Short columns with molecularly imprinted monolithic stationary phases for rapid separation of diastereomers and enantiomers

Three molecularly imprinted monolithic columns with different length but almost identical column volume had been prepared. It was observed that the separation factors of diastereomers and enantiomers were almost unaffected by column length. However, the short column with dimension of 38 mm x 8 mm W. showed much lower resistance to flow rate so that it could be operated at much higher flow rates. By combining stepwise gradient elution with elevated flow rate, the diastereomers of cinchonine and cinchonidine and the enantiomers of Cbz-DL-Trp and Fmoc-DL-Trp were successfully separated within 3 min on the short column with dimension of 38 mm. x 8 mm i.d.. Based on the above results, a cinchonine imprinted monolithic disk with dimension of 10 mm x 16 mm W. was further developed. The SEM image and the pore size distribution profile showed that large flow-through pores are present on the prepared monolith, which allowed mobile phase to flow through the disk with very low resistance. Chromatographic performances on the monolithic disk were almost unchanged compared with the long columns. A rapid separation of cinchonine and cinchonidine was achieved in 2.5 min at the flow rate of 9.0 ml/min. Furthermore, it was observed that there was almost no effect of the flow rate on the dynamic binding capacity at high flow rates. In addition, the effect of the loading concentration of analytes on the dynamic binding capacity, namely adsorption isotherm, was also investigated. A non-linear adsorption isotherm of cinchonine was observed on the molecularly imprinted monolith with cinchonine as template, which might be a main reason to result in the peak tailing of template molecule. (C) 2004 Elsevier B.V. All rights reserved.

Separation of enantiomers by nanoliquid chromatography and capillary electrochromatography using a bonded cellulose trisphenylcarbamate stationary phase

A cellulose trisphenylcarbamate-bonded chiral stationary phase was applied to nano-liquid chromatography (nano-LC) and capillary electrochromatography (CEC) with nonaqueous and aqueous solutions as the mobile phases. Several chiral compounds were successfully resolved on the prepared phase by nano-LC. The applicability of nonaqueous CEC on a cellulose derivative stationary phase was investigated with the organic solvents methanol, hexane, 2-propanol, and tetrahydrofuran (THF) containing acetic acid, as well as triethylamine as the mobile phases. Enantiomers of warfarin and praziquantel were baseline-resolved with plate numbers of 82 300 and 38 800 plates/m, respectively, for the first eluting enantiomer. The influence of applied voltage, concentration of nonpolar solvent, apparent pH, and buffer concentration in the mobile phase on the electroosmotic flow (EOF) and the mobility of the enantiomers was evaluated. Enantioseparations of traps-stilbene oxide and praziquantel were also achieved in aqueous CEC with plate numbers of 111 100 and 107 400 plates/m, respectively, for the first eluting enantiomer. A comparison between nonaqueous CEC and aqueous CEC based on a cellulose trisphenylcarbamate stationary phase was discussed. Pressure-assisted CEC was examined for the chiral separation of praziquantel and faster analysis with high enantioselectivity was acquired with the proper pressurization of the inlet vial.

Development of a precolumn derivatization method for the determination of free amines in wastewater by high-performance liquid chromatography via fluorescent detection with 9-(2-hydroxyethyl)acridone

A simple, sensitive, and mild method for the determination of amino compounds based on a condensation reaction with fluorescence detection has been developed. 9-(2-Hydroxyethyl)acridone reacts with coupling agent N,N-carbonyldiimidazole at ambient temperature to form activated amide intermediate 9-(2-acridone)oxyethylcarbonylimidazole (AOCD). The amide intermediate (AOCD) preferably reacts with amino compounds under mild reactions in the presence of 4-(dimethylamino)pyridine (base catalyst) in acetonitrile to give the corresponding sensitively fluorescent derivatives with an excitation maximum lambda(ex) 404 mn and an emission maximum at lambda(em) 440 nm. The labeled derivatives exhibit high stability under reversed-phase conditions. The fluorescence intensities of derivatives in various solvents or at different temperatures were investigated. The method, in conjunction with a gradient elution, offers a baseline resolution of the common amine derivatives on a reversed-phase C-18 column. The LC separation for the derivatized amines shows good reproducibility with acetonitrile-water including 2.5% DMF as mobile phase. The relative standard deviations (n = 6) for each amine derivative are <4.5%. The detection limits (at a signal-to-noise ratio of 3) per injection were 0.16-12.8 ng/mL. Further research for the field of application, based on the AOCD amide intermediate as derivatization reagent, for the determination of free amines in real water samples is achieved.

