Intensity Of Fluorescence Radiation Research Articles

X-ray fluorescent method for the analysis of trace elements in bio-materials with correction of the matrix effect.

A method for correcting the matrix effect by measuring the intensity of fluorescent radiation and its absorption by the sample material in the same x-ray optical scheme is proposed. The use of a complex secondary Ag-Ge emitter as a primary radiation source provides a low detection limit for a wide range of chemical elements from Ca (Z = 20) to Mo (Z = 42) in the K-series and from Cd (Z = 48) to Bi (Z = 83) in the L-series. To measure the absorption, the radiation of an additional secondary emitter is used, of which the wavelengthcan be varied in the range from 0.633 to 3.38 Å, depending on the measured impurity. An example of determining the mass fraction of an impurity in a sample of unknown composition prepared from a mixture of state standard samples of aqueous solutions is given. The x-ray optical scheme was assembled on the basis of a portable Energy Dispersive X-ray Fluorescence(EDXRF) spectrometer. The method is designed to study materials with a base consisting of chemical elements with a low atomic number.

Determination of heavy metal ions by energy dispersive X-ray fluorescence spectrometry using reduced graphene oxide decorated with molybdenum disulfide as solid adsorbent

Reduced graphene oxide (rGO) decorated with molybdenum disulfide (MoS2) was synthesized by hydrothermal method. The physicochemical properties of the nanoadsorbent were characterized by different spectroscopic techniques, namely Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). MoS2-rGO was used as a solid nanoadsorbent in a dispersive micro-solid phase extraction (DMSPE) for the preconcentration of heavy metal ions from different types of waters prior to energy dispersive X-ray fluorescence spectrometry (EDXRF) determination. To optimize extraction process parameters such as sample pH, contact time and sample volume, were examined. The determined adsorption capacities for Cr(III), Co(II), Ni(II), Cu(II), Zn(II) and Pb(II) ions were 242, 112, 145, 417, 550 and 498 mg g−1, respectively. Under optimal conditions (pH = 6.5, sample volume 50 mL, and sonication time of 10 min) the calibration curves showed linear response between analytes concentration and intensity of fluorescence radiation in the range 1–200 ng mL−1 for Cr(III), Cu(II), Zn(II) and Pb(II) ions, and 1–100 ng mL−1 for Co(II), Ni(II) ions. The limits of detection were 0.11, 0.12, 0.10, 0.07, 0.08, and 0.09 ng mL−1 for Cr(III), Co(II), Ni(II), Cu(II), Zn(II) and Pb(II), respectively. The precision of the method determined at two concentration levels, e.g. 2 and 20 ng mL−1 varied from 3% for Cu(II) to 5.1% for Co(II) and 1.4 for Cu(II) to 3.6% for Ni(II), respectively. The DMSPE-EDXRF procedure was suitable for determination of target analytes at ultra-trace level even in high salinity samples. The accuracy of the method was proved using certified material NIST 1640a (Trace elements in natural water). The ‘greenness’ of the procedure was calculated with the Analytical Eco-Scale tool.

Uncertainties in Secondary Fluorescence Correction in EPMA

Secondary fluorescence is an inevitable effect that has to be taken into account in any algorithm for quantitative electron probe microanalysis (EPMA) as an additional correction. Moreover, secondary fluorescence worsens spatial resolution of EPMA, as discussed once more in two recent papers. Secondary fluorescence is excited both by characteristic radiation and by the X-ray continuum. In most cases the correction is small. There are, however, cases, e.g. the determination of low heavy metal concentration in a light matrix, where the contribution of secondary fluorescence exceeds 10% of the measured X-ray line intensity. For secondary fluorescence correction the measured X-ray line intensity has to be divided by the correction factor (1+I_flchar/I_p +I_flcont/I_p )≈(1+I_flchar/I_p )(1+I_flcont/I_p ) in order to get those intensity I_p, which is excited only by the primary electrons and enables the determination of specimen composition. I_flchar and I_flcont mean the calculated characteristic and continuums fluorescence intensities. In order to get the intensity of fluorescence radiation, the absorption of the exciting radiation in the specimen, the photoionization probability and the self-absorption of the emitted line must be calculated. This can be performed in a straightforward way. The critical quantity is the X-ray yield of the exciting atoms in case of fluorescence by characteristic radiation and the bremsstrahlung yield of the specimen in case of continuum fluorescence. In the former case it is reasonable to apply the same physical model to calculate I_flchar and I_p.

Matrix Effects under the X-ray Fluorescence of Glass Based on Lithium Tetraborate

The experimental dependences of the X-ray fluorescent radiation intensity on the concentration of silicon dissolved in glass based on lithium tetraborate are determined. The experimental dependences are compared to the calculated ones. It is shown that both the experimental and the calculated dependences are described by the same type of equation.

