Rapid determination of molybdenum in botanical material by electrothermal atomic absorption spectrometry

Low levels of molybdenum in plant samples are determined by simple digestion in nitric acid followed by electrothermal spectrometry. Sensitivity is enhanced by nitric acid whereas chloride, sulfuric acid, and perchloric acid have inhibiting effects. Recovery of molybdate added to plant samples averaged 94.3%, with a relative standard deviation of 10% for 0.50 μg Mo g^-1 of plant material. Large numbers of samples can be screened for molybdenum content without tedious organic extractions or long dry ashing processes.     

Measurement of inorganic acids with rotating ball inlet mass spectrometry

Using a new acid resistant inlet we have evaluated the use of rotating ball inlet mass spectrometry (ROBIN-MS) as a tool for the measurement of inorganic acids in aqueous solution. EI-spectra of sulfuric, sulfurous, nitric, perchloric, bromic, iodic and boric acids were recorded and interpreted with respect to preionization decomposition and electron impact fragmentation. With the exception of sulfuric acid the detection limits for these acids were in the order of 1 mM and the response times are in the order of 1 s. Sulfuric acid had a significantly higher detection limit and response time than the other acids. No mass spectrum of phosphoric acid could be detected. High concentrations of phosphoric acid reduced the signals of other acids. HCl formed by decomposition of perchloric acid caused a strong and slowly recovering decrease of the sensitivity of the mass spectrometer. Sodium sulfate or sodium nitrate in neutral solution did not yield any mass spectrum. The intensity of the sulfuric acid peak of acid solutions of sodium sulfate was measured at different molar ratios of sodium and sulfate. The results indicate that the evaporation of such samples leaves a remnant containing three molecules of sulfuric acid per sodium ion. Similar measurements on acid solutions of sodium nitrate indicate that the remnant contains one molecule of nitric acid per sodium ion.     

Determination of traces of molybdenum in foods by electrothermal atomic absorption spectrometry

Low levels of molybdenum in different food samples were determined by atomic absorption spectrometry with electrothermal atomization after destruction of organic matter using four different methods, involving dry ashing at 600°C, wet digestion with heating with nitric/sulphuric and nitric/sulphuric/perchloric acid mixtures or direct extraction with dilute hydrochloric acid. In all cases the working conditions, reproducibility, precision and accuracy were investigated. The dry ashing method was generally the optimum destruction method.     

二苯硫脲-醋酸丁酯萃取-石墨炉原子吸收法测定地球化学样品中痕量银

对石墨炉原子吸收光谱法测定地球化学样品中痕量银进行了研究。样品经盐酸、硝酸、硫酸、高氯酸溶解,在盐酸(1.2mol/L)介质中用醋酸丁酯萃取银与二苯硫脲螯合物,用石墨炉原子吸收光谱法测定地球化学样品中痕量银,方法检出限为0.011ng/mL,相对标准偏差(RSD,n=11)为6.0%~12.2%,加标回收率为96.00%~105.00%。能满足地球化学样品中银含量为0.02~5μg/g范围内银测定的准确度和精密度的要求。     

碘量法测定铜冶炼烟尘中铜

试验研究了铜冶炼烟尘中铜含量的测定方法,试料用盐酸、氢氟酸、硝酸、高氯酸及硫酸分解,氢溴酸除去砷、锡、锑,硫酸除去硒的干扰。进一步对滴定条件和共存元素的干扰及消除进行了试验,最终确定了最佳条件。按照实验方法测定6个铜冶炼烟尘样品中铜量,结果的相对标准偏差为0.22%~0.65%,精密度高,准确度好。样品加标回收率在98.92%~100.38%之间, 适用于铜冶炼烟尘中铜含量为5.00 %～65.00 %的测定。     

Dynamic ion-exchange chromatography with post-column reaction detection for the determination of the rare earth elements in monazites

