可调移动重叠分离图法用于高效液相色谱多台阶梯度分离条件优化的研究

计算机辅助高效液相色谱（HPLC）分离条件优化可以低成本、快速地得到优化的分离条,因而已较为广泛地用于复杂样品的分离分析。基于移动重叠分离图方法,又发展了一种新型的多台阶梯度分离条件的优化方法可调移动重叠分离图法。该方法通过预测不同流动相条件下各组分的保留时间、峰宽和分离度,绘制出对于样品中各组分的重叠分离区域图。在对当前台阶流动相组成进行优化的同时,考虑其对后面一到两个台阶上流出组分保留的影响,实时地重新绘制对于后面台阶上流出组分的重叠分离区域图。通过观察当前台阶流动相条件对当前台阶和后面台阶上流出组分分离的影响,综合考虑样品中所有组分的分离情况,找到更接近全局最优的分离条件。通过扫描的方法对优化得到的分离条件进行微调,能够进一步提高分离效果。采用文献数据对可调移动重叠分离图法的应用加以说明,在二元流动相体系下,证明了该方法在HPLC方法建立方面的优越性。     

Rapid Optimization of Reaction Conditions Based on Comprehensive Reaction Analysis Using a Continuous Flow Microwave Reactor

Generally, the flow method has the advantage of a precise control over the reaction parameters and a facile modification of the reaction conditions, while a continuous flow microwave reactor allows for the quick optimization of reaction conditions owing to the rapid uniform heating. In this study, we developed a “9+4+1 method” to optimize reaction conditions based on comprehensive reaction analysis using a flow microwave reactor. The proposed method is expected to contribute to the synthesis of various fine and bulk chemicals by reducing cost and wastage, and by conserving time.     

Efficient and accurate three-dimensional Poisson solver for surface problems

We present a method that gives highly accurate electrostatic potentials for systems where we have periodic boundary conditions in two spatial directions but free boundary conditions in the third direction. These boundary conditions are needed for all kinds of surface problems. Our method has an O(N log N) computational cost, where N is the number of grid points, with a very small prefactor. This Poisson solver is primarily intended for real space methods where the charge density and the potential are given on a uniform grid.     

Determination of Acetic Acid in Vinegar by Gas Phase Molecular Absorption Spectrometry After Methyl Acetate Generation

 This paper describes a method for the quantitative determination of acetic acid by gas-phase molecular absorption spectrometry. The proposed method is based on the generation of methyl acetate with subsequent measureme nt of the volatile absorbance at 216 nm. The generation, transport and measurement conditions are optimized. Under the recommended conditions, the analytical characteristics are obtained, with a detection limit of 0.005 M. The method is tested with vinegar samples. The analytical results obtained by the proposed method agree with those of a reference method. Received October 27, 1999. Revision February 5, 2000.     

Thin-layer chromatography-densitometry and liquid chromatography analysis of alkaloids in leaves of Papaver somniferum under stress conditions

The effect of stress conditions on the concentrations of secondary metabolites were examined during various developmental stages of Papaver somniferum plants. P. somniferum plants were grown in laboratory conditions (Budakalász). The experiment consisted of 22 treatments. Significantly different alkaloid contents can be observed under different stress conditions. In general, the alkaloid contents of plants are very low; therefore, a highly sensitive and reliable method has to be developed for analysis. The amount of alkaloids was measured by 2 separation and detection techniques. Accuracy of the thin-layer chromatography method for quantitative analysis is limited. Without purification of samples the background is too noisy. Column liquid chromatography is a sensitive and relatively inexpensive method that allows precise quantitative determination of the alkaloid content.     

A shortened method for the assay with Centocor radioimmunoassay kit

We have conducted a series of basic studies about Centocor's CA125 RIA Kit, especially for the conditions of the incubation. The standard curve and the outcome of recovery test gained through the standard method and the shortened method are quite decent. As for the incubation time, it took longer than 20 hours and 6-18 hours inthe standard method and shortened one respectively. As our conclusion, these results suggest that the shortened method can be adopted as a practical one as well as the standard method, provided that careful attention is paid to several peripheral conditions in the assay.     

