Simultaneous determination of arsenic, antimony and tin by fast-scan differential-pulse polarography and its application to alloy steels

Arsenic, antimony and tin can be determined in the presence of one another by fast-scan differential-pulse polarography (FSDPP) on a single mercury drop in 1.5M hydrochloric acid. The reduction of As(III), Sb(III) and Sn(IV) to the metals is practically reversible and the reduction peaks are sufficiently separated. The lower limits of determination are 0.05, 0.005 and 0.001 μg/ml for As, Sb and Sn respectively, the calibration graphs exhibit very good linearity and the peak heights are reproducible. For application to alloy steels employed in nuclear technology, the elements to be determined must be separated from the matrix by extraction as their covalent bromides into toluene from concentrated sulphuric acid and back-extracted into the base electrolyte (1.5M HCl + 0.012M Br⁻ + 0.03M hydrazinium sulphate). The recoveries of As, Sb and Sn are 100, 95 and 92% respectively and the relative error of determination is a few per cent.     

Determination of traces of antimony, copper, and lead in titanium dioxide by pulse polarography

Summary Traces of antimony, copper, and lead impurities in titanium dioxide have been determined simultaneously by pulse polarography. The three metals were separated from titanium(IV) by sulphide precipitation at pH 3, using cadmium as carrier and complexing titanium with fluoride. The precipitation of lead was supplementary controlled with the radio-isotope ²¹⁰Pb, showing a quantitative recovery. In hydrochlorid-hypophosphite supporting electrolyte, antimony, copper, and lead in titanium dioxide can be determined as low as 0.15, 0.03, and 0.1 ppm respectively. The method was applied in the analysis of various titanium dioxide products commercially available, showing satisfactory sensitivity and resolution for divergent copper-antimony ratios.

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Zusammenfassung Zur gleichzeitigen Bestimmung von Spuren Antimon, Kupfer und Blei in Titandioxid wird ein impulspolarographisches Verfahren beschrieben. Die drei Elemente werden durch Sulfidfällung bei pH 3 von Ti^IV abgetrennt, wobei Cadmium als Träger dient und Titan mit Fluorid maskiert wird. Die Fällung des Bleis wurde mit Hilfe des Radioisotops ²¹⁰Pb geprüft und die eingesetzten Mengen quantitativ wiedergefunden. In einem Leitelektrolyten aus HCl-NaH₂PO₂ können noch 0,15 ppm Sb, 0,03 ppm Cu und 0,1 ppm Blei in Titandioxid bestimmt werden. Das Verfahren wurde für verschiedene handelsübliche Titandioxidsorten verwendet, wobei befriedigende Ergebnisse, auch für sehr unterschiedliche Cu-Sb-Verhältnisse, erhalten wurden.

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Dedicated to Prof. Dr. M. von Stackelberg on his 70th birthday.     

The determination of nickel, zinc, cobalt and manganese impurities in cadmium by pulse polarography

A pulse-polarographic method for the simultaneous determination of traces of nickel, zinc, cobalt and manganese in cadmium and its compounds is described. Interference from the reduction of the cadmium matrix was eliminated by a prior electrolytic deposition of cadmium on a mercury cathode at a controlled potential of –0.90 V vs. S.C.E. Iron in excess interfered with the determination of cobalt and was therefore extracted from the electrolysed solutions. The polarographic determination was performed in 0.1 M lithium acetate -0.025 M lithium thiocyanate as supporting electrolyte. A sample weight of 10 g and a final volume of 10 ml allowed the determination of about 0.08 p.p.m. nickel, 0.01 p.p.m. zinc, 0.02 p.p.m. cobalt and 0.003 p.p.m manganese. Less than 0.01 p.p.m. nickel could be determined with a 0.25 M pyridine 0.05 M potassium chloride supporting electrolyte. Several synthetic samples and commercially available cadmium products were analysed.     

Compounds of arsenic,antimony, and tin in mollusc shells

Inorganic arsenic(III) and arsenic(V), methyl-arsenicals, antimony(III), and antimony(V), and butyltin derivatives are present in the shells of molluscs found in the coastal waters of British Columbia.     

