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PubMed1999

[Neural cluster structure with single component prediction in multiple variable systems for X-ray fluorescence spectrometry].

A neural cluster structure with single component prediction (NCSCP) was proposed for X-ray fluorescence spectrometry in a multivariable system. The neural cluster structure is built by the collection of a group of neurons which have close relationships among one another. In X-ray fluorescence analysis, the structure is constructed by choosing the elements in which there exist serious matrix effects, and deleting the components containing large noise. The predictability of the neural cluster structure was compared with that of the classical backward error propagation algorithm with single component prediction. The results show that the neural cluster structure is significantly superior to the classical algorithm in prediction accuracy, antidisturbance and the predictabilty to outliers.

English Abstract↗
PubMedDate not supplied

Determination of ultratrace bismuth in milk samples by atomic fluorescence spectrometry.

A sensitive procedure was developed for determination of bismuth (Bi) in milk samples by hydride generation atomic fluorescence spectrometry (HG-AFS) after microwave-assisted sample digestion with HNO3 and H2O2. The method provides a sensitivity of 1832 fluorescence units (ng/mL) with a detection limit of 0.01 ng/mL, which corresponds to 20 pg absolute limit of detection, equivalent to 0.50 ng/g in the original sample. Application of the methodology to cow milk samples from the Spanish market showed the presence of Bi at a concentration of 11.8-28.8 ng/g, which compared well with data obtained after dry ashing of samples and with data obtained by inductively coupled plasma-mass spectrometry after microwave-assisted digestion.

Animals↗
PubMed2001

[Progress in knowledge-based X-ray fluorescence spectrometry].

The review focuses on the expert systems and knowledge engineering in X-ray fluorescence spectrometry. It includes mainly a knowledge-controlled strategy combining the scan-based method with the fixed channel measurements, a XRF interpretation system of spectra with fuzzy logic and pattern recognition, and an expert system for qualitative interpretation of XRF spectra using a certainty factor. In the review, a series of the studies of exploring the knowledge engineering system in XRF are also included, which consists of four parts, i.e. spectra identification, pattern recognition with decision-making, quantitative determination combined with the theoretical alpha coefficients and neural networks, and XRF analysis without standards.

Algorithms↗
PubMed1986

Trace elements in normal and cirrhotic human liver tissue. I. Iron, copper, zinc, selenium, manganese, titanium and lead measured by X-ray fluorescence spectrometry.

Trace elements (Fe, Cu, Zn, Se, Mn, Ti, Pb) were measured by X-ray fluorescence spectrometry in normal liver tissue obtained at autopsy from 74 subjects (44 male, 30 female), median age 62 years (range 20-87), and in tissue from 27 cirrhotic livers (14 alcoholic, 13 non-alcoholic cirrhosis). The element content (median and 5-95 percentile interval) in normal livers in mmol/kg dry tissue was: Fe, 16.51 (7.82-39.03); Cu, 0.378 (0.189-0.629); Zn, 4.01 (2.59-9.33); Se, 0.018 (less than 0.004-0.035); Mn, less than 0.055 (less than 0.055-0.237); Ti, less than 0.146 (less than 0.146-0.919); Pb, less than 0.0005 (less than 0.0005-0.0154). Only copper content showed a sex difference, being higher in males than in females (P less than 0.04). In both groups of cirrhotic liver, Fe content was within normal, Cu content above normal (P less than 0.05, P less than 0.02), and Se content below normal (P less than 0.0001, P less than 0.04). Alcoholic cirrhotic livers had lower Zn levels (P less than 0.02), higher Mn levels (P less than 0.06), and higher Pb levels (P less than 0.03) than normal livers.

Adult↗
PubMed2005

Forensic discrimination of sheet glass by a refractive-index measurement and elemental analysis with synchrotron radiation X-ray fluorescence spectrometry.

