Analysis of cast iron by x-ray fluorescence spectrometry

It is shown that a wide range of cast irons can be analysed on one calibration if the sample surfaces are prepared to a mirror finish with diamond paste. Polishing the samples with any abrasive material results in preferential removal of the softer constituents from the sample matrix. If coarser abrasives than diamond paste are used, the increased depth of the introduced sample inhomogeneity leads to unacceptable error limits for the determination of light elements.     

Dilution method in x-ray fluorescence spectrometry

The Lachance-Traill method was modified to a dilution method that retains all the advantages of the original method plus it enables the determination of as many elements as one pleases and is far simpler mathematically. The method had been tested with determination of copper, molybdenum, zinc, and arsenic in copper intermediates.     

Multivariate data analysis for x-ray fluorescence spectrometry

A multivariate data analysis procedure that uses singular value decomposition and the Ho-Kashyap algorithm is proposed to obtain calibration constants for x-ray fluorescence spectrometry. These calibration constants can be used to obtain results from experimental data by means of a simple dot product calculation. The method was tested on experimental data from the literature. Comparison of results showed that the method performs at least as well or better than the Rasberry-Heinrich method or its modifications. The method can be used to express calibration results obtained with a theoretically based program in such a way that they can be used conveniently in routine applications.     

Measurement of peak areas in energy-dispersive x-ray fluorescence spectrometry

An algorithm is outlined for the measurement of peak areas in spectra obtained by energy-dispersive x-ray fluorescence techniques. Each fluorescence line is assumed to be a pure Gaussian function. Initially, a calibration equation relating the full width at half maximum (FWHM) to the centre of the peak is set up. Then, in an unknown spectrum, the Gauss function parameters are found by a stepwise procedure making a non-linear minimization procedure redundant. First, the background is estimated and subtracted; then the peak centres are found, and the FWHM is given by the calibration equation, which relates FWHM to the position of the peak centre. Finally, the amplitudes are estimated from a set of linear equations. The reliability of the proposed algorithm was proved for a variety of samples. The method was compared with a non-linear x² minimization routine. Quantitative analysis of two standard reference alloys was accurate. Below 20 keV, a suitable FWHM calibration is obtained from a set of K_α lines. Above 20 keV, a set of K_β1,3 lines is recommended.     

Energy-dispersive x-ray fluorescence spectrometry of industrial paint samples

An energy-dispersive x-ray fluorescence method for the direct, simultaneous determination of major and minor elements in coatings is described. The method relies on the back-scatter/fundamental parameter concept and provides a general solution to matrix problems. The method has been implemented and verified on spectrometers based both on tube excitation and radioisotope excitation. Results demonstrating some performance characteristics are presented. Sample inhomogeneity problems that impede quantification of low-Z elements in some types of paint are discussed.     

Determination of total sulphur in coal by x-ray fluorescence spectrometry

A precise x-ray fluorescence method for the determination of sulphur in coat. The sample is mixed with calcium oxide and active carbon and is gradually heated to 900°C. After coding, lithium tetraborate and lead oxide are added and a prepared. The Pb M_α line is used as an internal standard for the KK_α line. The results for coal have a relative standard deviation of approximately 1% and exhibit.     

Multi-element analysis of urine by energy-dispersive x-ray fluorescence spectrometry

For multi-element analysis of human urine, 25-ml samples doped with yttrium as internal standard are evaporated gently and then ashed up to 460°C overnight. The residue is pelletized and analysed by energy-dispersive x-ray fluorescence. Acid addition to facilitate the digestion is not mandatory. Recoveries are nearly quantitative for traces of Fe, Ni, Cu, Zn and Sr, to a lesser extent for lead, but not for arsenic or selenium. The standard deviation per measurement is typically around 6%. The detection limits are such that some 10 elements can be determined simultaneously in normal urine, and possibly more in cases of importance to toxicology or industrial hygiene.     

