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).     

Element determination in medieval soil samples by total reflection X-ray fluorescence analysis

An aqua regia extraction procedure for heavy metals in soils optimised for total reflection X-ray fluorescence analysis is presented. The procedure is applied to 92 soil samples of medieval layers from the city area of Dortmund. Sixteen elements (P, S, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Rb, Sr, Ag, Sn, and Pb) were used to characterise 17 sample sites. The results are projected onto the medieval urban structure of Dortmund. Two sites loaded with non-ferrous heavy metal could be detected and correlated with archaeological data. The efficiency and repeatability of the proposed extraction procedure is discussed.     

Determination of technetium by total reflection X-ray fluorescence

The measurement of technetium in inorganic solutions is reported for the first time using total reflection X-ray fluorescence (TXRF). Sodium pertechnetate solutions eluted from decayed ⁹⁹Mo generators were efficiently excited with a silver-anode X-ray tube in a standard configuration. The technique has been developed to aid establishing the extent of stoichiometric relations between Tc and a ligand in organo-metallic compounds synthesized with diagnostic purposes for nuclear medicine. The precision attained was 5% and the detection limit achieved for Tc in inorganic solutions by TXRF at 1000 s was 0.039 μg/ml.     

Determination of trace elements in bee honey,pollen and tissue by total reflection and radioisotope X-ray fluorescence spectrometry

Multielemental determinations in samples of various types of bee honey, pollen and bee tissue have been carried out using total reflection X-ray fluorescence spectrometry (TXRF) and radioisotope excited X-ray fluorescence spectrometry (XRF). The objective was to establish whether the elemental content of bee honey, in particular, correlates with any useful information about the environment, variety of honey, etc. An attempt has also been made to determine the X-ray techniques' ability to compete with atomic absorption spectrometry (AAS) and inductively coupled plasma-atomic emission spectrometry (ICP-AES), with regard to elemental sensitivity, accuracy, sample preparation procedures, and in particular, economic performance, which is very important in selecting an appropriate technique for the analysis of large numbers of samples. The results confirm the advantages of the TXRF method for trace element analysis, but only when utilising monochromatic excitation and selecting a proper sample preparation procedure. The radioisotope XRF technique, which does not require any sample preparation, is still very competitive in analysis of elements with concentrations above a few ten ppm. Preliminary results also confirm some correlations between the elemental content of honey and the status of the environment, and encourage further work in this direction     

Matrix effect on the detection limit and accuracy in total reflection X-ray fluorescence analysis of trace elements in environmental and biological samples

The effect of matrix contents on the detection limit of total reflection X-ray fluorescence analysis was experimentally investigated using a set of multielement standard solutions (500 ng/mL of each element) in variable concentrations of NH₄NO₃. It was found that high matrix concentration, i.e. 0.1–10% NH₄NO₃, had a strong effect on the detection limits for all investigated elements, whereas no effect was observed at lower matrix concentration, i.e. 0–0.1% NH₄NO₃.     

Determination of heavy metals in macrozoobenthos from the rivers Tisza and Szamos by total reflection X-ray fluorescence spectrometry

In 2000, accidents in the Romanian mining industry in key catchment areas led to heavy metal contamination of the Hungarian rivers Tisza and Szamos resulting in substantial heavy metal loads in several sediments of the upper river basins. This enhanced metal content might have been bioaccumulated in benthic organisms during the following years. Therefore, the aim of this study was to test, whether the zoobenthic fauna showed an enhanced metal content 3 years after the industrial accident. Macrozoobenthic insect larvae (chironomids) were sampled 100 m below and above the confluent site of the rivers Tisza and Szamos during summer 2003 and for comparison purpose also in the river Maros, a tributary of the Tisza river, during 2005. In order to determine their heavy metal content, single specimens were prepared and analysed by Total Reflection X-ray Fluorescence Spectrometry (TRXF) according to the modified dry method. Fe was much lower and Mn and Zn much higher concentrated in benthos from the more contaminated Szamos river compared to the Tisza and Maros rivers. In this sense, the benthic organisms reflected very well the enhanced metal concentrations in the contaminated rivers being suitable as bioindicators of metal contamination. However, the sediment bioaccumulation factor was low at all sampling sites indicating a low bioavailability of trace metals for benthic organisms.     

Discriminant analysis of trace elements in normal,benign and malignant breast tissues measured by total reflection X-ray fluorescence

In this work total reflection X-ray fluorescence spectrometry has been employed to determine trace element concentrations in different human breast tissues (normal, normal adjacent, benign and malignant). A multivariate discriminant analysis of observed levels was performed in order to build a predictive model and perform tissue-type classifications. A total of 83 breast tissue samples were studied. Results showed the presence of Ca, Ti, Fe, Cu and Zn in all analyzed samples. All trace elements, except Ti, were found in higher concentrations in both malignant and benign tissues, when compared to normal tissues and normal adjacent tissues. In addition, the concentration of Fe was higher in malignant tissues than in benign neoplastic tissues. An opposite behavior was observed for Ca, Cu and Zn. Results have shown that discriminant analysis was able to successfully identify differences between trace element distributions from normal and malignant tissues with an overall accuracy of 80% and 65% for independent and paired breast samples respectively, and of 87% for benign and malignant tissues.     

