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1.
Gotthard Staats 《Fresenius' Journal of Analytical Chemistry》1995,352(5):413-419
The requirements for truth and trueness in inorganic bulk and trace analysis are discussed. Optimum conditions for the generation of true values by a defined number of atoms/molecules of the analyte are presented. Trueness of analytical values is established by traceability as defined by ISO Guide 25 to true values based on SI units. Consequences for the validation of methods, analysis of batches and the continuous analysis for production control are given and the role of statistics is discussed.Dedicated to Professor Dr. Klaus Doerffel on the occasion of his 70th anniversary in admiration of his life work 相似文献
2.
There exist large amounts of detergent fiber analysis data [neutral detergent fiber (NDF), acid detergent fiber (ADF), acid
detergent lignin (ADL)] for many different potential cellulosic ethanol feedstocks, since these techniques are widely used
for the analysis of forages. Researchers working in the area of cellulosic ethanol are interested in the structural carbohydrates
in a feedstock (principally glucan and xylan), which are typically determined by acid hydrolysis of the structural fraction
after multiple extractions of the biomass. These so-called dietary fiber analysis methods are significantly more involved
than detergent fiber analysis methods. The purpose of this study was to determine whether it is feasible to correlate detergent
fiber analysis values to glucan and xylan content determined by dietary fiber analysis methods for corn stover. In the detergent
fiber analysis literature cellulose is often estimated as the difference between ADF and ADL, while hemicellulose is often
estimated as the difference between NDF and ADF. Examination of a corn stover dataset containing both detergent fiber analysis
data and dietary fiber analysis data predicted using near infrared spectroscopy shows that correlations between structural
glucan measured using dietary fiber techniques and cellulose estimated using detergent techniques, and between structural
xylan measured using dietary fiber techniques and hemicellulose estimated using detergent techniques are high, but are driven
largely by the underlying correlation between total extractives measured by fiber analysis and NDF/ADF. That is, detergent
analysis data is correlated to dietary fiber analysis data for structural carbohydrates, but only indirectly; the main correlation
is between detergent analysis data and solvent extraction data produced during the dietary fiber analysis procedure. 相似文献
3.
Luisa Pasti Salvatore Roccasalvo Francesco Dondi Pierluigi Reschiglian 《Journal of Polymer Science.Polymer Physics》1995,33(8):1225-1234
In this paper the high-temperature thermal field flow fractionation method is exploited for the analysis of polyethylene (PE). The experimental apparatus set-up, obtained by simply modifying a commercial instrument, is presented. The numerical procedure for deriving retention calibration plot versus molecular weight is discussed with reference to the specific polymer-solvent pair, PE-o-dichlorobenzene (ODCB), here employed. Different methods for computing the physicochemical data set of the solvent, necessary for calibration, are compared. The selectivity of the checked PE-ODCB system proves comparable with respect to the values currently found in thermal field-flow fractionation (ThFFF) analysis. Differences are found between PE and polystyrene (PS) analysis in the same solvent. The conditions for high temperature ThFFF operation in PE analysis and their advantages are discussed with respect to the standard SEC technique for PE, PS, and PE-PS copolymer analysis. Molecular weight distributions obtained by ThFFF of two PE commercial samples agree with those obtained by SEC. © 1995 John Wiley & Sons, Inc. 相似文献
4.
The ion microanalyzer permits a localized mass spectrometric analysis, i.e. the qualitative and quantitative analysis of the
impurities contained in a small selected volume. This procedure makes possible the analysis of very thin epitaxial layers
(for example silicon and gallium arsenide). As regards qualitative analysis, the apparatus is designed for the selection of
ions. After the recording and analysis of the ion spectrum, a large number of the impurities present in the sample are determined
qualitatively. Quantitative analysis can be performed with the equipment, but this requires the analysis of a homogeneous
standard sample previously dosed by spark-source mass spectrometry. The quantitative analysis of bulk and epitaxial silicon
and gallium arsenide is described and the limits of detection of the principal impurities are given. It is also shown how
the possibility of localized analysis was exploited. A correlation was established between the existing impurities and the
chemically revealed crystal imperfections. A comparative analysis of the distribution of the impurities in the epitaxial layers
was also carried out. The periodic analysis of epitaxial layers makes it possible to follow the deterioration by contamination,
if any, under the epitaxial conditions, and to improve the sample quality. 相似文献
5.