高效液相色谱-质谱法测定花生中的植物螯合肽

以镉胁迫花生为原料,建立了液相色谱-电喷雾电离质谱联用仪测定花生中的植物螯合肽的LC-MS方法。以C18反相柱为分析柱,1%三氟乙酸、乙腈为梯度洗脱淋洗液,能够检测出花生中的植物螯合肽。在本实验条件下,检出限为0.2 mg/L;线性范围在0.50～20.0 mg/L(r≥0.9974);回收率大于80%。方法灵敏度高,实用性强。应用本方法对实际花生样品中的PC4进行了定量分析。初步证实了花生中存在丙氨酸类植物螯合肽。结果表明,受镉胁迫的花生中均检出不同浓度的PC4。

Synthesis of covalently bonded cellulose derivative chiral stationary phases with a bifunctional reagent of 3-(triethoxysilyl)propyl isocyanate

A bifunctional reagent of 3-(triethoxysilyl)propyl isocyanate (TEPI) was initially adopted as a spacer reagent to prepare the bonded types of chiral stationary phases (CSPs) with cellulose derivatives. The silica-based CSPs were chemically prepared with non-regioselective and regioselective approaches and their chiral resolving capabilities were evaluated in terms of HPLC resolution of test enantiomers. It was observed that the chiral recognition capabilities of the non-regioselectively prepared CSPs were influenced by the amount of TEPI used. And also, the regioselectively prepared CSP generally showed a slightly higher resolution power than the non-regioselectively prepared CSP, while the non-regioselective procedures were highly advantageous to rapid preparation. In addition, chiral recognition of the prepared CSPs was affected by the properties of the used silica matrices. (C) 2003 Elsevier B.V. All rights reserved.

Molecularly imprinted monolithic stationary phases for liquid chromatographic separation of enantiomers and diastereomers

The method for preparation of molecularly imprinted monolithic stationary phase has been improved to achieve liquid chromatographic separation of enantiomers and diastereomers. By adopting low polar porogenic solvents of toluene and dodecanol and optimal polymerization conditions, the molecularly imprinted monolithic stationary phases with good flow-through properties and high resolution were prepared. Enantiomers of amino acid derivatives and diastereomers of cinchona alkaloids were completely resolved using the monolithic stationary phases. The influence of porogenic composition, monomer-template ratio and polymerization conditions on the chromatographic performance was investigated. Some chromatographic conditions such as the composition of the mobile phase and the temperature were characterized. Scanning electron microscopy showed that the molecularly imprinted monolithic stationary phase has a large through-pore structure to allow the mobile phase to flow through the column at very low backpressure. Accelerated separations of enantiomers and diastereomers were therefore achieved at elevated flow rates. Finally, the chiral recognition performance of the prepared stationary phase in aqueous media was investigated. Hydrophobic interaction, and ionic and/or hydrogen bonding interactions were proposed to be responsible for the recognition mechanism. (C) 2002 Elsevier Science B.V. All rights reserved.

