Titanium dioxide determination in sunscreen by energy dispersive X-ray fluorescence methodology

Nowadays there are many sun-protection cosmetics incorporating chemical and/or physical UV filters as active ingredients and there are no official methods to determine these kinds of compounds in sunscreen cosmetics. The objective of this work is to estimate TiO₂ concentration, without sample preparation, employing a portable energy dispersive X-ray fluorescence (EDXRF), aiming to estimate the sun protection factor (SPF) due to the physical barrier in sunscreen composition, and also identify the metals present in the samples. A portable EDXRF system was used for the analysis of fifteen commercial samples. It was also prepared three formulations estimated in FPS-30 using TiO₂ at 5%. Quantification was performed using calibration curves with standards from 1 to 30%. The physical barrier contribution in the SPF, associated to Ti concentration, was determined for all samples. The presence of some elements, like K, Zn, Br and Sr was detected in the sunscreen, identifying chemical elements that were not cited in the formulations. Three commercial samples were analyzed for total SPF determination and the result shows that the measured value is 10% lower than the nominal one.     

Evaluation of analytical instrumentation. Part XX Instrumentation for energy dispersive X-ray fluorescence spectrometry

The reports of this series tabulate a number of features of analytical instruments that should be considered when making comparison between various systems. Scoring these features in a rational manner allows a scientific comparison to be made between instruments as an aid to selection. This is the XXth report of the series and deals with instrumentation for energy dispersive X-ray fluorescence spectrometry.     

能量色散X射线荧光光谱背景扣除方法的探讨

能量色散X射线荧光分析使得特征X射线的全能峰叠加在背景之上,针对能量色散X射线荧光谱线背景扣除算法的研究,简述了剥峰法和小波变换法扣除背景的原理,并将这两种方法用于对实际谱线的处理,取得了良好的效果.同时对两种方法的算法和处理效果进行了对比研究,表明剥峰法相对简单,而小波变换法需要考虑小波基和分解层次等的影响,但是对整个谱线的综合处理效果相对要好一些.     

Direct rapid analysis of trace bioavailable soil macronutrients by chemometrics-assisted energy dispersive X-ray fluorescence and scattering spectrometry

Precision agriculture depends on the knowledge and management of soil quality (SQ), which calls for affordable, simple and rapid but accurate analysis of bioavailable soil nutrients. Conventional SQ analysis methods are tedious and expensive. We demonstrate the utility of a new chemometrics-assisted energy dispersive X-ray fluorescence and scattering (EDXRFS) spectroscopy method we have developed for direct rapid analysis of trace ‘bioavailable’ macronutrients (i.e. C, N, Na, Mg, P) in soils. The method exploits, in addition to X-ray fluorescence, the scatter peaks detected from soil pellets to develop a model for SQ analysis. Spectra were acquired from soil samples held in a Teflon holder analyzed using ¹⁰⁹Cd isotope source EDXRF spectrometer for 200 s. Chemometric techniques namely principal component analysis (PCA), partial least squares (PLS) and artificial neural networks (ANNs) were utilized for pattern recognition based on fluorescence and Compton scatter peaks regions, and to develop multivariate quantitative calibration models based on Compton scatter peak respectively. SQ analyses were realized with high CMD (R² > 0.9) and low SEP (0.01% for N and Na, 0.05% for C, 0.08% for Mg and 1.98 μg g⁻¹ for P). Comparison of predicted macronutrients with reference standards using a one-way ANOVA test showed no statistical difference at 95% confidence level. To the best of the authors’ knowledge, this is the first time that an XRF method has demonstrated utility in trace analysis of macronutrients in soil or related matrices.     

Application of energy dispersive X-ray fluorescence spectrometry as multielemental analysis to determine the elemental composition of crumb rubber samples

The elemental content of different rubber samples was analyzed using different analytical methods (inductively coupled atomic emission spectroscopy and non-polarized energy dispersive X-ray fluorescent spectroscopy). A new application of energy dispersive X-ray spectrometry as an analytical method for the determination of elemental content of rubber samples was investigated. Control analyses were also carried out to compare the results by ICP-AES. In one hand four samples contained same quality of elements (Mg, Si, P, S, Ca, Fe, Zn), while another four samples were without phosphorous. On the other hand there were significant differences in the ratio of C/H in the case of each sample. Based on the results, it was concluded that the X-ray spectrometry as an analytical method is well-applicable to determine the elemental composition of rubber samples, but the calibration is a key part of the analysis. A good correlation was observed between the different methods, but the correlation was the function of characteristic of matrices. Significant matrix effect from the presence of phosphor was observed in the case of some samples, while the change of C/H ratio could not result notable matrix effect.     

