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At least 181 records · Page 10Linked to original sources
PubMed2005

Grazing incidence-X-ray fluorescence spectrometry for the compositional analysis of nanometer-thin high-kappa dielectric HfO2 layers.

In future microelectronic devices, SiO2 as a gate dielectric material will be replaced by materials with a higher dielectric constant. One such candidate material is HfO2. Thin layers are typically deposited from ligand-containing precursors in chemical vapor deposition (CVD) processes. In the atomic layer deposition (ALD) of HfO2, these precursors are often HfCl4 and H2O. Obviously, the material properties of the deposited films will be affected by residual ligands from the precursors. In this paper, we evaluate the use of grazing incidence--and total reflection-X-ray fluorescence spectrometry (GI-XRF and TXRF) for Cl trace analysis in nanometer-thin HfO2 films deposited using ALD. First, the results from different X-ray analysis approaches for the determination of Hf coverage are compared with the results from Rutherford backscattering spectrometry (RBS). Next, we discuss the selection of an appropriate X-ray excitation source for the analysis of traces within the high-kappa: layers. Finally, we combine both in a study on the accuracy of Cl determinations in HfO2 layers.

Journal Article↗
PubMed2006

Multiple and simultaneous fluorophore detection using fluorescence spectrometry and partial least-squares regression with sample-specific confidence intervals.

Fluorescent labeling is widely used in biological and chemical analysis, and the drive for increased throughput is stretching multiplexing capabilities to the limit. The limiting factor in multiplexed analyses is the ability to subsequently deconvolute the signals. Consequently, alternative approaches for interpreting complex data sets are required to allow individual components to be identified. Here we have investigated the application of a novel approach to multiplexed analysis that does not rely on multivariate curve resolution to achieve signal deconvolution. The approach calculates a sample-specific confidence interval for a multivariate (partial least-squares regression (PLSR)) prediction, thereby enabling the estimation of the presence or absence of each fluorophore based on the total spectral signal. This approach could potentially be applied to any multiplexed measurement system and has the advantage over the current algorithm-based methods that the requirement for resolution of spectral peaks is not central to the method. Here, PLSR was used to obtain the concentrations for up to eight dye-labeled oligonucleotides at levels of (0.6-5.3) x 10(-6) M. The sample-specific prediction intervals show good discrimination for the presence/absence of seven of the eight labeled oligonucleotides with efficiencies ranging from approximately 91 to 100%.

Confidence Intervals↗
PubMed2004

Rapid and simultaneous determination of coproporphyrin and protoporphyrin in feces by derivative matrix isopotential synchronous fluorescence spectrometry.

BACKGROUND: Measurement of fecal porphyrins is important in the diagnosis of porphyria, but conventional methods to measure them have drawbacks. We explored the use of derivative matrix isopotential synchronous fluorescence (MISF) spectrometry for the measurement of coproporphyrin and protoporphyrin. METHODS: The MISF scanning route was selected based on information from the three-dimensional fluorescence spectrum, which was a combination of the contour line of protoporphyrin via a detection point of coproporphyrin and that of coproporphyrin via a detection point of protoporphyrin. Derivative technique eliminated the constant interfering signals. MISF was used to measure porphyrins in stools from 2 pregnant women and 20 healthy volunteers. RESULTS: The coproporphyrin and protoporphyrin spectra were resolved with almost no mutual interference. The amplitudes of the derivative peaks were linearly related to the concentrations of coproporphyrin up to 310 nmol/L and protoporphyrin up to 590 nmol/L. The detection limits for coproporphyrin and protoporphyrin were 1.2 and 1.7 nmol/L, respectively. The within-run imprecision (CV; n = 6) was 2.2% at 175 nmol/L for coproporphyrin and 2.3% at 500 nmol/L for protoporphyrin. Bland-Altman analysis indicated no significant differences between the proposed MISF method and conventional spectrophotometry or fluorimetry. Mean (SD) recoveries of porphyrins added to fecal samples were of 98 (7)% for coproporphyrin and 102 (4)% for protoporphyrin. CONCLUSIONS: This technique provides spectral resolution of coproporphyrin and protoporphyrin, obviating the need for chromatographic separation, and measurements can be made in a single scanning. The method also appears suitable for routine testing of large numbers of samples.