Determination of peptides and amino acids from wool and beer with sensitive fluorescent reagent 2-(9-carbazole)-ethyl chloroformate by reverse phase high-performance liquid chromotography and liquid chromotography mass spectrometry

A new method for the sensitive determination of amino acids and peptides using the tagging reagent 2-(9-carbazole)-ethyl chloroformate (CEOC) with fluorescence (FL) detection has been developed. Identification of derivatives was carried out by liquid chromotography mass spectrometry. The chromophore in the 2-(9-fluorenyl)-ethyl chloroformate (FMOC) reagent was replaced by carbazole, which resulted in a sensitive fluorescence lerivatizing agent CEOC. CEOC can easily and quickly label peptides and amino acids. Derivatives are stable enough to be efficiently analyzed by high-performance liquid chromatography. Studies on derivatization demonstrate excellent derivative yields over the pH range 8.8-10.0. Maximal yields close to 100% are observed with three- to fourfold molar reagent excess. Derivatives exhibit strong fluorescence and allow direct injection of the reaction mixture with no significant disturbance from the major fluorescent reagent degradation by-products, such as 2(9-carbazole)-ethanol and bis-(2-(9-carbazole)-ethyl) carbonate. In addition, the detection responses for CEOC derivatives are compared to those obtained with FMOC. The ratios AC(CEOC)/AC(FMOC) = 1.00-1.82 for fluorescence (FL) response and AC'(CEOC)/AC'(FMOC) = 1.00-1.21 for ultraviolet (UV) response are observed (here, AC and AC' are, respectively, FL and UV F response). Separation of the derivatized peptides and amino acids has been optimized on a Hypersil BDS C18 column. Excellent linear responses are observed. This method was used successfully to analyze protein hydrolysates from wool and from direct-derivatized beer. (C) 2003 Elsevier Science (USA). All rights reserved.

平菇菌丝体对Cd、Pb及其复合污染的生长与富集响应

在PDA平板培养条件下,研究Cd、Pb及其复合污染对平菇菌丝体生长的影响以及平菇菌丝体对生长基质中Cd、Pb的生物富集作用.结果表明,在实验浓度范围内,菌丝生长势、菌落直径和菌丝体干重等均随着重金属浓度的增大而减弱(小)或降低.平菇菌丝体对Cd、Pb均具有生物富集作用,并且随着重金属浓度的增大菌丝体中重金属含量逐渐增大.Cd、Pb复合污染能促进平菇菌丝体对Pb的吸收,而抑制对Cd的吸收.

