Direct determination of tin in tap waters by electrothermal atomization atomic absorption spectroscopy

Summary A method is described for the direct determination of tin in tap waters by electrothermal atomization atomic absorption spectroscopy (ETA-AAS), using magnesium-nitric acid and palladium-magnesium as chemical modifiers. The charring and atomization temperatures and times, and the amount of modifier were optimized. The calibration and addition graphs, detection limit, quantitation limit, precision, accuracy, interferences and characteristic mass were also investigated. The method was applied to the determination of tin in tap water samples.     

Influence of volatile hydride-forming elements on antimony determination by atomic-absorption spectrometry with hydride-generation

A study was undertaken to determine the interfering effects of arsenic, bismuth, germanium, lead, selenium, tin and tellurium on trace determination of antimony by atomic-absorption spectrometry with hydride-generation. A 1% NaBH(4) solution was used as reductant and a small amount of oxygen was added to the hydrogen produced, to support the combustion and atomization of SbH(3). The interference from selenium in the determination of antimony is removed if potassium iodide-ascorbic acid solution or copper sulphate is added to the sample solution. The interference of tin and tellurium can also be avoided by adding potassium iodide-ascorbic acid solution. A possible interference mechanism is discussed.     

Determination of total tin in geological materials by electrothermal atomic-absorption spectrophotometry using a tungsten-impregnated graphite furnace

An electrothermal atomic-absorption spectrophotometric method is described for the determination of total tin in geological materials, with use of a tungsten-impregnated graphite furnace. The sample is decomposed by fusion with lithium metaborate and the melt is dissolved in 10% hydrochloric acid. Tin is then extracted into trioctylphosphine oxide-methyl isobutyl ketone prior to atomization. Impregnation of the furnace with a sodium tungstate solution increases the sensitivity of the determination and improves the precision of the results. The limits of determination are 0.5-20 ppm of tin in the sample. Higher tin values can be determined by dilution of the extract. Replicate analyses of eighteen geological reference samples with diverse matrices gave relative standard deviations ranging from 2.0 to 10.8% with an average of 4.6%. Average tin values for reference samples were in general agreement with, but more precise than, those reported by others. Apparent recoveries of tin added to various samples ranged from 95 to 111% with an average of 102%.     

Ascorbic acid as a matrix modifier for determination of tin in concentrated boric acid solutions by electrothermal atomic-absorption spectrometry

It has been found that the atomic-absorption signal for tin is reduced in the presence of 5 micro1 of 0.05-0.30M boric acid at STPF-conditions. It has been proposed that the reason for the boron interferences is the formation of SnB(g) at the atomization stage. In the presence of palladium chloride the interferences from 0.2M boric acid are reduced by a factor of 1.3. The interferences are reduced most effectively when the sample is atomized from a polycrystalline graphite platform or in the presence of ascorbic acid. The interference of up to 0.2M boric acid can be suppressed and the area of the tin signal doubled. It is proposed that the observed phenomenon is connected with the bonding of boron as non-volatile B(4)C. Ascorbic acid is the most effective matrix modifier for the determination of different trace elements in boron compounds.     

Minimizing the effect of organic matrices in the analysis of tin-containing extracts by electrothermal atomic absorption spectrometry: Determination of Tin in rocks

The effect of the nature of the extracted complex and of the organic solvent on the sensitivity of the extraction/atomic absorption determination of tin in a graphite-furnace atomizer is investigated. It is recommended that extracts of tin as its chloride complex, or chelates with N-benzoyl-N-phenylhydroxylamine or 8-quinolinol, in organic solvents which do not contain chlorine should be used. The depressive effect of the organic matrix can be significantly decreased by using ascorbic acid as matrix modifier, by atomization from a graphite platform, and by using an atomizer coated with tungsten carbide. The procedure developed is applied to the determination of tin in rocks. For tin concentrations of 0.1–10 μg g^?1, the relative standard deviation does not exceed 10%.     

The stability sequence of the trivalent rare earth chelates of 2-nitroso-1-naphthol-8-sulphonic acid in aqueous solution

A method is described for estimating the concentration of di(n-octyltin) bis-maleate in five food-simulating solvents recommended by the United States Food and Drug Administration for migration studies on food containers. Atomic absorption spectrometry with electrothermal atomization provides a detection limit of 0.01 ppm tin stabilizer in the food simulators. Both calibration curve and standard addition methods were employed to check for possible matrix effects. Analysis time was less than 90 s per sample. Ethanol solutions were difficult to analyze because of residual inorganic tin blanks, presumably arising from the ethanol container. Water, acetic acid and heptane were free of residual tin blanks. Amounts of tin stabilizer extracted from several different resins ranged from 0.01 to 0.18 ppm.     

