五味子提取物高效液相色谱分析方法的优化

针对五味子乙醇提取物的复杂体系,借助于复杂样品分析系统软件(CSASS),根据组分在4次简单线性梯度下42个峰的保留时间,快速准确地计算出各组分的液相色谱保留参数a,c值和峰形参数σ,W1/2。借助这些参数,对五味子色谱的分离情况进行高精度仿真预测。在此基础上,应用移动重叠分辨分离图和谱图仿真技术,发展了计算机辅助的五味子提取物的高效液相色谱全局优化方法。在优化条件下,五味子提取物的高效液相色谱分析可在40 min内完成,且常量成分和部分低含量成分都能够得到较好的分离。所建立的方法已成功地用于五味子中化合物保留时间及峰形的预测,并在此基础上对其色谱分离条件进行优化。     

HPLC柱效对检测水中磺胺二甲基嘧啶色谱条件的影响

研究色谱柱的柱效降低后对高效液相色谱测定水中磺胺二甲基嘧啶色谱条件的影响。比较了新旧色谱柱的分离效果、色谱峰的对称性和峰面积,结果表明,旧色谱柱的柱效降低,对目标物的分离效果变差,目标物的吸收峰面积变小,峰形不对称。对色谱条件进行了优化试验,结果表明,对流动相水相添加0.125%的冰乙酸调节p H值为4.5后色谱峰的峰形对称性和分离效果得到改善。     

反相高效液相色谱法测定呋喃西林中有关物质

建立反相高效液相法测定呋喃西林含量和有关物质的方法。采用Phenomenex Synergi Max-RP C12色谱柱（250 mm×4.6 mm,4μm）为分离柱，以乙腈-水（30∶70）为流动相，流量为1.0 mL/min，检测波长为375 nm，色谱柱温度为30℃。在该色谱条件下，呋喃西林色谱峰与相邻杂质峰的分离度大于1.5，呋喃西林的质量浓度在1.04～104.0μg/mL范围内与色谱峰面积线性关系良好（r=0.999 2），检出限为0.3μg/mL。样品中单一杂质测定值的相对标准偏差为6.5%(n=6)，杂质总和测定值的相对标准偏差为4.6%(n=6)，平均加标回收率为100.4%～101.3%。该方法操作简单，专属性强，准确性好，可有助于控制呋喃西林的质量。     

自制混合型固相萃取柱-高效液相色谱法同时测定食品中黄曲霉毒素B1、M1

建立了基于自制混合型固相萃取柱的样品净化/高效液相色谱测定食品中黄曲霉毒素B1、M1的方法。样品经60%乙腈水溶液提取、离心后,通过自制固相萃取柱排除杂质干扰,流出液以Shim-pack VP-ODS C18色谱柱为分离柱,水和乙腈为流动相,用荧光检测器检测,外标法定量。考察了柱类型、柱容量、取样量、提取溶液和流速等对检测的影响,优化了实验条件。在优化条件下,2种毒素在0.40～100μg/L质量浓度范围内与峰面积呈良好的线性关系,相关系数为0.999 4～0.999 7,检出限(S/N=3)为0.050μg/kg。在样品中分别加入0.40、1.0、100μg/L 3种浓度水平的标准品,其加标回收率为53%～112%,相对标准偏差为2.7%～7.1%。该法灵敏度高,操作简单﹑快速,适用于花生、开心果和奶粉等食品中痕量黄曲霉毒素B1和M1的测定。     

