反相液相色谱中离子抑制剂的有机调节剂作用

在离子抑制反相液相色谱(IS-RPLC)中,流动相中的有机酸、有机碱离子抑制剂,包括用于调节缓冲溶液pH的有机酸和有机碱均具有离子抑制剂和有机调节剂的双重作用.本文研究了在RPLC流动相中作为离子抑制剂的酸、碱及缓冲溶液对中性化合物保留行为的影响,探讨了有机酸、有机碱离子抑制剂的有机调节剂作用,考察了甲醇和乙腈、甲醇和乙酸、甲醇和三乙胺、乙腈和乙酸、乙腈和三乙胺在十八烷基硅烷键合相上洗脱强度之间的关系.     

离子抑制剂对苯甲酸等9种食品添加剂的反相液相色谱行为的影响

研究了反相高效液相色谱(RP-HPLC)流动相中酸性离子抑制剂三氟乙酸(TFA)与缓冲盐离子抑制剂TFA-乙酸铵(AmAc)对安赛蜜、糖精、咖啡因、阿斯巴甜、苯甲酸、山梨酸、甜菊糖苷、脱氢乙酸和纽甜等9种食品添加剂色谱保留行为的影响。着重探讨了TFA与TFA-AmAc作为离子抑制剂的有机调节剂作用,考察了乙腈-TFA水溶液和乙腈-TFA-AmAc水溶液流动相体系中溶质的保留因子与离子抑制剂体积分数之间的关系。在最佳流动相组成(乙腈-TFA (0.01%, v/v)-AmAc (2.5 mmol/L)水溶液)条件下梯度洗脱,苯甲酸等9种食品添加剂实现了基线分离。9种食品添加剂在10.0～100.0 mg/L内具有良好的线性关系(r2＞0.9991);检出限为0.33～2.36 mg/L,定量限为1.11～7.80 mg/L;9种食品添加剂在空白干红葡萄酒中的添加回收率为87.61%～108.4%,其相对标准偏差为2.2%～9.4%。本实验结果对于食品中多组分食品添加剂的RP-HPLC分离分析方法的建立和优化具有较好的指导意义。     

薄层色谱法拆分手性药物对映体

用性能稳定的薄层色谱用β-环糊精(β-CD)、硅胶手性固定相拆分手性药物对映体.在适当比例的乙腈-1%乙酸三乙胺(TEAA)、己烷-异丙醇、乙腈-甲醇-乙酸-三乙胺、甲醇-1%TEAA及乙腈-1%TEAA-三乙胺溶剂系统中展开,8种临床常用的手性药物对映体得到有效分离,对映异构体之间的相对比移值α为1.53～4.89.     

加压毛细管电色谱在建立中药黄柏指纹图谱中的方法学研究

以加压毛细管电色谱（pCEC）为技术平台,对其在建立中药黄柏指纹图谱中的方法学进行了研究．通过对提取溶剂、流动相中有机相种类、盐溶液等条件的优化,发现1％盐酸的甲醇溶液为提取溶液,20mmol／LNH4C1溶液．乙腈为流动相梯度洗脱,紫外检测波长为230nm时对其分离效果最好．并通过在色谱柱上施加不同的电压,详细地阐明了pCEC的双重分离机制对分离选择性的影响,发现黄柏中的主要成分药根碱、巴马汀和小檗碱在pCEC模式中随电压的不同,有不同的出峰顺序．当电压为0—4kV时出峰顺序为药根碱、巴马汀和小檗碱,当电压为8—14kV时出峰顺序为药根碱、小檗碱和巴马汀．对此原因进行了详细讨论,同时与微径液相色谱模式进行了比较,说明pCEC可以为复杂样品的分离提供更多更好的分离途径．     

β-环糊精键合手性固定相分离苯并恶嗪类对映体

研究了在反相高效液相色谱模式下,基于点击化学的β-环糊精手性固定相对苯并恶嗪类对映体的手性分离情况。考察了流动相中有机改性剂的类型和比例、缓冲盐的浓度和pH值对分离的影响。考察结果表明: 乙腈作为有机改性剂比甲醇更有利于苯并恶嗪对映体的分离;乙酸三乙胺缓冲盐体积分数从0.1%增大到1.0%时,苯并恶嗪对映体的保留时间和分离度都随之减小,在pH 4.1时苯并恶嗪对映体具有最大分离度。因此确定乙腈和体积分数为0.1%的乙酸三乙胺缓冲盐流动相(pH 4.1)为最佳分离条件。分离机理研究结果表明,固定相和样品之间的包容络合相互作用以及样品和固定相之间的氢键作用,是样品得以分离的基础。本研究为进一步深入研究β-环糊精固定相提供了实验基础,同时也证明了点击化学在手性环糊精固定相制备中具有极大潜力。     

