Fundamental Parameters Program Research Articles

A maximum information utilization approach in X-ray fluorescence analysis

X-ray fluorescence data bases have significant contradictions, and inconsistencies. We have identified that the main source of the contradictions, after the human factors, is rooted in the signal processing approaches. We have developed signal processors to overcome many of the problems by maximizing the information available to the analyst. These non-paralyzable, fully digital signal processors have yielded improved resolution, line shape, tailing and pile up recognition. The signal processors account for and register all events, sorting them into two spectra, one spectrum for the desirable or accepted events, and one spectrum for the rejected events. The information contained in the rejected spectrum is mandatory to have control over the measurement and to make a proper accounting and allocation of the events. It has established the basis for the application of the fundamental parameter method approach. A fundamental parameter program was also developed. The primary X-ray line shape (Lorentzian) is convoluted with a system line shape (Gaussian) and corrected for the sample material absorption, X-ray absorbers and detector efficiency. The peaks also can have, a lower and upper energy side tailing, including the physical interaction based long range functions. It also employs a peak and continuum pile up and can handle layered samples of up to five layers. The application of a fundamental parameter method demands the proper equipment characterization. We have also developed an inverse fundamental parameter method software package for equipment characterisation. The program calculates the excitation function at the sample position and the detector efficiency, supplying an internally consistent system.

The necessity of maximum information utilization in x‐ray analysis

AbstractThere are significant discrepancies in the experimental data needed in the analysis of x‐ray spectra. Examination of the data in detail shows that they often contradict simple logic, elemental arithmetic, even parity and angular momentum conservation laws. We have identified that the main source of the problems, other than the human factor, is rooted in the signal processing electronics. We have developed a line of fully digital signal processors that not only have excellent resolution and line shape but also allow proper accounting. We achieve this by processing all events and separating them into two or more spectra where the first spectrum is the accepted or good spectrum and the second spectrum is the rejected spectrum. It is not enough to know that an event was rejected, and increment the input counter—it is necessary to know what happened and why, whether it was pure noise, a noisy or disturbed event, a true event, or any pile up combination of the above in order to account properly for true event input rate and processor dead time. The data processing methodology cannot be reliably established on the partial and fractional information offered by other approaches. The availability of all the events allows one to see the other part of the spectrum. To our surprise the total information explains many of the shortcomings and contradictions of the x‐ray database. We call this a maximum information utilization approach in signal processing. Also a fundamental parameter x‐ray fluorescence analysis program (CSX‐XRF) has been developed to utilize all the information offered by the signal processor. The fundamental parameter method is only as good as the database it uses and the description of the x‐ray fluorescence analysis system. This latter poses significant difficulties, and to ease the demand we have developed an inverse fundamental parameter program package for x‐ray tube based equipment characterization. Copyright © 2009 John Wiley & Sons, Ltd.

Determination of Ti, Zn, and Pb in lead-based house paints by EDXRF

Energy dispersive X-ray fluorescence (EDXRF) spectrometry with a fundamental parameters program was used to non-destructively determine the relative concentrations of Ti, Zn, and Pb in lead-based house paints manufactured by National Lead (Dutch Boy), Sherwin-Williams, DeVoe, Davis of Baltimore, Benjamin-Moore, Eagle-Picher, Lowe Brothers and by several lesser known companies. The relative concentrations of Ti, Zn, and Pb in the paints were plotted three dimensionally which showed that the major paint manufacturers can be discriminated and identified. Spectral digital libraries were constructed from our manufacturers' paint reference collection to determine who produced the paint in a homeowner's paint chips. The analytical method discussed in this paper is well suited for the analyses of paint chips that have separated naturally from the substrate.

Correction method for the matrix effect in x-ray fluorescence spectrometric analysis

With the help of a fundamental parameter program, the matrix effect of multi-component complex samples and the composition of each element’s X-ray fluorescence intensity were calculated. A mathematical model for correcting the multi-component matrix effect was deduced theoretically. It provides two methods for calculating theoretical influence coefficients α and β. The correction model and the influence coefficient introduced in this paper have clear and definite physical meanings. They gave satisfactory results when utilized in analyzing stainless-steel samples. The results also indicate that the effect of tertiary fluorescence cannot be neglected in some cases. From the results of comparison experiments, it is concluded that the tertiary fluorescence effect must be taken into consideration while analyzing Cr in a steel sample with a high concentration of Ni. © 1998 John Wiley & Sons, Ltd.

