微波辅助萃取与超声波萃取丹参中丹酚酸B的比较研究

本文对微波辅助萃取和超声波萃取丹参中丹酚酸B进行了比较研究,并用高效液相色谱法(HPLC)测定了丹参中丹酚酸B.考察了微波辅助萃取和超声波萃取参数的影响,在各自最佳萃取条件下进行了丹参中的丹酚酸B提取率的比对,结果表明:微波辅助萃取6 min的提取率高于超声波萃取30 min的提取率.微波辅助萃取法与超声波萃取法相比具有省时、高效和溶剂用量少的特点.利用指纹图谱比较了两种萃取方式提取的化学成分的差异,结果显示两种萃取方法提取的主要成分组成基本相同,其共有成分比例相近.     

天然黄酮物质提取技术和分析方法的研究进展

综述了黄酮类化合物的提取技术及分析方法.新型提取技术如微波萃取法、超声波法、超临界萃取法、酶法、半仿生提取法;分析方法有分光光度法、高效液相色谱法、高效毛细管电泳法、薄层色谱法等.旨在为黄酮类化合物的研究、开发、应用提供参考.     

自制SPME涂层顶空萃取-气相色谱法分析废水中的芳香胺类化合物

建立了顶空固相微萃取与毛细管气相色谱法(HS—SPME-GC)测定废水中芳香胺类化合物的新方法。采用溶胶-凝胶法,自制新型单苯并冠醚探针．对萃取温度,萃取时间、解吸时间、离子强度和pH值等实验条件进行了优化选择：结果表明,该方法精密度良好,在标准溶液为0．1mg／L时,相对标准偏差(RSD)为4．0％～7．8％,线性范围为0．05～100μg/L,检出限达到0．005～0．01μg/L,加标回收率在97％～105％之间。运用该法对药厂废水中芳香胺类化合物进行了检测,结果令人满意由此可见,对环境中的芳香胺化合物进行检测,固相微萃取是一种快速、经济、有效的方法。     

水中联苯胺分析方法研究进展

对水中联苯胺的萃取方法及检测方法进行了综述。水中联苯胺的萃取方法主要为液–液萃取法和固相萃取法,检测方法主要有分光光度法、流动注射分析法、离子色谱法、气相色谱–质谱法、高效液相色谱法和高效液相色谱–质谱法等,对这些检测方法的优缺点进行了比较。对水中联苯胺的萃取技术及检测方法发展前景进行了展望。     

土壤和沉积物中多环芳烃分析技术研究进展

综述了近年来土壤和沉积物中多环芳烃分析技术的研究进展。重点阐述了索氏提取、超声波提取法、加速溶剂萃取法、微波辅助萃取法、超临界流体萃取法、固相微萃取法、柱层析法、固相萃取法、凝胶渗透色谱法等前处理技术和气相色谱-质谱法、高效液相色谱法和超高效液相色谱法等分析方法,并展望了未来发展的趋势(引用文献71篇)。     

微波加热对以槲皮素为甙元的黄酮甙的稳定性的影响

以乙醇为溶剂．分别采取微波和回流加热萃取法从番石榴叶中萃取槲皮素．高效液相色谱法测定槲皮素的萃取收率。对回流萃取液进行微波加热．槲皮素收率随微波加热温度的增加而显著增加。分别测定了温度为100、110、120℃的微波萃取动力学曲线以及60、70和78℃的回流加热萃取动力学曲线,计算结果显示,微波萃取和回流加热萃取均符合一级动力学方程,微波萃取槲皮素的活化能是回流加热萃取活化能的2倍多．平均表观速率常数是回流加热萃取的125倍。计算得到的活化能数据和实验结果均显示微波加热产生的高温可导致以槲皮素为甙元的黄酮甙发生分解。     

赛默飞推出高效液相色谱法快速测定茶叶中嘧霉胺的解决方案

<正>赛默飞世尔科技近日推出高效液相色谱法快速测定茶叶中嘧霉胺的解决方案。嘧霉胺是近年来开发的一种结构新颖、作用机制独特的嘧啶胺类内吸性杀菌剂,主要用于灰霉病的防治。嘧霉胺的常见测定方法有气相色谱法、气相质谱法、高效液相色谱法和高效液相质谱法。样品的前处理是茶叶中嘧霉胺测定的关键步骤之一。Qu ECh ERS是"快速、简易、廉价、有效、稳定、安全"的萃取方法。该方法利用乙腈萃取     

对酞内酰胺苯甲酰氯荧光衍生法液相色谱测定苯酚和氯代酚

近年来气相色谱法、薄层色谱法和高效液相色谱法已成为应用最广的测定酚类的方法。Tsuruta等提出了对酞内酰胺苯甲酰氯(4-2(phthalimidyl)benzoyl chloride,简称PIB-Cl)的合成方法,并将PIB-Cl作为胺类和醇类化合物的荧光衍生化试剂,但将它与酚类化合物进行衍生反应及相应的色谱应用还未见报道。本文提出了PIB-Cl与酚的反应,并以苯酚     