Measurements of the refractive index (RI) and elemental analysis using synchrotron radiation X-ray fluorescence spectrometry (SR-XRF) were applied to the forensic discrimination of sheet-glass samples from different origins. The refractive index was calculated from the matching temperature at which the glass fragments became invisible in silicone oil. Fragments smaller than 1 mm in maximum diameter were taken from each of 11 sheet glasses and subjected to analysis by SR-XRF. The XRF spectrum of these samples indicated that a comparison of 6 elements (Ca, Fe, Sr, Zr, Ba and Ce) was useful for the discrimination of sheet glasses. Cluster analysis was performed using 33 sets of SR-XRF data obtained by triplicate measurements for the 11 glasses. Comparing 528 pairs among 33 samples, 515 pairs could be correctly discriminated. The number of indistinguishable pairs could be reduced from 36 to 4 by comparing the SR-XRF data. Elemental analysis by SR-XRF could provide small glass fragments with a more evidential value than the solely measurement of only RI, through a significant improvement of the discrimination capability.

Journal Article↗
PubMedDate not supplied

Analysis of selected elements in tobacco by wavelength dispersive X-ray fluorescence spectrometry.

A rapid method for the determination of 16 elements in tobacco by wavelength dispersive X-ray fluorescence spectrometry has been developed. The method is accurate and precise, and requires only 9 min per sample for quantitation. Sample preparation consists of placing a portion of dried, ground tobacco in a sample cup, and pressing at 25 tons pressure to make a compressed pellet. This pellet is then automatically analyzed by X-ray fluorescence for 16 elements. The results are stored on a computer disk for future recall and report generation.

Elements↗
PubMed2002

Whole-surface analysis of semiconductor wafers by accumulating short-time mapping data of total-reflection X-ray fluorescence spectrometry.

Total-reflection X-ray fluorescence (TXRF) spectrometry with no chemical preconcentration, often called "straight-TXRF", is now widely used in the semiconductor industry. The small detection area of TXRF enablesmapping measurement of contamination of the semiconductor surface, which is very useful in process characterization. However, the small detection area had been believed to limit rapid whole-surface analysis. Contrary to this general understanding, in this study we demonstrated that a new method, called "sweeping-TXRF", which is essentially short-time multipoint mapping by straight-TXRF, can rapidly provide an average concentration. A considerable problem of this method is the contribution of errors in glancing angle and areal element distribution to the fluorescence. Using statistics, we examined the errors and demonstrated that most of them are canceled and are not significant in actual semiconductor applications. The results of an experiment that measured localized 6 x 10(10) atoms cm(-2) nickel contamination supported the above conclusion. Applying sweeping-TXRF to existing TXRF instruments is easy-the only requirement is a small software modification. We believe that sweeping-TXRF will be utilized for rapid whole-surface analysis in many fields, especially in the semiconductor industry.

Journal Article↗
PubMed2001

ArtTAX--a new mobile spectrometer for energy-dispersive micro X-ray fluorescence spectrometry on art and archaeological objects.

A newly developed spectrometer for energy-dispersive micro X-ray fluorescence spectrometry has been designed for the demands of archaeometry. ArtTAX combines the advantages of non-destructive and sensitive multi-elemental analysis at sub-mm resolution with the possibility of working outside the laboratory. The spectrometer consists of an air-cooled, low-power molybdenum tube, new generation polycapillary X-ray optics, a silicon drift detector without the need for liquid-nitrogen cooling, a CCD camera, and three light diodes for sample positioning. The motor-driven measurement head is fixed on a x,y,z-flexible tripod support which can be assembled and dismantled within minutes. The spot size of the primary X-ray beam was determined to be 94 microm for the Cu(Kalpha) energy, the detection limits are in a range of a few tens of microg g(-1) for the medium energy-range in glass. Additional open helium purging in the excitation and detection paths enables the determination of elements down to sodium, thus avoiding vacuum conditions or a size-limiting sample chamber. A selection of qualitative and quantitative results on pigment, metal, glass, and enamel analyses are presented to show the potential of ArtTAX in the field of art and archaeology.

Journal Article↗
PubMed2002

On-line coupling of capillary electrophoresis to hydride generation atomic fluorescence spectrometry for arsenic speciation analysis.