Coproporphyrins↗
PubMed2003

Monitoring of microbial diversity by fluorescence in situ hybridization and fluorescence spectrometry.

The goal of the research was the development of a simple method to quantify microbial groups in environmental samples. Fluorescence intensity was measured in the sample before and after whole cell fluorescence in situ hybridization with rRNA-targeted, fluorochrome-labeled oligonucleotide probes. To determine specific and non-specific binding of different oligonucleotide probes the following approaches have been used: (1) incubation of the sample with probes at two different temperatures; (2) hybridization of labeled probe in the presence of unlabeled probe; (3) incubation of the sample with labeled specific probe or labeled nonsense probe. Specific binding (hybridization) of the probe was calculated as the difference between total binding and non-specific binding of the probe. Specific binding was 40-50% of total binding in the environmental samples tested. The ratio of the specific binding of different probes may be used to quantify the ratio of different microbial groups in the environmental samples. This quantification is suitable for the microbiological monitoring of microbial aggregates because it is a simple technique and the results can be measured by a portable fluorometer.

Bacteria↗
PubMed1995

Determination of pyridoxamine in urine by matrix isopotential synchronous fluorescence spectrometry.

A spectrofluorimetric technique was applied to the determination of compounds in samples with unknown background fluorescence, consisting of performing synchronous scans through a trajectory joining points of equal intensity of a fluorescence matrix three-dimensional spectrum, which is called 'matrix isopotential synchronous fluorescence'. This technique can be improved by application of derivatives. The determination of pyridoxamine in urine was performed using this technique and the validity, applicability and simplicity of the method were demonstrated. With first-derivative matrix isopotential synchronous fluorescence the maximum sensitivity was 12.5 mg l-1 for pyridoxamine in real urine samples. The measurements were performed in aqueous medium at pH 7.0, adjusted by adding 0.05 mol l-1 phosphate buffer, and without any previous derivatization reactions. A complete statistical analysis of the experimental data was performed. Pyridoxamine in urine was determined by this method with good results and without the need for tedious prior separation.

Adolescent↗
PubMed1984

Simultaneous determination of trace elements in serum by energy-dispersive x-ray fluorescence spectrometry.

Energy-dispersive x-ray fluorescence is applied in the analysis of human serum to determine the concentrations of several elements simultaneously with minimal manipulation of the sample. The analytical procedure has been developed with standard sera, and standardization, detection limits, and reproducibility have been established. A 50-microL sample of diluted serum, to which an internal standard has been added, is deposited on a thin (4-microns thick) polypropylene film and analyzed by x-ray fluorescence. We report the statistical distributions of the concentrations of Fe, Cu, Zn, and Br obtained in the population (103 samples) studied, and report detection limits for the other 22 elements studied. The simplicity of the method, the high throughput, and the possibility of automating the measurements make this procedure suitable for screening large numbers of sera.

Bromine↗
PubMed1983

[Simultaneous determination of multiple elements in airborne particulate samples by X-ray fluorescence spectrometry].

