Determination of atmospheric iron particulates by X-ray fluorescence spectroscopy

A method is described for the determination of atmospheric iron particulates by X-ray fluorescence spectroscopy. Samples are collected, with a low-volume air sampler, on organic membranes which are used directly for measurement by comparison with standards prepared by precipitation of hydrous iron(III) oxide on similar membranes. The method is simple and rapid, and offers a precision and error of about 6% for the range 10-200 mug of iron.     

Determination of titanium in bauxite: A comparison of neutron activation analysis with the X-ray fluorescence method

The determination of the titanium content of bauxite samples of various origin was studied by thermal neutron activation and X-ray analysis. A²⁵²Cf-fission neutron source and a Ge(Li) detector as well as a³H exciting source and a Si(Li) detector were used in the investigations. Within equal measuring times and with a sample weight of 8 g the sensitivity of the activation method is 0.35 w% Ti with an absolute statistical error less than 10%, while that of the X-ray method is 0.06 w% Ti and the absolute statistical error does not exceed 5%.     

Determination of the oxidation state of iron by X-ray fluorescence spectroscopy using chemometric approaches

A possibility of identification of the oxidation state of iron by wavelength dispersive X-ray fluorescence spectroscopy using both the position and intensity of L _α and L _β spectral lines of iron and by principal component analysis score data obtained by the decomposition of the spectral region corresponding to spectral L-series lines of iron is demonstrated. The application of scores ensures a more reliable identification in comparison with line parameters (position and intensity). Two approaches based on projection on latent structures (PLS) regression for the determination of the concentration of iron in different oxidation states are proposed. The first approach consists in using reference models with compositions similar to those of analyzed samples. In the second approach, PLS regression was build using model spectra obtained from spectra of readily available iron compounds.     

X射线荧光光谱(XRF)法测定绿泥石中镁、铝、硅、磷、钾、钙、钛、铁元素含量

建立了X射线荧光光谱法测定绿泥石中镁、铝、硅、磷、钾、钙、钛、铁元素含量的快速分析方法。以标准物质及标准物质与基准试剂氧化镁、氧化钙人工混合配制标样的方法建立标准工作曲线,重点讨论了熔剂和脱模剂的选取。最佳熔样条件：采用8.0g四硼酸锂和偏硼酸锂混合熔剂(质量比67: 33)+0.8g样品并添加溴化锂作为脱模剂,熔样温度1100℃,熔样时间10min。该方法相对标准偏差(n=12)均小于5.57%,绿泥石样品测定结果与化学法一致,硅酸盐标准物质测定结果均满足不确定度要求。     

The application of ion-exchanger foils in the determination of trace amounts of some metals in water by means of the non-dispersive X-ray fluorescence method

Preliminary enrichment by means of strong acid ion-exchanger foils has been used to determine trace amounts of metals in water. The kinetics of the exchange reaction between the hydrogen ions in the cation-exchanger foil and metal ions in the solution has been studied. The time needed for the attainment of equilibrium and the values of the distribution coefficients have been determined for Fe²⁺, Zn²⁺, Pb²⁺, Ca²⁺, Cd²⁺ and Ba²⁺ ions. The metal contents in the cation-exchanger foil were determined by means of non-dispersive X-ray fluorescence. The feasibility of the method was determined on the examples of Pb, Zn and Cd ions. The method permits trace amounts of these elements to be determined above 0.01 ppm in the solution. No significant matrix effect due to the presence of Ca and Ba was found for concentration in the solution below 60 ppm.     

Determination of copper,iron and zinc in spirituous beverages by total reflection X-ray fluorescence spectrometry

The concentration of copper in traditional homemade alcoholic distillates produced in Venezuela (Cocuy de Penca) were determined by total reflection X-ray fluorescence (TXRF) using vanadium as internal standard. The results were compared to those obtained by flame atomic absorption spectrometry (FAAS). Three preparative methods of addition of vanadium were compared: classical internal standard addition, ‘layer on layer’ internal standard addition and in situ addition of internal standard. The TXRF procedures were accurate and the precision was comparable to that obtained by the FAAS technique. Copper levels were above the maximum allowed limits for similar beverages. Zinc and iron in commercial and homemade distilled beverages were also analyzed by TXRF with in situ addition of internal standard demonstrating the usefulness of this technique for trace metal determination in distillates.     

