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1.
分光光度法测定富硒酵母中有机硒的含量   总被引:23,自引:1,他引:22  
在 p H2~ 3、60℃水浴下 ,硒与 3,3’-二氨基联苯胺 ( DAB)反应 ,形成稳定的 Se- DAB络合物 ,显色反应在2 0 min内完成。在 p H7.0~ 7.5时 ,通过甲苯萃取 ,在该体系中络合物最大吸收波长为 42 0 nm。  相似文献   

2.
王瑞琪  徐刚 《食品与机械》2008,24(1):115-117
目的:研究钴(Ⅱ)-丁二酮肟(H2D)络合极谱波的性质;方法:在pH为9的氨性环境中,0.2 moL/L亚硝酸钠存在下,钴(Ⅱ)与丁二酮肟(H2D)络合反应,在-1.30 V(VsSCE)处产生灵敏的极谱波,讨论该络合物的电极反应机理,建立测定痕量钴的方法;结果:钴(Ⅱ)在0.004~0.10μg/mL内符合线性范围,检出限(3σ)为1.2×10-3μg/mL,电活性络合物组成为钴(Ⅱ)∶(H2D)=1∶1;结论:该法可用于猪肝中痕量钴的测定,分析结果的相对标准偏差小于2.8%.回收率在97~103%,结果满意.  相似文献   

3.
本文以 meso-四(对磺基苯)卟啉(简称 TPPS_4)作显色剂,使用分光光度法研究了烟草中锰的测定方法。方法以硝酸消化样品,高氯酸冒烟驱赶氮氧化物,在pH10±1的硼酸钠缓冲溶液中以 Cd~(2+)和邻二氮菲作助催化剂.以乙二胺(TEA)、抗坏血酸和乙二胺四乙酸二钠盐(EDTA)作联合掩蔽剂,Mn~(2+)与 TPPS_4形成黄绿色1∶1络合物。在波长466nm 处用2cm 比色皿测定锰含量,ε′=7.9×10~4,0~5μg/25ml 间呈线性,回收率在92.5%~106%。  相似文献   

4.
四川软玉猫眼的红外光谱和X射线粉晶衍射特征   总被引:1,自引:0,他引:1  
通过对四川软玉猫眼进行 X射线粉晶衍射 (XRD)、傅立叶变换红外光谱 (FTIR)分析 ,结果表明 :四川软玉猫眼主要由透闪石矿物组成。利用 XRD计算的晶胞参数为 :α0 =0 .984 nm~ 0 .985 nm,ь0 =1.780 nm~ 1.782 nm,с0 =0 .5 2 7nm~ 0 .5 2 8nm,β=10 6 .13°~ 10 6 .35°。傅立叶变换红外谱带中 :36 70 cm- 1附近的吸收谱带归属透闪石结构中 OH伸缩振动的 A带。 96 0 cm- 1~ 110 0 cm- 1间的谱带归属 (Si4 O1 1 )的伸缩振动。 6 0 0 cm- 1~ 80 0 cm- 1范围内谱带归属 υs Si- O- Si振动 ,4 0 0 cm- 1~ 6 0 0 cm- 1范围内的谱带归属(Si4 O1 1 )的弯曲振动和 Mg- O伸缩振动。  相似文献   

5.
杨会琴  韩士田 《食品科学》2007,28(8):414-417
本实验研究了铅与非水溶性试剂四苯基卟啉(TPP)的显色反应。采取分光光度法,测定了酸碱度、温度、反应时间、共存离子等多个方面的因素对络合物的生成量及稳定性的影响,确定了反应进行的最适条件,建立起一种新型的测定食品中铅含量的分析方法。实验发现,在盐酸羟胺存在的条件下,四苯基卟啉(TPP)能与铅在碱性介质(pH12)中生成较稳定的络合物,络合比为1:1,该反应在沸水条件下只需20min即可完成。经实验测得,该络合物的最大吸收波长在466nm处。当铅含量在0~1μg/ml范围内时,测得的曲线呈线性关系,服从比尔定律。将其用于松花蛋中痕量铅的测定,结果令人满意。  相似文献   

