微波辅助萃取新鲜芦荟叶中芦荟甙的研究

应用密闭微波萃取装置对芦荟中的有效成分芦荟甙进行了微波萃取研究,并利用透射电子显微镜对微波萃取机理进行了初步探讨.讨论了不同萃取剂、溶剂浓度、萃取时间和微波功率等对提取率的影响.在萃取剂为乙醇-水体系,溶剂(乙醇)体积分数为70%、萃取时间为4min及微波功率为340W的条件下,萃取效果最佳.与索氏提取及超声波萃取法相比,本法具有萃取速度快、提取率高及溶剂用量少等特点.     

密闭微波辅助萃取天麻中天麻素的研究

应用密闭微波萃取装置,对中药天麻中有效成分天麻素的萃取进行了研究。分别讨论了药材颗粒粒径、提取溶剂浓度、微波提取时间和提取剂的用量对微波萃取天麻素的影响。结果表明:当药材粒径<50μm,乙醇体积分数为50%,微波辐射时间为2min,提取剂质量为药材质量的30倍时,天麻素提取率最高。此外,将微波萃取与索氏萃取和超声波萃取进行了比较。     

密闭微波辅助萃取丹参中有效成分的研究

应用具有压力控制附件的MSP-100D密闭微波萃取装置,对丹参中的有效成分丹参酮、丹参酮A及隐丹参酮进行微波萃取研究.在乙醇体积分数为90%,微波辐射时间为4min,溶剂体积对样品质量比为20∶1和样品粒径为120目的条件下,有效成分提取率最佳.对比了密闭微波萃取同索氏萃取和超声萃取丹参有效成分的差异.     

密闭微波辅助萃取当归粉中的阿魏酸

利用密闭微波样品制备系统(具有压力控制部件),对当归中的有效成分阿魏酸的萃取进行研究,比较了密闭微波萃取同超声波萃取和索氏萃取阿魏酸提取率的差异.结果表明:微波萃取与其他两种萃取方法相比,具有速度快和萃取率高的特点.并得到了阿魏酸提取的最佳条件:微波功率为400 W,萃取剂为90%的乙醇(体积分数),固-液比为1∶15,微波辐射为240 s,当归粒径为75μm.     

翻白草中熊果酸的微波提取工艺研究

采用单因素实验与正交实验法结合,以提取剂浓度、固液比、微波功率、微波提取时间为考察因素,以熊果酸提取率作为评价指标,优化了熊果酸的微波提取工艺。最优微波提取条件为:90 % 乙醇作为提取剂、料液比1∶20 g/mL、微波功率250 W、微波提取时间120 s。     

藜蒿中黄酮类化合物的微波辅助萃取研究

应用密闭微波萃取装置，分别对藜蒿茎和藜蒿叶中黄酮类化合物进行微波萃取研究。采用正交试验方法得到微波提取藜蒿中黄酮类化合物的最佳条件。微波提取藜蒿茎的最佳条件为乙醇体积分数70％，微波功率800W，提取温度80℃和料液比1：20；微波提取藜蒿叶的最佳条件为乙醇体积分数70％，微波功率600W，照射时间12min，提取温度70℃和料液比1：20；在最佳条件下，藜蒿茎和叶中总黄酮提取率分别为6．43％和7．01％。并将微波萃取与乙醇回流提取进行了比较。     

超声微波协同萃取/气相色谱法测定土壤中的多溴联苯醚

建立了同时测定土壤中7种多溴联苯醚(PBDEs)的超声微波协同萃取/气相色谱测定方法.考察了萃取溶剂的种类和用量、微波功率、萃取时间等因素对模拟土壤中PBDEs回收率的影响,得到了最佳萃取条件:萃取剂为50 mL正己烷-丙酮(1:1),微波辐射功率为90W,萃取时间为10 min.在最佳条件下,PB-DEs在10～40...     