纸张中溶剂绿7、2,4-二硝基苯酚和对羟基苯甲酸丙酯及其钠盐含量的测定方法

本发明涉及一种纸张中溶剂绿7、2,4-二硝基苯酚和对羟基苯甲酸丙酯及其钠盐含量的测定方法,包括样品溶液的制备,液相色谱分析及测定结果的计算等步骤。经优化之后的检测方法具有检测时间短、操作简便、灵敏度高、回收率高及重复性好等优点,本发明方法的色谱条件使溶剂绿7、2,4-二硝基苯酚和对羟基苯甲酸丙酯的色谱峰与杂质色谱峰分离较好,并且具有较好的相关性,检出限在0.23~0.40μg/g之间,平均回收率分别为96.4%,88.9%和96.2%,样品测试结果的平均相对标准偏差分别为2.91%,2.06%和3.08%,说明本法的回收率较高,重复性较好。     

去除血浆中高丰度蛋白质的二维液相色谱体系的建立

血浆中高丰度蛋白质的存在严重干扰低丰度蛋白质的检测,是困扰血浆蛋白质组学研究的技术瓶颈之一。针对这一热点问题,建立了一种二维液相色谱(强阴离子交换色谱-反相高效液相色谱)分离系统,对血浆中的高丰度蛋白质进行了色谱定位并进行去除。选择TSKgel SuperQ-5PW为第一维色谱分离柱,第二维色谱分离采用Jupiter C4柱,对第一维的馏分进行进一步的分离。通过梯度优化,血浆样品经过二维系统得到充分分离。第二维分离过程中从紫外信号强度高(215 nm,大于20 mAU)的峰中选择10个峰,利用液相色谱-串联质谱鉴定出32种高丰度蛋白质,包括人血清白蛋白、免疫球蛋白G等高丰度蛋白质。该体系为血浆中更多高丰度蛋白质的去除以及血浆蛋白质组学的更深入研究提供了重要思路。     

高效液相色谱法测定庆大霉素C组分的不同检测方式测定结果的比较

各国药典中关于庆大霉素C组分的测定方法均为高效液相色谱法,但检测方式及分离效果不同。为此采用直观推导式演进特征投影法(HELP),对高效液相色谱-二极管阵列检测采集的庆大霉素C组分色谱数据进行解析,分辨出各物质的色谱曲线,在扣除了未分离的杂质峰对庆大霉素C1组分的干扰后,对柱前邻苯二醛衍生化-二极管阵列检测法及目前中国药典 2005 版收载的高效液相色谱-蒸发光散射检测方法测定庆大霉素C组分的准确性进行了比较,并运用柱切换技术,证明二者测定结果的一致性。     

高效液相色谱法测定合成样品中溴酚磷及其杂质含量的研究

研究了一种同时测定合成样品中溴酚磷及其杂质含量的高效液相色谱法，用ＭｉｃｒｏｐａｋＭＧＨ色谱柱，柱温４０℃，流动相为乙腈－甲醇－水－醋酸（２６：５７：１７：０．２，ｖ／ｖ），紫外检测波长２９８ｎ ｍ，在本色谱条件下，各组份得到较好地分离。     

超临界流体色谱对吴茱萸中吲哚类生物碱的快速分析

建立了超临界流体色谱快速分析吴茱萸中吲哚类生物碱的方法。以标准品混合物和复杂样品为对象比较4种色谱柱的分离效果,进行色谱柱的筛选;考察了进样体积、改性剂、添加剂、温度和背压对保留行为的影响。结果表明,进样体积对峰形影响显著;添加剂对保留时间和色谱峰形影响有限;改变改性剂能使保留时间显著改变;降低温度,升高背压,保留时间减小。经过优化,确定采用Waters ACQUITY UPC² BEH色谱柱,以甲醇为改性剂,在35 ℃柱温和2.07×10⁷ Pa背压条件下,15 min内完成复杂样品的分析。同时采用超高效液相色谱完成复杂样品的快速分析。结果表明,超临界流体色谱可用于天然产物的高效快速分析,同时该方法与超高效液相色谱在分离选择上的差异有助于天然产物分析方法的拓展。     

