Determination of tungsten in rocks and minerals by chelate extraction and atomic-absorption spectrometry

An atomic-absorption method for determination of tungsten in rocks and minerals is proposed. The method involves sample decomposition by acid digestion or by pyrosulphate fusion, followed by chelate extraction of tungsten by N-benzoylphenylhydroxylamine in toluene. Atomic-absorption measurements are made on the organic phase aspirated into a nitrous oxide-acetylene flame. Quantitative extraction with efficient separation from other elements is achieved in a single extraction from strong acid media. The method is rapid and reliable in terms of precision and accuracy and is applicable to rocks and minerals containing tungsten in the range from 100 ppm to 15%.     

X射线荧光光谱法测定铀钼合金中钼

建立铀钼合金中钼的X射线荧光光谱测定方法.用硝酸–盐酸混合酸溶解样品,调节样品溶液pH值为1～2,在选定的仪器工作条件下进行测定,采用α校正消除干扰.钼的质量分数在1.0％～16.0％范围内与X荧光强度呈良好的线性关系,线性相关系数为0.9999,检出限为0.039％.样品加标回收率为99％,测定结果的相对标准偏差为0...     

Determination of vanadium,molybdenum and tungsten in chloralkali electrolysis brines by x-ray fluorescence spectrometry

The levels of vanadium, molybdenum and tungsten are critical in chloralkali electrolysis brines because these elements catalyze the hydrogen-producing side-reaction. Preconcentration by chelation with 8-quinolinol and subsequent adsorption on activated carbon, can be combined with energy- or wavelength-dispersive x-ray fluorescence. Under optimized conditions, the detection limits are in the μg 1^-1 range, and below the critical levels. Up to 100 /smg l^-1, reliable results are obtained for V, Mo and W. The coefficient of variation is typically 15% in the 25–100 μg l^-1 range.     

超声辅助溶剂萃取-原子荧光法用于土壤中汞的形态分析

建立了超声辅助溶剂萃取联用原子荧光法测定土壤样品中迁移毒性态汞中无机汞和有机汞的分析方法.实验优化了萃取溶剂种类,溶剂浓度,各种辅助措施和超声波振荡时间等各种萃取条件.方法的检出限为0.01 μg/L,相对标准偏差(n=11)为2.1%.方法已应用于珠江三角洲4个代表性菜园土壤样品汞形态分析.     

Analysis of tungsten carbides by X-ray fluorescence spectrometry

Five sample presentation techniques were examined for the X-ray fluorescence spectrometric analysis of tungsten carbide alloys in powder and cemented forms. Powder samples may be oxidized by air at 600° before fusion (I), or preferably by lithium nitrate during fusion (II); the fusion is effected with lithium-lanthanum tetraborate followed by briquetting with graphite. Powder samples may also be blended with wax and briquetted (III). Cemented carbides are surface-prepared with silicon carbide before analysis (V). Briquettes prepared by blending carbide powder, lithium-lanthanum tetraborate and graphite (IV), give poor reproducibility, however, owing to micro-absorption effects the technique is not recommended. The determination of eight common elements in tungsten carbide is discussed and the relative standard deviations are 0.002–0.004 for major and 0.008–0.01 for minor elements.     

Determination of organically-associated trace metals in estuarine sea-water by solvent extraction and atomic-absorption spectrometry

Chloroform extraction of trace metals (Ni, Cu, Mo, Mn, Cd and Pb) in estuarine sea-water was studied at pH 8 and pH 3, on the basis that the metals would be associated with dissolved organic matter (DOM), which has recently been characterized by reversed-phase liquid chromatography. Ni, Cu, Mo and Mn were extracted more at pH 8 than at pH 3. Cd and Pb were not associated with the DOM at either pH 8 or 3. The percentage of the total dissolved trace metals in sea-water associated with DOM varied from 0 to 14%. The metals extracted into chloroform at pH 8 were assumed to be associated with neutral or weakly basic DOM while at pH 3 they could be associated with either the neutral (or weakly basic) DOM or two types of acidic DOM.     

Determination of trace amounts of molybdenum in plant tissue by solvent extraction-atomic-absorption and direct-current plasma emission spectrometry

Methods are presented for determination of molybdenum in plant tissue by flame and graphite-furnace atomic-absorption spectrometry and direct-current argon-plasma emission spectrometry. The samples are digested in HNO(3)-H(2)SO(4)-HC1O(4) mixture, and Mo is separated and concentrated by chelation and extraction. Three organic solvents (methyl isobutyl ketone, di-isobutyl ketone and isoamyl alcohol) and two ligands (8-hydroxyquinoline and toluene-3,4-dithiol) were studied. The procedure were tested on pine needle and birch leaf samples.     