Tamara M. Huber Margit Schwikowski Heinz W. Gggeler 《Journal of chromatography. A》2001,920(1-2):193-200
A new method for determining concentrations of organic and inorganic ions in ice cores by continuous melting and contemporaneous ion chromatographic analyses was developed. A subcore is melted on a melting device and the meltwater produced is collected in two parallel sample loops and then analyzed simultaneously by two ion chromatographs, one for anions and one for cations. For most of the analyzed species, lower or equal blank values were achieved with the continuous melting and analysis technique compared to the conventional analysis. Comparison of the continuous melting and ion chromatographic analysis with the conventional analysis of a real ice core segment showed good agreement in concentration profiles and total amounts of ionic species. Thus, the newly developed method is well suited for ice core analysis and has the advantages of lower ice consumption, less time-consuming sample preparation and lower risk of contamination. 相似文献
6.
Sensitivity analysis is an important tool in model validation and evaluation that has been employed extensively in the analysis of chemical kinetic models of combustion processes. The input parameters of a chemical kinetic model are always associated with some uncertainties, and the effects of these uncertainties on the predicted combustion properties can be determined through sensitivity analysis. In this work, first- and second-order global and local sensitivity coefficients of ignition delay time with respect to the scaling factor for reaction rate constants in chemical kinetic mechanisms for combustion of H2, methane, n-butane, and n-heptane are examined. In the sensitivity analysis performed here, the output of the model is taken to be natural logarithm of ignition delay time and the input parameters are the natural logarithms of the factors that scale the reaction rate constants. The output of the model is expressed as a polynomial function of the input parameters, with up to coupling between two input parameters in the present sensitivity analysis. This polynomial function is determined by varying one or two input parameters, and allows the determination of both local and global sensitivity coefficients. The order of the polynomial function in the present work is four, and the factor that scales the reaction rate constant is in the range from 1/e to e, where e is the base of the natural logarithm. A relatively small number of sample runs are required in this approach compared to the global sensitivity analysis based on the highly dimensional model representation method, which utilizes random sampling of input (RS-HDMR). In RS-HDMR, sensitivity coefficients are determined only for the rate constants of a limited number of reactions; the present approach, by contrast, affords sensitivity coefficients for a larger number of reactions. Reactions and reaction pairs with the largest sensitivity coefficients are listed for ignition delay times of four typical fuels. Global sensitivity coefficients are always positive, while local sensitivity coefficients can be either positive or negative. A negative local sensitivity coefficient indicates that the reaction promotes ignition, while a positive local sensitivity coefficient suggests that the reaction actually suppresses ignition. Our results show that important reactions or reaction pairs identified by global sensitivity analysis are usually rather similar to those based on local sensitivity analysis. This finding can probably be attributed to the fact that the values of input parameters are within a rather small range in the sensitivity analysis, and nonlinear effects for such a small range of parameters are negligible. It is possible to determine global sensitivity coefficients by varying the input parameters over a larger range using the present approach. Such analysis shows that correlation effects between an important reaction and a minor reaction can have relatively sizable second-order sensitivity coefficient in some cases. On the other hand, first-order global sensitivity coefficients in the present approach will be affected by coupling between two reactions, and some results of the first-order global sensitivity analysis will be different from those determined by local sensitivity analysis or global sensitivity analysis under conditions where the correlation effects of two reactions are neglected. The present sensitivity analysis approach provides valuable information on important reactions as well as correlated effects of two reactions on the combustion characteristics of a chemical kinetic mechanism. In addition, the analysis can also be employed to aid global sensitivity analysis using RS-HDMR, where global sensitivity coefficients are determined more reliably. 相似文献
7.
A commercially available system is described for the fully automated clean-up and high-performance liquid chromatographic (HPLC) analysis of aflatoxins in foods and animal feeds. The system marketed primarily for handling solid-phase extraction columns has modified software to facilitate use with immunoaffinity columns. Sample extract clean-up followed by injection onto an HPLC column with post-column iodination and fluorescence detection is carried out completely unattended. A coefficient of variation of 5.1% for aflatoxin B1 analysis was obtained, and the accuracy of the system was demonstrated by the analysis of peanut butter certified reference material. 相似文献
8.