Indirect determination of traces of thiosulphate by differential-pulse polarography

Two methods are reported for the indirect determination of thiosulphate down to ca. 0.02 microg/ml by differential-pulse polarography. Both methods involve prior oxidation of thiosulphate with iodine, either in acidic medium to tetrathionate or in alkaline medium to sulphate, whereby ultimately one and eight equivalents of iodate are obtained, respectively. The concentration of iodate in the resulting solution is then measured by differential-pulse polarography under optimum conditions. The average recovery for each method amounted to 100.1%, and the relative standard deviations were 1.3 and 1.4% for the two methods.     

Detection of arsenic, antimony and tin in forensic toxicology by paper chromatography

Summary A paper chromatographic technique for the detection of arsenic, antimony and tin as applied to toxicological analysis has been described.     

The atomic absorption determination of antimony,arsenic, bismuth, cadmium, lead, and tin in iron, copper,and zinc alloys with the graphite furnace

Antimony, arsenic, bismuth, cadmium, lead, and tin can be determined in metallurgical samples by flame atomic absorption spectrometry at levels of 0.005 wt%, but lower concentrations frequently necessitate preconcentration. The graphite furnace allows determination of these elements at concentrations 1–2 orders of magnitude lower than is possible with flame techniques. All six elements have detection limits at or below 1μg g⁻¹ in a variety of alloys. Calibration for antimony and load was done with standards containing the principal component of the alloy as a synthetic matrix. Bismuth, cadmium, and tin could be determined accurately only by the standard addition method. Arsenic could be determined in iron alloys with synthetic standards, but standard additions were required for copper alloys.     

Development and validation of a quantitative method for the selective determination of tin species in tin octoate by differential pulse polarography

Tin octoate is used as a catalyst in the synthesis of polydimethylsiloxane (PDMS), a room temperature vulcanizing (RTV) silicone rubber. This rubber is largely used in the medical field due to its great biocompatibility. In this framework, a high-speed and costless analytical method for the determination of stannic ions, Sn(IV), in the presence of stannous ions, Sn(II), has been developed.The separation of these two ions was carried out using differential pulse polarography (DPP). For this purpose, the tin species contents in the catalyst is quantitatively extracted under inert condition to avoid any changes in the ratio Sn(IV)/Sn(II). Polarography showed well-shaped oxidation and reduction peaks respectively at −650 and −860 mV for stannous ions. The peak of the stannic ion was well separated and appeared at −1210 mV. Many parameters such as extraction process, extraction time, pH, chelating agents and polarographic conditions were optimized. We have also demonstrated that no oxidation of the stannous ions occurred during the sample preparation.The dosing range considered in this study extends between 10 and 40 μg/mL, corresponding to 6.8% and 27.2% of the degradation product (Sn(IV)) in the catalyst, regarding to the sampling. Finally this method was successfully validated using the total error concept.     

Determination of traces of antimony and tin in copper by anodic stripping voltammetry

The determination of antimony and tin impurities in copper by anodic stripping voltammetry on a hanging mercury drop electrode is described. Antimony and tin were previously separated from copper by distillation with hydrobromic acid or a mixture of hydrobromic acid and hydrochloric acid. The method was applied to the analysis of various high-purity copper samples, commercially available, showing satisfactory sensitivity and precision. The determination limit was about 1.4· 10^-9M for antimony and 7·10^-10M for tin in solution, for pre-electrolysis times of respectively 15 and 25 min; this corresponds to 0.8 p.p.b. of antimony and 0.3 p.p.b. of tin for a 2-g sample and a final volume of 10 ml after separation.     

Radiochemical determination of traces of arsenic(III) and antimony(III)

Very simple and rapid radiochemical procedures for the determination of traces of arsenic(III) (up to 0.1 μg) and antimony(III) (up to 0.01 μg) have been developed. The method is based on the isotope exchange between labelled metal diethyldithiocarbamate in carbon tetrachloride and an aqueous sample containing the metal to be determined. The selectivity of the method is rather high; in the presence of thiourea most common metals do not interfere with the determination.     

Determination of traces of indium, manganese, arsenic and antimony in zinc by neutron-activation analysis

Destructive activation determination of the trace elements indium, manganese, arsenic and antimony in different samples of pure zinc metal by solvent extraction techniques is described. Determination of indium and manganese is based on the quantitative co-precipitation of both elements with lanthanum hydroxide, followed by their extraction with sodium diethyldithiocarbamate in the presence of potassium cyanide and their subsequent separation by selective stripping. The quantitative determination of arsenic and antimony is based on the extraction of their iodides from sulphuric acid solution with toluene.     

