Substoichiometric determination of inorganic tin in organotin compounds

Inorganic tin(IV) present in organotin compounds is determined substoichiometrically by complexation with salicylideneamino-2-thiophenol in a non-aqueous medium, after isolation of the tin(IV) by iodide extraction. The method is applied to the degradation products in commercial chemicals and those formed by u.v.-irradiation.     

Citrate complexes of tin(IV) studied by liquid-liquid extraction with 5,7-dichloro-8-quinolinol

The tin(IV)/5,7-dichloro-8-quinolinol/chloroform extraction system is used to determine the composition and the stability constants of the aqueous complexes of tin(IV) with citric acid, in the pH range 2.0–3.5. The tin(IV):citric acid ratios found are 1:1 and 1:2, depending on the concentration of the acid. The conditional stability constants are (5.5 ± 0.4) × 10³ and (1.3 ± 0.3) × 10³ for the 1:1 and 1:2 complexes, respectively. This extraction system is convenient in studies of aqueous tin(IV) complexes that cannot be extracted into chloroform.     

Determination of fluoride and tin in fluoride-doped tin oxide films on glass

Time-consuming fusion and pyrohydrolysis methods for quantifying fluoride and tin in fluoride-doped tin oxide films on glass are replaced by a simple electrolytic reduction for sample preparation. The unusual conductivity of these films enables solutions to be produced in which fluoride can be quantified by ion chromatography. Tin is quantified in the original sample by x-ray fluorescence spectrometry. Electrolytic reduction and the fusion/pyrohydrolysis methods are compared for films with Sn/F ratios of 10–40 (71–183 μg cm^?2 tin and 0.54–2.8 μ cm^?2 fluoride). The Sn/F ratios and precision are similar for the two methods. The older method only yields the tin/fluoride ratio; the electrolytic method gives results as mass per unit area and requires much less time per sample.     

Carbonyl allylations by allylic chlorides utilizing a reduction of tin(IV) iodide to triiodostannate(II) species with iodide sources

Carbonyl allylations by allylic chlorides either with tin(IV) iodide and tetrabutylammonium iodide (TBAI) in dichloromethane or with tin(IV) iodide and sodium iodide in 1,3-dimethylimidazolidin-2-one at room temperature produced the corresponding homoallylic alcohols. The carbonyl allylations probably proceeded via the reduction of tin(IV) iodide to triiodostannate(II) species with iodide sources such as TBAI and NaI, which led to the construction of a tin(IV)-catalytic cycle based on regeneration of tin(IV) iodide via the transmetalation of homoallyloxytriiodotin to homoallyloxytrimethylsilane with iodotrimethylsilane.     

Rapid EDTA determination of lead in binary alloys of lead and tin

Binary alloys of lead and tin were dissolved in nitric acid (1 + 1) containing 10% sodium fluoride. The tin(IV) was effectively masked by the fluoride. The lead was quickly and accurately titrated with EDTA in a hexamine-buffered solution, with Xylenol Orange as indicator.     

Beitrag zur Abtrennung und Bestimmung sehr kleiner Zinngehalte in Roheisen und St?hlen

Zusammenfassung Bei der Bestimmung sehr kleiner Zinngehalte ( 10^–3%) in Eisen und StÄhlen ist vor der Extraktion des Zinn(IV)-jodids mit Benzol eine Abtrennung des Eisens erforderlich. Diese Abtrennung wird bei 1 m Eisen(III)-lösungen aus 10,5 n SalzsÄure mit 2,5 m Tributylphosphatlösung in Benzol durchgeführt. Dabei wird Eisen(III) zu 99,0%, Zinn dagegen nicht me\bar extrahiert. Bei der photometrischen Endbestimmung des Zinns erwies sich nach überprüfung mehrerer Verfahren die Bestimmung mit HÄmatein als die genaueste. Die relative Standardabweichung in Kontrollproben betrÄgt 1,7%.

---

Summary In the determination of very small tin concentrations ( 10^–3%) in iron and steel it is necessary to separate iron before the extraction of tin(IV) iodide with benzene. For a 1 M iron(III) solution in 10.5 N hydrochloric acid the iron separation is carried out with a 2.5 M solution of tributylphosphate in benzene. Under these conditions iron(III) is extracted for 99% but tin is not measurably extracted. Among the numerous procedures for the photometric determination of tin, the method using haematein was found to be the most accurate. The relative standard deviation in test samples was 1.7%.