超声微波协同萃取-气相色谱法测定土壤中邻苯二甲酸酯类化合物

研究了超声微波协同萃取-气相色谱测定土壤中的邻苯二甲酸酯类化合物。考察了萃取溶剂、微波功率、萃取时间等因素对回收率的影响,得到了最佳萃取条件为:以正己烷/丙酮(1∶1)为萃取剂,溶剂用量为60 mL,微波辐射功率为100 W(超声功率固定为50 W),萃取12 min。该条件下,模拟土样中酞酸酯的平均回收率可达92.5%。方法的检出限为0.05~0.16 mg/kg,相对标准偏差(RSD)5.8%。与直接超声、开放式微波萃取法相比,此法具有明显的优势。方法用于实际土样的测定,所得结果与索氏抽提的结果相当。     

超高压提取桑叶芦丁

考察了常温下超高压提取桑叶芦丁的提取工艺,观察了不同提取溶剂、提取压力、溶剂与原料比、提取时间及桑叶颗粒大小等因素对桑叶芦丁提取率的影响,并对提取工艺进行了优化。桑叶芦丁的最佳萃取条件为:70%乙醇水溶液为提取溶剂,提取压力为500MPa,提取时间为8min,桑叶颗粒大小为0.18～0.25mm,溶剂与原料比为20∶1,桑叶芦丁提取率达23.9mg/g。     

微波辅助萃取满山红叶中总黄酮的研究

用带可控温的Star-2型开罐式微波消解仪对满山红叶中的总黄酮进行了微波萃取研究。通过正交试验考察了微波萃取溶剂、微波辐照时间、萃取温度和液固比等条件对满山红中总黄酮萃取率的影响。结果表明,在乙醇浓度为80％、萃取温度为90℃、微波辐照时间为10min、液固比为40：1的条件下,微波萃取满山红叶中总黄酮萃取率最佳。与传统回流法相比,萃取率提高了16％。     

新型L-羟脯氨酸聚合物键合手性固定相的制备及对手性化合物的拆分

以单分散亲水性交联聚甲基丙烯酸环氧丙酯-甲基丙烯酸乙二醇双酯(PGMA/EDMA)树脂为载体,制备新型L-羟脯氨酸聚合物键合高效手性配体交换固定相。该固定相在配体交换分离模式下,以0.2mol/LNaAc和0.1mmol/LCu(Ac)2水溶液(pH5.2)为流动相,柱温为30℃～50℃,对衍生和非衍生的D,L-氨基酸和α-羟基酸等9种手性化合物进行了高效液相色谱拆分。详细考察了流动相pH值、温度、流速和进样量对手性分离的影响,选择了合适的色谱分离条件。结果表明,所拆分的9种手性化合物,有5种手性化合物能得到基线分离,最好的分离因子α=2.32。     

Determination of Enantiomeric Purity and Absolute Configuration of β-Lactams by High-Performance Liquid Chromatography on Chiral Columns

Enantiomers of β-lactams bearing aryl, furyl or styryl substituents in the 4-position were chromatographically separated by means of high-performance liquid chromatography on chiral column packed with amino acid-derived chiral stationary phase. Separation factors are generally modest. To improve further the resolution of enantiomers, the rings of these β-lactams were opened with octanol in acidic conditions and converted into N-3,5- dinitrobenzoyl ester derivatives of the resulting β-amino acids. Enantiomers of these derivatives are efficiently separated on an amide-derived chiral stationary phase. The chromatographic separations enable accurate determination of optical purity of the chiral β- lactams, prepared from homochiral ester enolate-imine condensation. The absolute configuration of the major enantiomer of the β-amino acid derivatives was determined from elution order on a chiral column.     

D-苯甘氨酸手性固定相的制备及对多种手性化合物的拆分

以D-3,5-二硝基苯甲酰苯甘氨酸和3-氨丙基硅烷化硅胶合成了D-苯甘氨酸衍生手性固定相,并自制了手性高效液相色谱分离柱,用正己烷-异丙醇作流动相,对非衍生化的氨基酸、胺、醇和羧酸类等10种手性化合物进行了高效液相色谱拆分。结果表明:所拆分的10种手性化合物,有7种手性化合物能得到基线分离,最好的分离度Rs=5.56。该文还用苯对柱性能进行了评价,理论塔板数达每米8万块。     

New chiral crown ether stationary phase for the liquid chromatographic resolution of α-amino acid enantiomers

A new chiral stationary phase (CSP) for the liquid chromatographic separation of enantiomers was prepared by bonding a novel enantiopure (diphenyl-substituted 1,1′-binaphthyl) crown ether to 5 μm silica gel. The resulting CSP was applied to the separation of the enantiomers of various natural and unnatural α-amino acids. All α-amino acids tested were resolved very well on the new CSP, with the exception of proline, which does not contain a primary amino group. The resolution of α-amino acid enantiomers on this new CSP was found to be dependent on the type and amounts of organic and acidic modifiers, and on column temperature.     