反相液相色谱对多肽的分离、纯化与制备

用反相高效液相色谱（RPLC）对两种化学合成多肽－－32肽和21肽进行了分离、纯化和制备。在用分析型RPLC色谱柱对多肽样品的制备过程中，对其进样量和洗脱梯度进行了选择。每次进样量为5mg，在最优化色谱条件下，用RPLC一步就可对21肽进行分离纯化，其纯度达到98.6%。而32肽由于样品组分更加复杂，RPLC一步纯化后其纯度仅有80％。通过对色谱分离条件的再次优化，对32肽进行二次分离纯化，纯度达杂，RPLC一步纯化后其纯度仅有80％。通过对色谱分离条件的再次优化，对32肽进行二次分离纯化，纯度达到96.4%。在其最优化条件下，通过多次样品收集和冷冻干燥，分别制备了高纯度的21肽和32肽各100mg。     

Calculation of the stabilization energies of oxidatively damaged guanine base pairs with guanine

DNA is constantly exposed to endogenous and exogenous oxidative stresses. Damaged DNA can cause mutations, which may increase the risk of developing cancer and other diseases. G:C-C:G transversions are caused by various oxidative stresses. 2,2,4-Triamino-5(2H)-oxazolone (Oz), guanidinohydantoin (Gh)/iminoallantoin (Ia) and spiro-imino-dihydantoin (Sp) are known products of oxidative guanine damage. These damaged bases can base pair with guanine and cause G:C-C:G transversions. In this study, the stabilization energies of these bases paired with guanine were calculated in vacuo and in water. The calculated stabilization energies of the Ia:G base pairs were similar to that of the native C:G base pair, and both bases pairs have three hydrogen bonds. By contrast, the calculated stabilization energies of Gh:G, which form two hydrogen bonds, were lower than the Ia:G base pairs, suggesting that the stabilization energy depends on the number of hydrogen bonds. In addition, the Sp:G base pairs were less stable than the Ia:G base pairs. Furthermore, calculations showed that the Oz:G base pairs were less stable than the Ia:G, Gh:G and Sp:G base pairs, even though experimental results showed that incorporation of guanine opposite Oz is more efficient than that opposite Gh/Ia and Sp.     

Single-point titrations: Part II. Experimental determination of bases

An acid—base mixture is described which has linear pH response when titrated with strong base. The concentrations of the separate components in the mixture are given. Determinations of bases in the tange 0.05 M—0.25 M with a relative standard deviation of less than 0.5 % are reported. The method of preparing the mixture as well as some interferences of high salt concentrations in the sample are discussed.     

Effect of O6-methylguanine on the stability of G-quadruplex DNA

The effects of substitution of O6-methylguanine on the structure and stability of a human telomere quadruplex was studied by circular dichroism, thermal denaturation, analytical ultracentrifugation, and molecular dynamics simulations. The results show that, while quadruplex structures can form containing the modified base, they are much less stable than the normal unmodified structure. The extent of destabilization is critically dependent on the exact position of the modified base within the quadruplex structure.     

Single-point titrations: Part-I. The determination of bases

Equations are derived for the calculation of acid mixtures, which upon titration with base show a linear relation between pH and the amount of base. Three to five weak acids were used and a linearity of better than ±0.02 pH units was obtained. The use of such mixtures for analysis of the base content of samples by means of a single pH measurement is described. A procedure for obtaining conditional pK_a values of the components of the acid mixture is also described. The single-point titration method is advocated for use when better accuracy than that of direct potentiometry is desired but less than that of an ordinary titration can be accepted. It is not necessary to know the pK_b or the number of weak bases.     

