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1.
a—Fe2O3粉体材料的制备与气敏性能研究   总被引:1,自引:0,他引:1  
采用相转移法研制单分散a-Fe2O3超细粉,研究了制备工艺对Fe2O3萃取率的影响,并对超细粉进行了X射线衍射、透射电镜和红外光谱表征,结果表明:无机溶胶的pH值、表面活性剂的用量、萃取剂等对超细粉的产率有影响,超细粉的颗粒尺寸的40nm,为稳定的非晶态单分散Fe2O3。就所制备的超细a-Fe2O3粉末的气体灵敏度而言,相转移法优于化学沉淀法。  相似文献   

2.
通过α-Fe2O3单分散溶胶在不同羟基羧酸中的絮-稳定情况阐述了该类絮凝剂对α-Fe2O3的絮凝特点:羟基酸絮凝剂使α-Fe2O3单分散溶胶发生絮凝和再稳定的机理不同于一般电解质,属于吸附络合絮凝。  相似文献   

3.
通过α-Fe2O3单分散溶胶在不同羟基羧酸中的絮凝-稳定情况阐述了该类絮凝剂对α-Fe2O3的絮凝特点:羟基酸絮凝剂使α-Fe2O3单分散溶胶发生絮凝和再稳定的机理不同于一般电解质,属于吸附络合絮凝.絮凝能力因絮凝剂的结构差异而不同,絮凝-稳定性均受体系中絮凝剂浓度及pH值的制约.  相似文献   

4.
采用溶胶-凝胶法制备了α-Fe2O3-Al2O3-Na2O复合超微粉,对微粉及其烧结后的物相及粒度进行了分析。湿敏特性测试结果表明:纳米级α-Fe2O3-Al2O3-Na2O陶瓷元件的感湿灵敏度高于简单氧化物机械混合后制成的α-Fe2O3-Al2O3-Na2O陶瓷元件,并具有较快的响应特性及较好的稳定性。  相似文献   

5.
采用α-FeOOH脱水法合成了Mn,Co,Ni,Zn等二价金属离子掺杂的α-Fe2O3气敏材料,用X射线衍射仪测定了材料的结构和组成;用动态气敏测试法测试了气氛、温度对α-Fe2O3电导和气敏性能的影响;用空间电荷层模型讨论了这些材料的气敏机理。  相似文献   

6.
用Sol-gel法制备了平均粒径6nm的均匀α-Fe_2O_3超微细粉,用TG-DTA,XRD和TEM分析了样品的稳定性和结构,并测定了该样品的气敏性能;结果表明,用该材料制成的气敏元件对酒精有较高的灵敏度和较好的选择性。  相似文献   

7.
染色体显带技术在烟草遗传育种方面有着重要的应用价值。本试验在比较常规制片和F一BSG酶解火焰干燥制片方法的基础上,提出用6%NaHCO_3代替F一BSG中的5%Ba(OH)_2对染色体进行变性处理,处理时间-20~25分钟显带效果较好。用对二氯苯饱和水溶液对烟草根尖预处理3~5小时可以积累较多的细胞有丝分裂相。  相似文献   

8.
分别用胶溶法和微乳液法合成了纳米尺寸的α-Fe2O3,并对其制备工艺进行了研究和讨论.气敏材料试验表明,两种方法得到的α-Fe2O3皆具气敏性,其气体灵敏度较化学沉淀法材料高,有可能用作可燃气体普敏材料.此外,该材料在水和有机溶剂中皆有较好的分散性和透明性,可做透明铁红颜料.  相似文献   

9.
超微粒a-Fe_2O_3气敏机理初探徐甲强,沈瑜生(化学工程系)(中国科技大学)关键词气敏机理;超微粒氧化铁;表面吸附;气敏效应;电子能谱中图分类号TQ174.05O649.4氧化物气敏材料的敏感机理主要有两种类型:一种是表面控制型(借助气体的表面吸...  相似文献   