X-ray fluorescence analysis of titanium alloys

An X-ray solution method is proposed for determining major amounts of Mo, Sn and Zr in Ti alloys. The method utilizes adjacent elements in the periodic table as internal standards and has been successfully applied to levels of 3-10% Sn, 11-40% Mo and 6-20% Zr. The procedure involves three steps: dissolving the sample with a suitable acid mixture; adding the suitable internal standard at the concentration levels experimentally found to give optimum accuracy and precision; analysing the resulting solution mixture by X-ray fluorescence. Antimony was found to be a suitable internal standard for its adjacent element tin at a concentration ratio of 3:1 Sb:Sn. Niobium was successfully used for both its adjacent elements, molybdenum and zirconium, at 2:1 concentration ratios, Nb:Mo and Nb:Zr. A number of elements non-adjacent to tin, molybdenum and zirconium (i.e., copper, bromine, titanium, bismuth and tantalum) were experimentally found unsuitable as internal standards. Concentration factors of the internal standard and the adjacent elements sought were found to affect significantly the precision of analysis.     

Thin film analysis of gadolinium iron oxide and gadolinium iron by a combined ion exchange X-ray fluorescence method

Summary The composition of thin gadolinium iron oxide and alloy films of limited size (weighing from 500 to 2000g and ranging from 0.7 to 2.3 nm in thickness) was determined by first collecting and simultaneously concentrating gadolinium and iron ions from very dilute solutions on ion-exchange resin-loaded paper disks, and then analyzing the concentrated samples by X-ray fluorescence. This method of analysis allows the preparation of standards by normal solution techniques without the problem of matrix effects.

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Zusammenfassung Die Zusammensetzung dünner Filme aus Gadolinium-Eisenoxid bzw. Gadolinium-Eisenlegierung (Gewicht: 500 bis 2000g; Dicke: 0,7 bis 2,3 nm) wurde bestimmt. Dazu wurden die Gadolinium- und Eisenionen aus sehr verdünnten Lösungen auf Filterscheiben angereichert, die mit Ionenaustauscherharz beladen waren. Die angereicherten Proben wurden dann durch Röntgenfluoreszenzmessung analysiert. Dieses Analysenverfahren eignet sich zur Herstellung von Standards durch gewöhnliche Lösungstechnik und vermeidet das Problem der Matrixeffekte.

     

Determination of low atomic number elements by X-ray fluorescence fundamental parameter method

Two versions of the X-ray fluorescence fundamental parameter method are compared in the analysis of the materials that contain low atomic number elements (fluorine, oxygen, nitrogen, carbon, and boron). It is shown by the examples of carbon and oxygen that, in using the classical version, the account of C and O atom ionization by photo and Auger electrons of the irradiated sample is obligatory. A change to absolute intensities in combination with the regression approach makes the method more flexible. In particular, the computational modeling of analytical signals for elements with Z < 10 becomes possible without taking into account the ionizing effect of photo and Auger electrons when the contribution of these electrons to the fluorescence intensity changes insignificantly. The error of the analysis grows with an increase in the variation of this contribution. If the contributions for the test samples differ significantly, the computational modeling of the effect of photo and Auger electrons in the iterative process becomes necessary.     

Determination of calcium in uranium by X-ray fluorescence

Summary An X-ray fluorescence method for the analysis of calcium in uranium in the range of 20 to 500 ppm is described. U₃O₈ samples are mixed with boric acid binder and double-layer pellets are prepared. The pellets are analysed using Philips PW 1220 semi-automatic X-ray spectrometer. Calculated lower limits of detection are better than 5 ppm for calcium in uranium.

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Bestimmung von Calcium in Uran durch Röntgenfluorescenz

Zusammenfassung Ein Verfahren für den Bereich von 20–500 ppm wird beschrieben. Die U₃O₈-Proben werden mit BorsÄure als Bindemittel vermischt zu Doppelschicht-Tabletten gepre\t, die mit Hilfe eines halbautomatischen Philips PW 1220 Röntgenspektrometers analysiert werden. Die untere Nachweisgrenze liegt bei 5 ppm Ca.

     

Determination of gold by X-ray fluorescence methods

X-ray fluorescence methods for the determination of gold in silver beads and in hydrochloric acid solutions are described. These techniques may be applied to silver containing 0.2-5 % of gold and to solutions containing 0.004-0.1% of gold. Platinum, palladium, rhodium and indium do not interfere.     

