微波协同阳离子交换树脂催化合成阿魏酸乙酯

以732型强酸性阳离子交换树脂为催化剂,在微波辐射下用阿魏酸与乙醇酯化合成了阿魏酸乙酯.通过单因素实验,考察了催化剂活化方法对催化剂活性的影响,结果表明,微波法活化阳离子交换树脂的催化性能好.通过单因素实验和正交实验,考察了催化剂用量、醇酸摩尔比、微波辐射时间、微波辐射功率等因素对反应的影响.确定了最佳反应工艺条件:阿魏酸0.1mol,酸醇摩尔比5:1,催化剂用量为反应物质量的35%,微波功率300w,反应时间30min,产率达84.2%.732型树脂催化剂可再生循环使用,重复使用4次,产率不低于80%.     

气相色谱-负化学源质谱法对水中2-甲-4-氯和2,4-滴的测定

建立了气相色谱-负化学源质谱法(GC-NCI MS)测定水中2-甲-4-氯(MCPA)和2,4-滴(2,4-D)2种酸性除草剂的分析方法.水样经过Oasis HLB柱萃取后,进行五氟苄基溴(PFBBr)衍生化,用2,4-二氯苯乙酸(2,4-DCPA)作内标进行定量分析,并以2-甲-4-氯丙酸(mecoprop)作回收率指示物对整个分析过程进行监控,以保证分析结果的准确性.mecoprop、MCPA和2,4-D在5、100、200 ng/L 3个不同添加水平下的回收率在82% ～135%范围内,RSD在1.3% ～9.3%范围内,在1 ～200 μg/L线性范围内,相关系数r大于0.997,MCPA、2,4-D的方法检出限分别为0.60、0.45 ng/L.2007年11月采用GC-NCI MS方法对南方地区某河流中的MCPA和2,4-D含量进行调查,其质量浓度分别不大于19.4 ng/L和6.2 ng/L,监测结果表明,该河流水质没有受到MCPA和2,4-D酸性除草剂的污染.     

高效液相色谱法测定椰油酰基谷氨酸钠中的月桂酰基谷氨酸含量

建立了高效液相色谱法(HPLC)测定表面活性剂椰油酰基谷氨酸及其钠盐中月桂酰基谷氨酸含量以及不同碳链酰基谷氨酸相对含量的分析方法。采用甲醇作溶剂,涡旋混合器溶解样品,经Agilent TC-C_(18)(250 mm×4.6 mm×5μm)色谱柱分离,以乙腈-0.002 mol/L硫酸水溶液为流动相,梯度洗脱,用紫外检测器在203 nm处检测。该方法的线性范围为0.050~2.0 mg/m L,检出限(S/N=3)为0.015 mg/m L,回收率为92.0%~101%。方法快速、准确、重现性好,可用于不同质量椰油酰基谷氨酸及其盐的测定,为此类原料的质量控制提供了有效的技术参考。     

甲醛测定方法的进展概述

甲醛是一种重要的化工原料,因其价格低、用途广、易制备等原因被广泛应用到化工、建材、食品、材料、纺织等行业。但甲醛毒性较高,对人体健康、空气质量都有着严重的影响,其污染问题愈来愈受到人们的关注。因此,甲醛的及时准确检测显得尤为重要。该文综述了几种常用的甲醛测定方法。     

Controlled construction of nanostructures in graphene

We report on the laser-assisted fabrications of nanostructures in graphene membranes supported on polymer films. By using a laser beam to deposit heat locally, irradiated polymer instantaneously melts and vaporizes. During laser drilling of the polymer, the single-layer graphene membrane adheres to the polymer surface and consequently forms tens of nanometer deep wells. Due to the short time scale of laser irradiation, heat diffusion in the polymer is negligible, and the excitation energy is highly confined in the polymer. As a result, graphene nanowells of hundreds of nanometers in diameter can be pat- terned with high fidelity. With the increasing of nanowell density, we observe the spontaneous formation of nanowrinkles connecting pairs of nanowells in the graphene membranes. Importantly, Raman spectra confirm that no defects are intro- duced in graphene membranes by laser irradiation under our experimental conditions. Our results highlight the possibility to construct nanostructures and to design novel devices based on graphene.     

提取方式对信阳山茶油品质影响与评价研究

采用超临界CO2法、超声波辅助提取法和索氏提取法提取山茶籽油,对它的理化指标、脂肪酸组成进行测定,并对茶粕有效成分进行分析。研究表明,超临界CO2法和超声波法提油率高,环保安全性和工艺效率好;索氏法提取的油茶籽油酸值过大;从茶粕有效成分含量来看,超声波辅助提取法更优。综合考虑3种提取方法,超声波辅助提取山茶油品质最优。     

薯莨鞣质成分及生物活性的研究进展

研究表明,薯莨含有大量的生物活性成分,其中鞣质是最重要有效成分之一。结合近10年来有关薯莨鞣质最新研究成果,阐述了薯莨鞣质化学成分提取工艺、种类、药用及生物活性的研究进展。     

Fabrication of suspended graphene devices and their electronic properties

Suspended graphene devices are successfully fabricated by using a novel PMMA/MMA/PMMA tri-layer resist technique. The gap between graphene and dielectric substrate can be easily controlled by the thickness of the bottom PMMA layer, and no wet-etching with hazardous hydrofluoric acid is involved in our fabrication process. Electrical characterizations on suspended graphene devices are performed in vacuum when in-situ current annealing directly leads to a significant improvement on transport properties of graphene, i.e., the increase of carrier mobility with the reduction of width of Dirac peak. Our results make a new opportunity to study intrinsic properties of graphene.