Analysis of elemental concentration censored distributions in breast malignant and breast benign neoplasm tissues

The total reflection X-ray fluorescence method was applied to study the trace element concentrations in human breast malignant and breast benign neoplasm tissues taken from the women who were patients of Holycross Cancer Centre in Kielce (Poland). These investigations were mainly focused on the development of new possibilities of cancer diagnosis and therapy monitoring. This systematic comparative study was based on relatively large (∼ 100) population studied, namely 26 samples of breast malignant and 68 samples of breast benign neoplasm tissues. The concentrations, being in the range from a few ppb to 0.1%, were determined for thirteen elements (from P to Pb). The results were carefully analysed to investigate the concentration distribution of trace elements in the studied samples. The measurements of concentration of trace elements by total reflection X-ray fluorescence were limited, however, by the detection limit of the method. It was observed that for more than 50% of elements determined, the concentrations were not measured in all samples. These incomplete measurements were treated within the statistical concept called left-random censoring and for the estimation of the mean value and median of censored concentration distributions, the Kaplan–Meier estimator was used. For comparison of concentrations in two populations, the log-rank test was applied, which allows to compare the censored total reflection X-ray fluorescence data. Found statistically significant differences are discussed in more details. It is noted that described data analysis procedures should be the standard tool to analyze the censored concentrations of trace elements analysed by X-ray fluorescence methods.     

Total-reflection X-ray fluorescence — a tool to obtain information about different air masses and air pollution

Atmospheric aerosols are solid particles dissolved in air and change their chemical composition frequently depending on various parameters. In order to identify regional air circulation atmospheric aerosol filter samples were taken at Loyola University Chicago's Lake Shore Campus during the months of July and August 2000 with sampling times ranging between 1 and 2 h. The samples were digested in a microwave oven and analyzed by total-reflection X-ray fluorescence (TXRF) spectrometry. One diurnal variation comprising five consecutive sampling events was selected and discussed as well as 4 days experiencing different meteorology were compared to exemplify the variation in trace elemental concentration according to air mass movements and highlight the capability of total-reflection X-ray fluorescence analysis. It was found that due to changes in meteorological conditions particularly wind direction and wind speed, trace elemental compositions varied rapidly and could be used to distinguish between ‘Lake Michigan air’ and ‘metropolitan Chicago air’ on such short-term time scale like one hour. Back trajectory analysis was applied to support and corroborate the results. The outcome of this study clearly shows that total-reflection X-ray fluorescence is an optimal tool for analysis of atmospheric aerosols.     

Data processing technique for mercury determination by total-reflection X-ray fluorescence,using amalgamation with gold

We have developed a method to determine mercury concentrations using total-reflection X-ray fluorescence (TXRF) which leads to reliable results. The usual sample preparation procedure of TXRF is not applicable due to element loss by evaporation on account of its high vapor pressure. The method we developed consists of forming an amalgam on a thin layer of gold affixed in a specular-surface quartz reflector while it is in contact with a mercury ionic solution. Subsequently, a traditional TXRF analysis is performed. Since the mercury and gold peaks overlap, we have developed a data processing scheme to achieve the most precise results. Using a molybdenum anode X-ray tube at 40 kV and 20 mA, the limit of detection achieved for a 10-μl specimen with 2000 s counting time is 250 ppb.     

Total-reflection X-ray fluorescence analysis of Austrian wine

The concentration of major, minor and trace elements in Austrian wine was determined by total-reflection X-ray fluorescence using gallium as internal standard. A multi-elemental analysis was possible by pipetting 6 μl of wine directly on the reflector and drying. Total-reflection X-ray fluorescence analysis was performed with Atomika EXTRA II A (Cameca) X-rays from a Mo tube with a high-energy cut-off at 20 keV in total-reflection geometry. The results showed that it was possible to identify only by the elemental analysis as fingerprint the vineyards and year of vintage among 11 different wines.     

An electrochemical enrichment procedure for the determination of heavy metals by total-reflection X-ray fluorescence spectroscopy

An electrolytic separation and enrichment technique was developed for the determination of trace elements by total-reflection X-ray fluorescence spectroscopy (TXRF). The elements of interest are electrodeposited out of the sample solution onto a solid, polished disc of pure niobium which is used as sample carrier for the TXRF measurement. The electrochemical deposition leads to a high enrichment of the analytes and at the same time to a removal of the matrix. This results in substantially improved detection limits in the lower picogram per gram region. The deposited elements are directly measured by TXRF without any further sample preparation step. The homogeneous thin layer of the analytes is an ideal sample form for TXRF, because scattered radiation from the sample itself is minimized. The proposed sample preparation method is useful particularly for the analysis of heavy metals in liquid samples with for TXRF disturbing matrices, e.g. sea water.     