薄层色谱用苯基异氰酸酯衍生化的β-环糊精键合固定相的制备及应用

合成了苯基异氰酸酯衍生化的β－环糊精键合固定相,并用红外光谱、元素及热重分析方法对此键合相进行了表征。实验结果表明此键合相性能稳定,适用于正相及反正色谱。用此衍生化的β－环糊精键全相做薄层色谱的手性固定相,结合己烷－异丙醇－１％乙酸三乙胺和乙腈－甲醇－１％乙酸三乙胺展开剂系统,６种手性药物查到完全分离,△Ｒｆ为０．０４～０．５５。苯基异氰酸酯衍生化的β－环糊精键合相与手性药物之间发生多种作用模式的     

负载型碱催化剂的制备及其在酯交换和醇、胺羰化反应中应用

以三乙胺和甲醇钠为活性碱组分,以Ａ,Ｘ和Ｙ型分子筛及硅胶和有机高聚物担体为载体制备了负载型碱性催化剂。考察了催化剂在甲醇和二乙胺羰化以及酯交换反应中的活性,并考察了催化剂制备过程中多种因素对活性的影响,结果表明,在催化剂制备过程中,溶剂和制备方法对催化剂活性的影响较大,而载体粒度的影响较小,在适当的条件下,上述载体能较好地负载有机碱三乙胺和甲醇钠,所得负载型碱性催化剂在环氧丙烷作用下具有较高的甲醇和二乙胺羰化催化活性及酯交换催化活性。     

液相色谱法测定生物发酵液中水溶性维生素的研究

本文采用反相离子对色谱测定了生物发酵液中的七种水溶性维生素。提出了用自行装填的酸性氧化铝（０．１９～０．１５ｍｍ）前置柱，和５％乙酸洗脱样品的前处理方法；并就有关的色谱条件进行了选择。色谱柱为ＮｏｖａＰａｋＣ１８；流动相Ａ液为０．０５ｍｏｌ／Ｌ庚烷磺酸盐（ＰＩＣＢ７），冰乙酸调ｐＨ＝２．５；Ｂ液为甲醇＋三乙胺（１００＋０．５）；梯度洗脱；ＵＶ２５４ｎｍ、２９０ｎｍ、３６０ｎｍ同时测定。线性范围为０．１～１０μｇ，各种维生素的ＲＳＤ在１．２％～３．０％之间（ＶｉｔａｍｉｎＢ１２除外），回收率大于９０％。     

表阿霉素及其相关物质在反相离子对色谱中的色谱行为

以表阿霉素及其6种相关物质为研究对象,系统评价了其在反相离子对色谱模式下的色谱行为.分别考察了流动相中有机相种类、有机相比例、水相中离子对试剂浓度、pH值对表阿霉素及其相关物质的影响.结果表明,使用乙腈作为有机相洗脱能力及分离效果优于甲醇,保留时间随乙腈比例增大而减小;随着离子对试剂十二烷基硫酸钠浓度增加,杂质阿霉素酮及柔红霉酮几乎无影响,其他5种物质保留时间增加.同时,表阿霉素及其杂质的保留行为受流动相pH值影响较大,当pH不高于4时可获得较好的分离效果.通过对表阿霉素及其相关物质反相离子对模式下的保留行为进行了系统的评价和定量描述,研究结果将有助于该类化合物液相色谱分离方法的发展.     

液相色谱质谱测定中甲醇乙腈对农药响应的影响

在等度洗脱条件下,分别用甲醇和乙腈作液相色谱/串联质谱法(LC/M S/M S)测定有机流动相,考查了35种农药的质谱响应差异。同样有机相占比和流速时,相较于甲醇,乙腈洗脱力更强,疏水性相对强的农药出峰更快。各农药在甲醇和乙腈中出峰时间差存在差异,出峰早的农药差异小,出峰晚的农药差异大。相较于乙腈,甲醇可增加农药的质谱峰面积响应。甲醇对用加氢峰测定农药质谱峰面积响应增加最大,对用加铵峰测定农药质谱峰面积响应增加次之,对用负离子模式测定农药质谱峰面积响应增加较小。     