A novel hyphenated technique, on-line coupling of capillary electrophoresis (CE) to atomic fluorescence spectrometry (AFS), was developed for speciation analysis of four environmentally significant and toxic forms of arsenic: arsenite, arsenate, monomethylarsenic acid, and dimethylarsenic acid. Baseline separation of the four arsenic species was achieved by capillary electrophoresis in a 50 cm x 100 microm i.d. fused-silica capillary at 20 kV and using a 20 mmol L(-1) phosphate buffer (pH 6.5). A hydride generation (HG) technique was employed to convert the arsenic species from the CE effluent into their respective hydrides. The CE-AFS interface was constructed on the basis of a cross design for introducing a sheath flow around the CE capillary and a Pt electrode, which provided an electrical connection for stable electrophoretic separations and allowed on-line volatile hydride formation. A laboratory-made gas-liquid separator was used to isolate the generated volatile species from the reaction mixture solution, and an argon flow was used to transport the volatile hydrides into the atomizer of AFS for on-line detection. The precision (RSD, n = 7) ranged from 2.1 to 3.1% for migration time, from 2.8 to 4.2% for peak area response, and from 2.0 to 4.1% for peak height response for the arsenic species at the 1 mg L(-1) (as As) level. The detection limits were in the range of 9-18 microg L(-1) (as As). The recoveries of the four arsenic species in locally collected water samples and urine sample ranged from 91 to 115%. The developed technique was successfully applied to the speciation of the water-methanol extractable arsenic in a sediment sample.

Arsenic↗
PubMed1980

Microanalysis and X-ray fluorescence spectrometry of platelets in diseases with elevated muscle calcium.

Electron microscopic X-ray microanalysis and X-ray fluorescence spectrometry were done on platelets from patients with Duchenne muscular dystrophy and idiopathic scoliosis (both these conditions are known to be associated with increased intramyofibre calcium). A significant increase in calcium and phosphorus concentrations was found in the dense granules and whole cells of both conditions. The findings suggest that idiopathic scoliosis like Duchenne muscular dystrophy is a multisystem disease with detectable changes in platelets.

Adolescent↗
PubMed2006

Stoichiometry determination of (Pb,La)(Zr,Ti)O3-type nano-crystalline ferroelectric ceramics by wavelength-dispersive X-ray fluorescence spectrometry.

Analysis of small samples of lanthanum-doped lead zirconate titanate (PLZT) by wavelength-dispersive X-ray fluorescence spectrometry (WDXRF) is presented. The powdered material in ca. 30 mg was suspended in water and collected on the membrane filter. The pure oxide standards (PbO, La2O3, ZrO2 and TiO2) were used for calibration. The matrix effects were corrected using a theoretical influence coefficients algorithm for intermediate-thickness specimens. The results from XRF method were compared with the results from the inductively coupled plasma optical emission spectrometry (ICP-OES). Agreement between XRF and ICP-OES analysis was satisfactory and indicates the usefulness of XRF method for stoichiometry determination of PLZT.

Journal Article↗
PubMed2005

Multielement analysis of soft drinks by X-ray fluorescence spectrometry.

Several commercial soft drinks and respective plastic bottles were analyzed for their multielement contents employing the synchrotron radiation total reflection X-ray fluorescence spectrometry technique (SRTXRF). The SRTXRF method has been developed and validated, and about 20 elements were detected in the investigated samples, including some trace elements, which can be toxic for human beings, such as Ti, Cr, Sb, As, and Pb in soft drinks and Al, Sb, As, and Pb in poly(ethylene terephthalate) (PET) containers. Statistical analysis was performed using chemometric techniques (principal component analysis and cluster analysis), and similarities were verified in the multielement contents of the samples. The results demonstrated that the SRTXRF offers a good multielemental approach for the quality control of food products. Moreover, on the basis of enrichment factors, the possibility of the trace elements in the PET container may be leached to the beverages under normal commercial situations and other results were discussed.