Liquid-phase microextraction as an attractive tool for multielement trace analysis in combination with X-ray fluorescence spectrometry: an example of simultaneous determination of Fe, Co, Zn, Ga, Se and Pb in water samples

In recent years, liquid-phase microextraction (LPME) has become one of the most valuable techniques for the preconcentration and separation of trace and ultratrace elements. LPME can be combined with an atomic technique which requires only a few microlitres of liquid to perform a measurement, e.g. electrothermal atomic absorption spectrometry. In this study, combining LPME with X-ray fluorescence spectrometry (XRF), a dried-spot technique is proposed. Since the X-ray beam can be focused on a small spot size and simultaneously LPME produces a very small drop of a volume ranging from 2 to 30 μL, the combination of these two techniques is a very promising tool for multielement trace and ultratrace analyses. The present research was performed using dispersive liquid–liquid microextraction (DLLME) with APDC as a chelating agent. Nevertheless, any LPME technique, e.g. single-drop microextraction (SDME), can be applied in combination with XRF. Because XRF measurement follows the microextraction, deposition and drying of the small drop, the influence of the diameter of the dried residue on the intensity of fluorescent radiation is discussed in detail. Pipetting and spray-on techniques are proposed for the deposition of the small drop onto the substrate (membrane filter or Mylar foil). Under the optimized conditions, the detection limits were 2.8, 1.6, 2.5, 1.7, 2.1 and 4.1 ng mL−1 for Fe, Co, Zn, Ga, Se and Pb, respectively, with a preconcentration factor of 250 for 5 mL of the water sample.

Influence of X-ray tube spectral distribution on uncertainty of calculated fluorescent radiation intensity

The relative radiation intensity ( R i ) defined as fluorescent radiation intensity of analyte in specimen to fluorescent radiation intensity of pure element or compound, e.g., oxide is used in calculation in both fundamental parameter methods and in theoretical influence coefficient algorithms. Accuracy of calculated R i is determined by uncertainties of atomic parameters, spectrometer geometry and also by X-ray tube spectral distribution. This paper presents the differences between R i calculated using experimental and theoretical X-ray tube spectra evaluated by three different algorithms proposed by Pella et al., Ebel, and Finkelshtein–Pavlova. The calculations are performed for the most common targets, i.e., Cr, Mo, Rh and W. In this study, R i is calculated for V, Cr, Mn, Fe, Co, Ni, Cu and Mo in steels as an example. The differences between R i calculated using different X-ray tube spectrum algorithms are presented when pure element standard, multielement standard similar to the analyzed material and one pure element standard for all analytes is used in X-ray fluorescence analysis. The differences between R i for intermediate-thickness samples (and also for thin films) and for X-ray tube, which ran for many hours, are also evaluated.

Laser-spectroscopic methods for diagnostics of electric fields in plasma (review)

Methods for measuring electric fields in plasma based on laser spectroscopy and the Stark effect on Rydberg atomic levels and rotational levels of polar diatomic molecules are considered. These methods feature high sensitivity and allow measurements of both static and alternating electric fields in plasma with high temporal and spatial resolutions. It is shown that laser-spectroscopic techniques also allow measurements of relatively weak magnetic fields in plasmas of facilities with magnetic plasma confinement. Such measurements can be based on the use of Stark splitting of highly excited energy levels of hydrogen atoms in a Lorentzian electric field, while a decrease in the fluorescent-radiation intensity at the Balmer-α line can serve as a recorded signal.

Structural and spectral analysis of thin films of FeCr alloys

A structural X-ray analysis and an analysis of chemical composition using X-ray fluorescence have been carried out for thin films of FeCr alloys of different compositions deposited onto glass substrates in a high vacuum. A nomogram which enables the determination of the percentage composition and the thickness of thin films in relation to the intensity of fluorescence radiation has ben derived. Some electrical parameters of the films have also been measured and quantitative changes of these parameters corresponding to films of different crystalline structures and alloy phases have been found.

Über die berücksichtigung von streuanteilen bei der messung von röntgenfluoreszenzintensitäten

A theoretical treatment of the contributions of scattered X-rays to the intensity of fluorescent radiation is given. These contributions are caused as well by scattering of white X-rays as by scattering of characteristic X-rays. The amount is calculated for different elements and thin films. From these considerations follows an increase of the X-ray fluorescence intensity of approximately 1 per cent for bulk materials and up to 30 per cent for thin films. Since for a quantitative analysis reference samples are needed, values of the concentration or mass per unit area are found, which are higher or lower as compared with the true value, depending on the amount of fluorescent X-rays caused by scattering.

Metallurgical Applications of X-Ray Fluorescent Analysis

Techniques are described for fluorescent analysis using an x-ray Geiger counter goniometer. Consideration is given to the influence of potential variations, specimen preparation, and thickness of the diffracting crystal. The observed intensity of fluorescent radiation from a number of common commercially pure metallic elements was compared under a constant primary radiation that can be closely maintained in practice. Intensities of fluorescent spectra were measured on constituents of Fe-Ni, Fe-Cr, and Fe-Ni-Cr alloys. Calibration curves correlating line intensity with weight percentage are included for binary Fe-Ni and Fe-Cr alloys. The thickness beyond which the fluorescent intensity becomes constant has been determined for pure iron, nickel, and chromium. Up to the above thickness for each element an empirical plot of fluorescent intensity against thickness of layer has been established. These empirical plots can be applied to measure the thickness of very thin coatings. Illustrations are given indicating the applications of the fluorescent analytical technique to the study of oxidation and diffusion processes in metallic systems. An aluminum holder is used for analyzing small quantities of powder derived from chemical or electrolytic extraction of certain phases from alloys. Fluorescent analysis on the extracted phase supplements the diffraction data when a wide solid solubility exists.