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 109 毫秒
1.
杨运发  王斌 《分析化学》1995,23(5):547-550
本文对乙酰螺旋霉素在GCE上的伏安行为进行了研究,发现在磷酸盐缓冲溶液(pH=7.78)中,於+0.85V(vs,Ag/AgCl)左右产生一良好的阳极氧化伏安峰,浓度在0.5~100μg/mL之间与峰电流呈线性关系,分析了制剂中乙酰螺旋霉素的含量,相对标准偏差为4.5%,平均回收率为101%,经循环伏安法验证,电极反应为不可逆反应。  相似文献   

2.
脱乙酰壳多糖化学修饰电极测定铂的研究   总被引:8,自引:0,他引:8  
用脱乙酰壳多糖修饰电极为工作电极,阳极溶出伏安法测定痕量铂。在pH=2 ̄3的KCl-HCl底液中,-0.3V富集2min,静止15s,以0.2V/s扫速阳极溶出,峰电位在-0.16V(vs.SCE),铂(Ⅳ)离子浓度在0.5 ̄5.0μg/mL范围内与峰高呈线性关系。富集10min后,可检测0.025μg/mL铂(Ⅳ)。该法用于贵金属矿样的测定,无需分离,结果满意。用循环伏安法、紫外光谱和拉曼光谱研  相似文献   

3.
研究了研磨法(CM型)和结晶沉淀反应法(MG-2型)制备的2种乙烯聚合钛系载体催化剂。CM型催化剂含钛3.4% ̄4.0%,三价钛占总钛含量15% ̄25%,比表面积为130m^2/g,催化剂活性为9.20kgPE/gTi·h聚合反应衰减快。MG-2型催化剂含钛7.0% ̄8.0%,三价钛占总钛含量55% ̄69%,比表面积为78m^2/g,催化活性为4.45kg PE/(g Ti·h),聚合反应衰减慢,  相似文献   

4.
反相高效液相色谱分离—安培法检测酚类化合物   总被引:4,自引:0,他引:4  
辛梅华  徐金瑞 《分析化学》1994,22(5):505-508
本文报道了RP-HPLC-安培法检测测定酚类化合物的条件,在Shim-packCLC-C8柱上用含0.5mol/L NaH2PO4缓冲溶液的5%甲醇水溶液洗脱分离,于E+1.0V处检测,线性范围在0-7μg/ml,检测限达ng/ml。  相似文献   

5.
从合成气制取液体燃料的浆态床FT合成/固定床2SM-5改质的反应系统由Ⅰ段鼓泡浆液反应器(内径40mm,高450Omm)和Ⅱ段固定床ZSM-5反应器(内径40mm,高900mm)组成,在温度250~280℃(Ⅰ段),300~340℃(Ⅱ段),压力1.5~2.5MPa,空速2.0NL/gFe·h(Ⅰ段),500~1000h ̄-1(Ⅱ段),H_2CO比0.5~1.5和气速1~2cm/s范围内,考察了工艺参数对反应性能的影响,1000h以上的寿命试验的平均结果为:合成气单程转化率65.1%,产率100g/Nm ̄3(Co+H_2),总烃生产达350g/Fe。使用富CO合成气时,达110g/Nm ̄3(CO+H_2)。实测的FT合成反应热为2938;5kJ/Nm ̄3(CO+H_2)。长期运转试验表明,工艺流程合理,设备操作和温度控制可靠。采用的浆液循环回路方法可初步分离蜡中的催化剂。  相似文献   

6.
罗毅  刘锋  冯建林  张理汉  胡绪英 《色谱》1994,12(5):342-344
 建立了粮食中互隔交链孢霉醇(AOH)、互隔交链孢霉醇单甲醚(AME)和玉米赤霉烯酮(ZEA)三个毒素的HPLC定性定量分析法和粒子束LC-MS/EI ̄+鉴定方法。采用反相色谱,以80%的甲醇水溶液作流动相,这三个毒素在C_(18)色谱柱上彼此间均获得较好的分离。方法对粮食中AOH,AME两个毒素的回收率均在79%以上。AOH,AME两个毒素的最低检出限为1×10 ̄(-9)g。用所建方法对100多个大骨节病病区、非病区的粮食样品进行了检测,结果为阴性。  相似文献   