中草药中槲皮素的毛细管电泳法测定

近年来,毛细管电泳法用于中药的分析正在逐渐展开．微波辅助萃取是微波与传统的溶剂萃取法相结合后形成的一种新的萃取方法,目前已被用于环境、食品和天然产物的提取等领域,我们也曾用微波萃取法研究了中药刺五加和黄芩中的黄酮类化合物。     

饮用水中有机污染物检测方法研究进展

介绍水中有机污染物的富集方法如顶空法、萃取法、固相微萃取法、液相微萃取法、棒吸附萃取等,对饮用水中有机污染物的检测技术如气相色谱法、气相色谱–质谱联用法、液相色谱法、液相色谱–质联用法等进行了综述并对检测技术的发展趋势进行了展望。     

水溶性CdSe/CdS量子点的合成及其与牛血清蛋白的共轭作用

用巯基乙酸(TGA)作为稳定剂，合成了水溶性的CdSe和核壳结构的CdSe/CdS半导体量子点。吸收光谱和荧光光谱研究表明，核壳结构的CdSe/CdS半导体量子点比单一的CdSe量子点具有更优异的发光特性。用TEM、电子衍射(ED)和XPS分别表征了CdSe和CdSe/CdS纳米微粒的结构、形貌及分散性。红外光谱和核磁共振谱证实了巯基乙酸分子中的硫原子和氧原子与纳米微粒表面的金属离子发生了配位作用。在pH值为7.4的条件下，将合成的CdSe和CdSe/CdS量子点直接与牛血清白蛋白(BSA)相互作用。实验发现，两种量子点均对BSA的荧光产生较强的静态猝灭作用；而BSA对两种量子点的荧光则具有显著的荧光增敏作用，存在BSA时CdSe/CdS量子点的荧光增强是不存在BSA时体系荧光强度的3倍。     

Fabrication of Luminescent CdS Nanoparticles on Short‐Peptide‐Based Hydrogel Nanofibers: Tuning of Optoelectronic Properties

The pH‐induced self‐assembly of three synthetic tripeptides in water medium is used to immobilize luminescent CdS nanoparticles. These peptides form a nanofibrillar network structure upon gelation in aqueous medium at basic pH values (pH 11.0–13.0), and the fabrication of CdS nanoparticles on the gel nanofiber confers the luminescent property to these gels. Atomic force microscopy, field‐emission scanning electron microscopy, and high‐resolution transmission electron microscopy clearly reveal the presence of CdS nanoparticles in a well‐defined array on the gel nanofibers. This is a convenient way to make organic nanofiber–inorganic nanoparticle hybrid nanocomposite systems. The size of the CdS nanoparticles remains almost same before and after deposition on the gel nanofiber. Photoluminescence (PL) measurement of the CdS nanoparticles upon deposition on the gel nanofibers shows a significant blue shift in the emission spectrum of the nanoparticles, and there is a considerable change in the PL gap energy of the CdS nanoparticles after immobilization on different gel nanofibrils. This finding suggests that the optoelectronic properties of CdS nanoparticles can be tuned upon deposition on gel nanofibers without changing the size of the nanoparticles.     

CdS纳米粒子制备的影响因素及 CdS纳米粒子-酚藏花红体系的光谱特性

室温条件下在水溶液中合成了粒度分布均匀、分散性好的CdS纳米粒子. 研究了pH值、反应时间等条件因素对其吸收光谱和荧光光谱特性的影响, 并探讨了CdS纳米粒子-酚藏花红体系的光谱特性、可能的作用机理和应用前景.     

Fluorescence quenching of bovine serum albumin.

The fluorescence emission spectra and 3D fluorescence spectra of bovine serum albumin (BSA) in cetyltrimethylammonium bromide (CTAB) reversed micelles were affected by the microenvironment. Blue shifts of the fluorescence emission peaks were found when BSA was present in CTAB reversed micelles. The fluorescence intensity changed with the water content. Similar changes in the peak regions of the 3D fluorescence spectra were also observed. CdS nanoparticles prepared in CTAB reversed micelles quenched the fluorescence of BSA significantly. The fluorescence of BSA was more effectively quenched by negative CdS nanoparticles than by positive or neutral CdS ones. The quenching degree increased linearly with increasing the concentration of negative CdS nanoparticles over the range of 5.0 x 10(-6) - 3.0 x 10(-5) mol L(-1). The quenching mechanism is discussed and the quenching constant is 1.32 x 10(4) L mol(-1).     

表面修饰的Q态纳米CdS的荧光性能研究

以硫醇为表面修饰剂,通过控制硫醇与Cd²⁺的比例,得到性能稳定的Q-CdS,而后将Q-CdS与聚合物通过共混复合成膜.通过荧光光谱研究了硫醇和聚合物对Q-CdS的表面修饰作用,研究发现硫醇的长碳链有效阻止了CdS粒子间的团聚,碳链的增加导致Q-CdS稳定性的增强,Q-CdS的激子发射峰强度增大,且这种表面修饰效应随硫醇加入量的增大而增强,在一定硫醇加入量时的激子荧光发射强度达到最大.由于介电局域效应,聚合物的加入使Q-CdS的表面态荧光发光强度呈数量级增大.另一方面,随着聚合物加入量的增加又会导致Q-CdS的表面钝化,缺陷减小,表面态荧光发射峰相对减弱,而激子发射峰却增强.     