A solid phase extraction procedure for the simultaneous determination of total inorganic arsenic and trace metals in seawater: Sample preparation for total-reflection X-ray fluorescence

In this paper we present a procedure allowing total-reflection X-ray fluorescence spectrometry (TXRF) determinations of arsenic in water samples, especially in seawater samples. The procedure consists of an arsenate reduction step (performed by using a l-cysteine solution) followed by a complexation of As⁺³ with sodium dibenzyldithiocarbamate and solid phase extraction. The new procedure is a modification of a method developed by Prange and allows a simultaneous determination of As together with V, Fe, Ni, Cu, Zn, Pb, and U in seawater by TXRF. The procedure was tested using the Certified Reference Material CASS-4 and was later applied to regular seawater samples collected from the North Sea. The detection limit for arsenic is 10 ng L^− 1.     

Beijing synchrotron radiation total-reflection X-ray fluorescence analysis facility and its applications on trace element study of cells

The feasibility of total-reflection X-ray fluorescence (TXRF) analysis excited by synchrotron radiation applied to trace element analysis of biological cells is investigated. The Beijing synchrotron radiation TXRF facility and the related experimental method are also described. The elemental minimum detection limits of some standard reference materials are determined. The elemental compositions of a cluster of small intestine cells of a small white mouse are given, and hence the average trace element contents of the single small intestine cell are also obtained. With this technique, the changes of some trace elements in the cells of lung and cervix cancer before and after apoptosis are also preliminarily studied.     

Determination of metal additives and bromine in recycled thermoplasts from electronic waste by TXRF analysis

A new method for analysis of metal additives in recycled thermoplasts from electronic waste was developed, based on dissolving the samples in an organic solvent and subsequent analysis of the corresponding solutions or suspensions by total-reflection X-ray fluorescence spectroscopy (TXRF). The procedure proved to be considerably less time consuming than the conventional digestion of the polymer matrix. Additives containing Ti, Zn, Br, Cd, Sn, Sb, and Pb were analyzed in a hundred randomly selected samples from recycling, which provided an overview of the range of elemental concentrations in thermoplasts utilized for consumer electronics. The results were validated independently by instrumental neutron activation analysis (INAA), subsequent regression analysis confirmed the trueness of the chosen approach.     

Determination of metal additives and bromine in recycled thermoplasts from electronic waste by TXRF analysis

A new method for analysis of metal additives in recycled thermoplasts from electronic waste was developed, based on dissolving the samples in an organic solvent and subsequent analysis of the corresponding solutions or suspensions by total-reflection X-ray fluorescence spectroscopy (TXRF). The procedure proved to be considerably less time consuming than the conventional digestion of the polymer matrix. Additives containing Ti, Zn, Br, Cd, Sn, Sb, and Pb were analyzed in a hundred randomly selected samples from recycling, which provided an overview of the range of elemental concentrations in thermoplasts utilized for consumer electronics. The results were validated independently by instrumental neutron activation analysis (INAA), subsequent regression analysis confirmed the trueness of the chosen approach. Received: 7 February 2000 / Revised: 25 February 2000 / Accepted: 1 March 2000     

Calibration of total-reflection X-ray fluorescence using a nickel bulk sample

A standard-free calibration procedure for total-reflection X-ray fluorescence has been developed which is based on the Fresnel theory for the reflection and refraction of X-rays on surfaces at grazing incidence. The technique requires only a pure metal surface as reference. The formalism is described in more detail for the measurement of contaminants on silicon wafer surfaces for both film-like and particulate distributions. Only natural constants are involved in the calculations. The resulting calibration factor is compared with those obtained from the droplet method normally applied elsewhere.     