Determination of traces of lead and cadmium in high-purity tin by polarized zeeman atomic-absorption spectrometry with direct atomization of solid sample in a graphite-cup cuvette

Lead at the mug g level and cadmium at ng g -mug g levels in high-purity tin have been determined by polarized Zeeman atomic-absorption spectrometry with direct atomization of the solid sample. Pieces of high-purity tin weighing up to 5 mg for lead and 20 mg for cadmium were analysed. Calibration graphs were constructed by use of standard solutions of lead and cadmium in the presence of pure tin having lead and cadmium contents below the detection limit. The tin matrix remained in the graphite-cup cuvette after atomization and did not adhere to the wall of the cuvette, so it could be easily removed and the same cuvette repeatedly used.     

Effect of anions on atomization temperatures in furnace atomic-absorption

Atomization temperatures have been measured for silver, cadmium, chromium, copper, nickel, lead, tin and zinc. The effect of various anions on the atomization temperatures of these metals has been examined. Of the anions investigated which were added as acids, only phosphate affected the atomization temperatures. For elements which atomized at a lower temperature than tin, phosphate addition resulted in an increased atomization temperature but those which atomized at a higher temperature than tin were not affected. These observations suggested that there are two mechanisms of atom formation in the graphite furnace. The first involves reduction of the metal oxide by carbon and is applicable only to compounds which can form oxides at temperatures lower than those required for the reduction process to occur. The second mechanism is direct decomposition of the metal compound to give metal atoms and is applicable to compounds of higher thermal stability which decompose at temperatures higher than those required for the reduction process.     

A sensitive atomic-absorption spectrometric method for the determination of tin with atomization from impregnated graphite surfaces

The atomization of Sn from graphite surfaces is potentially hindered by reactions with the surface. The impregnation of graphite tubes with other carbide-forming elements (W, Zr, Ta, Mo) favourably alters the surface characteristics of the graphite furnace for the atomization of Sn. At the acid concentrations needed to prevent the hydrolysis of Sn, these surfaces are considerably more stable (even after more than 100 atomization cycles) than those of pyrolytic graphite. Two graphite furnaces of different design, the HGA 72 and the HGA 76, were tested. With impregnated graphite tubes the determination of Sn is possible in the HGA 72 with a detection limit of approximately 15 pg. In the HGA 76 the tin determination is vastly improved with respect to prolonged lifetime of the furnaces and stable signals over much longer periods of time. Detailed interference studies reveal that the use of the "gas stop" mode minimizes the influence of many ions that are frequently either introduced by the decomposition reagents or present in the sample itself. The practical potential of this method is demonstrated for the determination of Sn in a slag material and in copper- and aluminium-based alloys.     

镧涂层表面效应初探

本实验通过对涂镧石墨管和非涂镧石墨管的电子显微分析，证实了镧涂层并未能对石墨管壁的孔洞起到有效的填充作用，这与测定金时吸收信号未明显变化的实验现象相吻合。通过对锡原子化前后石墨表面的Ｘ光电子谱分析，尝试提出了镧在管中的催化作用及影响某些元素原子化机理、从而改变其灵敏度的观点。     

Factors influencing the free oxygen content in an electrothermal atomizer

A considerable decrease in the partial pressure of free oxygen in the gas phase within a graphite atomizer during atomization with the use of ascorbic acid as a matrix modifier was proved by using the method suggested by L'vov and Ryabchuk. A similar change in the gas-phase composition was observed in graphite tubes treated with compounds of refractory metals. A mechanism for this oxygen binding is suggested. It is shown that the sensitivity of the determination of tin is improved by decreasing the free oxygen content of the gas phase.     

Critical study of the determination of tin by electrothermal atomic-absorption spectrometry using resonance and non-resonance lines

The 235.48 nm non-resonance line of tin gives a sensitivity for AAS determination equal to that given by the most sensitive resonance line. Vaporization from a platform improves some twofold the sensitivities of all lines investigated. The atomization temperature has only slight influence on the relative sensitivities given by the non-resonance tin lines studied. Phosphoric acid shows a rather peculiar interference pattern, low concentrations (0.05%) depressing the signal, but high concentrations (1%) enhancing it. Contrary to expectation, the resonance and non-resonance lines are affected to the same extent by phosphoric acid. Platform-vaporization does not change the interference pattern of phosphoric acid. Calibration can be done by injecting various volumes of a single standard solution onto a platform coated with tantalum carbide. This method yields calibration graphs that are just as linear as those obtained with identical volume of standards of various concentrations. Some suggestions are made for further improvement of the analytical potential of non-resonance lines.     