Jaime Gallego Catherine Batiot-Dupeyat Fanor Mondragón 《Journal of Thermal Analysis and Calorimetry》2013,114(2):597-602
In this work, we studied the effect of acid type in the final properties of CNTs as the resistance to air oxidation; for this, different techniques of characterization were used such as Raman spectroscopy, thermogravimetric analysis, and chemical analysis by ICP-AES. Through Raman spectroscopy, it is possible to monitor the structural changes induced by acids and this is reflected in changing of the activation energies for the different processes determined by thermogravimetric analysis; also by ICP-AES analysis, it was shown that the inorganic material was eliminated efficiently with the acid treatments used in this study. 相似文献
9.
The use, for analysis, of K X-rays proceeding from metastable and beta-emitting radionuclides—produced by neutron activation—is an undeveloped aspect of activation analysis. Consequently, this study examines the feasibility of applying X-ray spectrometry to isotope source activation analysis and in particular the determination of Sm and Eu at low levels is described. Generally speaking, the sensitivity is seriously restricted by the thermal neutron flux of the source but in certain specific cases the analysis is favoured by the nuclear properties of the elements concerned. Therefore, the selection of elements was based largely on their demand for analysis and their ability to produce a practicable yield. Optimum signalto-noise ratios were attained by employing a detector that was particularly sensitive at energies below 150 keV. Analytical conditions are demonstrated for the elements of interest over a wide range of concentrations in small samples, and ultimately the applicability of the method was tested by the analysis of a typical monazite sample. The analytical potential of the method is thoroughly appraised and possible practical applications are discussed. 相似文献
10.
11.
D. G. Filatova V. V. Es’kina A. S. Chizhov M. N. Rumyantseva P. A. Shaposhnik V. B. Baranovskaya Yu. A. Karpov 《Journal of Analytical Chemistry》2016,71(5):496-499
An approach is proposed to the determination of selenium and cadmium dopants in new nanocomposites based on zinc and indium oxides. The approach is based on a combination of highly efficient high resolution continuous source electrothermal atomic absorption spectrometry (ETAAS) for the analysis of suspensions and inductively coupled plasma mass spectrometry for the analysis of solutions. A procedure is developed for the determination of Se and Cd dopants and matrix components based on Zn and In in nanocomposite solutions by inductively coupled plasma mass spectrometry. Stabilizing agents for the preparation of suspensions are studied for the ETAAS analysis of powders without their decomposition. The results of determination of CdSe dopants by high resolution ETAAS are validated by inductively coupled plasma mass spectrometry. 相似文献
12.
Scriba GK 《Electrophoresis》2003,24(15):2409-2421
Capillary electrophoresis is often considered an ideal method for the chiral analysis of compounds due to the high separation power of the technique and has therefore found widespread acceptance for the analysis of drugs and pharmaceuticals. In contrast, capillary electrochromatography is still more or less in an infancy state searching for its place among the analytical separation techniques although interesting applications have been published. The present review summarizes recent developments and applications of chiral pharmaceutical analysis by electromigration techniques published in 2002 and early 2003. 相似文献
13.
Kil-Yong Lee Sang-Kwan Shim Yoon-Yeol Yoon Yong-Sam Chung Gae-Ho Lee 《Journal of Radioanalytical and Nuclear Chemistry》1999,241(1):129-134
Neutron activation analysis (NAA) has been studied to improve the accuracy and sensitivity of the analysis of trace and ultratrace
metallic impurities in plastic materials. There are two main problems in the analysis of plastics by NAA. First the contamination
during sample preparation, especially sample crushing procedure is very serious for ultratrace analysis. Another problem is
the destruction of the sample capsule due to the pressure build-up by the gases formed during neutron irradiation. A simple
preparation technique of the sample crushing method using liquid nitrogen and reducing the capsule pressure by a pin hole
was developed to solve the above problems. Two different irradiation and seven cooling conditions were also investigated to
optimize the experimental conditions. A SRM from NIST (1632b coal) has been used to investigate the accuracy of the analysis.