Spectrophotometric determination of traces of antimony

Antimony(III) is extracted into carbon tetrachloride from 4M sulphuric acid that is 0.05M in potassium iodide. 8-Mercaptoquinoline and acetone are added to the organic extract and the absorbance of the complex formed is measured at 390 nm. Repeating the extraction procedure greatly increases the selectivity of the method.     

The determination of phenobarbital and diphenylhydantoin in blood by differential pulse polarography

A sensitive differential pulse polarographic assay was developed for the determination of phenobarbital or diphenylhydantoin in blood. The assay involves the selective extraction of the compound into chloroform from whole blood buffered to pH 7.0. After suitable “clean-up” of the sample, each compound is nitrated in 10% potassium nitrate in sulfuric acid at 25° for 1 h. The nitro-derivatives are extracted into ethyl acetate, and the residues are dissolved in 1 M phosphate buffer (pH 7.0) or 0.1 M sodium hydroxide for phenobarbital and diphenylhydantoin, respectively; the solutions are deoxygenated, and analyzed by differential pulse polarography. The overall recovery of phenobarbital and diphenylhydantoin from blood was 72.3% ±6.5 (s_r) and 76.7 ±2.3 (s_r) respectively. The sensitivity limit is 1–2 μg ml^-1 of blood for both compounds. A modified assay for the determination of both compounds in blood with t.l.c. separation was also developed.     

Interferences of hydride forming elements and of mercury in the determination of antimony, arsenic, selenium and tin by hydride-generation AAS

Summary By means of the radiotracer technique supplemented by conventional absorption measurements, the interferences of As, Bi, Hg, Pb, Sb, Se, Sn and Te in amounts between 10 g and 1 mg with the determination of As, Sb, Se and Sn by hydride generation AAS using heated quartz tube were investigated during the hydride-generation and the atomization stages. Amounts up to 100 g of Hg and Pb do not cause any detectable interference. The interference of Bi and Te is dominant in the hydride-generation stage and that of As, Se, Sb and Sn in the atomization stage. Tin is retained to a considerable extent in the quartz tube and the resulting memory effect makes the determination of As, Sb, and Se impossible. In the absence of interfering elements, the efficiency of the formation of hydrides of As, Sb, Se and Sn was close to 100%. However, a reduction of Sb(V) to Sb(III) prior to the hydride-generation is necessary for which an improved procedure was developed.

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Störungen von Hydridbildnern und von Quecksilber bei der Bestimmung von Antimon, Arsen, Selen und Zinn durch die Hydrid-AAS

Zusammenfassung Mittels der Radiotracertechnik und Atomabsorptionsspektrometrie wurde der Störeinfluß unterschiedlicher Mengen (10–1000 g) von As, Bi, Hg, Pb, Sb, Se, Sn und Te auf die Bestimmung von As, Sb, Se und Sn mit der Hydrid-AAS untersucht. Durch diese Verfahrenskombination war es möglich, das Ausmaß der Störungen durch diese Elemente sowohl im Hydrierungs- als auch im Atomisierungsschritt zu bestimmen sowie zum großen Teil auch die Gründe für ihr Auftreten aufzuklären. Keine nachweisbare Störung verursachen Hg und Pb bis zu jeweils 100 g. Die Störung durch Bi und Te tritt hauptsächlich im Hydrierungsgefäß auf, hingegen die durch As, Sb, Se und Sn im wesentlichen in der Quarzabsorptionszelle. Bei Zinn wurde ein starker Memoryeffekt festgestellt, der aus der Ablagerung dieses Elements in der Quarzküvette resultiert und der die Bestimmung von As, Sb und Se völlig unmöglich macht. Ohne diese Störelemente liegen die Hydrierungsausbeuten für As, Sb, Se und Sn bei nahezu 100%. Bei Antimon ist allerdings eine vorherige Reduktion von Sb(V) zu Sb(III) notwendig, für die ein verbessertes Verfahren vorgeschlagen wurde. Denn durch die Radiotracertechnik konnte nachgewiesen werden, daß die während der Alterung von Sb(V)-Lösungen durch Kondensationsprozesse entstehenden Polysäuren nicht mehr hydriert werden können.