An energy dispersive X-ray fluorescence spectrometer (EDX) has been applied to determine multielements in the workplace air. The standards for X-ray fluorescence analysis were prepared by the chelate precipitation method on polyvinyl chloride (PVC) membrane filter. And, the specimens were prepared to deposit various metal compounds of different chemical forms by the suspension method on PVC membrane filter, and they were determined with EDX and atomic absorption spectrometer (AAS). The results obtained were as follows. Though there is a difference by each element, an amount less than 3 microgram/cm2 per unit area makes it possible to undergo multielement analysis, that is, is has no influence on fine particle effect (particle size; under 5 microns). Then, effects of the X-ray intensity by different chemical forms are negligible. At the presence the neighboring element and other elements this technique showed greater precision by carrying out on corrective treatment, etc. The coefficient of variation of this technique was in the range of 2.5-6.5% at DDTC-Cu of 0.5-5.0 micrograms/cm2, with the limit of detection for As : 0.002 microgram/cm2, Zn : 0.003 microgram/cm2, Pb : 0.003 microgram/cm2, Cu : 0.004 microgram/cm2, Ni : 0.003 microgram/cm2, Fe : 0.005 microgram/cm2, Mn : 0.008 microgram/cm2, Cr : 0.013 microgram/cm2, respectively. Aerosols collected at the workplace were analyzed with EDX and AAS, and the obtained results showed good agreement with such regression line as y = 1.04 chi + 0.04, the coefficient of correlation being r = 0.995. From these results, this technique was found to be a very excellent method for monitoring of multielements in the workplace air.

Aerosols↗
PubMed1983

Iron, copper, zinc and selenium in human liver tissue measured by X-ray fluorescence spectrometry.

The content of iron, copper, zinc and selenium was measured by energy-dispersive X-ray fluorescence (XRF) spectrometry in normal liver tissue obtained at autopsy from 16 females and 12 males 46-87 years old. The precision of the XRF analysis, expressed by the coefficient of variation was: iron, 1.8%; copper, 3.2%; zinc, 1.0%; and selenium, 26.7%. In large liver samples, mean amount-of-substance contents of elements in dry liver tissue were: iron, 16.95 mmol/kg (range 7.90-27.31 mmol/kg); copper, 0.33 mmol/kg (0.08-0.76 mmol/kg); zinc, 5.12 mmol/kg (2.92-9.47 mmol/kg); selenium 0.02 mmol/kg (less than 0.004-0.04 mmol/kg). Furthermore the amounts of iron, copper and zinc were measured in wet-ashed Menghini needle biopsy specimens taken from the centre of 20 large liver samples. There was good agreement between results obtained in biopsy specimens and large samples concerning iron (r = 0.96, P less than 0.001) and zinc (r = 0.97, P less than 0.001), but not concerning copper (r = 0.66, P less than 0.01). XRF analysis appears to be a convenient method for element analysis in liver tissue and for measurement of iron and zinc in needle biopsy specimens.

Aged↗
PubMed1991

[Determining the level of histamine in canned fish by the fluorometric method using the Spekol-10 apparatus with FK device for fluorescence spectrometry].

The content of histamine in canned fish products was determined by fluorometric method recommended by AOAC with final determination of fluorescence on spectrophotometer Spekol 10 with FKC equipment of wave excitation for maximum of emission: lambda = 365 nm, filter GVK--48). The method makes possible quick, reproducible, and sensitive determination (limit of detection: 1 mg/100 g of product) of histamine in canned fish products, on simple equipment available in every laboratory of count Sanitary Stations.

Animals↗
PubMed1992

The application of energy-dispersive x-ray fluorescence spectrometry (EDXRF) to the analysis of cosmetic evidence in Indian nail polishes.

The application of energy-dispersive x-ray fluorescence (EDXRF) spectrometry in the quantitative analysis of samples of Indian nail polishes of apparently similar shades from different manufacturers has been examined by evaluating the possibility of detecting spurious material which is marketed under the guise of a popular brand. On the basis of the number of elements detected, and from the ratios of particular elements [Fe/Ti, Fe/Cu, Ti/Cu] the results are very encouraging.

Cosmetics↗
PubMed1996

Determination of pyridoxal in human serum by matrix isopotential synchronous fluorescence spectrometry.

