence of lead and cadmium

The influence of catechol, gallic acid and tiron on the voltammetric behaviour of tin(IV) in the presence of lead(II) and cadmium(II) was investigated at hanging drop and mercury film electrodes in perchloric acid, oxalic acid and formate supporting electrolytes. Under cyclic conditions, well separated peaks of tin, lead and cadmium are obtained in oxalic acid and formate solutions containing gallic acid or catechol; tiron suppresses the tin peaks significantly. The efficiency of the deposition of tin in the presence of catechol or gallic acid is less than that of lead, particularly at long deposition time. The best separation of the stripping peaks of tin, lead and cadmium is obtained in oxalic acid solution containing gallic acid or catechol. In perchloric acid solution containing gallic acid or catechol the second peak corresponding to tin oxidation is useful for determinations of tin in the presence of lead. Tin(IV) at the 10^-8 mol l^-1 level can be detemined in various salt solutions and in water samples in the presence of five-fold amounts of lead and cadmium.     

Separation of niobium and tantalum with benzo- and phenylacetylhydroxamic acids

Benzohydroxamic acid (I) or phenylacetylhydroxamic acid (II) is suggested for the quantitative separation of tantalum from niobium in an oxalate solution. The tantalum precipitate must be ignited for weighing; niobium is determined in the filtrate with another reagent. The pH range for complete separation is 4.0–6.4 for I and 4.5–6.2 for II. Single precipitation is satistactory for Nb: Ta ratios of 18 : 1 to 1 : 20 for I, and 8 : 1 to 1 : 23 for II. Titanium, zirconium, tartrate, citrate and a large excess of oxalate interfere.     

Proton-ionizable acyclic dibenzopolyethers and their polymers for use in selective lead(II) separation

Abstract

2,2′-[1,2-Ethanediylbis(oxy)]bisbenzoic acid (1), 2,2′-[oxybis(1,2-ethanediyloxy)]bisbenzoic acid (2), 1,2-[2′-(acetoxy)phenoxy] ethane (3), and 1,5-[2′-(acetoxy)phenoxy]-3-oxopentane (4) have been prepared for use in selective Pb(II) separation. The extraction of Pb(II) and Cu(II) from buffered aqueous solutions of varying pH into chloroform by 1–4 is examined in relation to their molecular structure. Compound 1 with an ethylene glycol spacer unit exhibits excellent extraction selectivity for Pb(II) over Cu(II). Lengthening the spacer group to a diethylene glycol unit diminishes the extraction efficiency and selectivity. For 3 and 4, extraction was inefficient due to low lipophilicity and solubility of the ligands in chloroform. Condensation polymerization of compounds 3 and 4 with formaldehyde in formic acid provides stable chelating resins 5 and 6 which contain both ion-exchange and polyether binding sites for metal complexation. Resin 5 with an ethylene glycol spacer group is found to be an effective chelating resin for Pb(II) separation. The sorption mechanism and selectivity are studied and compared with the commercially available iminodiacetic acid resin CR-10.