微波辅助萃取儿茶素优化条件的研究

[目的]采用微波萃取法并结合正交试验研究提取儿茶素的优化条件.[方法]通过正交实验对儿茶素与茶多酚的指标体系进行对比分析.[结论]在以儿茶素为评价指标时最佳提取条件为微波功率为400W、乙醇浓度为60%、萃取时间为70 s、料液比为1∶20,在此条件下,儿茶素的得率和含量分别为8.9%和26.6%,高于以茶多酚为评价指标的体系.     

不同环境下普洱茶儿茶素类差异研究

普洱茶在不同生长环境下其化学成分不同,因此深入研究普洱茶,让人们进一步认识了解普洱茶,有利于古树茶的合理开发利用和保护。采用30℃真空干燥后温浸提取茶液,用 Waters 高效液相色谱法梯度洗脱测定儿茶素类。儿茶素类含量及其中 EGCG 含量最高的是栽培型野生古树茶(23.15%、10.98%),最低的是野生古树茶(7.874%、3.52%);低海拔、土壤的 PH 值偏低的地方儿茶素类含量高;与树龄没有什么关系。     

公司

纳川股份:中标一路网BT项目纳川股份(300198)公告称,公司于8日收到《竞争性谈判中选通知书》,正式中标"诏安金都工业集中区路网一期工程(BT)"。据了解,该项目主要为建设五条规划道路,总估算金额为9099.7万元;在收到中标通知书后10天内,公司将与招标单位福建诏安金都资     

高效液相色谱法同时测定肿节风中3种有效成分

分别采用2010年版<中国药典>方法和甲醇梯度法色谱条件对比测定肿节风药材不同部位、不同种源异嗪皮啶、迷迭香酸、反丁烯二酸三种有效成分的含量.试验绪果表明:用甲醇梯度法检测更简捷、快速、准确.测定不同产地15个种源肿节风药用有效成份含量,结果表明福建三元2#、3#种源样品中异嗪皮啶含量最高,分别达0.04990A、0.0470%;江西九江、福建三元3#种源样品中迷迭香酸含量最高,分别达0.0483%、0.0471%;福建三元1#、广西格州种源样品中反丁烯二酸含量最高,分别达0.3290%、0.3110%,分析表明,三元种源三种主要药用效成份含量相对校高,市场前景广阔开发价值大,产业化发展前景良好.     

固相萃取-高效液相色谱法测定茶叶中儿茶素

建立一种用高效液相色谱法测定茶叶中儿茶素的含量.方法:样品经乙醇提取,超声30min后,过C18小柱净化,样品溶液经0.45μm滤膜过滤后,用于HPLC分析.使用C18(5 um,150 mm×6.0 mm)色谱柱进行分离,用不同体积比混合的流动相A及流动相B的混合液作梯度淋洗,流速为1.0 ml/min,检测波长为280 nm,柱温为40℃.以甲醇∶水∶乙酸-26∶73.5∶0.5(体积比)为流动相.儿茶素在0.02～0.3 g/L范围内线性关系良好,回收率在98.2%～100.3%之间,相对标准偏差为1.6643%.该方法具有操作简便、快速、精密度高、回收率好、重现性较好、检测限低等优点.     

神话般的南靖土楼

<正>南靖土楼遍布福建省漳州市南靖、华安、平和、诏安、云霄、漳浦等县的山区。它以历史悠久、数量众多、规模宏大、造型奇异、风格独特而闻名于世,被誉为“神话般的山区建筑”。当地还专门建有福建南靖土楼国家森林公园。土楼一般高三至五层：第一层是厨房,第二层是仓库,     

高效液相色谱法测不同茶叶中EGCG的含量

采用高效液相色谱法对不同茶叶中的表没食子儿茶素没食子酸酯(EGcG)的含量进行分析.采用C18色谱柱(4.6mm×250 mm,5μm),流动相为甲醇:水:乙酸(23:75:2,v/v),流速1.0 mL·min-1,柱温35℃,检测波长为272nm.EGCG线性范围为0.11～1.71μm,相关系数r=0.9996,平均回收率98.7%,RSD为0.7%.本方法分析速度快,灵敏度高,分离效果好,可作为测定茶叶中EGCG含量的方法.     

儿茶素对鲜牛奶的防腐测定

本试验在恒温36℃条件下,以儿茶素作为防腐剂,测定儿茶素在鲜牛奶中的抑菌作用.结果表明:儿茶素在鲜牛奶中的抑菌效果非常显著.在恒温36℃条件下,添加儿茶素的鲜牛奶比对照样品牛奶的细菌数成百倍的减少,有效地延缓鲜牛奶的腐败.     

儿茶素对鲜牛奶的防腐测定

本试验在恒温36℃条件下,以儿茶素作为防腐剂,测定儿茶素在鲜牛奶中的抑菌作用.结果表明:儿茶素在鲜牛奶中的抑菌效果非常显著.在恒温36℃条件下,添加儿茶素的鲜牛奶比对照样品牛奶的细菌数成百倍的减少,有效地延缓鲜牛奶的腐败.     

LC/MS法测定茶叶中4种儿茶素

利用Agilent LC/MSD TOF建立了快速测定茶叶中4种主要儿茶素的分析方法.首先以儿茶素对应的质谱峰的强度和质谱峰分辨率为基准,采用正交实验设计方法对质谱联用仪的仪器参数进行了优化选择,包括流速,毛细管高压,干燥气体流速及温度,裂解电压,雾化器压力等;依据优化后的质谱测定条件,应用标准加入法,对实际的样品测定进行了重现性、精密度和回收率的考察;最后对实际的茶叶样品的含量进行了测定,该方法单次进样测量时间为2 min,为快速测定茶叶中儿茶素提供了一种可供参考的分析方法.     

卡思卡特城堡

It is worthy of noting that, whilst Crookston Castle witnessed the earlier and happier portion of Mary's variegated life,     

不同的吃喝玩乐

一、吃和喝吃苹果 eat an apple, 吃药 take medicine,吃糖 have some sweets,吃饭 have one's meals,吃馆子 dine out,吃惊 be surprised/     

漏洞百出的教育

Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help?     

只要努力,不要后悔

There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love.     

浅谈移民问题

Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject.     

Sister Carrie, an Adherent of Desires

Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities.     

Improvement of one-cycle controller by use of proportional integral differential controller

1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec…     

库克斯顿城堡

城堡, 是欧洲典型的建筑之一, 每个城堡都有一个美丽的传说或是一段历史。从本期开始, 我们将推出“城堡之旅”, 带各位读者去浏览、观赏欧洲各地的城堡, 开始一段文化与历史的旅途!     

胡主席在印度,我却在中国

Today, Sunday morning, I sit thinking and typing at my computer. My thoughts are in my homeland, India and my body is in China. The body is here and mind there for a good reason. Mr. Hu is president and I am resident and both are in each other's countries (what a difference the absence of one small letter makes!). Mr. Hu will return in a few days and I will stay on longer.