Development of the Method of Calibration Equations for the X-Ray Fluorescence Analysis of Multicomponent Samples in the Presence of Undetectable Elements

New calibration equations are proposed based on the use of intensity ratios of spectral lines and peaks of coherently and incoherently scattered characteristic radiation of an X-ray tube. Prospects for their application to the X-ray fluorescence analysis of samples containing undetectable light elements are shown. The proposed method ensures high precision of determination and performance of analysis in the lack of adequate reference samples. The method was tested on an example of analysis of standard samples of bronze and samples of iron oxide materials.     

Influence of the distance between a spectrometer and sample on the intensity of X-ray fluorescence

Expressions for calculating the extreme point coordinates of focal spots of X-ray tubes and a detector’s sensitive area are found. These coordinates are used in calculations of the sample area. The dependence of the X-ray fluorescence intensity on the distance between a spectrometer and an analyzed sample is studied experimentally. The intensities of the FeK _α spectral lines in iron-containing materials are calculated at different geometric parameters of a spectrometer. It is found that the distance between a sample and detector at which the maximum of the measured intensity is observed depends on the size and position of the detector and X-ray tube collimators, as well as on the relative position of the X-ray tube and detector. Recommendations on how to achieve the maximum intensity of X-ray fluorescence are proposed. The results of the present work can be used for the development of X-ray fluorescence analysis techniques applicable for free-flowing materials directly in technological processes.     

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。     

A correction method of matrix,density and thickness effects in thin samples analysed by X-ray fluorescence spectrometry

This paper deals with X-ray fluorescence spectrometry of powdered materials deposited on collection filters. The general applicability of this method is limited because the spectral response is affected by sample density and thickness and interelement effects may occur due to the specimen composition.The present work is aimed at contributing to the solution of the above mentioned problems, and reports a mathematical correction method which changes fluorescence intensity measurement data into fluorescence intensity values free from density and thickness effects. The correction of the thickness effect was obtained by overlapping the powder sample with a standard pellet containing some reference elements.The method allows the evaluation of the thickness of the unknown samples by measuring the intensity decrease of the X-ray fluorescence radiation coming from the reference pellet and passing through the unknown sample. These data are used to correct the intensity fluorescence values of the unknown samples.A computer program to elaborate spectral data by means of different and selected mathematical algorithms was set up.     

Sources of Error in Total Reflection X-Ray Fluorescence Analysis and Error Correction Using the Internal Standard Method

An analytical equation is proposed for the fluorescence intensity excited in total reflection X-ray fluorescence analysis. Errors in the results of analysis of solutions of hair samples caused by the mutual influence of elements and by the nonuniformity of the distribution of the material in the emitter are quantitatively estimated. It is shown that these effects are small. They can be efficiently corrected using the internal standard method, provided the difference between wavelengths of the compared lines is small. Otherwise, a decrease in the systematic error is insignificant. Experiments confirmed the theoretical conclusions.     

Filtration of Amplitude Spectra for Reducing the Background Level in X-Ray Fluorescence Analysis

The formation of a background signal in the X-ray fluorescence equipment based on the Soller and Johansson X-ray optics was considered. It was noted that the loss peak arising in the detector should be taken into account. It was proposed that the filtration of the amplitude spectrum coming from the detector to the recording system be used in the scheme with the Johansson crystal. In this method, the intensity of the analytical background can be reduced by several times at a constant level of the analytical signal.     

Substitution–dilution method to correct the matrix effect in multi-element quantitative analysis by X-ray fluorescence

A mathematical model based on the dilution–addition method (DAM) for multi-elemental analysis using an X-ray fluorescence technique is proposed. The conditions for sample preparation do not require both the unknown and standard samples to be similar in composition and mineralogy, and the unknown sample is replaced quantitatively by the standard sample, hence the denomination substitution–dilution method (SDM). This method makes it possible to correct the matrix effect in multi-elemental quantitative analysis by X-ray fluorescence for each analyte. The proposed model presents hyperbolic behaviour of the experimental data when the X-ray fluorescence intensities are represented versus the substitution factor (h) for each analyte. After calculating the A/B parameter relations, which depend on the X-ray fluorescence intensity of each analyte (I_i^ns) and the substitution factor (h) and determining the analyte concentration in the multi-element standard sample (C_i^p), it is possible to calculate the analyte concentration in the multi-element unknown using an algorithm suggested for this purpose. This work studies the substitution–dilution phase proposed in the method, and the factors arising from incorporation of the standard and diluent are established according to the nature of the samples and the modifications. These factors make it possible to establish the experimental interval of analyte concentration, generally narrow, which corresponds to a section of the hyperbolic function which is so short that it can be accepted as linear. This linear model can be accepted for a wide variety of samples with a diluent/sample ratio greater than 10. The proposed linear method provides satisfactory results which are comparable to those calculated by applying the hyperbolic method. The proposed method (SDM) has been applied to two different types of matrices, a binary alloy (without diluent, using the hyperbolic model) and a geological sample (with diluent, using both hyperbolic and linear models). In all cases the results were satisfactory.     