Summary Separation and determination of lanthanum, cerium, praseodymium, neodymium and samarium in monazites have been achieved by dynamic ion-exchange chromatography. The ore samples are decomposed by sulfuric acid and the rare earths are separated in a group as oxalates. The rare earth elements are then separated from each other on a column of bonded phase silica by gradient elution with 0.05 to 0.5 M lactic acid (pH 3.5) in the presence of 0.01 M sodium 1-octanesulfonate. Post-column reaction with Arsenazo III is used for detection and quantification of the individual rare earth elements. Results are quoted for lanthanum, cerium, praseodymium, neodymium and samarium in monazites. Detection limit is 1 μg ml⁻¹ with a S/N ratio of 3. The separation is complete within 27 min valley to valley resolution. Precision of better than 1% can usually be obtained.     

电位滴定法测定抛光液中的三酸含量

探讨了利用自动电位滴定仪对抛光液中磷酸、硫酸及硝酸的分析方法,以及对溶剂的标定方法。电位滴定法测定三酸,先用硫酸亚铁铵滴定硝酸,再用氢氧化钠滴定磷酸和硫酸,从而计算三酸含量。结果表明,与传统滴定法相比,电位滴定法标定硫酸亚铁铵的相对标准偏差(RSD)从1.1%降至0.13%,标定氢氧化钠的RSD从0.72%降至0.06%。电位滴定法测定自配样品及工厂抛光产品中的硝酸,回收率分别在96%及93%以上。电位滴定法测定自配样品及工厂抛光产品中磷酸和硫酸的回收率偏差在3%以内。手动滴定法测定磷酸和硫酸的回收率偏差在5%~10%,回收效果不如电位滴定法。电位滴定法测定工厂抛光液的三酸加标回收率偏差均小于3%。自动电位滴定法比手工滴定的准确性和精密度明显提高,弥补了手工滴定法只能分析磷酸和硫酸,而无法测定硝酸的缺陷。     

火焰原子吸收光谱法测定预熔型精炼渣中的氧化镁

建立了测定预熔型精炼渣中氧化镁的火焰原子吸收光谱法。样品采用氢氟酸–王水–高氯酸分解后,加入少量硫酸可使溶液底部的絮状不溶物溶解完全。在盐酸介质中,加入氯化锶消除干扰,利用空气–乙炔火焰以原子吸收光谱仪进行测定。测定结果的相对标准偏差为0.50%~1.08%(n=12),测定标准物质的相对误差为–0.92%,加标回收率为97.56%~102.14%。该法操作简便,分析速度快,适用于大批量样品分析。     

Electrolytic investigations : Electrolytic determination of silver after a silver chloride precipitation

A procedure is described for determining silver electrolytically after first precipitating the silver as silver chloride. The silver chloride is filtered through a filter paper, and the filter paper and precipitate are treated with a mixture of perchloric, sulfuric, and nitric acids. The solution is then evaporated to fumes of sulfuric acid, and the silver determined electrolytically by the cyanide method.     

Rapid and sensitive determination of total vanadium inairborne particulates by an extraction—spectrometric method with N-benzoyl-N-phenylhydroxylamine

A method is described for the rapid and sensitive determination of 0.06 μg of total vanadium in airborne particulates collected in the filter bag of an air-cleaner or on a membrane filter attached to an air sampler. The method is based on decomposition of organic matter in the sample and membrane filter by successive use of nitric, sulfuric and perchloric acids, and decomposition of the suspended silicate residue in a sulfuric—hydrofluoric acid mixture, followed by the extraction of a vanadium—N-benzoyl-N-phenylhydroxylamine complex into chloroform for spectrophotometric measurement. A comparison with the troublesome fusion method for the residue is included.     

Determination of antimony in steel by hydride generation and by electrothermal zeeman atomic absorption spectrometry

Procedures are described for the determination of antimony in steel. Samples by decomposed with a nitric/perchloric acid mixture and antimony is determined either by a.a.s. after hydride generation with sodium tetrahydroborate or by graphite-furnace a.a.s. with Zeeman background correction. Some reference steel samples were analyzed by both methods and by instrumental neutron activation. The results obtained (45–680 μg g^?1 antimony) were in very good agreement; detection limits were about 3 μg g^?1. The relative standard deviation for samples with > 50 μg g^?1 antimony was 〈 5%.     