Determination of trace elements in sediment reference materials by monochromatic X-ray excitation X-ray fluorescence spectrometry.

A new reliable analytical method, "Monochromatic X-ray Excitation X-ray Fluorescence Spectrometry", has been proposed. For validating the method, trace elements in sediment certified reference materials were determined. In the method X-ray fluorescence spectra are measured for specimens and pure metals; in addition the mass-attenuation coefficients of the specimens for various X-ray wavelengths are also measured. The data are analyzed by the fundamental parameter method and the uncertainty of the analysis is evaluated. The obtained results were in satisfactory agreement with the certified values within their uncertainties. This method will be applicable to the certification of reference materials, in the field of which reliable results with uncertainty statements are required.     

Determination of trace chromium(VI) in drinking water using X-ray fluorescence spectrometry after solid-phase extraction

A new, simple, and selective method for preconcentration and determination of Cr(VI) in aqueous samples. After adsorption in “batch mode” on Aliquat 336-AC, determinations were made directly on the solid by X-ray fluorescence spectrometry, which had the advantage of not requiring the step of elution of the chromium retained. The enrichment factor was calculated considering that the tablets obtained from 10 mL solution of Cr(VI) (1000 μg L^-1) had a final thickness of 0.64 mm and a diameter of 16.7 mm; the volume deposited on the pellet was 0.14 cm³. The preconcentration factor obtained was 71-fold, which was highly satisfactory for chromium trace analysis by XRF. Finally, the method was successfully applied to the determination of Cr(VI) in drinking water samples.     

熔片X射线荧光光谱法测定钼精矿中多种元素

建立了用波长色散X射线荧光光谱测定钼精矿中多元素分析方法.采用Li2B4O7:LiBO2混合熔剂(67:33),加入氧化剂LiNO3,减少钼和硫的挥发并保护铂-金坩埚免受腐蚀,且严格控制脱模荆LiBr和NH4I加入量,熔融制备样片.对熔融制样温度和时间进行了讨论,并对钼的分析线作了仔细的选择.用经过多次化学分析的钼精矿...     

Determination of trace elements in Syrian medicinal plants and their infusions by energy dispersive X-ray fluorescence and total reflection X-ray fluorescence spectrometry

X-ray fluorescence (XRF) and total-reflection X-ray fluorescence (TXRF) techniques suited well for a multi-element determination of K, Ca, Mn, Fe, Cu, Zn, Rb, and Sr in some Syrian medicinal plant species. The accuracy and the precision of both techniques were verified by analyzing the Standard Reference Materials (SRM) peach-1547 and apple leaves-1515. A good agreement between the measured concentrations of the previously mentioned elements and the certified values were obtained with errors less than 10.7% for TXRF and 15.8% for XRF. The determination of Br was acceptable only by XRF with an error less than 24%. Furthermore, the XRF method showed a very good applicability for the determination of K, Ca, Mn, Fe, Cu, Zn, Rb, Sr, and Br in infusions of different Syrian medicinal plant species, namely anise (Anisum vulgare), licorice root (Glycyrrhiza glabra), and white wormwood (Artemisia herba-alba).     

Determination of trace amounts of uranium in plutonium oxide by wavelength dispersive X-ray fluorescence spectrometry

Journal of Radioanalytical and Nuclear Chemistry - 149Tb, 152Tb, 155Tb and 161Tb can cover all the modalities of diagnostic and therapeutic purposes of nuclear medicine. The production cross...     

钽内标X射线荧光光谱法测定钨精矿中WO_3

提出了以钽为内标波长色散X射线荧光光谱法测定钨精矿中WO3的新方法。以Na2B4O7和Li2B4O7(质量比65:35)的混合物作为熔剂,Ta2O5为内标,同时加入LiNO3为氧化剂,在1200℃下进行熔融制样,最后将本方法应用于实际样品的分析,结果表明,以钽作为内标测定WO3,不仅可以在很大程度上降低实验操作和仪器测量带来的偏差,也可以消除基体效应的影响。方法用于测定白钨精矿和黑钨精矿中WO3,其准确度和精密度优于重量分析法。     

Determination of cadmium in rice and water by tungsten coil electrothermal vaporization-atomic fluorescence spectrometry and tungsten coil electrothermal atomic absorption spectrometry after cloud point extraction