Effect of Type and Concentration of Organic Modifier in Aqueous Eluents on Retention in Reversed Phase Systems

Abstract

Retention - eluent composition relationships were determined for 18 compounds (phenols, quinoline bases, anilines) in chromatographic systems of water + organic modifier - oleyl alcohol (fixed on cellulose). Six organic modifiers were investigated: methanol, acetone, acetonitrile, 1,4-dioxane, dimethyl sulphoxide, acetic acid. Different eluotropic series were obtained depending upon the donor-acceptor properties of the solutes; for instance, dimethyl sulphoxide exhibited high eluent strength relative to phenols and anilines and acetic acid - to quinolines and anilines.     

Investigation on liquid chromatographic separation of basic compounds using silica column with aqueous/organic mobile phase containing triethylamine and acetic acid

A high-performance liquid chromatography (HPLC) method using silica column eluted with aqueous solvent mobile phase containing triethylamine (TEA) and acetic acid (ACH) at trace percentages was characterized for the analysis of basic compounds. The key mechanism of this system is ion-exchange accompanying interaction of silanol groups. The increase in the ACH concentration in the mobile phase minimizes the ionization of the silanol group, leading to reduced retention time. However, the greater extent of ionization of silanol caused by the increase of TEA concentration helps to retain basic compounds in the column. Further, the protonated TEA that is positively charged also competes for the ionized silanol group with basic compounds, resulting in the modification of retention time. On the other hand, the retention becomes longer with increasing proportion of either organic or aqueous solvent in mobile phase, and partial replacement of methanol with acetonitrile.     

Preliminary study of the analysis of oligogalacturonic acids by electrospray ionization mass spectrometry

During systematic studies of the behavior of oligogalacturonic acids (OGAs) under different conditions using electrospray ionization mass spectrometry (ESI-MS), cation adduction, fragmentation and non-covalent binding were found to be the three major problems that compromised the analysis of OGAs by ESI-MS. By adjusting solution components, capillary temperature and capillary voltage in the ESI source, an optimized condition was found that gave a clean and clear spectrum of trigalacturonic acid. A direct injection ESI-MS technique based on the use of aqueous acetonitrile and acetic acid and triethylamine (TEA) as modifiers has been applied to analyze a mixture including mono-, di- and trigalacturonic acids, which will facilitate further applications of ESI-MS in the analysis of mixtures of OGAs.     

Study on the conversion of three natural statins from lactone forms to their corresponding hydroxy acid forms and their determination in Pu-Erh tea

Conversions of statins, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, from lactone forms to their corresponding hydroxy acid form in 0.1 N NaOH or 0.05 N KOH (prepared with 25, 50, 75, 90% acetonitrile or methanol in water or 100% water) were evaluated. Results showed that lactone form statins could be transformed almost completely only in alkaline solutions prepared with 25 or 50% acetonitrile. In all methanolic alkaline solutions, lactone form statins could also be converted entirely, nevertheless, they would be further transformed to the methyl ester of the hydroxy acid form and the transformation increased as methanol rises. When lactone and hydroxy acid forms of statins were in methanol, ethyl acetate, 70% acetonitrile in water (with 0.5% acetic acid or no) for 0-48 h at room temperature or in 100 degrees C water for 0-2 h, lactone form statins were converted to their corresponding hydroxy acids, which were raised as time extends and the highest conversions of them were about 35% in 100 degrees C water and 70% acetonitrile, slightly transformed for lactone form statins in 70% acetonitrile (with 0.5% acetic acid) after 8 h, and the other treatments for all statins showed no significant changes. Interferences would be reduced efficiently when statins were extracted from Pu-Erh tea with methanol, ethyl acetate or 100 degrees C water followed by purifying through a C18 solid-phase extraction cartridge. Lovastatin was the only statin found in Pu-Erh tea and the highest content of it was found under ethyl acetate extraction. In ethyl acetate and methanol extracts, lovastatin existed merely as lactone form. The lowest content of lovastatin was found in the 100 degrees C water extract of Pu-Erh tea, however, both of lactone and hydroxy acid forms were found to exist in the extract.     