石墨炉原子吸收光谱法测定锡和锗时基体改进剂硝酸钙的作用

石墨炉原子吸收光谱法测定低温易挥发元素锡和锗时灵敏度较低。本文以硝酸钙为基体改进剂,使锡和锗的灵敏度分别比不加基体改进剂时提高9倍和50倍,同时也显著提高灰化温度,并降低原子化温度。本文也探讨了基体改进剂硝酸钙对锡和锗的增感机理。锡的增感是由于固相和气相中钙的作用,而锗的增感仅是气相钙的作用。     

A simplified procedure for the determination of butyltin species in water

A method is described for the analysis of solutions containing inorganic tin and butyltin compounds. It can be used to determine total tin at a concentration of 20 ng dm^?3 using a 5 dm³ sample. The method is based on solvent extraction with dichloromethane containing tropolone and determination of the tin as inorganic tin by atomic absorption spectroscopy using electrothermal atomization. The extracted butyltin compounds can be separated by paper chromatography and the tin content of the individual spot determined as above. Observations on the stability of butyltin compounds in water at the ～2 mg dm^?3 (Sn) are included.     

Use of Metal Carbide Coated Graphite Cuvettes Eor the Atomic Absorption Analysis of Organotins

Abstract

Organotin compounds are analyzed by graphite furnace atomic absorption (GFAA) spectrometry. The graphite cuvette furnaces which were used were treated chemically with solutions containing V, Mo, Cr, and Zr. The zirconium treatment shows the greatest reduction in atomization interferences for the analysis of tin. The tin atomic absorption signals observed for the organotin compounds can be directly compared t o the aqueous tin standard, in terms of sensitivity.     

Ultratrace determination of tin by hydride generation in-atomizer trapping atomic absorption spectrometry

A quartz multiatomizer with its inlet arm modified to serve as a trap (trap-and-atomizer device) was employed to trap tin hydride and subsequently to volatilize collected analyte species with atomic absorption spectrometric detection. Generation, atomization and preconcentration conditions were optimized and analytical figures of merit of both on-line atomization as well as preconcentration modes were quantified. Preconcentration efficiency of 95 ± 5% was found. The detection limits reached were 0.029 and 0.14 ng mL⁻¹ Sn, respectively, for 120 s preconcentration period and on-line atomization mode without any preconcentration. The interference extent of other hydride forming elements (As, Se, Sb and Bi) on tin determination was found negligible in both modes of operation. The applicability of the developed preconcentration method was verified by Sn determination in a certified reference material as well as by analysis of real samples.     

Application of experimental design in a method for screening sediments for global determination of organic tin by electrothermal atomic absorption spectrometry (ETAAS)

An experimental design was developed to obtain a simple procedure for global determination of organic tin compounds in sediment. Sediment was extracted by a two-phase method and tin was determined in the organic extract by electrothermal atomic absorption spectrometry (ETAAS), with palladium as chemical modifier. A Plackett-Burman design for screening and a fractional central composite design (CCD) for optimizing were used for evaluation of the effects of several variables. The results showed that sediment mass, volume and concentration of extracting acid, pyrolysis and atomization temperatures, and modifier concentration affect the determination. Reference material PACS-2 was analyzed to evaluate the procedure. It was possible to extract 82% of the organotin content certified in the reference sediment. The limit of detection (LOD) was 0.08 microg g(-1) and the relative standard deviation was 4%. The method was applied to the analysis of estuarine superficial sediments from Gipuzkoa (Spain). The organotin content of these samples ranged from 0.7 to 7.7 microg g(-1), as tin, on a dry-weight basis.     

Spectroscopic determination of the degree of atomization in an electrothermal atomizer

The degree of atomization, β, is measured for an electrothermal atomizer by comparing the emission lines of copper atoms and CuCl molecules. Hydrogen increases the β value. The determined β value of CuCl is used as a standard for the determination of β values of other elements (nickel, chromium, tin and lead).     

Column preconcentration of organotin with tropolone-immobilized and their determination by electrothermal atomization absorption spectrometry

A method for the determination of total organic tin from marine water samples by electrothermal atomization absorption spectrometry (ETAAS) is described. Samples are previously preconcentrated with a chelating molecule (tropolone) impregnated on a macroporous polymer (Amberlite XAD-2). The graphite furnace programme and preconcentration parameters were optimized. Calibration and addition graphs were performed. Sensitivity obtained with this procedure was 13 ng l⁻¹. Relative standard deviation was always >10% and analytical recovery were satisfactory, 100%. Some possible interferences were investigated, having no problems with this factor. This procedure allows the distinction between organotin compounds and inorganic tin IV, since the latter is not retained on the column.     

Thermochemical study of gaseous salts of oxygen-containing acids: XXII. Tin molybdates

Gas-phase reactions involving tin molybdates were studied. Standard enthalpies of formation and atomization of gaseous salts SnMoO₄ and Sn₂MoO₅ were determined.