Determination of fluorine by total reflection X-ray fluorescence spectrometry

There is a growing interest in determination of low Z elements, i.e. carbon to phosphorus, in various samples. Total reflection X-ray fluorescence spectrometry (TXRF) has been already established as a suitable trace element analytical method with low sample demand and quite good quantification limits. Recently, the determinable element range was extended towards Z = 6 (carbon).     

Determination of trace elements in small water samples by total reflexion X-ray fluorescence (TXRF) and by neutron activation analysis (NAA)

The problems encountered in the determination of trace elements in small sample volumes of the order of 1 to 10 l (e.g. in droplets of water) are discussed. Total reflexion X-ray fluorescence (TXRF) and neutron activation analysis (NAA) are applied for the determination of Na, Mg, K, Ca, Mn, Fe, Co, and Cu in concentrations of 0.01 to 10 mg/L in 1 to 10 L of water. The applied methods are described, the results are discussed and the advantages of TXRF are brought forward.     

Direct determination of trace elements in boron nitride powders by slurry sampling total reflection X-ray fluorescence spectrometry

The use of slurry sampling total reflection X-ray fluorescence spectrometry (SlS-TXRF) for the direct determination of Ca, Cr, Cu, Fe, Mn and Ti in four boron nitride powders has been described. Measurements of the zeta potential showed that slurries with good stabilities can be obtained by the addition of polyethylenimine (PEI) at a concentration of 0.1 wt.% and by adjusting the pH at 4. For the optimization of the concentration of boron nitride in the slurries the net line intensities and the signal to background ratios were determined for the trace elements Ca and Ti as well as for the internal standard element Ga in the case of concentrations of boron nitride ranging from 1 to 30 mg mL⁻¹. As a compromise with respect to high net line intensities and high signal to background ratios, concentrations of 5 mg mL⁻¹ of boron nitride were found suitable and were used for all further measurements. The limits of detection of SlS-TXRF for the boron nitride powders were found to range from 0.062 to 1.6 μg g^– 1 for Cu and Ca, respectively. Herewith, they are higher than those obtained in solid sampling and slurry sampling graphite furnace atomic absorption spectrometry (SoS-GFAAS, SlS-GFAAS) as well as those of solid sampling electrothermal evaporation inductively coupled plasma optical emission spectrometry (SoS-ETV-ICP-OES). For Ca and Fe as well as for Cu and Fe, however, they were found to be lower than for GFAAS and for ICP-OES subsequent to wet chemical digestion, respectively. The universal applicability of SlS-TXRF to the analysis of samples with a wide variety of matrices could be demonstrated by the analysis of certified reference materials such as SiC, Al₂O₃, powdered bovine liver and borate ore with a single calibration. The correlation coefficients of the plots for the values found for Ca, Fe and Ti by SlS-TXRF in the boron nitride powders as well as in the before mentioned samples versus the reference values for the respective samples over a concentration range from 2.5 to 1470 μg g^– 1 were found to be 0.995, 0.991 and 0.997, respectively.     

Applications of total reflection X-ray fluorescence spectrometry in trace element and surface analysis

Total reflection X-ray fluorescence spectrometry (TXRF) is presented as a genuine surface analytical technique. Its low information depth is shown to be the characteristic feature differentiating it from other energy dispersive X-ray fluorescence methods used for layer and surface analysis. The surface sensitivity of TXRF and its analytical capability together with the limitations of the technique are discussed here using typical applications including the contamination control of silicon wafers, thin layer analysis and trace element determination. For buried interfaces and implantation depth profiles in silicon a combination of TXRF and other techniques has been applied successfully. The TXRF method has the particular advantage of being calibrated without the need for standards. This feature is demonstrated for the example of the element arsenic.     

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.     

Pretreatment of special samples from waste incineration for analysis by total reflection X-ray fluorescence

The use of ion exchange processes as sample pretreatment steps for TXRF analysis has been studied in order to improve the detection sensitivity or to provide information on the speciation of individual elements. EDTrA cellulose proved to be an excellent exchange material for heavy metal enrichment, for Hg separation, and for elimination of alkaline and earth-alkaline salts. Sephadex SP C25 and QAE A25 can be used to separate Pb and As and to verify the ionic state of the elements V, Cr, As, Se, Mo, Sb and W.     