基于L-半胱氨酸修饰的锰掺杂ZnS量子点应用于叶酸测定

以L-半胱氨酸为表面修饰剂制备了稳定性和水溶性均优的ZnS∶Mn2+纳米晶,并应用于叶酸的检测。在pH 7.4的KH2PO4-Na2HPO4 缓冲溶液中,叶酸的加入使ZnS∶Mn2+体系的荧光发生猝灭,荧光强度的变化与叶酸浓度呈良好的线性关系,其线性范围为1.0×10-6~7.0×10-5 mol?L-1 （4.4×10-4~3.1×10-2 g?L-1）,方法检出限为9.6×10-7 mol?L-1 （4.2×10-4 g?L-1）。该方法用于叶酸片剂和健康人尿液中叶酸的测定,结果满意。采用荧光光谱、紫外可见吸收光谱及X-ray光谱等研究了ZnS∶Mn2+纳米晶及其水溶液的特性,通过热力学参数对叶酸测定的可能机理进行了探讨。     

A mathematical model based on the limit dilution method to obtain linear calibration curves which eliminate the matrix effect in quantitative analysis by X-ray fluorescence

We propose a mathematical model from an analytical application viewpoint inspired in the limit dilution method. The theoretical development of the model and its results are given. The model shows that there is a linear relation between the inverse of fluorescence intensity and the inverse of the dilution factor; each analytic system (sample, diluent and analyte) is characterised by a general linear function which is easily obtained. The analytical applications arising from this linearity are of great importance in X-ray fluorescence analysis. The following immediate applications are proposed: direct procurement of the total correction factor Y/H, rapid calculation of the fluorescence intensity of the analyte in a sample (I_i^s) and direct calculation of the corrected fluorescence intensity (I_i^sF). The suggested model makes it possible to deduce a linear function between the fluorescence intensity of the analyte and the analyte concentration in successive dilutions of a standard; this straight line behaves as a calibration curve with direct application in X-ray fluorescence analysis. The proposed model may be applied to complex samples of geological origin, with elimination of the matrix effect. The results obtained in the determination of Ca, K, Fe and Ti in a standard soil show complete agreement with the certified reference values with a relative error about 0.5%, even using a standard shale with very different chemical composition as reference sample.     

High-sensitivity X-ray fluorescence analysis of solutions with the use of a sorption accumulation microsystem

A mass-transfer kinetic model is proposed for an embedded sorption accumulation microsystem based on polycapillary structures to be used in the developed X-ray fluorescence analyzer with preconcentration. The model is used to substantiate a kinetic method for high-sensitivity X-ray fluorescence determination of elements in multicomponent solutions. With the use of this model, experimental data on X-ray fluorescence spectra are analyzed and kinetic and equilibrium parameters are found for the sorption of copper, nickel, manganese, iron, and zinc on the selective DETATA sorbent.     

About the dependence of the intensity of X-ray spectra of elements on their concentrations expressed in atomic and mass percents

The consideration of the classical physical fundamentals of X-ray spectrometry suggests that the properties of X-ray spectra of elements are determined by their atomic number rather than atomic weight. The intensity of X-ray spectra is determined by the number of excited atoms rather by their mass. However, in the middle of the 20th century, the dependence of intensity on the mass concentration of elements was introduced without any physical grounds. The paper presents physical, analytical, and metrological evidences for the idea that this dependence does not correspond to a real physical process. It results in distorted calibration characteristics and extra errors and hinders the development of a method of universal (for all element systems) quantitative X-ray fluorescence analysis instead of specific procedures with empirical parameters for each particular system. The dependence on atomic concentrations eliminates these difficulties.     

铝青铜合金样品的X射线荧光光谱分析

建立了X 射线光谱测定铝青铜系列铜合金中Al、Mn、Fe、Si、Ni、Zn、Sn和Pb 8种元素的方法,探讨电流、电压对荧光强度的影响,基体效应校正采用基本参数法.用该方法对实际样品进行分析,分析结果与化学法分析结果相吻合.各元素测定结果的相对标准偏差为0.10%-5.56%(n=10).     

Synthesis and Analysis of Tm3+ Doped YF3 Upconversion Luminescent Nano-materials

<正>Upconversion(UC)phosphor Tm~(3+)doped YF_3 nano-crystals were prepared by hydrothermal method under different conditions and characterized by Field Transmission electron microscopy(TEM),Scanning electron microscopy(SEM)and X-ray diffraction(XRD).Their UC luminescence properties were studied by fluorescence spectrophotometer with 980 nm diode laser excitation,and impact of different grain sizes and morphology on the UC luminescence intensity was discussed.The fluorescence decay lifetime was calculated by Multi-exponential function fitting method.Results show that UC emission intensity was enhanced with the reduction of grain size,and the decay lifetime is 0.60 us.     