Carbonated Beverages↗
PubMed1989

[Absorption and fluorescence spectrometry measurement of intraocular lenses].

Light absorption and fluorescence measurements can be used to detect accumulations of small molecules in intraocular lenses (IOLs). It was shown that HEMA IOLs can store and to some extent release a variety of drugs and fluorescein. PMMA and silicone IOLs, however, do not have this characteristic. UV-blocking IOLs absorb UV light completely. The absorption limit varies between 390 and 410 nm, depending on the make. Neither absorption nor fluorescence response were affected by exposure to UV light or heat.

Acebutolol↗
PubMed2001

Elements in autopsy liver tissue samples from Greenlandic Inuit and Danes. III. Zinc measured by X-ray fluorescence spectrometry.

The aim of the study was to measure the content of zinc (Zn) in liver tissue samples from Greenlandic Inuit using X-ray fluorescence spectrometry, and compare the results with those obtained in liver samples from Danes. Normal liver tissue samples was obtained at autopsy from 50 Greenlandic Inuit (27 men) with a median age of 61 years (range 23-83) and from 74 Danes (44 men) with a median age of 60 years (range 15-87). In the entire series, liver zinc content in Inuit was not significantly different compared with Danes. There was no significant gender difference in liver zinc content either in Inuit or in Danes. The content of zinc given as median (5-95 percentile) was in Inuit 3.809 mmol/kg dry liver (2.355-7.406), and in Danes 3.992 mmol/kg dry liver (2.499-8.645). There was a significant, positive correlation between liver zinc content and age in Danish women (r(s) = 0.43, p = 0.02), which could not be demonstrated in Danish men or in Inuit. Median hepatic zinc index (zinc content in mmol/kg dry weight divided by age in years) in Inuit was 0.073, and in Danes 0.080 (p = 0.3) without any significant difference between the two genders. In Inuit and Danes there was an inverse correlation between hepatic zinc index and age both in the two genders and in the entire series: Inuit: r(s) = -0.62, p < 0.0001; Danes: r(s) = -0.70, p < 0.0001. The results indicate that Inuit have liver zinc levels, which are similar to those found in Danes.

Adolescent↗
PubMed1998

[Determination of trace selenium and tellurium in steel by hydride-generation nondispersive atomic fluorescence spectrometry].

A method was developed for the determination of trace Se and Te in steel by ion-exchange-separation hydride-generation nondispersive atomic fluorescence spectrometry. 40% (V/V) chlorhydric acid was selected as the best medium for hydride reaction. The detection limits of Se and Te are 0.27 and 0.33 ng/mL, relative standard deviations are 6.99 and 6.11%, respectively. The recovery was in the range of 96.7-102.0%. The results are satisfactory.

English Abstract↗
PubMedDate not supplied

Simultaneous determination of methylmercury and ethylmercury in rice by capillary gas chromatography coupled on-line with atomic fluorescence spectrometry.

A comprehensive method for simultaneous determination of methylmercury (MeHg) and ethylmercury (EtHg) in rice by capillary gas chromatography (GC) coupled on-line with atomic fluorescence spectrometry was developed. The experimental conditions, including the pyrolyzer temperature and flow rates of the make-up gas and sheath gas, were optimized in detail. The absolute detection limits (3sigma) were 0.005 ng as Hg for both MeHg and EtHg. The relative standard deviation values (n=5) for 10 ng Hg/mL of MeHg and EtHg were 2.5 and 1.3%, respectively. The method was evaluated by analyzing 2 certified reference materials (DORM-2 and GBW08508), and the determined values of MeHg and total mercury concentrations were in good agreement with the certified values. In addition, the recoveries of MeHg and EtHg spiked into a rice sample collected from Jiangsu province in China were 86 and 77%, respectively. The proposed method was applied to analysis of MeHg and EtHg in 25 rice samples cultivated in 15 provinces of China. In all samples, MeHg was detectable and no EtHg was found. The MeHg contents in rice samples ranged from 1.9 to 10.5 ng/g, accounting for 7-44% of the total mercury measured.

Calibration↗