Picoliter solution deposition for total reflection X-ray fluorescence analysis of semiconductor samples

A deposition system capable of delivering picoliter quantities of solution in programmable arrays was investigated as a method for sample preparation for total reflection X-ray fluorescence (TXRF) spectroscopy. Arrays of trace metals in solution were deposited on Si wafers. The array deposits provide a capability of depositing closely spaced (100 μm or less), typically 5–20 μm diameter droplets in an area that can be matched to the analysis spot of the TXRF detector. The dried depositions were physically characterized and the effect of deposition type and matrix on the TXRF signal was investigated.     

Determination of uranium in human urine by total reflection X-ray fluorescence

Uranium has been classified as a toxic chemical. It affects the kidneys, with nephritis being the primarily chemically-induced effect in animals and humans. Intermediate-term studies on animals indicate that increased uranium doses are positively correlated with various biochemical effects and histopathological changes. Since the kidneys efficiently excrete in urine the major portion of solubilized uranium circulating in blood, an increased urinary uranium excretion can provide a sensitive quantitative measure of exposure, especially in the case of acute exposure. In the present work a method was developed for the quantitative determination of uranium in human urine. It combines the chemical treatment of urine, which results in a significant pre-concentration of uranium, with its subsequent detection by means of total reflection X-ray fluorescence (TXRF). The method has been proven to be relatively fast, offering detection limits that allow for monitoring uranium intake above normal levels.     

Characterization of trace elements in high viscosity materials by total reflection X-ray spectrometry

This paper proposes the use of radiation scattered by the sample instead of the internal standard method for quantifying impurities in high viscosity materials using X-ray fluorescence with total reflection geometry. The method has been performed for checking trace elements in gels of polymers. Advantages include no sample preparation and a minimum amount of sample (10 μl). The method is also insensitive to instrumental variations, sample amount and particle size of the sample. The ratio of coherent to incoherent scattering intensities of X-ray was also investigated to estimate the content of C plus O in these polymers.     

Automated nanoliter solution deposition for total reflection X-ray fluorescence analysis of semiconductor samples

In this study, a BioDot BioJet dispensing system was investigated as a nanoliter sample deposition method for total reflection X-ray fluorescence (TXRF) analysis. The BioDot system was programmed to dispense arrays of 20 nL droplets of sample solution on Si wafers. Each 20 nL droplet was approximately 100 μm in diameter. A 10 × 10 array (100 droplets) was deposited and dried in less than 2 min at room temperature and pressure, demonstrating the efficiency of the automated deposition method. Solutions of various concentrations of Ni and Ni in different matrices were made from stock trace element standards to investigate of the effect of the matrix on the TXRF signal. The concentrations were such that the levels of TXRF signal saturation could be examined. Arrays were deposited to demonstrate the capability of drying 100 μL of vapor phase decomposition-like residue in the area of a typical TXRF detector.     

Determination of trace elements in pharmaceutical substances by graphite furnace atomic absorption spectrometry and total reflection X-ray fluorescence after flow injection ion-exchange preconcentration

Flow injection iminodiacetic acid ethyl cellulose (IDAEC) microcolumn preconcentration and graphite furnace atomic absorption spectrometry determination of trace metals (Cd, Co, Ni, Pb) were carried out without decomposition of the drug matrix. The two forms of chromium Cr(III) and Cr(VI) were separated using IDAEC and anion exchanger diethylaminoethyl (DE)-cellulose, respectively. The detection limits of trace elements in pharmaceutical substances (sugars, sorbitol, mannitol, paracetamol, amidopyrine, chloral hydrate) after a 10-fold preconcentration in 1–5% m/v solution of pharmaceuticals were in the 0.3–29 ng g⁻¹ range. The measured concentration of trace elements in substances investigated was below 100 ng g⁻¹. The spike recovery was close to 100%. The capability of total reflection X-ray fluorescence technique for the determination of trace elements in pharmaceuticals with and without preconcentation was explored.     

A novel total reflection X-ray fluorescence procedure for the direct determination of trace elements in petrochemical products

A total reflection X-ray fluorescence (TXRF) procedure was developed for the determination of metal traces in petrochemical end products or intermediates for surfactant synthesis. The method combines a fast and straightforward sample preparation, i.e. deposition on the sample holder and evaporation of the sample matrix, with an efficient quantification method based on internal standardization (organic gallium standard). The method developed showed detection limits below 0.05 μg g^-1 and in most cases below 0.005 μg g^-1. Fifteen elements (Ca, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Rh, Sn, Sr, V and Zn) were determined in matrices such as paraffins, n-olefins, linear alkylbenzenes, long-chain alkyl alcohols and esters: typical metal contents were below 1 μg g^-1. The results were compared with the reference method ASTM D5708 (test method B) based on inductively coupled plasma optical emission spectroscopy: advantages and drawbacks of the two procedures were critically evaluated. The TXRF method developed showed comparable precision and absence of bias with respect to the reference method. A comparison of the performances of the two methods is presented.