Determination of lead concentration and film thickness in electroluminescent calcium sulfide thin films by X-ray fluorescence

For the analysis of electroluminescent thin films, X-ray fluorescence (XRF) provides a convenient method as both the concentration of the dopant and the film thickness can be determined rapidly and non-destructively. An XRF method for the determination of thickness and lead concentration in lead doped calcium sulfide thin films was developed. Calibration standards made of polyvinyl alcohol and gelatin as well as filter paper standards were used. In addition, the applicability of a fundamental parameter program UniQuant was investigated. For comparison, the concentrations of lead and calcium were determined after dissolution by atomic absorption spectrometry. Generally, the correlation between the different methods excluding the use of filter paper standards was satisfactory. When the dopant concentration was very low or very high, however, the fundamental parameter program yielded best results. Determination of thicknesses by XRF was made by comparing the sulfur K α intensities of the sample and those of a zinc sulfide standard. A correction factor for molar masses and densities was applied. The thicknesses obtained were compared to those measured with a profilometer after etching and the deviations were found to be less than 10%.

Quantitative multi-element analysis of denitration ceramics by X-ray fluorescence spectrometry

A procedure for the determination of C, Na, Mg, Al, Si, S, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Zn, Ga, As, Se, Zr, Mo, Sb, La, Tl, Pb, and Th based on two X-ray fluorescence (XRF) methods and combined with instrumental neutron activation analysis and infrared combustion analysis was developed to give quantitative analytical information on a large number of ceramic catalyst samples used for the denitration of flue gas from a coal-fired power plant. A special sample preparation method for small amounts (20 mg) of powder was used for XRF analysis. Two types of synthetic calibration standards were prepared: (1) single-element standards with an Fe2O3 matrix for the minor elements and limited concentration ranges (nine elements) and (2) multi-element standards with simulated matrices for the major elements and large concentration ranges (ten elements). The quantitative evaluation of minor elements was performed with a linear calibration graph. Major elements were determined using the so-called fundamental parameters program.

Use of Scattered Secondary Target Radiation in EDXRF Analysis: A Fundamental-Parameter Method for Matrix Correction

AbstractA new fundamental-parameter program has been developed which corrects for light element absorption based on the mean atomic number of the sample. The mean atomic number, in turn, is determined from the Compton/Rayleigh scatter intensity ratio. The program is quite flexible with regard to the number and the type of standards which may be used. The accuracy and precision of the method has been evaluated with several geological and biological standards. The results are in good agreement with those obtained by some other methods (CEMAS, XRF-11).

Fundamental Parameters vs. Multiple Regression Calculations for the Determination of Europium in Oxide Catalyst Supports by XRF

AbstractFundamental parameters calculations are used for the analysis of europium in the concentration range of 0.1 WT% to 30.0 WT% in the oxidic catalyst supports alumina, calcia, magnesia lanthania, and thoria. The precision and accuracy of this method is dependent on how the sample matrix is defined in the fundamental parameters program and the number and concentration of the standards used. Results comparable to the multiple regression method are obtained when the matrix stoichiometry is defined as Eu2O3 and the catalyst oxide (i.e. Al2O3 etc). It is also necessary to use standards which bracket the europium concentration in the samples. When these conditions are met, the results are comparable to those obtained from a ten point multiple regression calibration curve but with a considerable saving of standard preparation time. The precision is better than ±2% relative. The % relative difference between the fundamental parameters and multiple regression results is also 2%. Data is presented which illustrates the effect of defining the sample stoichiometry in the XRF11 computer program.

Energy Dispersive XRF Analysis of Lubricating Oil Additives with Secondary Target Excitation and the EXACT Fundamental Parameters Program

The need for rapid and accurate analysis of lubricating oil additives is firmly established by the petroleum industry. The application of energy dispersive X-ray fluorescence spectrometry techniques to this analysis is a valuable aid in achieving reliable and fast quality control of these product types.Due to the large concentration variations possible for the elements of interest within these materials (principally Zn, Ca, P, S at 0-20%), interelement effects can become significant. In order to correct for interelement effects, historical XRF methods have relied on a large number of standards for each element to be determined or matrix matching with standards closely bracketing the unknown sample concentrations.

X-Ray Fluorescence Analysis of Stainless Steels and Low Alloy Steels Using Secondary Targets and the Exact Program

Exact is a mini-computer based fundamental parameters program which is utilized for matrix corrections in energy-dispersive X-ray analyses. We have previously shown this technique to work well with radioactive sources. However, due to the limited selection of isotopic sources available and their inherent low X-ray flux, we have investigated the use of Fe, Sn, and Dy secondary-targets as sources of monochromatic X-rays. Results to date indicate that the secondary-targets provide X-ray radiation which has sufficient monochromaticity for our technique to remain valid.