Laser-induced fluorescence as a powerful detection tool for capillary electrophoretic analysis of heparin/heparan sulfate disaccharides

In quest for high sensitivities necessary for determining the disaccharide composition of heparin/heparan sulfate present in trace amounts in biologic samples, an ultrahighly sensitive capillary electrophoresis (CE) method using laser-induced fluorescence (LIF) detection was developed. Heparin/heparan sulfate-derived Delta-disaccharides were derivatized with the fluorophore 2-aminoacridone and resolved by a reversed-polarity CE method. Estimation of the limit of detection in concentration term and limit of quantitation showed that LIF detection of AMAC-derivatives of Delta-disaccharides resulted in 27-744 times higher sensitivity as compared to those detected by UV at 255 nm. These data suggest that CE-LIF is a powerful tool to quantify minute amounts of heparin/heparan sulfate disaccharides.     

低温水相合成巯基化聚乙烯醇/CdS量子点纳米复合物及用于测定环境水样中痕量Cu~(2+)

采用水相合成法,在低温N2气保护条件下,以巯基化聚乙烯醇(PVA)为基体材料合成一种环境友好型PVA/CdS量子点纳米复合物,并通过红外光谱(IR)、X射线粉末衍射(XRD)、透射电子显微镜(TEM)、热重(TG)、荧光光谱(PL)和紫外可见光谱(UV-Vis)等技术手段对复合物进行结构表征和光学性能研究。测试结果表明,复合物中CdS量子点为立方晶型结构,形状为球形,粒径小于5nm,具有很好的稳定性、分散性及发光性质。此外,Cu~(2+)对PVA/CdS水溶液荧光具有良好的猝灭作用,其荧光猝灭程度与Cu~(2+)浓度在1~1000nmol/L范围内呈良好的线性关系,线性相关系数为0.9923,方法检出限为0.12nmol/L。该纳米复合物荧光分析方法简便快速、灵敏度高、检出限低,已应用于实际黄河水样中痕量Cu~(2+)的分析与检测。     

Ultrasensitive and selective determination of trace amounts of nitrite ion with a novel fluorescence probe mono[6-N(2-carboxy-phenyl)]-β-cyclodextrin

A novel fluorescence probe, mono[6-N(2-carboxy-phenyl)]-β-cyclodextrin (OACCD), has been developed for the determination of trace nitrite, In dilute HCl medium, the fluorescence intensity of the newly synthesized fluorescence probe OACCD was quenched in presence of trace nitrite at room temperature. Based on this, a simple, sensitive, and selective method for rapid determination of nitrite was described. Furthermore, common ions do not interfere the determination of trace amounts of nitrite. The fluorescence quenching intensity was linear over a nitrite concentration of 0.02-1.7 μmol l⁻¹ with a detection limit of 0.2 nmol l⁻¹ (S/N = 3). The method was applied to the determination of nitrite in different water samples, soil samples, and food samples with satisfactory results.     

Multielement neutron activation analysis of human scalp hair a local population survey in the Tokyo metropolitan area

Applying instrumental neutron activation analysis, multielement analysis of human hair was carried out to elucidate the levels of various trace element concentrations in hair of local population in the Tokyo metropolitan area. 202 hair samples were collected from the inhabitants classified by sex and five age groups. Using several combinations of irradiation time, cooling time and counting time, forty elements were quantitatively analyzed. The method of analysis for data including samples under detection limit is discussed, assuming that the frequanecy distribution of trace element contents in hair is log-normal.     

Aqueous synthesis of type-II core/shell CdTe/CdSe quantum dots for near-infrared fluorescent sensing of copper(II)

Type-II core/shell CdTe/CdSe quantum dots (QDs) were synthesized in aqueous medium by employing thiol-capped CdTe QDs as core template and CdCl(2) and Na(2)SeSO(3) as shell precursors, respectively. Compared with the original CdTe cores, the core/shell CdTe/CdSe QDs showed an obvious red-shifted emission with the color-tune capability to the near-infrared (NIR) wavelength, because of the formation of an indirect excitation. The prepared QDs exhibited high stability and moderate fluorescence quantum yields (10-20%), and their core/shell heterostructure was characterized by UV-vis absorption, steady-state and time-resolved fluorescence spectra, X-ray powder diffraction, X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy. The fluorescence of the core/shell QDs could be markedly quenched by Cu(II), and approximate concentrations of other physiologically important cations, such as Zn(II), Ca(II), Na(I) and K(I) etc., had no effect on the fluorescence. Based on this, a simple and rapid method for Cu(II) determination was proposed using the NIR CdTe/CdSe QDs as fluorescent probes. Under optimal conditions, the response was linearly proportional to the concentration of Cu(II) between 0.05 to 50.0 x 10(-6) mol L(-1), the limit of detection was 2.0 x 10(-8) mol L(-1). The developed method was successfully applied to the detection of trace Cu(II) in real samples.     