Multilayer characterization by energy dispersive X-ray reflectivity technique

An experimental setup was developed to verify the feasibility of silicon drift detector to be used for the multilayer characterization by means of multilayer energy dispersive X-ray reflectivity. Such a detector allows high count rates up to 3 × 10⁵ cps and can be used in principle for the direct beam intensity measurement, which is to be done for the X-ray multilayer reflectivity patterns obtaining. A series of measurements were performed for Mo/B₄C multilayer sample. A quality of the experimentally obtained data turns out to be enough to perform a sample structure exploration using a numerical procedure of experimental data fitting. Due to low cost and short time, required for the measurements, an experimental technique proposed has a good perspective to be used for some practical applications in industry.     

Characterization of an energy dispersive X-ray fluorescence imaging system based on a Micropattern Gaseous Detector

An energy dispersive X-ray fluorescence (EDXRF) imaging system based on a Micropattern Gas Detector has already shown good results for different applications. An X-ray tube, a pinhole camera and a Micro-Hole and Strip Plate (MHSP) based detector are the main components of the experimental system. The detector uses an MHSP in a Xe atmosphere at 1 bar, and acting as a photon counting device, i.e., it is capable to record each single event retaining the energy and the interaction position (2D-sensitive detector) information of the incident photon, demonstrating to be a promising device for EDXRF imaging applications. This work presents studies of energy resolution, energy linearity and spatial resolution/elemental mapping as a function of image magnification of the system.     

Direct chlorine determination in crude oils by energy dispersive X-ray fluorescence spectrometry: An improved method based on a proper strategy for sample homogenization and calibration with inorganic standards

Official guidelines to perform chlorine determination in crude oil are (i) American Society for Testing and Materials (ASTM) D6470, which is based on the extraction of water from the oil and subsequent determination of the chloride by potentiometry, (ii) ASTM D3230, that measures the conductivity of a solution of crude oil in a mixture of organic solvents and (iii) US Environmental Protection Agency (EPA) 9075 that uses energy dispersive X-ray fluorescence spectrometry to quantify chlorine and it is applicable for the range from 200 μg g^− 1 to percent levels of the analyte. The goal of this work is to propose method to quantify lower amounts of chlorine in crude oil using energy dispersive X-ray fluorescence spectrometry using a simple calibration strategy. Sample homogenization procedure was carefully studied in order to enable accurate results. The calibration curve was made with standards prepared by diluting aqueous NaCl standard in glycerin. The method presented a linear response that covers the range from 8 to at least 100 μg g^− 1 of chlorine. Chlorine in crude oil samples from Campos Basin - Brazil were quantified by the proposed method and by potentiometry after extraction of chlorine from the oil. Results achieved using both methods were statistically the same at 95% confidence level.     

Determination of trace elements in Syrian medicinal plants and their infusions by energy dispersive X-ray fluorescence and total reflection X-ray fluorescence spectrometry

X-ray fluorescence (XRF) and total-reflection X-ray fluorescence (TXRF) techniques suited well for a multi-element determination of K, Ca, Mn, Fe, Cu, Zn, Rb, and Sr in some Syrian medicinal plant species. The accuracy and the precision of both techniques were verified by analyzing the Standard Reference Materials (SRM) peach-1547 and apple leaves-1515. A good agreement between the measured concentrations of the previously mentioned elements and the certified values were obtained with errors less than 10.7% for TXRF and 15.8% for XRF. The determination of Br was acceptable only by XRF with an error less than 24%. Furthermore, the XRF method showed a very good applicability for the determination of K, Ca, Mn, Fe, Cu, Zn, Rb, Sr, and Br in infusions of different Syrian medicinal plant species, namely anise (Anisum vulgare), licorice root (Glycyrrhiza glabra), and white wormwood (Artemisia herba-alba).     