Charge-state reduction with improved signal intensity of oligonucleotides in electrospray ionization mass spectrometry

The shift of charge states of oligonucleotide negative ions formed in electrospray ionization mass spectrometry to higher mass-to-charge ratio has been accomplished by addition of organic acids and bases to the solution to be electrosprayed. The use of acetic acid or formic acid combined with piperidine and imidazole effectively reduced charge states. Signal intensity and stability were enhanced greatly when the infused solution contained a high percentage of acetonitrile. In addition, the cocktail that contained imidazole, piperidine, and acetic acid in 80% acetonitrile not only reduced charge states, but also substantially suppressed Na adduction. Several oligonucleotides that varied in base composition and length were investigated, and studies of mixtures showed a significant reduction in spectral complexity.     

Pyrazolylborate-zinc alkoxide complexes. 3. Acid-base reactions

The alkoxides TpPh,MeZn-OR (R = Me, Et, i-Pr) undergo acid-base reactions with all hydrogen compounds whose acidity is higher than that of the corresponding alcohol ROH. Thus, anion exchange occurs with the common acids acetic acid, acetohydroxamic acid, acetylacetone, phenol, and ethylmercaptan. Alkoxide exchange is observed using methanol, ethanol, and trifluoroethanol. With the NH acids cyanamide, trifluoroacetamide, and pyrazoles, the corresponding anions are attached to zinc, and likewise beta- and gamma-lactams, a thiazolidinedione, and the cyclic sulfimide saccharin are deprotonated. Of the CH acids acetonitrile forms the Tp*Zn-cyanomethanide. Acetone is deprotonated by the cyanomethanide complex and incorporated as the Tp*Zn-beta-ketoiminate.     

三(4-硝基苯基)甲醇及其氯化物的合成与表征

以三苯甲烷为原料,经硝化、氧化和氯化三步反应合成了三(4-硝基苯基)甲烷(TNPM),三(4-硝基苯基)甲醇(TNPMO)和三(4-硝基苯基)氯甲烷(TNPMCl)等一系列三芳基甲烷类化合物.三苯甲烷经混酸硝化制备TNPM;然后经CrO3/冰醋酸氧化生成TNPMO,最后与乙酰氯反应得到TNPMCl.各步产物的结构经核磁共振与红外光谱进行了表征.     

A kinetic study of the electron-transfer in the reaction of tribenzylchlorotin with[CoW_(12)O_(40)]~(5-)

A kinetic study of the electron-transfer in the reaction of tribenzylchlorotin with potassium 12-tungsto cobalt(Ⅲ) ate ion, K_5[CoW_(12)O_(40)],abbreviated as Co(Ⅲ)W,has been performed in different solvents.The studies were carried out in methanol, ethanol,acetonitrile and acetic acid/water.The rate constants,reaction rates and activation parameters were calculated. Our findings show that the rate of disappearance of the Co(Ⅲ) is pseudo-first order.The kinetic data is strongly affected by used solvents.T...     

The acidity constants of some pyrimidine bases in various water-organic solvent media

The acid ionization constants of some pyrimidine bases of nucleic acids were determined pH-metrically at 25 degrees C and at the constant ionic strength I = 0.10 mol l(-1) (KNO3) in pure water as well as in aqueous media containing variable mole percentages (5-30%) of organic solvents. The organic solvents used were methanol, ethanol, N,N-dimethylformamide (DMF), dimethylsulfoxide (DMSO), acetonitrile, acetone and dioxane. The results obtained indicated that the acidity constants are generally decreased as the content of an organic solvent in the medium is increased. It was deduced that the hydrogen bonding interactions and the solvent basicity in addition to the electrostatic effect are the major effects influencing significantly the acid ionization process of pyrimidine bases in the different water-organic solvent media. Some thermodynamic parameters (deltaH, deltaG degrees, deltaS degrees) of the ionization process over the temperature range 5-45 degrees C in pure water were also determined and discussed.     

Nonaqueous affinity capillary electrophoresis investigation of small molecule molecular recognition

The conditional binding constants for a bis-guanidinium-like receptor and a series of dicarboxylate ligands have been determined in two buffer/solvent systems, namely 25 mM ammonium acetate/1% acetic acid in acetonitrile/methanol (7:3 v:v) and 30 mM N-methyl morpholine/15 mM methanesulfonic acid in acetonitrile/methanol (9:1 v:v). The latter buffer has not been applied before in capillary electrophoresis. The binding constants in both solvent systems decrease as the dicarboxylate length increases. The binding constants are larger in the less competitive N-methyl morpholine buffer. The dicarboxylates associate only weakly with a dicationic analog of the receptor, p-xylyl trimethylammonium, which is not a hydrogen bond donor.