在线草图理解技术研究

手绘草图是一种自然而直接的思路外化和交流方式。用户传统使用草图的方式为先用草图记录早期想法，想法成熟时转化为正规电子文档，这样存在着冗余性和低效性的问题。随着笔计算设备的普及，数码笔、手写板、手写屏、电子白板、PDA、UMPC等设备不断融入人们的生活，在线手绘草图将成为笔计算设备的主要应用之一。近年来，手绘草图也开始在互联网上出现，成为用户体现个性的方式。理解在线手绘草图将为手绘草图的高效利用和高效编辑提供了保障。 草图理解包括在线草图理解和离线草图理解。在线草图理解的对象为用户用数字笔绘制的在线草图，而离线草图理解的对象为图像。目前，在线草图理解技术是当前的研究热点，但它仍然面临很多挑战，例如草图的自适应识别、新领域草图的理解、草图的高效交互等。本文的研究对象为在线草图理解技术以及面向在线草图理解的交互技术。具体地，从多个层次和角度展开研究，依次为：草图符号识别、手写公式理解、草图结构理解、面向在线草图理解的交互技术、原型系统。 本文首先概述了草图理解技术的发展历史，介绍了在线草图理解技术的需求、输入设备和关键技术，并分析了在线草图理解技术的研究进展。之后，本文对自适应的草图符号识别、手写无机化学公式理解、手绘概念图的结构理解这三个问题进行了讨论，并对面向在线草图理解的交互技术进行了分析，最后研发了一个原型系统IdeaNote。本文研究内容和创新点如下： 1. 自适应的草图符号识别 在草图符号的自适应学习中，不同用户的训练样本数量可能不同，保持在不同样本数量下良好的学习效果成为需要解决的一个重要问题。本文提出一种自适应的草图符号识别方法，该方法采用与训练样本个数相关的分类器组合策略将模板匹配方法和SVM统计分类方法进行了高效组合。它通过利用支持小样本学习的模板匹配方法和支持更多样本学习的SVM方法，并同时利用草图符号中的在线信息和离线信息，实现了不同样本个数下自适应的符号学习和识别。评估表明，该方法可以在24类草图符号分别使用1到20个训练样本时具有较高的识别正确率和较好的时间性能。 2. 手写无机化学公式理解 手写公式是人们学习和生活中的重要部分，本文提出手写无机化学公式的同步识别和异步识别方法。同步识别方法在用户书写无机化学公式的同时进行识别，异步识别方法在用户完成一个或几个化学公式的时候进行识别。两类方法均充分利用了无机化学领域的知识，具有较高的识别正确率。其中，异步识别方法的正确率为93.08%。基于手写无机化学公式的理解结果，可以支持无机化学公式的手写输入、多通道输入、自动错误检测和自动配平等。 3. 手绘概念图的结构理解 草图结构理解是草图编辑和草图应用的基础。手绘概念图是思维产生和交流的重要工具，与正规形式的概念图相比更加自然且符合用户的纸笔习惯。本文提出一种手绘概念图的结构理解方法。它采用动态规划方法提取概念图中的节点和连线笔划块，通过图划分的方法降低图的动态规划的时间复杂度，在此基础上提取由节点、连线和节点连线关系组成的概念图结构。评估表明，该方法可以取得95.18%的节点和连线提取正确率，且概念图结构理解的时间满足实时性要求。 4. 面向在线草图理解的交互技术 草图的交互技术对草图系统至关重要。本文提出手绘概念图的结构化编辑技术和基于语音和笔的多通道输入和纠错技术。其中，手绘概念图的结构化编辑技术，支持结构化的选择、移动、缩放和节点互换等编辑操作。评估表明，该结构化编辑方法比基于笔划的编辑方法更加高效。多通道交互技术包括基于语音和笔的多通道化学公式输入方法和基于语音和笔的多通道数学公式纠错方法。评估表明，基于语音和笔的手写数学公式识别纠错方法比基于笔的纠错方法取得更好的效果。 5. 原型系统IdeaNote 笔记系统是笔计算设备上的重要应用。IdeaNote是一个基于数字笔的笔记系统。它支持数字笔迹的自由输入，并支持笔迹的高效编辑。IdeaNote的基础为在线草图理解技术和面向在线草图理解的交互技术。在线草图理解技术包含笔手势识别方法、支持小样本学习的草图符号识别方法、列表结构理解方法、手绘概念图的结构理解方法和手写公式理解方法。面向在线草图理解的交互技术包括结构化编辑技术和多通道交互技术。另外，系统包含一个用于操纵笔迹的笔手势集合。

笔记采集工具的设计与开发

移动计算是当今主流的计算模式之一，以MID、UMPC、Tablet PC、PDA为代表的移动设备为移动计算的实现提供了可行性。在办公软件领域，随着用户需求的多样化发展，办公软件的非结构化、自由化输入是未来发展的趋势，以鼠标、键盘为主的传统办公软件已不能适应移动设备的需求。 思维是人接受信息、存贮信息、加工信息以及输出信息的活动过程。知识工作者是思维最为活跃的人群，是开发和使用知识的人。笔记是思维重要的呈现方式，笔记采集是知识工作者主要的活动之一。笔记采集正朝着个性化、智能化的方向发展，传统的办公软件已不能适应笔记采集的需求，以笔记采集为主要内容的移动办公软件将是办公软件发展的方向之一。 为适应笔记采集的移动性、自由性特点，本文设计和开发了面向知识工作者的笔记采集工具。本文的主要工作如下： 1． 笔记采集工具的需求分析 通过分析知识工作者的代表人群（老师和学生）在特定场景下的手写材料，总结得到笔记采集工具的功能需求。笔记采集工具需要支持笔迹的输入、笔迹结构的高级理解（如概念图理解等）以及一些特定领域下的功能（如动态几何作图等）。 2． 笔记采集工具的系统设计 依据PIBG界面范式，设计了笔记采集工具。具体地，通过剖析笔迹信息处理的层次关系，设计出笔迹处理解析机制；按照功能将系统划分为四个模块：笔迹采集、笔迹编辑、笔迹理解和笔迹管理；设计出包含交互层、任务层、算法层和数据层的软件体系结构。 3． 笔记采集工具的主要算法和特色功能 笔记采集工具的个性化和自由化需要各种高级功能（如概念图理解、动态几何）的支持。工具中采用的算法包括$1模板匹配算法、数学公式理解、概念图结构理解、笔迹搜索以及几何约束求解相关的算法。工具设计了一套笔手势，并为手势交互提供了有效的可视化反馈。 4． 笔记采集工具的实现与应用实例 实现了笔记采集原型工具，并给出一个学生使用该工具进行学习的实例。该工具的主要功能包括笔手势交互、动态几何、手写数学公式输入、概念图结构化编辑、笔迹搜索等。