Determination of wear metals in engine oil by mild acid digestion and energy dispersive X-ray fluorescence spectrometry using solid phase extraction disks

A simple, particle size-independent spectrometric method has been developed for the multi-element determination of wear metals in used engine oil. A small aliquot (0.5 ml) of an acid-digested oil sample is spotted onto a C-18 solid phase extraction disk to form a uniform thin film. The dried disk is then analyzed directly by energy dispersive X-ray fluorescence spectrometry. This technique provides a homogeneous and reproducible sample surface to the instrument, thus overcoming the typical problems associated with uneven particle size distribution and sedimentation. As a result, the method provides higher precision and accuracy than conventional methods. Furthermore, the disk sample may be stored and re-analyzed or extracted at a later date. The signals arising from the spotted disks, and the calibration curves constructed from them, are stable for at least 2 months. The limits of detection for Fe, Cu, Zn, Pb, and Cr are 5, 1, 4, 2, and 4 μg g⁻¹, respectively. Recoveries of these elements from spiked oil samples range from 92 to 110%. The analysis of two standard reference materials and a used oil sample produced results comparable to those found by inductively coupled plasma atomic emission spectrometry.     

Micro energy dispersive X-ray fluorescence analysis of polychrome lead-glazed Portuguese faiences

Several glazed ceramic pieces, originally produced in Coimbra (Portugal), were submitted to elemental analysis, having as premise the pigment manufacture production recognition. Although having been produced in Coimbra, their location changed as time passed due to historical reasons. A recent exhibition in Coimbra brought together a great number of these pieces and in situ micro Energy Dispersive X-ray Fluorescence (µ-EDXRF) analyses were performed in order to achieve some chemical and physical data on the manufacture of faiences in Coimbra.     

The infrared microspectroscopic and energy dispersive X-ray analysis of paints removed from a painted, medieval sculpture of Saint Wolfgang

A spectroscopic study of paints removed from a 15th century sculpture depicting Saint Wolfgang, which is housed in the Ball State Museum of Art, was performed. Infrared spectra on the minute paint samples were obtained using a microscope accessory in the transmission mode, and the spectra were compared to reference spectra of known art pigments and materials. In addition, energy dispersive X-ray spectra were obtained using a scanning electron microscope source. Although many of the pigments found are relatively modern pigments, the first application of paint is composed of materials consistent with the sculpture's medieval date. Pigments identified include brass gilding, calcium carbonate, China clay, lac dye, orpiment, Prussian blue, satin ochre, ultramarine blue and red, and zinc chromate. A zinc tungate finish was also identified.     

Combining synchronous fluorescence spectroscopy with multivariate methods for the analysis of petrol-kerosene mixtures

Synchronous fluorescence spectroscopy (SFS) is a rapid, sensitive and nondestructive method suitable for the analysis of multifluorophoric mixtures. The present study demonstrates the use of SFS and multivariate methods for the analysis of petroleum products which is a complex mixture of multiple fluorophores. Two multivariate techniques principal component regression (PCR) and partial least square regression (PLSR) have been successfully applied for the classification of petrol-kerosene mixtures. Calibration models were constructed using 35 samples and their validation was carried out with varying composition of petrol and kerosene in the calibration range. The results showed that the method could be used for the estimation of kerosene in kerosene-mixed petrol. The model was found to be sensitive, detecting even 1% contamination of kerosene in petrol.     

定量X-射线荧光光谱分析中用于计算理论α系数的计算机程序DRALPHA

在修改后的基本参数法程序NRLXRF基础上本文所研制的计算机程序DRALPHA可用于计算Lachance-Traill或Claisse-Quintin方程中的理论α系数以校正X-射线荧光定量分析中元素间的吸收-增强效应。     

能量色散X射线散射结合主成分分析对液体易制毒化学品的探测与鉴别分类

采用能量色散X射线散射(EDXRS)技术探测了8种液体易制毒化学品的X射线散射光谱, 结果显示液体易制毒物质具有各自特征的EDXRS散射图谱. 将液体易制毒化学品的EDXRS散射信息与主成分分析结合, 发现前2个主成分可以表达X射线散射光谱的主要信息, 在PC1～PC2得分分布图上可将液体易制毒化学品进行分类. 研究结果表明, EDXRS光谱技术结合主成分分析法可以实现探测、 鉴别分类液体易制毒化学品, 为隐藏液体易制毒化学品的监管控制提供一个可行的鉴别方法.     