Multi-segment linear gradient optimization strategy based on resolution map in HPLC

1 Introduction As a powerful tool of separating and analyzing complex samples, high performance liquid chroma- tography (HPLC) is widely applied. The key point of establishing stable and complete method of analysis is the selection of separation conditions. Accompanying the development of computer technology, it is possible to investigate the separation performance of each component in the sample under a wide range of ex- perimental conditions based on the information ob- tained by carrying …     

一种基于数值分析的矩形离子阱仿真优化方法

提出了一种对矩形离子阱进行仿真设计和优化的方法。该方法以数值分析为基础,对离子在矩形离子阱中的运动进行分析,得到相应的离子运动二阶微分方程。然后使用数值分析的Runge-Kutta法,对此二阶微分方程进行求解,可以得到理想状态下离子在离子阱中稳定的条件,从而完成对矩形离子阱的设计和优化。采用本方法,设计并优化了一种矩形离子阱,质量范围最大为260 amu/e,使用乙醇作为目标样品,紫外灯源作为离子源,法拉第筒作为检测器,对该矩形离子阱进行了质谱实验,成功得到了质谱结果,验证了所提出的数值分析仿真优化方法的实用性和正确性。本方法简单易行,便于修改,针对性强,可对多个参数使用循环遍历的方式来寻找最优值,特别适用于对未知结构或参数的探索研究。以此方法为基础可开发离子运动仿真软件,有很好的应用前景。     

硅酸盐矿物中低含量元素的电子探针异点分步定量法

以电子探针分析硅酸盐矿物国家标准样品 ,研究了不同分析方法和实验条件对硅酸盐矿物的主量元素和质量分数<2 %的低含量元素的电子探针定量分析精度的影响;结果表明 ,在硅酸盐矿物的电子探针定量分析中 ,在假定不含低含量元素的情况下先用常规实验条件分析主量元素的含量 ,尔后用非常规实验条件异点分析低含量元素的含量 ,并让主量元素参与低含量元素定量计算的ZAF校正 ,可以保证不同含量的被测元素均具有较高的分析精度 ,并称该法为“异点分步定量法”。     

Equilibrium saturation chromatographic method for studying the binding of ligands to human serum albumin by high-performance liquid chromatography. Influence of fatty acids and sodium dodecyl sulphate on warfarin-human serum albumin binding

A size exclusion chromatographic method for studying ligand-macromolecule binding parameters is described. This equilibrium saturation method allows the determination of the concentrations of constituents in equilibrium and is specially useful for characterizing ligand--protein binding under conditions that can be compared with physiological conditions. The method has been used for measuring warfarin--human serum albumin (HSA) binding and for studying the influence of free fatty acids (FFA) and sodium dodecyl sulphate on warfarin--HSA binding. Some comparisons with the Hummel and Dreyer method are given. The influence of the FFA is strongly dependent on their chain length, with an inversion of the effect for a 10-carbon chain.     

2,6-Diketopiperazines from amino acids, from solution-phase to solid-phase organic synthesis

A method to prepare 1,3-disubstituted 2,6-diketopiperazines (2,6-DKP) as useful heterocyclic library scaffolds in the search of new leads for drug discovery is described. The method can be used in solution-phase and solid-phase conditions. In the key step of the synthesis, the imido portion of the new molecule is formed in solution through intramolecular cyclization, under basic conditions, of a secondary amide nitrogen on a benzyl ester. A Wang resin carboxylic ester is used as the acylating agent under solid-phase conditions, allowing the cyclization to take place with simultaneous cleavage of the product from the resin ("cyclocleavage"). The synthetic method worked well with several couples of amino acids, independently from their configuration, and was used for the parallel synthesis of a series of fully characterized compounds. The use of iterative conditions in the solid phase (repeated addition of fresh solvent and potassium carbonate to the resin after filtering out the product-containing solution) allowed us to keep diastereoisomer content below the detection limit by HPLC and (1)H NMR (200 MHz).     

A simplex search for conditions giving maximal and/or minimal concentrations of species in distribution plots

A new method is proposed for finding the conditions which maximize or minimize the concentration of a particular species in a multicomponent system. A Simplex procedure is combined with an iterative method for solving mass-balance equations from the total concentrations of the constituents of the system, its pH and the pertinent equilibrium constants. The following examples of application are given: (a) the optimum conditions for maximizing the concentration of mixed-ligand species in systems with more than one ligand; (b) the conditions for maximal or minimal formation of monomeric and dimeric species in the Cu(II)-triethanolamine system; (c) a search for local maximum/minimum in species distribution plots.     