6.
在中性条件下,蛋白质与邻苯三酚红-铜(Ⅱ)络合物相互作用,可使络合物颜色加深,该反应在20℃,反应10 min后达到平衡。邻苯三酚红与铜的摩尔比为5∶2时显色效果最佳。在最大吸收波长517nm处测量邻苯三酚红-铜(Ⅱ)络合物的△A,蛋白质的含量与△A呈良好线性关系。方法回收率为93.1%~108.5%,回归方程为ΔA=0.010c-0.025 5,相关系数0.990 3。采用该方法检验了多个批次牛奶样品中的蛋白质含量,结果令人满意。  相似文献   

7.
建立高速逆流色谱法分离制备橘皮中4种多甲氧基黄酮类化合物的方法。以石油醚-乙酸乙酯-甲醇-水(1∶0.8∶1∶1.2,V/V)为两相溶剂系统,上相为固定相,下相为流动相。在主机转速800 r/min、流动相流速2.0 m L/min、检测波长254 nm条件下分离,从200 mg橘皮粗提物中一步分离制备得到5,6,7,8,3’,4’-六甲氧基黄酮32.8 mg、3,5,6,7,8,3’,4’-七甲氧基黄酮10.9 mg、5,6,7,8,4’-五甲氧基黄酮43.5 mg和5-羟基-6,7,8,3’,4’-五甲氧基黄酮18.7 mg。产物纯度经HPLC检测分别为98.9%,97.8%,99.2%和99.8%。通过质谱和核磁共振氢谱、碳谱等波谱分析确定各化合物结构。  相似文献   

8.
<正>1.2.2无机媒介体系对于氨基化合物类,羟基乙二胺三乙酸、N-二羟乙基甘氨酸、二乙醇胺和三乙醇胺(TEA)等作为铁络合物配位体的可行性已有研究。虽然在碱性溶液中它们都能与Fe~(2+)形成稳定的络合物,但目前最合适的铁络合物体系仍是Fe(Ⅱ)-TEA络合物,其相对于Ag/AgCl/3 mol/L KCl显示出高达-1 050 mV的还原电位,基本可以将目前所有的还原染料还原,并无需添加其他还原剂~([18])。在Fe(Ⅱ)-TEA基础上,无机媒介体系已经大致发展为铁盐单配体、铁盐混合配体以及铁钙双核复合物等体系。  相似文献   

9.
采用氯化胆碱-丙三醇-聚乙二醇200混合溶剂液化桉木粉的方法分离纤维素,再通过氯化胆碱-草酸二水合物低共熔溶剂(DES)在不同的条件下处理提取的纤维素制备纳米结晶纤维素(CNC)。探讨了固液比、温度以及时间对CNC得率的影响,用扫描电镜、透射电镜、红外光谱、X-射线衍射、Zeta电位、紫外可见光分析对制备的CNC进行了表征。结果表明,在固液比1∶100,温度100℃,反应时间4h的条件下,CNC的得率最高,可以达到90.06%;制备的CNC呈棒状结构,直径为3~13nm,长度为100~300nm;结晶度相比于原料纤维素略有降低,纤维素结构没有发生大的变化,仍然呈纤维素Ⅰ型结晶。  相似文献   

10.
邻二氮菲一铁(Ⅲ)分光光度法测定板栗刺壳中单宁含量   总被引:3,自引:0,他引:3  
建立了邻二氮菲—铁(Ⅲ)分光光度法测定板栗刺壳中单宁含量的方法。单宁可将铁(Ⅲ)定量还原成铁(Ⅱ),邻二氮菲可与铁(Ⅱ)形成络合物,在510nm处测定显色液的吸光度确定单宁的含量。以单宁酸为标样,单宁量在0.4~2.0mg/mL范围内,服从比耳定律,得标准曲线Y=0.3128X+0.1677,相关系数R2为0.9958。  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.
17.
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   

18.
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   

19.
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   

20.
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