Study of metal-loaded activated charcoals for the separation and determination of selenium species by energy dispersive X-ray fluorescence analysis

Conversion of adsorption properties of activated charcoal (C^∗) by metal modification towards selenite, selenate and seleno-dl-methionine (Se-Met) was studied. Several metals were included in modification studies and also a procedure was developed for the separation and independent determination of microgram quantities of these selenium species in aqueous solution. Selenium species were collected one by one from the same sample solution onto collector material by adsorbing them directly or after complex formation onto different metal-loaded activated charcoals (MgC^∗ and FeC^∗). The mass of selenium in these collectors was measured directly by energy dispersive X-ray fluorescence spectrometry (EDXRF). Detection limits for all three selenium species were better than 6 μg corresponding to concentration of 60 μg/l with 0.100 l of initial sample volume.     

X射线荧光光谱分析

本文评述了我国在2005年至2006年X射线荧光光谱,包括粒子激发的X射线光谱的发展和应用,内容包括仪器研制、激发源、探测器、软件、仪器改造、仪器维护和维修、样品制备技术、分析方法研究和应用.     

Determination of sulphur in liquids obtained by thermal cracking of waste polymers and commercial fuels with different analytical methods

Low sulphur concentration in hydrocarbon products as fuels or lubricants is an important requirement for the high quality standards of refineries. A non-polarised energy dispersive X-ray fluorescence spectroscopy (EDXRFS) and sample combustion technique (ASTM D6428-99) was compared. A new application of energy dispersive X-ray spectrometry as analytical method for the determination of sulphur in fuels and fuel-like fractions was investigated. Low sulphur containing fuels and hydrocarbon mixtures obtained by thermal cracking of waste polymers were measured and the influence of C/H ratio on accuracy was studied. The concentration of sulphur in samples was measured with calibration graphs of different hydrocarbon matrices (commercial gasoline, diesel oil and white oil were used). Good correlation was observed between the different methods, but the correlation was depending on the characteristics of the matrices. Detection limits of 1.0 ppm, 1.1 ppm and 0.9 ppm were obtained for S in gasoline, diesel oil and white oil, respectively.     

Factorial design for Fe, Cu, Zn, Se and Pb preconcentration optimization with APDC and analysis with a portable X-ray fluorescence system

Preconcentration of heavy metals in water with ammonium pyrrolydine dithiocarbamate (APDC) is a common practice in analytical chemistry. A literature review on this topic showed that several authors use this precipitation agent, but in different preconcentration conditions, conducting to divergent results. The objective of this work is to use factorial design to optimize the factors involved in the preconcentration process of heavy metals using APDC. Five factors were studied: sample volume, solution pH, APDC concentration, APDC volume and stirring time. The assays were performed by energy dispersive X-ray fluorescence (EDXRF). The values for detection limits within 95% confidence level, in μg L⁻¹, were: Fe (6.0 ± 0.1), Cu (4.0 ± 0.1), Zn (2.0 ± 0.1), Se (4.0 ± 0.1) and Pb (5.0 ± 0.1). The value for quantification limit for the five elements was 20 μg L⁻¹, with 3% deviation. Multi-element standard solutions were prepared. Precipitation procedure was applied in the spiked solutions and the samples were filtered in cellulose ester membrane for quantification measurements. The optimum values obtained were 300 mL of sample solution, pH 4, 1 mL of 2% APDC and 10 min of stirring time. The concentration results obtained for the validation measurements were satisfactory for in situ survey employing a portable instrument.     

X射线荧光光光谱分析

评述了我国在2007～2008年X射线荧光光谱,包括质子激发的X射线光谱的发展和应用,内容包括仪器、软件、仪器改造、仪器维护和维修、基础研究和分析方法研究及其应用.