The determination of pyridoxal in human serum was performed using a fluorimetric technique that is useful for the determination of compounds in samples with unknown background fluorescence, based on synchronous scans through a trajectory joining points of equal intensity of a fluorescence matrix three-dimensional spectrum. This technique, called matrix isopotential synchronous fluorescence can be improved by means of the application of derivatives. The determination of pyridoxal in human serum was performed with this technique without any prior separation steps. The validity, applicability and simplicity of the method were demonstrated. The measurements were performed in aqueous medium at pH 7.0 adjusted by adding 0.05 M phosphate buffer solution. A complete statistical analysis of the experimental data was performed and the results showed that correlation coefficients are between 0.9901 and 0.9958 for all the calibration graphs, and in all cases the intercepts on the ordinate were negligible. The experimental F (1.72) is smaller than theoretical value (3.89) as expected from an analysis of variance. The reproducibility of the method was tested and the results were a standard deviation of 0.0117 microgram ml-1 and a relative error of 4.91%.

Humans↗
PubMed1998

Determination of low levels of total mercury in blood and plasma by cold vapour atomic fluorescence spectrometry.

A sensitive and semi-automated analytical method allowing determination of low and normal levels of total mercury in human blood and plasma using cold vapour atomic fluorescence is described. Samples are digested overnight, or at an elevated temperature for 4 h, followed by bromination at room temperature. After reduction with tin (II), analysis is performed using automated continuous flow vapour generation coupled to a fluorescence detector, allowing 20 samples to be analysed per hour. Detection limits for blood and plasma were found to be 0.9 and 0.5 nmol Hg l-1, respectively. The method precision at various concentrations of mercury was determined. For whole blood at 8.1 nmol Hg l-1 and 12.9 nmol Hg l-1, the within-day precision was 5% and 6% and the between-day precision 9% and 6%, respectively. For plasma at 1.3 nmol Hg l-1, the within-day precision was 13% while the between-day precision was 17%. Accuracy was evaluated by an inter-laboratory comparison study. At blood mercury concentrations below 60 nmol Hg l-1 the results from the current method were almost identical to those obtained with radiochemical neutron activation analysis, commonly regarded as a reference method. The present method should have merits in relation to previously used methods using atomic absorption spectrometry.

Bromine↗
PubMed2005

Flow injection on-line solid phase extraction for ultra-trace lead screening with hydride generation atomic fluorescence spectrometry.

A flow injection (FI) on-line solid phase extraction (SPE) procedure for ultra-trace lead separation and preconcentration was developed, followed by hydride generation and atomic fluorescence spectrometric (AFS) detection. Lead is retained on an iminodiacetate chelating resin packed microcolumn, and is afterward eluted with 2.5% (v/v) hydrochloric acid to facilitate the hydride generation by reaction with alkaline tetrahydroborate solution with 1% (m/v) potassium ferricyanide as an oxidizing (or sensitizing) reagent. The hydride was separated from the reaction medium in the gas-liquid separator and swept into the atomizer for quantification. The chemical variables and the FI flow parameters were carefully optimized. With a sample loading volume of 4.8 ml, quantitative retention of lead was obtained, along with an enrichment factor of 11.3 and a sampling frequency of 50 h(-1). A detection limit of 4 ng l(-1), defined as 3 times the blank standard deviation (3 sigma), was achieved along with a RSD value of 1.6% at the 0.4 microg l(-1) level. The procedure was validated by determining lead contents in two certified reference materials, and its practical applicability was further demonstrated by analysing a variety of biological and environmental samples.

Flow Injection Analysis↗
PubMed1991

Simultaneous determination of acetylsalicylic and salicylic acids in human serum and aspirin formulations by second-derivative synchronous fluorescence spectrometry.

A second-derivative synchronous scanning spectrofluorimetric method for the simultaneous determination of acetylsalicylic acid (ASA) and salicylic acid (SA) is described. The method is based on the native fluorescence of both acids in a 1% acetic acid-chloroform solution. Both ASA and SA can be determined within the concentration ranges 0.2-70 and 0.03-10 micrograms ml-1, respectively. The effect of each acid on the signal of the other has been studied in detail. Empirical equations have been used to overcome this effect, thus allowing the accurate determination of both acids in binary mixtures, without a separation step. The method has been applied to the determination of ASA and SA in blood serum and to the determination of SA impurities in aspirin formulations. Recoveries from sera spiked with both ASA (2.5-50 micrograms ml-1) and SA (100-160 micrograms ml-1) varied from 99.5 to 106.7% (mean = 102.6%) and from 93.0 to 98.0% (mean = 95.8%), respectively. Recoveries of SA from spiked aspirin solutions (0.25-1.5 mg g-1 of aspirin) varied from 98.0 to 102.0% (mean = 100.3%).