Preparation and application of L-cysteine-modified CdSe/CdS core/shell nanocrystals as a novel fluorescence probe for detection of nucleic acid

The water-soluble L-cysteine-modified CdSe/CdS core/shell nanocrystals (expressed as CdSe/CdS/Cys nanocrystals) have been synthesized in aqueous by using L-cysteine as stabilizer. The size, shape, component and spectral property of CdSe/CdS/Cys nanocrystals were characterized by high-resolution transmission electron microscope (HRTEM), energy dispersive X-ray fluorescence (EDX), infrared spectrum (IR) and photoluminescence (PL). The results showed that the spherical CdSe/CdS/Cys nanocrystals with an average diameter of 2.3 nm have favorable fluorescent property, theirs photostability and fluorescence intensity are enhanced greatly after overcoating with CdS. The cysteine modified on the surface of core/shell CdSe/CdS nanocrystals renders the nanocrystals water-soluble and biocompatible. Based on the fluorescence quenching of the nanocrystals in the presence of calf thymus deoxyribonucleic acid (ct-DNA), a fluorescence quenching method has been developed for the determination of ct-DNA by using the nanocrystals as a novel fluorescence probe. The pH value of the system was selected at pH 7.4, with excitation and emission wavelength at 380 and 522 nm, respectively. Under the optimal conditions, the fluorescence quenching intensity of the system is linear with the concentration of ct-DNA in the range of 0.1-3.5 microg/mL (r=0.9987). The detection limit is 0.06 microg/mL. And two synthetic samples were analyzed satisfactorily.     

不同电性的纳米银对甲基橙光谱学性质的影响

通过吸收光谱和荧光光谱等手段研究了正/负电性纳米银对不同pH值的甲基橙(MO)溶液光谱学性质的影响.研究结果表明,正电性纳米银(P-Ag)与甲基橙作用形成新的复合物,吸收光谱表现为复合物体系的性质.负电性纳米银(N-Ag)与甲基橙静电排斥作用,相互作用较弱,吸收光谱仅表现为两者简单叠加.在正电性纳米银-甲基橙体系中,S1→S0荧光明显增强.当溶液pH=2.1时,荧光增强比率最大,当pH=4.8时,荧光增强比率最小;S2→S0荧光减弱,且与体系的pH值关系不大.在负电性纳米银-甲基橙体系中,仅少量纳米银存在条件下,S1→S0荧光略增强.在溶液pH=2.1时,荧光增强比率最大;S2→S0荧光明显减弱,且与体系的pH值关系不大.分析认为,不同电性的纳米银对甲基橙光谱学性质影响不同,与纳米银与甲基橙分子间相互作用、纳米银的局域场增强效应以及无辐射能量转移作用等密切相关.     

表面修饰CdS和(CdS)ZnS纳米晶的性能研究

在水相中合成了CdS纳米微粒,以ZnS对其进行表面修饰,得到具有核壳结构的(CdS)ZnS水溶性纳米晶。采用红外光谱、X射线衍射(XRD)、透射电镜(TEM)表征其粒度和形貌,紫外-可见吸收光谱(UV)、荧光光谱表征其光学特性。制得的CdS近似呈球形,直径为8nm;CdS纳米颗粒表面经ZnS修饰后,其荧光发射峰强度显著增强,表面态发射减弱。     

Dendron-tethered and templated CdS quantum dots on single-walled carbon nanotubes

CdS nanoparticles on the surface of single-walled carbon nanotubes (SWNTs) were templated and stabilized through the initial attachment of 1 --> 3 C-branched amide-based dendrons and were both photophysically and morphologically characterized. The CdS clusters were shown to be ca. 1.4 nm in diameter as calculated from their optical absorption spectra and exhibited reduced fluorescence emission intensity at 434 nm compared to that of CdS quantum dots stabilized by untethered dendrons due to partial emission quenching by the SWNT. Unchanged UV absorption behavior of these materials indicated that they are stable > 90 days at 25 degrees C.     

Size tunable synthesis of cysteine-capped CdS nanoparticles by gamma-irradiation

Highly water soluble and biocompatible L-cysteine-capped CdS nanoparticles having narrow size distribution were synthesized for the first time by gamma-irradiation technique without using any additional stabilizer. FTIR study shows that CdS nanoparticles are capped through mercapto-group of cysteine amino acid while its free amino and carboxylate groups make it amenable to bio-conjugation. Size and luminescence of the nanoparticles can be well controlled by varying the parameters like radiation dose, pH and concentration of cysteine. The observed results suggest that pH 7 can be optimum for the synthesis of L-cysteine-capped CdS nanoparticles. CdS nanoparticles synthesized with molar ratio of Cd(2+):cysteine, 1:60 at pH 7 were found to be most luminescent. All nanoparticles formed lie in the size quantization regime and exhibit good crystallinity. Remarkable improvement in stability and luminescence was achieved on changing pH of as-prepared nanoparticles from 7 to 11.