Chiral separation and determination of the optical purity of thiamphenicol-related chiral compound by capillary zone electrophoresis with cyclodextrins as chiral selectors

Summary One classical method for quantitation of amino acids in proteins is hydrolysis of the proteins and determination of the free amino acids. Although the drastic experimental conditions necessary for complete hydrolysis always cause degradation of some of the amino acids, if mild hydrolysis conditions are used, a mixture of amino acids and oligopeptides is obtained. If these conditions are adequately tuned, the oligopeptides are almost exclusively dipeptides. For this reason we have initiated a study to find a derivatizing agent suitable for the analysis of amino acids and dipeptides by an absolute method of quantitation already tested for amino acids. FMOC-Cl was found to be a suitable derivatizing agent for this purpose.     

循环连续流动分析法测定辣根过氧化物酶的活性

基于H2O2-辣根过氧化物酶(HRP)-邻苯二胺(OPDA)催化反应体系,建立了测定游离及固定化HRP酶活性的循环连续流动分析法(CCFA).CCFA实现了反应液、反应过程的循环连续检测.用CCFA法对酶催化反应条件进行研究,得到的最佳反应条件是:pH 5.0,反应温度27 ℃, 66.0 μmol/L H2O2 , 2 mg/L OPDA,缓冲液为0.1 mol/L柠檬酸-柠檬酸钠缓冲液; 测定游离HRP的线性范围为0～10 U/L,检出限为0.21 U/L,RSD＜1.03%.使用CCFA法测定了固定化HRP的活性,并对HRP酶促动力学进行了研究,得到的游离HRP的米氏常数为0.078 mmol/L,最大反应速度为0.26 mmol/(L min),催化常数为5.2 × 104 min-1.CCFA法操作简便、准确度高、节省试剂、易于实现自动化.     

从双多阶程升保留时间预测恒温保留指数可行性研究

由于程序升温保留值受多种操作条件的影响，缺乏数据的共用性，作者提出了根据组分双多阶程序升温保留时间预测其恒温保留指数的方法。以烃类化合物对象，从理论和实验两方面论证了该法的可行性。     

A method for the reductive scission of heterocyclic thioethers

A mild, chemoselective, and generally high-yielding method for the reductive scission of heterocyclic thioethers is described. Suitable heterocycles have a thioether substituent at the 2-position relative to a ring heteroatom. The convenient and straightforward method is demonstrated with reactants which are not compatible with the standard Raney nickel conditions such as sulfides, sulfones, and thiophenes. In addition, benzyl esters, benzyl amides, and benzyl carbamates are tolerated by the reductive reaction conditions.     

单纯形优化高效液相色谱法分离测定维生素E的各种异构体

本文用计算机辅助单纯形优化高效液相色谱法分离、测定了精炼植物油副产物中维生索E的各种异构体。探讨了单纯形优化法指导高效液相色谱选择分离的实验条件,并编写了实用的计算机程序。实验结果表明,本法可使比较困难的条件选择工作有章可循,从而提高工作效率。     

优化氰戊菊酯气相色谱检测条件的研究

应用计算机拟合技术进行了氰戊菊酯的毛细管气相色谱检测条件的设计与优化的研究,建立了相关的数学模型。成功地求出了柱温252℃、压力17Pa时能够满足出峰时间快、峰型好的气相色谱检测条件。文章提出的检测手段和方法与传统方法对比,具有即可减少实验次数,又可一次就准确地找到最佳检测条件的优点,而且拟合技术的处理过程全部通过计算机进行处理,比传统的处理方法简便,并且在其他类型样本的色谱检测条件的优化上有广泛的应用价值。     

Polarographic procedures without removal of oxygen, and other approaches to making the determinations more rapidly

One disadvantage of conventional d.c. polarography as an analytical method has always been its relative slowness. The possibility of simplifying and speeding up analyses by avoiding the necessity for removal of oxygen is demonstrated under suitable conditions with current-sampled d.c., pulse and a.c. polarography. In particular it is shown that high-frequency phase-selective a.c. polarography gives considerable discrimination against the oxygen electrode process in some aqueous media. Under these conditions, the high-frequency a.c. technique can be combined with the method of short drop-time, fast scan-rate rapid a.c. polarography to provide a most attractive method of routine analysis. Polarographic analysis in non-aqueous media without removal of oxygen is also discussed.     

A novel version of the method of radiofrequency labeling in chemical reactions

A novel version of the radiofrequency labeling method is described, which possesses essential advantages over the recently proposed method of “saturation transfer”. The conditions necessary, for realization of this method are discussed. The use of the method is exemplified by an investigation of a reaction mechanism.