田头菇菌丝体对镉、铅及其复合胁迫的生长与富集响应

在PDA平板培养条件下,研究了镉、铅及其复合污染对田头菇菌丝体生长的影响以及田头菇菌丝体对生长基质中镉、铅的生物富集作用。结果表明,在试验设置质量浓度范围内,菌丝生长势、菌落直径和菌丝体干质量等均随着重金属质量浓度的增大而减弱(小)或降低。田头菇菌丝体对Cd、Pb均具有生物富集作用,并且随着重金属质量浓度的增大菌丝体中重金属质量分数逐渐增大,初步认为Cd、Pb复合污染促进了菌丝体对Pb的吸收而抑制了对Cd的吸收。

N2O fluxes from the native and grazed semi-arid steppes and their driving factors in Inner Mongolia, China

This paper presents results of 2 years (from January 2005 to December 2006) of measurement of N2O fluxes from the native and grazed Leymus chinensis (LC) steppes in Inner Mongolia, China using the static opaque chamber method. The measurement was at a frequency of twice per month in the growing season and once per month in the non-growing season. In addition, the possible effect of water-heat factors on N2O fluxes was statistically analyzed. The results indicated that there were distinct seasonal patterns in N2O fluxes with large fluxes in spring, summer, and autumn but negative fluxes in winter. The annual net emission of N2O ranging from 0.24 to 0.30 kg N2O-N ha(-1) and from 0.06 to 0.26 kg N2O-N ha(-1) from the native and grazed LC steppe, respectively. Grazing activities suppressed N2O production. In the growing season, soil moisture was the primary driving factor of N2O fluxes. The high seasonal variation of N2O fluxes was regulated by the distribution of effective rainfall, rather than precipitation intensity. Air temperature or soil temperature at 0, 5, and 10 cm depth was the most restricting factor of N2O fluxes in the non-growing season.

Effect of the nucleating agent 1,3 : 2,4-di(3,4-dimethylbenzylidene) sorbitol on the gamma phase content of propylene/ethylene copolymer

The influence of the concentration of a nucleating agent (NA), namely 1,3:2,4-di(3,4-dimethylbenzylidene) sorbitol (DMDBS), on the gamma phase content in a propylene/ethylene copolymer was investigated by means of Differential Scanning Calorimetry (DSC), Wide-Angle X-ray Diffraction (WAXD), Small- Angle X-ray Scatter (SAXS) and Polarized Optical Microscopy (POM).

Grafting acrylic acid onto polypropylene by reactive extrusion with pre-irradiated PP as initiator

In this paper, the modification of polypropylene (PP) with acrylic acid (AA) by reactive extrusion using pre-irradiated PP (rPP) as initiator was investigated. It was found the relatively high graft degree (Gd) and slight degradation of modified PP was obtained when 20 wt% rPP was used. This result can be explained in terms of effective concentration of free radicals.