More than thirty elements could be analyzed in the range of sub-ppb to percent. Samples analyzed in this work were polyethylene
and polypropylene which were made by different manufacturing procedure, and pigments. Two kinds of plastic products used for
food and drug containers were also analyzed. It was found that NAA could be a powerful technique for the analysis of metallic
impurities in plastics even though their concentrations were at ultratrace levels. 相似文献
14.
N. N. Papadopoulos 《Journal of Radioanalytical and Nuclear Chemistry》1981,61(1-2):81-91
An inexpensive automatic pneumatic transfer system for uranium and thorium analysis by delayed neutron counting and for the
activation analysis of short-lived radioisotopes has been developed, constructed and installed at the Nuclear Research Center
Demokritos. Over 500 samples of solid uranium ore samples or liquid solutions of extracted uranium can be analysed daily by
this system. Simplicity, safety, speed of operation, flexibility, sensitivity, accuracy and especially low cost are the main
advantages of this analyzer. An improved version, with possibilities of cyclic activation analysis and faster capsule return
times for very short-lived radioisotope analysis, is being developed. 相似文献
15.
U Panne M Clara C Haisch R Niessner 《Spectrochimica Acta Part B: Atomic Spectroscopy》1998,53(14):1969-1981
Laser-induced plasma spectroscopy (LIPS) is employed for in situ and on-line process analysis of major glass constituents during a vitrification process for fly and bottom ashes from waste incineration. The system is based on an Nd:YAG laser for plasma ignition, while the elemental emissions from the plasma are detected time-resolved by an intensified multichannel analyzer. The perpendicular, single axis, imaging optics allow a remote sensing of the composition of the hot glass melt. Taking into account the plasma characteristics for calibration, good agreement between the LIPS analysis and the established reference analysis is achieved for the concentration ratios of SiO2, Al2O3, and CaO. In addition, LIPS is applied to the analysis of aerosols generated by homogeneous nucleation during the heating-up of the investigated fly ashes. A distinctive temperature dependence of the heavy metal concentration of the aerosols is observed. 相似文献
16.
17.
Quantitative analysis of particles, especially environmental particles in the submicron region, is hampered mainly by radiation
damage. It can already be observed for probe currents smaller than 1 nA and analysis times of 10 seconds. The main reason
for radiation damage is the storage of thermal energy in the particle, until the melting temperature is reached, and the subsequent
loss of one or more of the elements of the respective material, e.g. SOx in K2SO4. The lower the melting point, the more severe the specimen damage. The amount of specimen damage can vary substantially even
for particles of the same size and composition. Specimen damage on inorganic materials can be observed for energies as low
as 1 keV.
Thus radiation damage is the greatest obstacle to accurate quantitative analysis for particles in the submicron region, even
for analysis times as low as those used in automated particle analysis by CCSEM/EDXS. 相似文献
18.
The chemical analysis with inductively coupled plasma-mass spectrometry (ICP-MS) can help to examine the purity of ultra pure water (UPW) down to 10 part per trillion (ng/L) and lower. For a proper determination of a high number of samples per week the analysis must be divided into two parts: the routine analysis and the reference water analysis. The routine analysis is done by direct measurement of the ultra pure water samples. Applying a standard addition method under particular clean conditions, the reference water analysis leads to the definition of the accurate zero. A quick evaluation scheme is also presented for the reference water analysis. The method is tested for its fitness for application by examining LOD (for relevant element < 2 ng/L), reproducibility and linearity of calibration. The ICP-MS was optimized according to the methodology of G. Taguchi to improve reproducibility and LOD. 相似文献
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20.
Computerized image analysis (also known as video densitometry) is a low-cost and efficient technique for quantitative and qualitative analysis of planar separations, for example planar chromatography and gel electrophoresis. The plate is usually captured in black and white. Selecting the proper color channel of the image for analysis enhances the signal-to-noise ratio, however. Three-dimensional visualization of the planar image facilitates image inspection and is easy to achieve by use of OpenGL technology. Sensitivity is increased by use of longer acquisition times but this reduces the linearity of quantitative analysis. 相似文献