7.
研究了马来酸酐接枝的聚乙烯辛烯弹性体/半结晶性塑料共混物(TPEg)对热塑性共聚聚酯(PETG)/聚乙烯辛烯弹性体(TPE)共混体系增容增韧作用的影响。马来酸酐接枝物显著地改善了PETG与TPE之间的相容性,导致TPE分散相颗粒细化,并促使分散相颗粒面间距等于甚至小于实现脆韧转变所需的临界面间距。在固定PETG基体含量为85wt%的前提下,当TPEg在15%分散相中的含量由20%增加到30%时,即  相似文献   

8.
离子色谱法快速同时测定营养药物中微量铜、锰、锌   总被引:12,自引:0,他引:12  
吴介达  吕伟 《色谱》1994,12(2):132-133
 在HPLC-CS5阳离子分离柱上选用5.0×10 ̄(-2)mol/L草酸(pN为5.24)作淋洗液分离了微量Cu ̄2+、Mn ̄2+和Zn ̄2+离子,用4-(2-吡啶偶氮基)间苯二酚作显色剂在520nm处连续检测,方法快速、简便、准确。本法用于施尔康片中微量Cu ̄2+、Mn ̄2+和Zn ̄2+离子的测定,结果令人满意。  相似文献   

9.
蔗渣水解液及发酵液中糖及糖醇的高效液相色谱分析   总被引:8,自引:0,他引:8  
采用HPLC测蔗渣水解液及发酵液中木糖、木糖醇等。在SpherisorbNH2柱上用乙腈+水(80+20)分离,示差折光检测器检测, 15min内同时分离测定木糖、木糖醇及其它五种糖。线性范围在 0~7.5 g/L,相对偏差小于4.1%。  相似文献   

10.
 系统地研究了碱性条件下(pH8~10.8)As3+,As5+,MA,DMA和AB等砷化合物在PRP-X100阴离子交换柱上的保留行为。用火焰原子吸收光谱(FAAS)测定从HPLC分离的砷化合物,即通过一根1m×0.23mmi.d.不锈钢毛细管,将HPLC柱出口与FAAS的雾化器连接起来,采用乙炔/空气火焰,在193.7nm处测定。具体研究了两个流动相(20mmol/LNH4HCO3和2.5mmol/L对-羟基苯甲酸-1.0mmol/L苯甲酸水溶液)。  相似文献   

11.
采用高效液相色谱-质谱联用技术及高效液相色谱法对生熟普洱茶中的主要成分进行定性和定量分析。鉴定出普洱茶水溶液中8种主要成分,分别为没食子酸(GA)、没食子酸儿茶素(GC)、表没食子酸儿茶素(EGC)、儿茶素(C)、咖啡因(CAF)、表儿茶素(EC)、表没食子酸儿茶素没食子酸酯(EGCG)和表儿茶素没食子酸酯(ECG)。以这8种成分的含量为指标,对普洱生茶和熟茶各20批进行主成分分析、聚类分析和判别分析,能准确地区分普洱生茶与熟茶。  相似文献   

12.
The health benefits of green tea are associated with its high catechin content. In scientific studies, green tea is often prepared with deionized water. However, casual consumers will simply use their local tap water, which differs in alkalinity and mineral content depending on the region. To assess the effect of water hardness on catechin and caffeine content, green tea infusions were prepared with synthetic freshwater in five different hardness levels, a sodium bicarbonate solution, a mineral salt solution, and deionized water. HPLC analysis was performed with a superficially porous pentafluorophenyl column. As water hardness increased, total catechin yield decreased. This was mostly due to the autoxidation of epigallocatechin (EGC) and epigallocatechin gallate (EGCG). Epicatechin (EC), epicatechin gallate (ECG), and caffeine showed greater chemical stability. Autoxidation was promoted by alkaline conditions and resulted in the browning of the green tea infusions. High levels of alkaline sodium bicarbonate found in hard water can render some tap waters unsuitable for green tea preparation.  相似文献   

