首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 78 毫秒
1.
<正> 八、磷酸盐测定磷酸盐时,先将不完全干燥的样品灰化,然后使磷酸盐水解为正盐,再以磷钼酸喹啉形式离析出来.1.原理:首先,将磷酸盐生成磷钼酸(有柠檬酸盐存在时),然后磷钼酸再与碱、喹啉形成磷钼酸喹啉.柠檬酸能与铵离子络合,阻止磷钼酸铵沉淀的出现.最初,测定时需要制备种两溶液,以生成磷钼酸喹啉沉淀;即柠檬酸—钼酸溶液和喹啉溶液.后来使用了丙酮,使这两种溶液合二为一,即可用一种试剂作为沉淀剂.我们把该沉淀剂称为喹钼柠酮试剂,它是由混合物中的喹啉、钼酸盐、柠檬酸盐和丙酮的英文名称的字头命名的.  相似文献   

2.
介绍了合成电导率较高的无机质子导体磷钼酸的新方法——离子交换法,用这种方法制磷钼酸快捷易操作.将磷钼酸分散在几种体系中制成磷钼酸导电膜,并测定它们的性能,结果表明,用PC溶解PAN作粘合剂制备的磷钼酸导电膜,性能稳定,电导率可达2.27×10- 4 S·cm - 1,有望在MH/Ni电池中得到应用  相似文献   

3.
高环氧值环氧大豆油制备工艺的研究   总被引:3,自引:1,他引:2  
研究了用一种新型催化剂制备环氧值大于6.8%的环氧大豆油的新方法,考察了加料方式、反应时间、反应温度、双氧水用量、催化剂用量对环氧值的影响,确定了环氧大豆油的最佳制备条件:采用逐步加料,按m(大豆油):m(20%双氧水):m(催化剂)=100:(85~100):(0.5~1)的比例加料。反应时间9h,反应温度55℃。  相似文献   

4.
催化分光光度法测定粮食中的硒含量   总被引:6,自引:0,他引:6  
研究了在盐酸介质中,硒催化次磷酸钠还原磷钼酸的钼蓝反应动力学条件,建立了高灵敏度测定痕量硒方法。线性范围0.00-0.10μg/10ml,相对标准偏差小于5%,加标回收率为95.8%~101.2%。用此方法定粮食中硒含量,仪器简单,方法简便,分析速度快,测定结果令人满意。  相似文献   

5.
活性炭固载对甲苯磺酸催化乙酸与乙醇的酯化反应   总被引:3,自引:0,他引:3  
在常压下,用回流吸附方法制备了活性炭固载对甲苯磺酸(TsoH/C)催化剂,采用反滴定法测定固载量。通过正文实验,找到催化剂最佳固载量为(48±0.5)%,最佳活化温度为120℃。首次提出用固载量为(48±0.5)%的TsOH/C催化摩尔比为1.5:1的乙酸与乙醇的酯化反应,在液相温度达到(108±2)℃时,可以92%的收率连续制备出乙酸乙酯。其折光率及红外光谱与文献值一致。该酯化工艺及非固载型对甲苯磺酸工艺相比,具有催化剂用量少,使用寿命长,酯收卒高,反应后处理工序简单,不污染环境,不腐蚀设备,酯化反应既可间歇操作又可连续操作等优点.  相似文献   

6.
于艳  洪哲 《皮革化工》2002,19(2):27-29
首次采用固体硫酸铁作催化剂,用饱和噁唑酮与醛酮反应,合成了10种不饱和噁唑酮。并通过m.p测定,IR测定,IR测定等,对产物进行了表征。  相似文献   

7.
钼蓝比色法测定还原型维生素C   总被引:75,自引:1,他引:74  
李军 《食品科学》2000,21(8):42-45
食品中还原型维生素C(L-VC)能将磷钼酸盐定量还原成蓝色的钼蓝化合物,通过分光比色的方法即可测定出食品中还原型维生素的含量。本文进一步详细的研究了影响显色反应的各种因素,结果表明,在酸性介质中,VC与碘钼酸直的反应速度快,环境因素对其影响小,且反应体系的吸光度稳定。在本实验条件下,VC浓度在8-28ug/ml的范围内服从比耳定律。在此范围内,回归方程为:Y=0.0289292+3686.31X,  相似文献   