气相色谱-质谱法测定变压器油正构烃含量

环烷基油是生产高性能变压器油的优质原料,以此为基础油生产的变压器油其凝点一般都小于-40℃,而变压器油在使用过程中对凝点(即低温流动性)有着非常高的要求,凝点的高低直接影响着油品的物理化学性能及电器性能。而油品的低温流动性与其组成中的正构烃(蜡)含量密切相关,据有关     

Hydrolyse basique comparee d'esters allophaniques et phosphoriques en milieu mixte acetonitrile/eau faiblement aqueux; mise en evidence d'une entite catalytique,intermediaire de la reaction entre base et solvant

Kinetic study of base catalysed hydrolysis in acetonitrile-water Mixtures of allophanic esters (models of carboxybiotine) and phosphoric esters shows in the range of low water content (less than 1 molar) an enhancement in rate (10³) with a maximum at 0.1–0.3 molar in water. This rate enhancement is ascribed to ground state desolvation and the maximum is interpreted by a change in the rate determining step : leaving group departure in the tetrahedral intermediate is indeed the slow step for the reactions in acetonitrile/water mixture less than 0.1 molar in water. For charged phosphoric esters the rate enhancement from an aqueous medium (pH=10) to organic is larger since as high as 10⁶.On the other hand, in such a medium, an additional catalytic effect is observed; it is shown that it is due to the formation of a reactive species which results from reaction of the base on acetamide when accumulated in the medium from base catalysed hydrolysis of the solvent.     

Announcement

The thermal decomposition of biguanide, the biguanidinium chlorides, sulphates and carbonate have been studied. Biguanide decomposes in definite steps, producing an almost quantitative yield of ammonia leaving initially a solid residue, melamine, which then sublimes unchanged at higher temperatures. The biguanidinium chlorides and sulphates are thermally more stable than the parent base and do not decompose in well-defined steps, whereas the carbonate is thermally less stable than the parent base but does decompose in definite steps. In addition, the fragmentation of biguanide and biguanidinium carbonate in a mass spectrometer is reported.     

The effect of minor-groove hydrogen-bond acceptors and donors on the stability and replication of four unnatural base pairs

The stability and replication of DNA containing self-pairs formed between unnatural nucleotides bearing benzofuran, benzothiophene, indole, and benzotriazole nucleobases are reported. These nucleobase analogues are based on a similar scaffold but have different hydrogen-bond donor/acceptor groups that are expected to be oriented in the duplex minor groove. The unnatural base pairs do not appear to induce major structural distortions and are accommodated within the constraints of a B-form duplex. The differences between these unnatural base pairs are manifest only in the polymerase-mediated extension step, not in base-pair stability or synthesis. The benzotriazole self-pair is extended with an efficiency that is only 200-fold less than a correct natural base pair. The data are discussed in terms of available polymerase crystal structures and imply that further modifications may result in unnatural base pairs that can be both efficiently synthesized and extended, resulting in an expanded genetic alphabet.     

The Properties of Structurally Homogeneous Poly(l-vinyluracils) and Their Interactions with Polynucleotides

Abstract

It has been found that highly syndlotactic PVU has a greater hypochromism and fluorescence emission Intensity along with a different dimethyl sulfoxide denaturation profile than the less syndlotactic polymer in aqueous solutions. These results are probably attributable to an interrelation between the configurational arrangement of uracils, the conformation of the polymers, and base stacking between uracils. In the neutral pH range, before the onset of aggregation and precipitation, the polymers are thought to be in tightly packed coillike conformations which are stabilized by intramolecular base stacking forces. The reaction of highly syndlotactic PVU with Poly A was thought to form a triple stranded PVU:2 Poly A complex, while the less syndlotactic polymer formed a metastable double stranded 33.3% Poly A complex which on equilibration rearranged into a 25% Poly A complex probably containing PVU loops. In the presence of 20% DMSO this system formed a 13% Poly A complex indicative of partial denaturation of the base pairs with DMSO. PVU was also     

In situ assembly of layered double hydroxide nano-crystallites within silica mesopores and its high solid base catalytic activity

Mg-Al layered double hydroxide (LDH) nanocrystallites with a lateral size less than 9 nm were in situ synthesized within the pore channels of mesoporous silica materials, creating one of the most active heterogeneous base catalysts owing to the high number of active edge sites.