     

Use of isooctyl thioglycolate for the separation of tin and antimony

The extraction characteristics of isooctyl thioglycolate (IOTG), a chelating agent, in various diluents has been studied with respect to the metal ions, tin(IV) and antimony(III), in hydrochloric acid medium. It is concluded that antimony(III) can be separated from tin(IV) with 85% yield and with a decontamination factor of at least 1·10⁵ using IOTG diluted with petroleum ether and 3M HCl medium. Tin(IV) can be separated conveniently from antimony(III) in 2M HCl with 95% yield and with a decontamination factor greater than 7·10⁵ using IOTG diluted with carbon tetrachloride.     

The determination of tin in biological samples

A rapid method is described for the determination of tin in biological material, using¹²³Sn (T=40 m). The chemical procedure is based on the nearly quantitative extraction of tetravalent tin into toluene from an acid 1.3M iodide solution. The recovery is determined by spiking the solution with¹¹³Sn and measuring the activity of the^113mIn daughter in the counting sample. The lower limit of the determination is ?0.01μg. Results are given for standard kale powder and dried animal blood.     

The determination of tin in rocks by thermal neutron activation

A fast routine method for the determination of tin in rocks is discussed. The method is based on coprecipitation of tetravalent tin with ferric hydroxide, followed by a short irradiation in a high thermal neutron flux, extraction in toluene from 1∶1 sulphuric acid which is 5N in potassium iodide, and counting of^123mSn (T=40 m) or^125mSn (T=9.7 m) with a well-type NaI detector. In the present work^125mSn was used. The lower limit of determination is governed by the blank of the reagents. For a sample of at least one gram it is ≌ 0.2 μg Sn·g⁻¹.     

Radiochemical investigation of the electron exchange reaction between tin(II) and tin(IV) in hydrochloric acid solutions

This paper is concerned with the study of isotope exchange reaction between Sn(II) and Sn(IV) in hydrochloric acid solutions. The kinetics of the exchange reaction of tin in these solutions were studied by extraction of Sn(IV)-hydroxyquinolate into chloroform.¹¹³Sn tracer, initially in the Sn(IV) state, was used. The rate of exchange reaction was determined at 22°C in a wide range of hydrochloric acid concentrations (2.8–12M). The dependence of the exchange rate on the concentration of chloride and hydrogen ions in these solutions (ionic strength: I∼8 and I∼12) are given. The activation energy dependence on chloride ion concentration at I∼12 was determined. The possible mechanism of the exchange reaction between tin(II) and tin(IV) is discussed on the basis of these data.     

Neutron activation analysis of tin in biological materials and their ash using123Sn and125Sn

Tin has been determined in biological materials by NAA of the γ-emitting 40-min¹²³Sn and 9,7-min¹²⁵Sn isotopes at the sub-ppm level. For¹²³Sn, samples are wet-ashed after irradiation, whereas to allow fast radiochemistry for¹²⁵Sn, the samples are dry-ashed prior to the irradiation. Both separation techniques rely on selective solvent extraction of tin(IV) iodide, and NaI(TI) counting. Comparative analyses of several materials by both methods gave good agreement, indicating that tin is not lost on dry-ashing and that simple dissolution of the ash in an HCl?HI mixture is complete. Results by both techniques are presented for the standard materials Bowen's Kale and NBS Orchard Leaves, and for some other materials.     

Mössbauer and NMR characterization of tin octoate: Neat and residues in RTV foams

We have investigated hydrolysis and oxidation effects on tin octoate and on tin-octoate residues in RTV polysiloxane foams by means of Nuclear Magnetic Resonance (NMR) and Mössbauer spectroscopy (MS). ¹¹⁹Sn NMR showed the presence of various tin species whereas ¹¹⁹Sn MS detected the presence of two oxidation states: Sn(II) and Sn(IV). The relative abundance of Sn(IV) increased as both the tin octoate and the foam aged. Foams were also solvent extracted and no selective extraction of one tin oxidation state was observed; both oxidation states were detected. ¹³C NMR indicated that octanoic acid is present in the tin octoate and in the foams as a residue. MS data showed that aging treatments of the foams and of the neat catalyst have a great effect on the tin oxidation state. The two spectroscopic methods complement each other in following the effects of hydrolysis and oxidation.     