8.
淀粉磷酸酯取代度的分析方法   总被引:6,自引:0,他引:6       下载免费PDF全文
∶分光光度计法和磷钼酸喹啉容量法是测定淀粉磷酸酯取代度的常用方法.实验表明,磷钼酸喹啉容量法在数据精密度和重现性方面差于分光光度计法,且试剂配制繁琐.而分光光度计法可同时测多种未知样品,且操作方便,结果准确.  相似文献   

9.
复合催化剂合成香料乙酸异戊酯的研究   总被引:1,自引:0,他引:1  
刘晓庚 《食品科学》2007,28(2):121-124
探讨了以六水合氯化铝--水合硫酸氢钠为复合催化剂,冰醋酸、异戊醇为原料合成乙酸异戊酯的绿色合成工艺条件,着重考察各因素对合成产率的影响。通过四因素三水平的正交试验优化并确定了最佳反应条件为:反应物料的投料摩尔比n(冰醋酸):n(异戊醇)=1:1.2,催化剂为A1C13·6H20+NaHSO4·HzO催化剂;复合催化剂配料摩尔比为n(AlCl3·6HzO):n(NaHsO4·H2O)=1:1.5,催化剂用量2.0%(催化剂占反应物料的质量分数),带水剂用量20%,反应温度115±5℃,反应时间为90min,得到产率达98.4%。  相似文献   

10.
无机磷与钼酸能形成磷钼酸络合物,该络合物能被还原剂α-1,2,4-氨基萘酚磺酸钠还原成钼蓝,用分光光度计确定蔗糖发酵前后无机磷的含量,观察发酵过程中无机磷的消耗。发现高浓度的磷酸盐会对微生物合成具有抑制和阻遏作用,无机磷含量的减少使葡萄糖磷酸化减慢,进而也影响糖酵解速度。研究表明在pH为6、温度为37℃、无机磷浓度为5g/L左右,发酵最佳。  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.
A 9% whey protein (WP) isolate solution at pH 7.0 was heat-denatured at 80°C for 30 min. Size-exclusion HPLC showed that native WP formed soluble aggregates after heat-treatment. Additions of CaCl2 (10–40 mM), NaCl (50–400 mM) or glucono-delta-lactone (GDL, 0.4–2.0%, w/v) or hydrolysis by a protease from Bacillus licheniformis caused gelation of the denatured solution at 45°C. Textural parameters, hardness, adhesiveness, and cohesiveness of the gels so formed changed markedly with concentration of added salts or pH by added GDL. Maximum gel hardness occurred at 200 mM NaCl or pH 4.7. Increasing CaCl2 concentration continuously increased gel hardness. Generally, GDL-induced gels were harder than salt-induced gels, and much harder than the protease-induced gel.  相似文献   

16.
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   

17.
18.
Capillary electrophoresis (CE) and polarized light microscopy (PLM) were utilized in the detection of the adulteration of locust bean gum with guar gum. For CE analyses, standards of locust bean and guar gums were extracted with 30% CH3CN, removing the residual proteins from the gum matrix. A 8.75 mM NaH2PO4-20.6 mM Na2B4O7 buffer, pH 9, was used to separate these proteins and to identify marker proteins that were present in the guar gum. These markers did not co-migrate with components in the extracts of mechanically processed locust bean gum, and are used as indicators of adulteration. Using PLM with toluidine blue and iodine staining techniques, unadulterated locust bean gum samples were distinguished from mixed samples through the differential staining of components in locust bean versus guar and tara gums. These experiments in the use of CE and PLM provide orthogonal and complementary methods for the verification of 'true' positives and the elimination of 'false' positives.  相似文献   

19.
An investigation is described in which various polyfunctional compounds were applied to wool in attempts to stabilize the temporary improvements in wrinkle-recovery brought about by ‘annealing’. Several reactive systems involving formaldehyde were found to produce the desired permanently improved wrinkle-recovery.  相似文献   

20.
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   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号