10.
黄刺玫色素及其稳定性研究   总被引:9,自引:0,他引:9  
实验表明,黄刺玫色素的热稳定性、光稳定性、抗氧化性、抗还原性均较差,Fe2+和Fe3+使色素的吸光度下降,但Ca2+、Mg2+和Cu2+对色素没有影响。经统计学分析,黄刺玫色素的光解与热降解速度符合一级动力学,其中前者的动力学方程为1gOD=-0.2883-0.0185τ,后者的动力学方程为1gOD=1gOD0-τ·10(-2.645+0.0137T)。分析初步判定黄刺玫色素为花青素。  相似文献   

11.
Since grapevine ( Vitis spp .) rootstock material is being traded increasingly as disbudded woody material a lack of distinctive morphological features on such material necessitates an alternative and reliable means of identification. Methods described here were developed for rapid and efficient extraction of DNA from woody samples rich in phenolic compounds and polysaccharides, and for subsequent identification of varieties by RAPD PCR. Using these methods, and with the application of only one selected RAPD primer, we were able to differentiate sixteen rootstock varieties, including the seven varieties most commonly used in Germany. Problems commonly encountered with reproducibility of RAPD patterns were avoided by choosing primers with a dinucleotide sequence and a high G/C content that allowed a rather high annealing temperature of 45°C. Methods described here should also be useful for other horticultural crops, especially those with woody tissues rich in phenolic compounds and polysaccharides.  相似文献   

12.
An internet website (http://cpf.jrc.it/smt/) has been produced as a means of dissemination of methods of analysis and supporting spectroscopic information on monomers and additives used for food contact materials (principally packaging). The site which is aimed primarily at assisting food control laboratories in the European Union contains analytical information on monomers, starting substances and additives used in the manufacture of plastics materials. A searchable index is provided giving PM and CAS numbers for each of 255 substances. For each substance a data sheet gives regulatory information, chemical structures, physico-chemical information and background information on the use of the substance in particular plastics, and the food packaging applications. For monomers and starting substances (155 compounds) the infra-red and mass spectra are provided, and for additives (100 compounds); additionally proton NMR are available for about 50% of the entries. Where analytical methods have been developed for determining these substances as residual amounts in plastics or as trace amounts in food simulants these methods are also on the website. All information is provided in portable document file (PDF) format which means that high quality copies can be readily printed, using freely available Adobe Acrobat Reader software. The website will in future be maintained and up-dated by the European Commission's Joint Research Centre (JRC) as new substances are authorized for use by the European Commission (DG-ENTR formerly DGIII). Where analytical laboratories (food control or other) require reference substances these can be obtained free-ofcharge from a reference collection housed at the JRC and maintained in conjunction with this website compendium.  相似文献   

13.
The characterization of the aromatic profile of several apricot cultivars with molecular tracers in order to obtain objective data concerning the aromatic quality of this fruit was undertaken using headspace–solid phase microextraction (HS–SPME). Six apricot cultivars were selected according to their organoleptic characteristics: Iranien, Orangered, Goldrich, Hargrand, Rouge du Roussillon and A4025. The aromatic intensity of these varieties measured by HS–SPME–Olfactometry were defined and classified according to the presence and the intensity of grassy, fruity and apricot like notes. In the six varieties, 23 common volatile compounds were identified by HS–SPME–GC–MS. Finally, 10 compounds, ethyl acetate, hexyl acetate, limonene, β-cyclocitral, γ-decalactone, 6-methyl-5-hepten-2-one, linalool, β-ionone, menthone and (E)-hexen-2-al were recognized by HS–SPME–GC–O as responsible of the aromatic notes involved in apricot aroma and considered as molecular tracers of apricot aromatic quality which could be utilized to discriminate apricot varieties.  相似文献   