Determination of trace metals in water using x-ray fluorescence spectrometry

A simple, rapid and accurate method for water analysis is proposed. The analytical procedure for the determination of Fe, Mn, Zn, Cu, Cd, As, Pb and Se in water in concentrations as low as a few ppM involves precipitation with a carrier of the metals by diethyldithiocarbamate (DDTC) or 1-(2-pyridylazo)-2-naphthol (PAN) and filitration through a Millipore filter. The precipitates collected on the filter disc are examined by X-ray fluorescence analysis. PAN is excellent for the determination of several metal ions at the ppM level, and DDTC can be used with tartrate as a masking agent if water samples contain large amounts of iron(III).     

Use of x-ray fluorescence spectrometry in ion-exchange studies of leach liquors

Equilibrium and kinetic studies of ion exchange of a complex leach liquor from coal ash, with strongly basic resins and a liquid ion exchanger are reported. The multi-component system was studied by determining the composition of the effluents and by non-destructive analysis of the loaded ion exchangers by XRF spectrometry. In the case of column operation, the elution processes were investigated by the same method, which was very appropriate for non-destructive monitoring of resin regeneration steps done repeatedly with the same resin sample.     

Determination of trace elements in the water cycle by total-reflection x-ray fluorescence spectrometry

The determination of trace elements in the various stages of the water cycle is very important. Economic procedures for multi-element determinations of trace elements in various matrices are needed. The applications of total-reflection x-ray fluorescence spectrometry in this general area are reviewed briefly, with examples relating to rain, river and sea waters, sediments, particulate matter and manganese nodules and crusts, as well as mussel tissue. Up to 25 elements can be determined; these are S, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Pb, Se, Rb, Sr, Y, Zr, Mo, Ag, Cd, Sb and Ba. Preliminary treatments of the various matrices are described. Accuracy checks by analysis of reference standards and by application of independent techniques are reported.     

Determining of trace metals in nuclear-grade uranium dioxide by x-ray fluorescence spectrometry

A method is described for the simultaneous determination of low concentration of Ca, Cr, Cu, Fe, Mn and Ni in nuclear-grade uranium dioxide by x-ray fluroescence spectrometry, without the use of chemical treatment. The lower limits of detection range from 2 μg g^?1 for nickel and manganese to 5 μg g^?1 for copper. Samples are prepared in the form of double-layer pellets with boric acid as a binding agent. Standards are prepared in a U₃O₈ matrix, which is more chemically stable than UO₂ and has similar matrix behaviour. The correlation coefficients for calibration curves are better than 0.999. Errors range from 2.4% for chromium to 6.8% for nickel.     

The determination of antimony in nodular cast iron by wavelength-dispersive x-ray fluorescence spectrometry

Antimony is determined in cast irons by wavelength-dispersive x-ray fluorescence spectrometry. Excitation and detection conditions are evaluated for the three most intense x-rays of antimony, i.e., the K_α, L_α and L_β lines. Standard samples were obtained by precise determination of the antimony content of some specimen cast irons by neutron activation analysis. Calibration graphs are linear from 0 to 200 mg kg^?1. The precision of the determination by means of the most sensitive Sb L_α line, using a chromium tube and a 5-min measuring time, ranges from 6% for samples containing 20 mg kg^?1 antimony, to 1% for samples containing 200 mg kg^?1.     

Standard-addition procedure for the determination of traces of lead in solid samples by x-ray fluorescence spectrometry

A standard-addition procedure for analysis of powdered solid samples by energy-dispersive X-ray fluorescence is described. Different amounts of the element to be determined are added to 4–6 specimens of the unknown sample. The spiked samples are prepared by mixing the powdered sample with an aqueous standard solution and drying the mixture. Homogeneously spiked samples are thus obtained with analyte and spike concentrations at the ppm level. The procedure has been investigated theoretically, and it is found suitable for the quantitative determination of lead at the ppm level. The accuracy of the technique for traces of lead has been tested on solid reference materials for the determination of lead. The quantitative results obtained compare well with those found by potentiometric stripping analysis.     

Preconcentration methods for the determination of trace elements in water by x-ray fluorescence spectrometry: Part 2. Interference studies

Seven methods for the preconcentration of fifteen elements for their subsequent measurement by x-ray fluorescence spectrometry have been evaluated for their susceptibility to interferences. A two-level factorial experimental design has been used, enabling an economical and meaningful comparison of the seven methods to be made. A scheme for rating the methods on the basis of the effect of several interfering species is proposed. Use of such a scheme has enabled an objective comparison of the methods considered to yield their relative ranks. It is also shown that spectral and chemical interferences can be discerned to some extent. Combination of the response rating proposed earlier and the interference rating schemes reported here gives rise to an overall comparison and rank for the methods, allowing an objective choice of the optimal method(s) to be made.     