Precise non-destructive X-ray fluorescence method for uranium and thorium concentration measurements

A precise non-destructive radioisotope X-ray fluorescence method for uranium and thorium concentration measurements was developed. A beta-emitting⁹⁰Sr−⁹⁰Y source was used for excitation of characteristic X-ray lines. It is proved that the beta-excited X-ray fluorescence method (in spite of the significant bremsstrahlung intensity) has essential advantages for analysis of high concentrations of U and Th, characteristic for nuclear power cycle materials, because of the higher sensitivity of the method. (3% changes of the intensity per 1% change of the concentration.) Portable semiconductor or scintillation detectors and multichannel analysers are used for detection of analytical lines. The accuracy achieved by this method is 0.2–0.3% for 15 minutes measurement and 0.1 mCi activity of the source. This work was performed under contract with the International Atomic Energy Agency, Vienna.     

The use of the ratios of intensities of spectral lines for X-ray fluorescence analysis of metal alloys and oxide materials

An X-ray fluorescence analysis technique is proposed, which is based on using ratios of intensities of spectral lines. The technique includes performing calculations for evaluation of calibration equations, which allows using few reference samples or carrying out standardless analysis, if necessary. That parameters of the calibration equations depend linearly on concentrations of disturbing elements allows one to simplify taking their influence into account. To apply the developed technique to analysis of samples containing a significant amount of undetectable light elements, a use of a dependence of intensity ratio of the characteristic radiation of the X-ray tube’s anode, coherently and incoherently scattered by a sample, on a total content of undetectable elements is proposed. The technique’s adequacy is demonstrated by analysis of standard steel samples, metal cuttings and iron-ore materials.     

The determination of Fe,Zn and Pb in Zn-Pb ores by energy-dispersive X-ray fluorescence method

Energy dispersive X-ray fluorescence method for the determination of iron /3.5–26% of Fe/, zinc /0.5–9% of Zn/ and lead /0.05–5% of Pb/in zinc-lead ores containing arsenic has been worked out. In order to eliminate the interelement effect intensity correction equation had been proposed. The relative standard deviation of the determination varies from 3.6 to 9.2% depending on the element.     

CPFX-Al3+-CTMAB体系的荧光特性及环丙沙星的测定

研究了不同表面活性剂对环丙沙星（ciprofloxacin,CPFX）-Al^3＋体系荧光特性的影响,发现十六烷基三甲基溴化铵（CTMAB）对该体系有显著的增敏作用,系统研究了CPFX—Al^3＋—CTMAB反应体系的荧光特性,利用这一反应体系,建立了简单、快速、灵敏的测定环丙沙星的荧光方法,选择了最佳实验条件,并用于环丙沙星片剂和软膏的测定。     

Energy dispersive X-Ray fluorescence determination of thorium in phosphoric acid solutions

Energy dispersive X-ray fluorescence studies on determination of thorium (in the range of 7 to 137 mg/mL) in phosphoric acid solutions obtained by dissolution of thoria in autoclave were made. Fixed amounts of Y internal standard solutions, after dilution with equal amount of phosphoric acid, were added to the calibration as well as sample solutions. Solution aliquots of approximately 2–5 µL were deposited on thick absorbent sheets to absorb the solutions and the sheets were presented for energy dispersive X-ray fluorescence measurements. A calibration plot was made between intensity ratios (Th Lα/Y Kα) against respective amounts of thorium in the calibration solutions. Thorium amounts in phosphoric acid samples were determined using their energy dispersive X-ray fluorescence spectra and the above calibration plot. The energy dispersive X-ray fluorescence results, thus obtained, were compared with the corresponding gamma ray spectrometry results and were found to be within average deviation of 2.6% from the respective gamma ray spectrometry values. The average precision obtained in energy dispersive X-ray fluorescence determinations was found to be 4% (1σ). The energy dispersive X-ray fluorescence method has an advantage over gamma ray spectrometry for thorium determination as the amount of sample required and measurement time is far less compared to that required in gamma ray spectrometry.     

X射线荧光光谱法测定石化产品中的总氯

采用能量色散X射线荧光光谱法测定石化产品中的总氯含量。采用钛靶X射线管及高分辨率硅漂移半导体检测器,在管电压10 kV、管电流0.3 mA的最佳实验条件下,氯含量在30~1 000 mg/L范围内与荧光强度呈良好的线性关系,相关系数大于0.999,检出限为6.24 mg/kg。利用该法对90#石油醚、120#溶剂油、润滑油、基础油等中的氯含量进行测试,测定结果与GB/T 18612–2011方法相一致。该方法可以作为测定石化产品总氯含量的新的试验方法。