The small‐scale preparation and NMR characterization of isotopically enriched organotin compounds

Synthetic methods for the small‐scale laboratory preparation of isotopically enriched dibutyltin dichloride, dibutyltin di‐iodide, tributyltin chloride, tributyltin iodide, diphenyltin dichloride, triphenyltin chloride and triphenyltin iodide have been successfully established. Organotin iodides were prepared from redistribution reactions between tin(IV) iodide and the corresponding tetraorganotin, with the exception of dibutyltin di‐iodide, which was prepared directly from the reaction between tin metal and iodobutane. The development of novel procedures for the dealkylation/dearylation of tetraorganotins by acid hydrolysis produced superior yields of tributyltin chloride and diphenyltin dichloride in comparison with redistribution reactions. Organotin iodide redistribution reaction products were converted to their chloride analogues via the fluoride salts using an aqueous ethanolic solution of potassium fluoride. The insolubility of organotin fluoride salts was exploited to isolate and purify the isotopically enriched compounds, and to prevent losses during the purification procedure. The nuclear magnetic resonance (NMR) spectroscopic study of ‘natural abundance’ and isotopically enriched organotin compounds gave proton (¹H) and carbon‐13 (¹³C) spectra for butyltins, Bu_4−nSnX_n, and phenyltins, Ph_4−nSnX_n (X = I, Cl), allowing the assignment of ­¹H and ¹³C chemical shifts, and ¹¹⁹Sn–¹³C and ¹¹⁷Sn–¹³C coupling constants. The ¹³C NMR spectroscopic analysis of ¹¹⁷Sn‐enriched organotin compounds has allowed the assignment of certain resonances and tin–carbon coupling constants which were previously unobservable. The spectral patterns show that Δ(¹H) and Δ(¹³C) values are sensitive to structural changes, and that ¹³C shielding decreases with an increase in the electronegativity of the substituent. The tin–carbon coupling constants are also sensitive to structural changes, and for alkyl and aryl compounds the couplings decrease in the order ¹J > ³J > ²J > ⁴J. The ¹³C chemical shift values and the magnitude of tin–carbon coupling constants are shown to be solvent‐dependent. The ¹³C spectra of the isotopically enriched compounds show that the degree of isotopic enrichment and the nature of the isotope used (magnetic or non‐magnetic) are reflected in the spectral pattern obtained. Copyright © 2000 John Wiley & Sons, Ltd.     

Spectrophotometric determination of tin in copper-based alloys using pyrocatechol violet

In the present paper, a new procedure using Pyrocatechol Violet (PCV) for the determination of tin in copper-based alloys is proposed. The use of HEDTA as masking agent allowed tin to be determined in the presence of large amounts of copper, without any separation procedure. The method is more selective than previous methods. Cetyltrimethylammonium bromide (CTAB) and Tween-20 are used to increase the stability of the system.

The method can be applied directly to an acidic solution of Sn(IV) in the range 2.0–60.0 μg with a final volume of 50 ml. The pH is adjusted to 2.0 ± 0.2 with glycine buffer and, after 30 min, the absorbance is measured at 660 nm. Al(III), Cd(II), Co(II), Mg(II), Ca(II), Mn(II), Ni(II) and Pb(II) do not interfere at the 500 mg level; 20 000 μg of Cu(II) and 400 μg of NaCl can be present. The interference at 100 μg of Fe(III) can be masked with ascorbic acid. Bi(III), Sb(V), Ti(IV), Mo(VI), EDTA, tartrate, citrate and iodide interfere. The proposed method was used for tin determination in several copper-based alloys and a comparison of the analytical results with certified values indicates that the procedure provides accurate and precise results.     

Determination of tin in canned foods by UV/visible spectrophotometric technique using mixed surfactants

The complex of tin(IV) with bromopyrogallol red (BPR) in the presence of nonyl phenoxy polyethoxyethanol (OP) and cetyltrimethylammonium bromide (CTAB) has a sensitive absorption peak at 304 nm. Under the optimal conditions, Beer's law is obeyed over the range 0.1-2.5 mug ml(-1) Sn(IV) with molar absorptivity being 8.2 x 10(4) l mol(-1) cm(-1) and detection limit 0.018 mug ml(-1). As compared with the visible method which also uses BPR as chromogenic reagent (lambda(max) = 550 nm), our method is sensitive and selective because of the complex's high, sharp absorption peak. In addition, the present method is simple and rapid, no heating or standing is needed. By means of the mixed surfactants the precipitation caused by the ion association of cetyltrimethylammonium cation and I(-)(3) anion is avoided if iodide is used for separating micro amounts of tin(IV) from a sample matrix. An application of the proposed method to the determination of Sn(IV) in a canned food was made with satisfactory results.     