Detection limit calculations for the total reflection techniques of X-ray fluorescence analysis

In this work, theoretical calculations of detection limits for different total reflection techniques of X-ray fluorescence analysis are presented. Calculations include grazing incidence (TXRF) and gracing emission (GEXRF) conditions. These calculations are compared with detection limits calculated for conventional X-ray fluorescence (XRF). In order to compute detection limits, Shiraiwa and Fujino's model was used to calculate X-ray fluorescence intensities. This model makes certain assumptions and approximations to achieve the calculations, especially in the case of the geometrical conditions of the sample, and the incident and takeoff beams. Nevertheless, the calculated data of detection limits for conventional XRF and total-reflection XRF show a good agreement with previous results. The model proposed here allows us to analyze the different sources of background and the influence of the excitation geometry, which contribute to a better understanding of the physical processes involved in the XRF analysis by total reflection. Finally, a comparison between detection limits in total-reflection analysis at grazing incidence and at grazing emission is carried out. Here, a good agreement with the theoretical predictions of the Reciprocity Theorem is found, showing that, in theory, detection limits are similar for both techniques.     

Determination of low atomic number elements at trace levels in uranium matrix using vacuum chamber total reflection X-ray fluorescence

Determinations of low atomic number elements Na, Mg and Al present at trace concentrations in uranium matrix were made by vacuum chamber total reflection X-ray fluorescence spectrometer for the first time. For this purpose, synthetic samples of uranium with known amounts of these low atomic number elements were prepared by mixing different volumes of their solutions with U solution of high purity. The concentrations of these elements in the samples were in the range of 100–300 μg/g with respect to uranium and 10–20 μg/mL in the solutions. Major matrix uranium was separated by solvent extraction with 30% solution of tri-n-butyl phosphate in dodecane. After the solvent extraction, aqueous phase containing trace elements was mixed with Sc internal standard and the samples were analyzed by vacuum chamber total reflection X-ray fluorescence spectrometer having a Cr Kα excitation source. The total reflection X-ray fluorescence results obtained, after blank corrections, indicated an average deviation of 14% from the calculated concentrations of these low atomic number elements on the basis of their preparation. However, the total reflection X-ray fluorescence determined concentration of Mg was exceptionally lower than the calculated concentration in two samples. These studies have shown that vacuum chamber total reflection X-ray fluorescence is a promising technique for the determination of low atomic number elements in uranium matrix after its separation.     

HG-AFS 法测定多金属矿中的痕量锡

研究了酒石酸介质中氢化物发生原子荧光光谱法 ( HG- AFS)测定多金属矿中痕量锡的方法 ,考察了不同酸介质和浓度对氢化物发生效率的影响 ,试验了共存元素的干扰情况。方法的检出限为 1 .4× 1 0 - 10 g/ m L,精密度 ( n=5)为3.71 %～ 5.38%。     

Analysis of archaeological ceramics by total-reflection X-ray fluorescence: Quantitative approaches

This paper reports the quantitative methodologies developed for the compositional characterization of archaeological ceramics by total-reflection X-ray fluorescence at two levels. A first quantitative level which comprises an acid leaching procedure, and a second selective level, which seeks to increase the number of detectable elements by eliminating the iron present in the acid leaching procedure. Total-reflection X-ray fluorescence spectrometry has been compared, at a quantitative level, with Instrumental Neutron Activation Analysis in order to test its applicability to the study of this kind of materials. The combination of a solid chemical homogenization procedure previously reported with the quantitative methodologies here presented allows the total-reflection X-ray fluorescence to analyze 29 elements with acceptable analytical recoveries and accuracies.     

Dose determination of nickel implantations in silicon wafers

Summary The dose of nickel ions implanted with an energy of 300 keV or 6 MeV, respectively, into silicon wafers was measured by X-ray fluorescence analysis (XRFA) after the implantation process. Dose values for Ni were determined within the range from 5×10¹⁵ to 1×10¹⁸ ions/cm². The detection limit of this simple and non-destructive procedure amounts to about 10¹⁴ atoms/cm². The accuracy was confirmed by flame atomic absorption spectrometry (FAAS), total-reflection X-ray fluorescence analysis (TXRFA), and by Rutherford-backscattering spectroscopy (RBS). The study confirms XRFA to be a suitable method for dose determinations after the implantation process.