13.
A rapid and quantitative analytical method for the simultaneous determination of green tea catechins using ultra‐performance liquid chromatography/electrospray ionization–mass spectrometry was developed. Total analytical run time was 3.5 min for the detection of (?)‐epicatechin (EC), (?)‐epicatechin‐3‐O‐gallate (ECG), (?)‐epigallocatechin (EGC), (?)‐epigallocatechin‐3‐O‐gallate (EGCG) and myricetin as the internal standard (IS) in rat plasma. The calibration curves were linear over the range of 10–5000 ng/mL for all the catechins. The inter‐ and intra‐day precision (relative standard deviation) and accuracy (percentage deviation) of the method were both lower than 10%. The average extraction recoveries in plasma ranged from 68.5 to 86.5%, and the lower limits of quantification of EC, EGC, ECG and EGCG were 10 ng/mL with a signal‐to‐noise ratio of >10. The assay developed was successfully applied to a pharmacokinetic study of catechins following intravenous and intragastric administrations of green tea extract in rats. Plasma concentrations of four catechins were detected up to 5–24 h after administration, and the pharmacokinetic parameters of catechins were in agreement with previous studies. From these findings, taken together with the high productivity and precision, the developed method could be a reliable and reproducible tool for the evaluation of pharmacokinetic properties of catechins. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

14.
茶叶及茶多酚中儿茶素的高效液相色谱分析方法研究   总被引:41,自引:0,他引:41  
戴军  王洪新  陈尚卫  汤坚 《色谱》2001,19(5):398-402
 筛选出HypersilBDSC18和ZorbaxSBC18两种适合同时分离茶叶和茶多酚中 7种儿茶素和咖啡因的反相柱。采用甲醇 水 醋酸 (或三氟醋酸 )作流动相 ,分别以等强度洗脱和梯度洗脱 (均在 30min内 )分离测定了我国 6种不同产地茶叶样品和 3种茶多酚样品中 7种儿茶素的含量。考察了 7种儿茶素和咖啡因的保留值与流动相组成及柱温的关系 ,优化了色谱条件及样品前处理方法。用电喷雾电离质谱 (ESI MS)定性确认没食子儿茶素没食子酸酯(GCG)和儿茶素没食子酸酯 (CG)两组分 ,并用高效液相色谱制备两对照品用于定量分析。  相似文献   

15.
In this study, a capillary electrophoresis‐based online immobilized enzyme microreactor was developed for evaluating the inhibitory activity of green tea catechins and tea polyphenol extracts on trypsin. The immobilized trypsin activity and other kinetic parameters were evaluated by measuring the peak area of the hydrolyzate of chromogenic substrate S‐2765. The results indicated that the activity of the immobilized trypsin remained approximately 90.0% of the initial immobilized enzyme activity after 30 runs. The value of Michaelis–Menten constant (Km) was (0.47 ± 0.08) mM, and the half‐maximal inhibitory concentration (IC50) and inhibition constant (Ki) of benzamidine were measured as 3.34 and 3.00 mM, respectively. Then, the inhibitory activity of four main catechins (epicatechin, epigallocatechin, epicatechin gallate, and epigallocatechin gallate) and three tea polyphenol extracts (green tea, white tea, and black tea) on trypsin were investigated. The results showed that four catechins and three tea polyphenol extracts had potential trypsin inhibitory activity. In addition, molecular docking results illustrated that epigallocatechin gallate, epicatechin gallate, epicatechin, and epigallocatechin were all located not only in the catalytic cavity, but also in the substrate‐binding pocket of trypsin. These results indicated that the developed method is an effective tool for evaluating inhibitory activity of catechins on trypsin.  相似文献   

16.
Catechins are the principle polyphenolic compounds in green tea; the four major compounds identified are epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECg) and epigallocatechin gallate (EGCg). Tea catechins tend to attach externally to their targets, such as viral envelopes, cell membranes, or the surface of low-density lipoproteins. In order to further our understanding of the molecular mobility of these compounds in cells, we examined the interaction of tea catechins with lipid membranes using solid-state NMR techniques. Our previous work indicated that the EGCg molecule is incorporated into lipid bilayers in a unique orientation. However, the detailed configuration, orientation, and dynamics of EGCg in lipid bilayers have not been well-characterized. Here, we investigated the orientation and dynamics of EGCg incorporated into multi-lamellar vesicles (MLVs) and bicelles using solid-state NMR spectroscopy.  相似文献   