14.
The advent of the functional barrier concept in food packaging has brought with it a requirement for fast tests of permeation through potential barrier materials. In such tests it would be convenient for both foodstuffs and materials below the functional barrier (sub-barrier materials) to be represented by standard simulants. By means of inverse gas chromatography, liquid paraffin spiked with appropriate permeants was considered as a potential simulant of sub-barrier materials based on polypropylene (PP) or similar polyolefins. Experiments were performed to characterize the kinetics of the permeation of low molecular weight model permeants (octene, toluene and isopropanol) from liquid paraffin, through a surrogate potential functional barrier (25 μm-thick oriented PP) into the food simulants olive oil and 3% (w/v) acetic acid. These permeation results were interpreted in terms of three permeation kinetic models regarding the solubility of a particular model permeant in the post-barrier medium (i.e. the food simulant). The results obtained justify the development and evaluation of liquid sub-barrier simulants that would allow flexible yet rigorous testing of new laminated multilayer packaging materials.  相似文献   

15.
BADGE.2HCl and BFDGE.2HCl were determined in 28 samples of ready-to-drink canned coffee and 18 samples of canned vegetables (10 corn, 5 tomatoes and 3 others), all from the Japanese market. HPLC was used as the principal analytical method and GCMS for confirmation of relevant LC fractions. BADGE.2HCl was found to be present in one canned coffee and five samples of corn, BFDGE.2HCl in four samples of canned tomatoes and in one canned corn. No sample was found which exceeded the 1mg/kg limit of the EU for the BADGE chlorohydrins. However the highest concentration was found for the sum of BFDGE.2HCl and BFDGE.HCl.H2O at a level of 1.5mg/kg. A Beilstein test confirmed that all cans containing foods contaminated with BADGE.2HCl or BFDGE.2HCl had at lest one part coated with a PVC organosol.  相似文献   

16.
17.
A strong science base is required to underpin the planning and decision-making process involved in determining future European community legislation on materials and articles in contact with food. Significant progress has been made in the past 5 years in European funded work in this area, with many developments contributing to a much better understanding of the migration process, and better and simpler approaches to food control. In this paper this progress is reviewed against previously identified work-areas (identified in 1994) and conclusions are reached about future requirements for R&D to support legislation on food contact materials and articles over the next 5 or so years.  相似文献   

18.
19.
This paper describes the second part of a project undertaken to develop certified mussel reference materials for paralytic shellfish poisoning toxins. In the first part two interlaboratory studies were undertaken to investigate the performance of the analytical methodology for several PSP toxins, in particular saxitoxin and decarbamoyl-saxitoxin in lyophilized mussels, and to set criteria for the acceptance of results to be applied during the certification exercise. Fifteen laboratories participated in this certification study and were asked to measure saxitoxin and decarbamoyl-saxitoxin in rehydrated lyophilized mussel material and in a saxitoxin-enriched mussel material. The participants were allowed to use a method of their choice but with an extraction procedure to be strictly followed. The study included extra experiments to verify the detection limits for both saxitoxin and decarbamoyl-saxitoxin. Most participants (13 of 15) were able to meet all the criteria set for the certification study. Results for saxitoxin.2HCl yielded a certified mass fraction of <0.07 mg/kg in the rehydrated lyophilized mussels. Results obtained for decarbamoyl-saxitoxin.2HCl yielded a certified mass fraction of 1.59+/-0.20 mg/kg. The results for saxitoxin.2HCl in enriched blank mussel yielded a certified mass fraction of 0.48 +/- 0.06 mg/kg. These certified reference materials for paralytic shellfish poisoning toxins in lyophilized mussel material are the first available for laboratories to test their method for accuracy and performance.  相似文献   

20.
<正>We are pleased to announce the launch of a new international peer-reviewed journal-Food Science and Human Wellness,ISSN 2213-4530,which is an open access journal,produced and hosted by Elsevier B.V.on behalf of Beijing Academy of Food Sciences.Food Science and Human Wellness is an international peer-reviewed English journal that provides a forum for the dissemination of the  相似文献   

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