水溶液中几种芳香族氨基酸π-π自堆叠作用

利用精密的流动混合微量热法测定了298.15 K时D/L-色氨酸、L-色氨酸、L-组氨酸和L-苯丙氨酸四种天然芳香族氨基酸水溶液的稀释焓, 根据所建立的拟等步自堆叠作用的化学模型对实验数据进行了处理, 计算得到模型参数K△Hm. 该化学作用参数与McMillan-Mayer理论模型中的焓对作用系数具有高度一致性, 即hxx=K△Hm. 结合文献报道的结果, 认为芳核π-π自堆叠作用在本质上是一种特殊的疏水-疏水作用, 一般表现为吸热效应; 取代基空间位阻、芳核以外部分的静电、氢键和手性选择性作用等对芳核π-π自堆叠作用有显著影响; 组合参数K△Hm实际上描述了芳核π-π自堆叠作用平衡及焓变的综合效应.     

Synthesis of novel chiral stationary phases for high-performance liquid chromatography

Three novel chiral selectors 4a-c were synthesized from(S)-amino acids and(R)-1-phenyl-2-(4-methylphenyl)ethylamine.4a-cwere connected to 3-aminopropylsilanized silica gel to be used as the chiral stationary phase for HPLC.Five amino acid derivativesand two pyrethroid insecticides were fairly resolved on these three new chiral stationary phases under normal phase condition.     

单分散树脂键合手性配体交换色谱固定相拆分DL-氨基酸

以单分散交联聚甲基丙烯酸环氧丙酯-甲基丙烯酸乙二醇双酯(PGMA/EDMA)树脂为基质合成了L-脯氨酸键合手性配体交换固定相,并用于DL-氨基酸的直接光学拆分,考察了流动相pH值、金属离子浓度、流速及温度等因素对DL-氨基酸对映体拆分的影响。结果表明,该固定相在配体交换色谱模式下可对多对DL-氨基酸进行良好的拆分。     

Enantioseparation of protonated primary arylalkylamines and amino acids containing an aromatic moiety on a pyridino-crown ether based new chiral stationary phase

This paper reports the preparation and testing of a new pyridino-18-crown-6 ether based chiral stationary phase (CSP). The chiral crown ether was covalently bound to silica gel. Circular dichroism (CD) spectroscopy was used for probing the complex formation of the chiral crown ether with the enantiomers of protonated primary arylalkylamines. The (S,S)-dimethylpyridino-18-crown-6 ether selector having a terminal double bond was first transformed to a triethoxysilyl derivative by regioselective hydrosilylation, and then heated with spherical HPLC quality silica gel to obtain the CSP. The discriminating power of the HPLC column filled with the above CSP was tested by using the hydrogenperchlorate salts of racemic α-(1-naphthyl)ethylamine (1-NEA), α-(2-naphthyl)ethylamine (2-NEA) and the hydrochloride salts of aromatic α-amino acids and α-amino acids containing different aromatic side-chain protecting groups.     

LC Separation of γ-Amino Acid Enantiomers

Three underivatized γ-amino acids were successfully enantioseparated by high-performance liquid chromatography on macrocyclic glycopeptide based chiral stationary phases. The effects of the alcohol modifier in the mobile phase and the column temperature on the enantioseparation were investigated. Apparent thermodynamic parameters were calculated from the plots of ln k or ln α versus 1/T. Some mechanistic aspects of chiral recognition are discussed with respect to the structures of the analytes. It was found that the enantioseparations were enthalpy-driven, the double bond in the analyte exerting a significant influence on the chiral recognition.     

Electrochromatographic enantioseparation using chiral ligand exchange monolithic sol-gel column

This paper describes the development of a monolithic sol-gel column modified with l-hydroxyproline as a ligand exchange chiral stationary phase. It has been demonstrated that the monolithic chiral stationary phase can be used for the enantioseparation of dansyl amino acids, free amino acids, hydroxy acids, and dipeptides by capillary electrochromatography and micro-liquid chromatography. The recommended mobile phase was acetonitrile/0.50 mM Cu(Ac)₂-50 mM NH₄Ac (7:3) adjusted to pH 6.5. The characteristics of the monolithic column using hydroxyproline as chiral selector in CEC have been discussed.