共查询到17条相似文献,搜索用时 171 毫秒
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Matsumoto N Shimosaka T Watanabe T Kato K 《Analytical and bioanalytical chemistry》2008,391(6):2061-2069
One method of preparing a primary reference gas mixture is the gravimetric blending method. Uncertainty of a few mg in mass
measurements is unavoidable when preparing reference gas mixtures under current laboratory conditions with our facilities,
equipment, and materials. There are many sources of errors when using this method. In this study, several sources of errors
were re-evaluated for our process for preparation of carbon dioxide in synthetic air. As a consequence of the re-evaluation,
it was found that some sources of errors had significant effects on gravimetric concentrations of the gas mixtures. These
sources are: (1) different masses of the reference cylinder and sample cylinder (an error in the readings of the electronic
mass comparator), (2) leakage of the inner gas from valves of the cylinders, and (3) cooling of the gas cylinder caused by
filling with high-pressure liquefied carbon dioxide gas. When the mass measurements were performed under uncontrolled conditions,
the errors due to sources (1), (2), and (3) were as high as 20 mg, 24 mg, and 13 mg, respectively. In this paper, the detailed
results from re-evaluation of these sources of errors are discussed.
Figure Evaluation of the source of error (1) 相似文献
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Nobuhiro Matsumoto Takuro Watanabe Kenji Kato 《Accreditation and quality assurance》2005,10(7):382-385
There are many error sources in the preparation of primary reference gas mixtures by the gravimetric method. One of the error
sources is the adsorption/desorption of moisture on the external gas cylinder surface. Variation of relative humidity in atomospheric
air around the cylinder during the preparation process may cause an error in the mass measurement of the gas cylinder. Effect
of the adsorption/desorption on the surface is dependent on the condition of the external cylinder surface. In this study,
various types of cylinders are precisely weighed under different humidity conditions. Hairline finish and shot blast finish
are preferable treatments for the external cylinder surface in our experiments. The use of cylinders with painted surface
should be avoided as possible if the humidity control in the rooms is insufficient.Table 1 Tested cylinders with various finishes on external surfaces 相似文献
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Rhoderick GC 《Analytical and bioanalytical chemistry》2007,387(7):2425-2432
New US federal low-level automobile emission requirements, for example zero-level-emission vehicle (ZLEV), for hydrocarbons and other species, have resulted in the need by manufacturers for new certified reference materials. The new emission requirement for hydrocarbons requires the use, by automobile manufacturing testing facilities, of a 100 nmol mol(-1) propane in air gas standard. Emission-measurement instruments are required, by federal law, to be calibrated with National Institute of Standards and Technology (NIST) traceable reference materials. Because a NIST standard reference material (SRM) containing 100 nmol mol(-1) propane was not available, the US Environmental Protection Agency (EPA) and the Automobile Industry/Government Emissions Research Consortium (AIGER) requested that NIST develop such an SRM. A cylinder lot of 30 gas mixtures containing 100 nmol mol(-1) propane in air was prepared in 6-L aluminium gas cylinders by a specialty gas company and delivered to the Gas Metrology Group at NIST. Another mixture, contained in a 30-L aluminium cylinder and included in the lot, was used as a lot standard (LS). Using gas chromatography with flame-ionization detection all 30 samples were compared to the LS to obtain the average of six peak-area ratios to the LS for each sample with standard deviations of <0.31%. The average sample-to-LS ratio determinations resulted in a range of 0.9828 to 0.9888, a spread of 0.0060, which corresponds to a relative standard deviation of 0.15% of the average for all 30 samples. NIST developed its first set of five propane in air primary gravimetric standards covering a concentration range 91 to 103 nmol mol(-1) with relative uncertainties of 0.15%. This new suite of propane gravimetric standards was used to analyze and assign a concentration value to the SRM LS. On the basis of these data each SRM sample was individually certified, furnishing the desired relative expanded uncertainty of +/-0.5%. Because automobile companies use total hydrocarbons to make their measurements, it was also vital to assign a methane concentration to the SRM samples. Some of the SRM samples were analyzed and found to contain 1.2 nmol mol(-1) methane. Twenty-five of the samples were certified and released as SRM 2765. 相似文献
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Hans-Peter Haerri Timothée Deblock Pierre Pringalle José Garcia Andreas Ackermann Cédric Couret 《Accreditation and quality assurance》2012,17(3):253-264
A sampling method for the analysis of small amounts of gases from sealed containers is described. Liquefied pressurised gas samples were expanded into a vacuum box and statically diluted with ultrapure nitrogen. The equations for the sample dilution were established, relating the measured impurity amount fractions in the sample mixture to their partial pressures in the sealed container and, in the case of oxygen, to the air pressure. Ion?Cmolecule reaction mass spectrometry allowed identification and measurement of trace impurities corresponding to partial pressures in the range of 1?hPa in the container. The method was applied for determining the identity and amount of gaseous impurities in n-butane used in implantable gas pressure?Coperated drug infusion pumps. Impurities from the n-butane supply cylinder or from decomposition products, for example due to the laser welding of the Ti plugs of the containers, could be excluded by the results of saturation vapour pressure measurements, FID gas chromatograms and IMR mass spectra. The variability in pressure versus volume among tested infusion pump samples was associated with excess oxygen, attributable to an excessive residual air pressure in the gas containers before they were filled with n-butane. The sample preparation method is principally applicable to measure the composition of small amounts of gas mixtures and gaseous impurities with identified IMR mass spectra down to trace levels??even for ubiquitous substances like oxygen. The volume of the produced gas mixtures allows characterisation of the gas by standard gas analytical methods and for impurities by trace gas analytical methods. 相似文献
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A procedure was established for the determination of ethanol in water samples by isotope dilution analysis. After spiking the sample with labelled [13C2]ethanol, it was analysed by gas chromatography-combustion-isotope ratio mass spectrometry. Results are reported for two certified reference materials and also ethanol solutions prepared for a CITAC (Co-operation on International Traceability in Analytical Chemistry) interlaboratory comparison. The certified reference materials were certified using the dichromate titration method at nominal levels of 80 and 200 mg per 100 mL. The CITAC solutions were prepared gravimetrically at nominal levels of 50, 80 and 200 mg per 100 mL. The results of the analysis agree well to within 0.5% of the gravimetric values of the different samples. The relative expanded standard uncertainties (with a coverage factor equal to 2) associated with the results varied between 0.18 and 0.37%, a range that encompassed the gravimetric values for the different samples. A complete uncertainty budget was also drawn up so that the different contributions could be identified and quantified. The main contributions were due to variations in the measured isotope amount ratios and a 'between' blend component introduced to quantify the contribution of factors such as the degree of matching of the isotope amount ratios between standards and samples used in the isotope dilution analysis. 相似文献
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采用重量法对灰岩中的二氧化碳进行测定。首先用酸分解试样,在载气作用下,产生的二氧化碳被吸收液完全吸收,最后用重量法间接求出二氧化碳的含量。实验结果准确度高,矿石中的硫不干扰测定,可测定0.1%以上的二氧化碳。不经过复杂的气体净化步骤,操作准确、简单、易行,可用于灰岩中二氧化碳的测定。 相似文献