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51.
简便快速的硫化氢测定法 总被引:1,自引:0,他引:1
本文提出了有一种简易快速测定剂来测定水样中的硫化氢的方法。该法的检出限为0.1mg/L,对1.01mg/L的H2S样品7次测定的相对标准偏差<4.1%,1h能测定12个样品。用本测定了几种水样中的H2S含量,回收率为84%-105%。应用它可上标准法的4h左右缩短到5min;使分析成本降低9/10;不需配制一系列分析试剂和仪器,只需一支小型塑料管和几片药片,便于渔业水质和环境水质的野外现场监测。 相似文献
52.
IntroductionInthepastdecade ,itwasfoundthattwoaminoacidresidues ,SerandHis ,workastheactivesitesintheser ineprotease .1 3 Inourpreviouswork ,adipeptideseryl histidine (Ser His)wasfoundtohavetheproteinandnu cleosidescleavageactivity .4 7p Nitrophenylacetate (p NPA)w… 相似文献
53.
54.
Maiorova N. A. Khazova O. A. Tarasevich M. R. 《Russian Journal of Electrochemistry》2004,40(10):1060-1065
The kinetics of the hydrogen oxidation and the CO adsorption on a Pt (ultra)microelectrode is studied in a 0.5 M H2SO4 solution saturated with a mixture of gaseous H2 and CO at partial CO pressures p
CO = 10–500 ppm. The balance between rates of diffusion and adsorption of CO at different adsorption times is studied. Studied is the effect of CO impurities in H2 on steady-state polarization curves for the hydrogen ionization and nonsteady-state curves of the oxidation current decay with time at 0.02–0.05 V. Conditions under which in a certain time interval and at a certain CO concentration the slope of an I vs. t curve is proportional to p
CO are determined. The obtained dependence may be used when designing a technique for monitoring CO impurities in technical hydrogen. 相似文献
55.
Jocelyn Jalbert Roland Gilbert Pierre Tétreault Brigitte Morin Denise Lessard-Déziel 《Cellulose (London, England)》2007,14(4):295-309
In this study, headspace gas chromatography/mass spectrometry has been used to assess the volatile by-products generated by
the ageing of oil-impregnated paper insulation of power transformers. Sealed-glass ampoules were used to age under oxidative
conditions 0.5-g specimens of insulating paper in 9 mL of inhibited mineral oil in a temperature range of 60–120 °C and moisture
of 0.5, 1 and 2% (w/w). A linear relationship between one of the oil-soluble degradation by-products, i.e. methanol, and the
number of ruptured 1,4-β-glycosidic bonds of cellulose, regardless of the type of paper (ordinary Kraft or thermally-upgraded
(TU) Kraft paper), was established for the first time in this field. Ageing at 130 °C of model compounds of the Kraft paper
constituents (α-cellulose, hemicellulose and lignin) and two cellulosic breakdown by-products (D-(+)-glucose and 1,6-anhydro-β-d-glucopyranose) confirmed that the α-cellulose degradation was mostly responsible for the presence of this molecule in the
system. Furthermore, additional 130 °C-tests with six different papers and pressboard samples under a tight control of initial
moisture indicated that at least one molecule of methanol is formed for each rupture of 1,4-β-glucosidic bond of the molecular
chains. Stability tests showed that the ageing indicator is stable under the oxygen and temperature conditions of open-breathing
transformers. The presence of methanol was detected in 94% of oil samples collected from over than 900 in-service pieces of
equipment, confirming the potential for this application. Lastly, the tests have shown that oil-oxidation by-products and
TU-nitrogenous agents modify the methanol partitioning coefficients in the paper/oil/air system, which makes their study essential
over a range of field conditions encountered by power transformers. Results are presented and discussed in comparison with
2-furfuraldehyde, which is the current reference in the domain. 相似文献
56.
李和 《广东微量元素科学》2002,9(3):66-68
为研制司帕沙星软膏,建立其含量测定方法。用差示紫外分光光度法在306nm外测定司帕沙星的含量。平均回收率为99.98%,RSD为0.72%,线性范围15.62-40.14μg/ml。该法简便、准确、快捷。 相似文献
57.
58.
GC-MS法测定焦化厂气溶胶中多环芳烃 总被引:2,自引:0,他引:2
利用气相色谱-质谱(GC-MS),电子轰击离子化(EI)法测定焦化厂气溶胶中多环芳烃的含量。超声波抽提气溶胶样品,用GC-MS的选择离子监测(SIM)方式测定EPA提出的优先监测的16种多环芳烃的含量。该法的检出限为0.167pg·m~(-3),PAHs的回收率为85.1%~110.5%,相对标准偏差为4.62%~19.4%。应用该法测定气溶胶中PAHs获得满意的结果。 相似文献
59.
Proficiency testing involves the performance of test procedures on routine samples by a number of laboratories. Interlaboratory proficiency testings provide multiple benefits to participants since they play a key-role in the total quality control of laboratory activities. They serve as a means of self-improving, as a mechanism of continuing education and as a source of information for accreditation agencies. This review highlights basic principles, benefits, criteria and capabilities of a proficiency testing programme for food analysis laboratories as well as their role in the implementation of rapidly developing food control legislation. 相似文献
60.
C. Gonalves Joaquim C.G. Esteves da Silva M.F. Alpendurada 《Analytica chimica acta》2006,560(1-2):164-171
An extensive monitoring programme of pesticides was carried out in soil samples from an intensive horticulture area in north of Portugal, putting into practice the needs for increased control of soil quality as far as organic pollution is concerned. The area under investigation was additionally defined as vulnerable to nitrates due to local soil and aquifer characteristics, which might be extended to pesticides contamination. Five sampling sites were selected and soils analysed at three depths in eight sampling campaigns, for the period of 2 years. A stepwise multivariate statistical approach was selected to uncover most relevant patterns inside a complex environmental data matrix. Cluster analysis was applied both to group pesticides and samples, giving a primary and unsupervised overlook of privileged relationships. Clusters of persistent pesticides and selected herbicides were identified, whereas sample classes were also formed and disposed geographically. Thirty eight percent of analysed soils samples fell into one class characterized by low contamination (class 1 in cluster analysis), which is entirely representative of the sampling site no. 1. Afterwards, linear discriminant analysis was applied to identify those pesticides, which had a higher impact in the definition of classes. Finally, factor analysis using a five component model was implemented in order to bring to light the constitution and data variance explained by each of the five main principal components, as well as, their relation to pest management practices. A factor was identified (PC1 – 22% variance) composed of chlorinated pesticides, which was representative of one of the investigated sites indicating its high contamination status. Qualitative main findings and class average concentration values were obtained through this multivariate statistical approach. 相似文献