17.
高效液相色谱法测定绿茶中茶多酚及咖啡因   总被引:2,自引:0,他引:2  
应用高效液相色谱法测定绿茶中没食子酸(GA)、咖啡因(CAF)及5种儿茶素类化合物,包括儿茶素(C)、表儿茶素(EC)、表没食子儿茶素没食子酸酯(EGCG)、表儿茶素没食子酸酯(ECG)、没食子儿茶素没食子酸酯(GCG)。对国家标准方法GB/T 8313-2008中流动相组成进行了调整,用0.5%乙酸代替2%的乙酸,在AT.Lichrom ODS色谱柱(4.6mm×250mm,5μm)上进行分离,流量为1.0mL.min-1,在波长278nm处进行紫外检测。7种组分在40min内达到完全分离。7种组分的质量浓度分别在一定的范围内与其峰面积呈线性关系。方法用于绿茶的分析,7种组分的加标回收率在96.0%~102.8%之间。  相似文献   

18.
This paper indicates the possibility to use near infrared spectroscopy (NIR) combined with PLS as a rapid method to estimate the quality of green tea. NIR is used to build calibration models to predict the content of caffeine, epigallocatechin gallate (EGCG) and epicatechin (EC) and for the prediction of the total antioxidant capacity of green tea. For the determination of the total antioxidant capacity, the trolox equivalent antioxidant capacity (TEAC) method is used. Until now, the prediction of the antioxidant capacity as such by use of NIR has not been reported. For caffeine and TEAC, models are build for the whole green tea leaves and also for the ground leaves. For the polyphenols (EGCG and EC), only models for the whole leaves are investigated. A partial least squares (PLS) algorithm is used to perform the calibration. To decide upon the number of PLS factors included in the PLS model, the model with the lowest root mean square error of cross-validation (RMSECV) for the training set is chosen. The correlation coefficient (r) between the predicted and the reference results for the test set is used as an evaluation parameter for the models: for the TEAC results r=0.90 for the model with the whole leaves, r=0.86 for the model with the powdered leaves are obtained. The caffeine prediction model has a correlation coefficient r=0.96 for the whole leaves and r=0.93 for the ground leaves. The correlation coefficient for the EGCG and the EC content models are, respectively 0.83 and 0.44.  相似文献   

19.
A high-performance liquid chromatographic method with electrochemical detection was developed for the determination of twelve tea catechins including four major catechins: epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECG) and epigallocatechin gallate (EGCG); four of their epimers at the C-2 position, C, GC, CG and GCG; and four methylated catechin derivatives, epigallocatechin-3-O-(3-O-methyl)gallate, gallocatechin-3-O-(3-O-methyl)gallate, epigallocatechin-3-O-(4-O-methyl)gallate and epicatechin-3-O-(3-O-methyl)gallate. These catechins were separated on an ODS C18 reversed-phase column by isocratic elution with 0.1 M NaH2PO4 buffer (pH 2.5)-acetonitrile (87:13) containing 0.1 mM EDTA.2Na. The detection limits (S/N = 3) of these catechins were approximately 10-40 pmol ml-1 at an applied voltage of 600 mV. Extracting these catechins from tea leaf powder with H2O-acetonitrile (1:1) at 30 degrees C for 40 min inhibited the epimerization at C-2 significantly from these epicatechins compared to extraction with hot water at 90 degrees C. This analytical method is sensitive to and appropriate for the simultaneous determination of various biologically active catechins in green tea.  相似文献   

20.
Potential of an “electronic tongue” multisensor system in identification of various tea samples and in quantitative analysis of separate tea components was studied. As a reference method for quantitative analysis of antioxidants of the polyphenolic type served micellar electrokinetic chromatography with a UV detector. The contents of epicatechin gallate, epigallocatechin gallate, epicatechin, epigallocatechin, gallic acid, gallocatechin gallate, and caffeine alkaloid in various tea samples were quantitatively estimated.  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