Aspirin↗
PubMed2001

Microwave treatment of biological samples for methylmercury determination by high performance liquid chromatography-cold vapour atomic fluorescence spectrometry.

A simple and rapid microwave-assisted alkaline digestion procedure was developed in combination with high performance liquid chromatography-ultraviolet post-column oxidation-cold vapour atomic fluorescence spectrometric detection for methylmercury determination in biological tissues. Since the stability of methylmercury in methanolic potassium hydroxide solution under microwave irradiation was verified, the microwave-assisted extraction procedure was optimized in terms of quantitative recovery of methylmercury and minimum time required. The alkaline extracts were subjected to clean-up steps with dichloromethane and hydrochloric acid in order to reduce matrix interferences in methylmercury determination. The effects of matrix interferences were checked by comparison of the slopes corresponding to calibration and standard addition curves. The accuracy of the method was evaluated by the analysis of two biological certified reference materials, NRC TORT-2 and BCR 463. The results obtained by the proposed method were in good agreement with the certified values of methylmercury concentration in both materials. The detection limit was 10 microg kg(-1) and the relative standard deviation was < 8% for methylmercury concentrations ranging from 0.15 to 3.0 mg kg(-1).

Animals↗
PubMed2002

Determination of mercury by continuous flow cold vapor atomic fluorescence spectrometry using micromolar concentration of sodium tetrahydroborate as reductant solution.

Systematic experiments were conducted to evaluate and compare the analytical figures of merit of two reducing agents (SnCl2 and NaBH4) in a continuous flow cold vapor atomic fluorescence mercury analyzer. It was found that sodium tetrahydroborate can efficiently reduce Hg2+ in various environmental samples at a concentration as low as 10 microM (ca. 3.8 x 10(-5)% w/v). Most commonly encountered transition metals (Fe2+, Fe3+, Zn2+, Cu2+, Ni2+, Pb2+ and Cr3+) did not interfere with total Hg determination. No interference from hydride-forming elements (Se4+, Sb3+ and As3+) was observed. Interference caused by Mn2+ and Ag+ could be readily removed by dilution and by using appropriate modification of the reaction matrix. A higher concentration of NaBH4 (0.1 M) is stable for I month when stored in the NaOH matrix (0.2 M) and at low temperature (4 degrees C). A working solution of NaBH4 can be freshly prepared by dilution. With NaBH4, the whole continuous flow system is kept clean much more easily as no precipitate is formed, which in turn considerably reduces memory effects, simplifies analytical operation and reduces the chemical cost six-fold.

Animals↗
PubMed2004

[Constant-energy synchronous fluorescence spectrometry for simultaneous determination of anthracene and 9,10-dimethylanthracene].

A new method of constant-energy synchronous fluorimetry to determine anthracene and 9,10-dimethylanthracene simultaneously is suggested. The spectral resolution of the constant-energy synchronous fluorescence spectra of these two compounds was much higher than that of conventional spectra. The linear ranges for anthracene and 9,10-dimethylanthracene were 0-2 microg x mL(-1) and 0-5 microg x mL(-1) respectively. The detection limits of anthracene and 9,10-dimethylanthracene were 2.2 ng x mL(-1) and 1.7 ng x mL(-1) respectively, and the relative standard deviation was less than 2%. When the new method was used for the determination of anthracene and 9,10-dimethylanthracene in water samples, the recoveries were in the range of 85% to 103%. This method has proved to be simple and rapid.

Anthracenes↗