Oxidation of cerium(III) to cerium(IV) using a mixture of hot concentrated perchloric and sulfuric acids

The oxidation of cerium(III) to cerium(IV) using a hot concentrated mixture of perchloric and sulfuric acids is shown to be quantitative Optimum conditions for the oxidation are described Complete removal of chlorine, an interfering decomposition product of boiling perchloric acid, is achieved by purging the concentrated acid solution with nitrogen before dilution with water The presence of sulfuric acid is essentral, the chief role of sulfuric acid apparently being to stabihze the cerium(IV) as a sulfatocerate complex.     

Accurate determination of selenium in biological materials without perchloric acid for digestion

Selenium (10–80 μg kg^?1) is determined by hydride-generation atomic absorption spectrometry in mixed diet, faecal and urine samples and in standard reference materials (bovine liver, rice flour, wheat flour and horse kidney) after two digestion procedures. No difference was found in digestion efficiency between a nitric/sulphuric acid mixture and a nitric/sulphuric/perchloric acid mixture. The results suggest that the digestion of most biological materials for the determination of selenium does not require the use of perchloric acid.     

Mechanism of oxidation of cyclohexanehexol (inositol) by quinquevalent vanadium

The oxidation of inositol by quinquevalent vandadium in acid medium is a first-order reaction both in vanadium (V) and inositol. The stoichiometry of the reaction is consistent with the use of two equivalents of vanadium (V) per mole of inositol with the formation of one mole of inosose. The reaction is catalyzed both by sulfuric and perchloric acid, but the rate is faster in sulfuric acid than in perchloric acid. In 1M–6M perchloric acid solutions the reaction has shown a variable order in H⁺, but in solutions of 2M–5M sulfuric and perchloric acid of constant ionic strength, the rate has a linear dependence on [H⁺]². There is also a linear correlation between the rate and bisulfate ions in sulfuric acid at constant hydrogen ion concentration. The energy of activation is found to be 19 kcal/mole and a negative entropy value of ? 14 e.u. A suitable mechanism, consistent with the kinetics in 2M–5M acid solutions, is suggested and the values of various rate constants are evaluated.     

Determination of tin in titanium alloys

Tin-titanium alloys are becoming increasingly important; consequently a good method is needed for the determination of tin in this type of material. In this paper an accurate iodometric procedure is proposed for the determination. The sample is dissolved in sulfuric acid and the titanium oxidized with potassium permanganate. Tartaric acid is added and the tin precipitated with hydrogen, sulfide. The sulfide precipitate is dissolved in a mixture of sulfuric, perchloric and nitric acids and the solution evaporated to fumes of sulfuric acid. Water and hydrochloric acid are added, and the tin is reduced with lead and antimony trichloride and titrated with iodine. A study was made of the interfering elements that might be found in titanium alloys. The effect of antimony trichloride in reducing interference from copper was investigated. The method is recommended for titanium alloys containing 0.05 to 5.0 per cent. tin.     

Semi-automated fluorimetric determination of nanogram quantities of selenium in biological material

A semi-automated method, based on the solvent extraction and fluorescence of 4,5-benzopiazselenol, is described for the determination of selenium in biological material. Samples, in batches of up to 150, are digested in a mixture of nitric and perchloric acids in temperature-controlled aluminium blocks. Selenate formed in the perchloric acid is reduced to selenite with hydrochloric acid. Metal ion interferences, including hydroxide adsorption of selenite, are prevented by ethylenediaminetetraacetic acid. Sulphate above 50 mM precipitates the 2,3-diaminonaphthalene, so wool digests were diluted accordingly. The digests are analysed from their digestion tubes at the rate of 40 per hour by the semi-automated method. Results for blood and a variety of food samples compare favourably with those obtained by other methods including hydride/atomic absorption and instrumental neutron-activation analysis.     