Methylation of tin(II) by methyl iodide in porewater

The methylation of tin(II) chloride by methyl iodide in porewater and formation of monomethyltin as the only methyltin product are described. A factorial experiment tested the effects of concentrations of tin(II), methyl iodide, and oxygen on monomethyltin yields. The experiments gave 0.18 to 12.8 % yield. Analysis of variance (ANOVA) calculations showed that all three variables were significant at the 95 % level. Comparison of yields in aqueous 23 g kg^?1 sodium chloride solutions to those in porewater and to those containing fulvic acid, salicylic acid, and EDTA showed that only fulvic acid significantly reduced yields. Reasons for this observation are discussed and the findings in the model system are related to methylation of tin compounds in sediments.     

Tuning physical surface properties of tin dioxide nanopowders using zinc oxide as template

With a view to energetic and (opto)electronic applications, tin (IV) oxide (SnO₂) nanoparticles have been successfully prepared at the nanoscale by a templating approach based on the use of zinc (II) oxide (ZnO) as template. The procedure consisted in preparing a mixture of tin precursor and template, subsequently calcined at 650 °C under air to lead to the formation of a SnO₂/ZnO composite material. Finally, the material was washed with an alkali solution to remove the template. The template/tin precursor mass ratio was varied in order to tailor the tin (IV) oxide material, especially with a view to main particle size. The resulting SnO₂ nanomaterials were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, nitrogen adsorption and electron microscopy. The tin (IV) oxide nanomaterial exhibited enhanced textural and physical surface properties (particle size, surface area, pore size) correlated to an increasing template/tin precursor mass ratio. For instance, from optimized experimental conditions, the specific surface area and pore volume were heightened twofold, reaching values of 49 m²/g and 0.32 cm³/g, respectively.     

Sensitive spectrophotometric determination of tin with Pyrogallol Red and cetyldimethylbenzylammonium ions

Summary Tin(IV), in the presence of cetyldimethylbenzylammonium chloride (CDBA), forms with Pyrogallol Red (PR) a complex SnPR-CDBA. This complex floates at the interface between hexane and aqueous medium. It dissolves in acetone and can be advantageously used for the determination of tin. The molar absorptivity is 6.5×10⁴ l·mole^–1·cm^–1 at 480 nm. The method is selective when citric acid is used as masking agent. Phosphate, fluoride, EDTA, nitrite and sulphide interfere.

---

Zusammenfassung Zinn(IV) bildet mit Pyrogallolrot (PR) in Gegenwart von Cetyldimethylbenzylammoniumchlorid (CDBA) einen Komplex. Dieser wird flotiert, in Aceton gelöst und zur Bestimmung von Zinn verwendet. Der molare Absorptionskoeffizient bei =480 nm beträgt =6,5·10⁴ l·mol^–1 cm^–1. Die Methode ist selektiv, wenn Zitrate zur Maskierung verwendet werden. Es stören Phosphat, Fluorid, ÄDTA, Nitrit und Sulfid.

     

Effect of citric acid and hydrochloric acid on the polarographic behaviour of tin: Application to the determination of tin(II) in presence of tin(IV) in the activating solutions of the electroless plating of polymers

A new method for the determination of tin(II) in presence of tin(IV) is described. The method is based on differential pulse polarography on the hanging mercury drop electrode (HMDE). The effect of citric acid and hydrochloric acid concentrations on the polarographic peaks of tin(II) and tin(IV) has been studied. In 1 M HCl, the total quantity of tin can be determined, as under these conditions, in the absence of complexing agents, eventual variations in the oxidation states, in any concentration ratio, do not affect the peak height and the peak potential. In 0.2 M HCl and 0.2 M citric acid, tin(II) can be determined selectively in presence of tin(IV), as under these conditions, tin(IV) does not present polarographic response, while a well-defined peak is observed for tin(II). The method is applied to determine tin(II) and total tin in the activating solutions of the electroless plating of polymers.     

Separation of tin from some metals by extraction chromatography

Much attention has been devoted to Sn (IV) strongly retained on the TBP-Daiflon column from 2M HCl in extraction chromatography. The separations of Sn?Cu, Zn, As, Cd, Sb, Pb,¹¹³Sn-¹²⁵Sb,¹¹³Sn-^113mIn (^113mIn milking) and Sn?Hg?Fe were successfully achieved without any contamination. In the separations, except for the last, only tin was retained separately on the column upon passing the mixed solution. The daughter indium was eluted with 0.5M HCl. In the last separation, iron was eluted with 0.5 M HCl, tin with 0.1M HCl and mercury with 2M HNO₃, for these metals retained on the column. Radioactive tracers for tin, iron, mercury and antimony were used.