The coprecipitation of an organophosphate fraction from harbour water for x-ray fluorescence spectrometry

The film x-ray fluorescence spectrum of a cobalt pyrrolidinedithiocarbamate carrier complex, precipitated in harbour-water samples, contains a previously unreported peak at the wavelength of the first-order K_α line of phosphorus. The coprecipitated phosphorus is an organophosphate fraction of biological origin, constituting approximately 10% of the dissolved organophosphorus in the waters.     

Preconcentration methods for the determination of trace elements in water by x-ray fluorescence spectrometry: Part 1. Response characteristics

Seven methods for the preconcentration of the elements Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Ag, Cd, Sb, Hg, Tl, and Pb in trace quantities from water have been evaluated. All the methods involved incorporation of the dissolved species into a solid resulting in large concentration factors and yielded samples well-suited to quantitation by either energy- or wavelength-dispersive x-ray fluorescence. On the basis of measurable criteria such as method sensitivity, linear range, and overall reproducibility, a scheme for ranking the seven methods is proposed. Application of such a rating scheme has enabled an objective, critical comparison of the available methods to be made on the basis of performance characteristics.     

Multi-element determination of dissolved heavy metal traces in sea water by total-reflection x-ray fluorescence spectrometry

Dissolved heavy metal traces in sea water are determined by a procedure based on total-reflection x-ray fluorescence spectrometry (t.x.r.f.). The trace elements are separated from the salt matrix by chelation with sodium dibenzyldithiocarbamate, selective chromatographic adsorption of the metal complexes onto a lipophilized silica-gel carrier, and subsequent elution of the metal chelates by a chloroform/methanol mixture. Aliquots of the eluate are then dispensed onto highly polished quartz sample carriers and evaporated to thin films for the t.x.r.f. measurements. The following elements can be determined: V, Mn, Fe, Co, Ni, Cu, Zn, Se, Mo, Cd, (Hg), Pb, and U. For 200-ml samples and a measuring time of 1000 s, detection limits of 5–20 ng kg^?1 are achieved for most of these elements. The limits are slightly higher for iron, zinc and mercury because of fluctuations in the blank values. Systematic investigations of the yield in the separation and enrichment step are described, and the procedure is characterized with regard to blanks, detection limits, precision and accuracy. The accuracy was checked with the aid of the sea-water reference material NASS-1. Some applications to Baltic sea water and open ocean waters are reported and discussed in terms of their information content.     

Determination of gold in geological samples by x-ray fluorescence spectrometry after extraction with tributyl phosphate

The behaviour of gold and elements impeding its x-ray fluorescence spectrometric (XRF) determination, namely zinc, lead and arsenic, was studied during their extraction from hydrochloric acid, nitric acid, and aqua regia solutions using tributyl phosphate as a solid extractant [SE(TBP)]. Extraction of gold from pulps after aqua regia leaching was found to be the most favourable approach for the quantitative and selective recovery of gold. The gold distribution ratio, D_Au, is ca. 10⁴ ml g^?1. For extraction from hydrochloric acid solutions the D_Au value also exceeds 10⁴ in the whole range of gold concentrations studied (10^?8?10^?4 M), but it decreases substantially with increasing extraction temperature, from 5 × 10⁵ ml g^?1 at 20°C to 9 × 10³ ml g^?1 at 70°C. An anomalously high distribution ratio of lead, D_Pb ≈ 10³ ml g^?1, was observed during extraction from hydrochloric solutions in the presence of chlorine. This could be explained by the formation of the chloro complexes of lead(IV). An XRF method for the determination of gold in natural samples was developed, which includes back-extraction of gold from SE(TBP) using a hot 0.025 M thiourea solution, providing a thin sample layer for secondary XRF. For 25 g of sample material the limit of determination is 10 ng g^?1 (10^?6%). The accuracy of the technique was checked using different reference materials. The results agreed within 10%.     

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.