An evaluation of acid digestion methods for amniotic fluid phospholipids

Five methods of acid digestion of amniotic fluid phospholipids for inorganic phosphate release were evaluated at a temperature of 225 °C and a heating time of 30 min. The methods used the following digestants: (A (perchloric acid), B (perchloric acid containing molybdate), C (sulfuric acid, 30% hydrogen peroxide, 5% urea), D (sulfuric-perchloric acids), and E (sulfuric-perchloric acids with vanadium pentoxide). After digestion and dilution with water, a hydrogen ion concentration of about 2.5 mol/ liter was obtained that permitted the use of stannous chloride-hydrazine sulfate as the reducing agent for phosphate color development. Recoveries of the different amniotic fluid phospholipids and aqueous phosphate standards were quantitative for all methods. A comparative study with amniotic fluids showed similar results for all methods. Since all methods were found to be equivalent under the specified conditions described, the choice was dependent upon the user's preference.     

电感耦合等离子体质谱(ICP-MS)法测定玻纤滤筒中金属元素本底值的预处理方法探讨

探讨了不同预处理方法对国产玻纤滤筒本底值的降低效果,便于废气样品的分析测定。分别对空白滤筒、热硝酸、硝酸+硫酸和硝酸+EDTA、HCl处理后的滤筒进行分析,测得滤筒中金属元素的含量;对处理效果较好的一批滤筒进行空白加标,考察加标回收率,全程用电感耦合等离子体质谱(ICPMS)法对样品进行测定,结果发现空白滤筒中部分金属元素含量较高;热硝酸处理后,滤筒本底中铅含量有所降低,但其它元素去除效果不显著;硝酸+硫酸处理后,滤筒中铅含量剧增;硝酸+EDTA处理滤筒,铅可以得到较好的去除效果,大部分金属元素含量有了明显降低;基于HCl对金属有较好的溶出效果,浸泡可较好地降低滤筒中金属元素的含量,但大量氯离子存在对ICP-MS法测定的干扰较大。对硝酸+EDTA处理后的滤筒进行空白加标,大部分金属元素加标回收率75%。故以硝酸+EDTA处理玻纤滤筒可以使国产玻纤滤筒适用于废气样品的分析。     

A semi-automated and manual method for serum phospholipids

Five methods of acid digestion of amniotic fluid phospholipids for inorganic phosphate release were evaluated at a temperature of 225 °C and a heating time of 30 min. The methods used the following digestants: (A (perchloric acid), B (perchloric acid containing molybdate), C (sulfuric acid, 30% hydrogen peroxide, 5% urea), D (sulfuric-perchloric acids), and E (sulfuric-perchloric acids with vanadium pentoxide). After digestion and dilution with water, a hydrogen ion concentration of about 2.5 mol/ liter was obtained that permitted the use of stannous chloride-hydrazine sulfate as the reducing agent for phosphate color development. Recoveries of the different amniotic fluid phospholipids and aqueous phosphate standards were quantitative for all methods. A comparative study with amniotic fluids showed similar results for all methods. Since all methods were found to be equivalent under the specified conditions described, the choice was dependent upon the user's preference.     

Separation and spectrophotometric determination of thorium contained in uranium concentrate

A method for the determination of thorium in uranium concentrate by spectrophotometry with Arsenazo III has been developed. Preliminary solvent extraction procedures were used to eliminate interfering species. Samples were dissolved in nitric, perchloric and sulfuric acid and the uranium extracted from the solution using tri-octylamine. The aqueous layer was evaporated to dryness and the residue re-dissolved with hydrochloric acid, thorium was extracted by tri-n-octyl phosphine oxide and stripped with oxalic acid. For a typical uranium concentrate produced from the phosphate rock of Itataia, Brazil, concentrations of thorium as low as 5 g·g^-1 can be determined.