In this work, the microsampling nature of tungsten coil electrothermal vaporization Ar/H₂ flame atomic fluorescence spectrometry (W-coil ETV-AFS) as well as tungsten coil electrothermal atomic absorption spectrometry (W-coil ET-AAS) was used with cloud point extraction (CPE) for the ultrasensitive determination of cadmium in rice and water samples. When the temperature of the extraction system is higher than the cloud point temperature of the selected surfactant Triton X-114, the complex of cadmium with dithizone can be quantitatively extracted into the surfactant-rich phase and subsequently separated from the bulk aqueous phase by centrifugation. The main factors affecting the CPE, such as concentration of Triton X-114 and dithizone, pH, equilibration temperature and incubation time, were optimized for the best extract efficiency. Under the optimal conditions, the limits of detection for cadmium by W-coil ETV-AFS and W-coil ET-AAS were 0.01 and 0.03 μg L⁻¹, with sensitivity enhancement factors of 152 and 93, respectively. The proposed methods were applied to the determination of cadmium in certified reference rice and water samples with analytical results in good agreement with certified values.     

Determination of tungsten in ores by energy dispersive X-ray fluorescence analysis

The possible determination of tungsten in low grade ores from Northern India, Rajasthan State has been explored by energy dispersive X-ray fluorescence analysis /EDXRF/ technique using radioisotope based excitation of W L X-rays and high resolution Si/Li/ detector system. Finely powdered ore has been diluted with optimal quantity of cellulose and converted into pellets to make it suitable for X-ray analysis after homogenization. The experiments have shown the minimum detectable limit of 33 ppm in diluted matrix. The results are compared with the spectrophotometric stannous chloride-thiocyanate method. EDXRF appears to be encouraging for routine and precise analysis of tungsten in low grade ores.     

能量色散-X射线荧光光谱测定中草药痕量镉、铅、铜

为寻求一种能够直接对中草药中重金属进行快速检测的方法,采用压片法对样品进行前处理,建立了能量色散-X射线荧光光谱法快速检测中草药中痕量重金属镉、铅、铜元素的方法。在20 min即可完成检测,镉、铅、铜检出限分别为0.072、0.207、0.340 mg/kg,测试结果表明与原子吸收和ICP-MS相比,本方法数据稳定性和准确度良好,具有快速、准确、简单的优点,能够满足药典中对重金属元素的限量要求,适用于现场快速检测与质量控制检测。     

Determination of europium in minerals and rocks by neutron activation and gammagamma-coincidence spectrometry

Neutron activation followed by gammagamma-coincidence measurements of 9-3 hr (152)Eu is shown to be a convenient method for routine determination of europium in minerals and rocks. In the concentration range 10-150 ppm the method is free of interference from other elements, and neutron shielding effects do not interfere seriously in the analysis. The precision of the method is about 5%.     

Determination of trace metals in sea water by chelex-100 or solvent extraction techniques and atomic absorption spectrometry

Determinations of cadmium, lead, nickel, copper and zinc in sea water are discussed. Two different methods of preconcentration are compared: the trace metals are preconcentrated either by extraction with ammonium pyrrolidinedithiocarbamate/diethylammonium diethyldithiocarbamate into freon followed by back-extraction into nitric acid, or by collection on a Chelex-100 resin followed by elution with nitric acid. Cd, Pb, Ni, and Cu are determined by graphite-furnace atomic absorption spectrometry, while zinc is determined by flame atomic absorption spectrometry. The comparison of methods shows that cadmium can be determined accurately whereas results for the other trace metals may be biased by reagent contamination in the Chelex-100 method. Recovery data are given for both methods of preconcentration. Filtering experiments with Chelex-100 method are described. Results are compared for sea-water samples preconcentrated immediately after sampling and some weeks after sampling, with only freezing for preservation. The present results are consistent with other recent work. The importance of blank values is discussed.     

Determination of trace elements in suspensions and filtrates of drinking and surface water by wavelength-dispersive X-ray fluorescence spectrometry

An X-ray fluorescence method (XRF) is presented that allowed low detection limits (at the 0.1–23 ng mL⁻¹ level) to be obtained for Cr, Mn, Fe, Ni, Zn, Sr, Pb, Bi and Br in water. The samples were prepared using a thin layer method. Trace elements were determined via the calibration curve and standard addition. Absorption effects and inhomogenities in prepared samples were checked for using the emission–transmission method and internal standards, respectively. The results from the XRF method were compared with the results from the inductively coupled plasma atomic emission spectrometry method.