Determination of iron(III) with salicylic acid by the fluorescence quenching method

The spectrofluorimetric determination of Fe³⁺ using salicylic acid as an emission reagent has been investigated by measuring the decrease of fluorescence intensity of salicylic acid due to the complexation of Fe³⁺–salicylic acid. An emission peak of salicylic acid, which is decreased linearly by addition of Fe³⁺, occurs at 409 nm in aqueous solution with excitation at 299 nm. The determination of the ferric ion is in the range 1×10⁻⁶–10×10⁻⁶ M Fe³⁺ (0.0558–0.558 μg/ml) and the detection limit is 5×10⁻⁸ M. The quenching effect of Fe³⁺ on the fluorescence intensity of salicylic acid may be considered on the basis of complexation between salicylic acid and Fe³⁺. The effects of foreign ions were investigated.     

Determination of platinum in ores by a combined fire assay—X-ray fluorescence method

A combined fire assay—x-ray fluorescence procedure for the determination of platinum in ores is described. Silver beads obtained by cupellation in the classical fire assay process are flattened to constant thickness before placement in the x-ray beam. A standard plot of platinum—silver intensity ratio versus platinum concentration is used to measure the platinum content of ore samples.     

Application of the emission-transmission method for overcoming matrix effects in non-dispersive x-ray fluorescence analysis

An emission-transmission method in X-ray fluorescence analysis, based on theoretical considerations, has been applied for eliminating matrix effects due to variations in the chemical composition of samples. The measurements have been carried out in so-called compact geometry, using¹⁵³Gd source of the primary radiation and a NaI(Tl) crystal (3″ in diameter, 2 mm thick). The element to be determined was antimony in a CaCO₃ matrix with various admixtures of CuO. A method of semitheoretical construction of nomograms has been introduced for the evaluation of the measurements. Six variants of the method are discussed, and a criterion permitting to find the most useful variant is given. The theoretical considerations have been confirmed by the experiments.     

Determination of technetium by total reflection X-ray fluorescence

The measurement of technetium in inorganic solutions is reported for the first time using total reflection X-ray fluorescence (TXRF). Sodium pertechnetate solutions eluted from decayed ⁹⁹Mo generators were efficiently excited with a silver-anode X-ray tube in a standard configuration. The technique has been developed to aid establishing the extent of stoichiometric relations between Tc and a ligand in organo-metallic compounds synthesized with diagnostic purposes for nuclear medicine. The precision attained was 5% and the detection limit achieved for Tc in inorganic solutions by TXRF at 1000 s was 0.039 μg/ml.     

The enhancement effect in non-dispersive X-ray analysis

A theoretical model of the enhancement effect in non-dispersive X-ray analysis is proposed. The considerations relate to a point source and detector localized in the same place (which is an approximation of the conditions of compact geometry). The results obtained in this work are different from those of other authors. Possibilities are suggested for the elimination of the influence of the enhancement effect on the results in non-dispersive X-ray fluorescence analyses.     

Determination of arsenic and zinc in tin oxide by X-ray fluorescence

Summary An XRF method to determine arsenic and zinc in high-purity tin oxide in the range of 10–1,000 ppm is described. The sample is pressed as a double-layer pellet and the analysis is carried out by using Philips PW-1220 X-ray spectrometer. Limits of detection are 13 ppm (As) and 8 ppm (Zn). Accuracy is better than 10% at a level of 50ppm; standard deviations are 8 and 9 % at this level.

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Bestimmung von Arsen und Zink in Zinnoxid mit Hilfe der Röntgenfluorescenz

Zusammenfassung Das beschriebene Verfahren eignet sich zur As- und Zn-Bestimmung im Bereich von 10 ppm–1000 ppm in Zinnoxid. Die Probe wird zu einer Doppelschichttablette gepreßt und die Analyse mit Hilfe eines Philips PW-1220 Röntgenspektrometers durchgeführt. Die Erfassungsgrenzen sind 13 ppm (As) bzw. 8 ppm (Zn). Die Genauigkeit ist besser als 10 % (50 ppm-Bereich); die Standardabweichung in diesem Bereich beträgt 8 bzw. 9 %.

     

Determination of zirconium and hafnium in solution by X-ray fluorescence spectrometry

The samples were introduced into the XRF spectrometer in ordinary flat bottom polyethylene bottles for the estimation of Zr or Hf in presence of one another in solution. By using high voltage (50 kV) and high current (50 mA) least limits of detection obtained were an order of magnitude better than other conventional analytical techniques. Relations of intensity to concentration in various concentration ranges have been determined and the results are compared with those of other analytical techniques.