重水氘代率的NMR测定方法

本文提出一种利用含水量的定量调制测定重水氘代率的核磁共振(NMR)实验方法,并通过实验和推理为所建实验方法提供理论依据。该方法操作环节少,易于定量操控,因而所得结果可信度高。实际样品的测量表明可满足普通核磁共振实验室对重水试剂评估的要求。     

核磁共振样品旋转和液面下降

本文讨论了核磁共振样品旋转问题。指出增加样品旋转速度是提高核磁共振谱仪分辨本领和降低旋转边带的有效方法,给出了核磁共振样品旋转时液面下降深度的计算公式,实验测定了液面下降深度与样品旋转速度之间的关系曲线,与理论计算曲线很相符合。给出了核磁共振谱线的分辨本领和旋转边带随样品转速提高而得到改善的实验例证。     

二维碳—13核磁共振谱的实验方法及应用

本文研究了二维碳-13核磁共振谱的实验方法和实验条件,采用球形样品管并精确调整脉冲宽度以后,基本上可以消除那些经常出现的伪信号的影响。文中给出了顺式和反式十氢萘和吡啶的二维碳-13核磁共振谱,用以说明这种新的核磁共振方法在结构分析中的某些特殊用途。本文还提出在二组核磁共振谱中用强迫恢复脉冲序列来缩短延迟时间,以提高记谱的工作效率,并且还作了用弛豫溶剂来缩短延迟时间的二维核磁共振实验。     

二维异核相关实验方法的比较研究

本工作在实验的基础上对几种同类功能的二维异核相关实验的优势和局限进行讨论。结果反映核磁共振具有实验方法多样化的技术特点,并重要指出:在实际工作中,为获取丰富和可靠NMR谱图信息,核磁共振工作者应该根据实验目的、样品特点和拟解决的问题对实验方法与实验参数进行合理的选择。     

浓度对“微量”样品NMR信号影响

本工作利用微量核磁管(Φ2.5 mm)和常规核磁管(Φ5 mm)对同一化合物同等质量(2 mg)两份样品进行多种核磁共振实验,对两种不同浓度下NMR信号进行分析,并利用微量样品管顺利完成对头孢硫脒的结构确认。实验结果表明:当可用于测试样品量较少时,利用微量样品管提高样品测试浓度可明显地改善核磁谱图质量;微量样品管在小样品量的NMR分析中具有潜在应用价值。     

食品检测流程中重点环节分析与管理实践

本文以食品检测实验室为研究对象,通过对食品检测流程中食品检测工作流程10个基本环节中的样品采集、样品接收、样品制备、样品流转4个重点环节进行分析,详细描述了其内在逻辑规律,突出了留痕表格化特色,从而力争保证在质量可控的条件下,提高检测工作效率。同时,对进一步提高承担流程运行工作的人员专业素质水平、加强信息化建设提出建议,从而不断提升食品检测流程的科学管理水平。     

核磁共振基础(四)——四、核磁双共振

1.核磁双共振的原理及应用前面所讲的核磁共振实验,是把样品放在静磁场 (?)_0中,并在其垂直方向上加上一个交变场 (?)_1,当 (?)_1的频率 v_1满足核磁共振条件时,v_1=((γ_1)/(2π))H_0就发生核磁共振现象。用扫场法或扫频法可以得到核磁共振波谱。但是,这种核磁共振波     

核磁共振基础(三) 三、核磁共振波谱仪概况

1.核磁共振仪器的分类(1)按射频场施加的方式分类根据核磁共振实验中射频场施加的方式,可以把核磁共振仪分为两种。一种是连续波核磁共振仪,它是把射频场连续不断地加到样品上,得到频率谱(或者称波谱)。另一种是脉冲核磁共振波谱仪,它是把射频场以窄脉冲的方式加到样品上,得到时间谱,或者称自由感应衰减信号(FID)。以观察自旋回波方式工作     

Varian MercuryPlus 400型核磁共振波谱仪~1H/~(19)F/~(13)C/~(31)P四核探头的调谐

超导核磁共振波谱仪在化学、物理、生物、医学、材料等领域的应用中,具有非常重要的地位。使用高场超导核磁共振波谱仪分析样品时,要得到较好的信噪比且使某些高级实验得到有意义的结果,就必须将探头准确调谐到特定样品的观测频率上。准确的调谐可以减少能量的反射,保护功放和探头,并获得最佳的灵敏度和最小的90度脉冲宽度。因为四核探头构造特殊,轻微的调谐改动就可能使仪器异常,导致实验无法进行,所以仪器厂家工程师一般不建议对四核探头进行调谐,因此到目前为止作者没有检索到相关方面的文献资料。本文就如何对Varian1 H/19F/13 C/31P四核探头在MercuryPlus 400型核磁共振波谱仪上进行准确调谐进行研究探索。     

水域放射性监测新方法的研究

概述了湘江水及自来水进行样品处理和制备样品源的实验方法,用BH1217B型低本底弱理、卢金硅面垒测量仪对样品源进行了总α、β活度的精确测量,对实验数据和某些影响实验结果精确性的不确定因素进行了详细的分析。正确的计算了水中总α、β放射性比活度值及其标准偏差。     

介质辅助微波消解用于火焰原子吸收测定沸石分子筛中Na

利用介质辅助微波消解溶样,火焰原子吸收测量,准确测定分子筛中Na含量,加标回收率在92%~102%之间。介质辅助微波消解可使消解和赶酸一次进行,具有快速高效、酸消耗量小、安全清洁等优点。     

Self contained high pressure cell, apparatus and procedure for the preparation of encapsulated proteins dissolved in low viscosity fluids for NMR spectroscopy

The design of a sample cell for high performance nuclear magnetic resonance (NMR) at elevated pressure is described. The cell has been optimized for the study of encapsulated proteins dissolved in low viscosity fluids but is suitable for more general NMR spectroscopy of biomolecules at elevated pressure. The NMR cell is comprised of an alumina toughened zirconia tube mounted on a self-sealing non-magnetic metallic valve. The cell has several advantages including relatively low cost, excellent NMR performance, high pressure tolerance, chemical inertness and a relatively large active volume. Also described is a low volume sample preparation device which allows for the preparation of samples under high hydrostatic pressure and their subsequent transfer to the NMR cell.     

微波溶样技术的进展

样品制备技术的改革是分析化学中的重大研究课题。微波技术的引进,使样品制备的技术进入了新的生命性的阶段。     

Surface roughness of preparations for backscattered electron-scanning electron microscopy: the image differences and their Monte Carlo simulation

Patterns and levels of mineralisation in the biological hard tissues have been studied using the backscattered electron (BSE) mode in the scanning electron microscope (SEM). To prevent gross topographic detail overwhelming changes in signal from composition, samples are embedded in polymethylmethacrylate (PMMA) and a flat block surface produced by polishing or micromilling. This study was undertaken to establish the degree of residual topography achieved in these finishing processes. A sample of human rib was embedded in PMMA and prepared, as for examination in the SEM, by polishing on graded abrasives and pre- and, finally, ultramilling. After each preparation step, the block face was imaged using a confocal reflection microscope surface mapping facility. The recorded topographies were used in a Monte Carlo simulation to model the surface interface and thus, for each of the sample preparation techniques, to calculate predicted variations in BSE signal. The latter were compared with experimental data derived under standard operating conditions in the SEM. Micromilling produced block faces with typical peak-trough relief of 80 nm, while hand polishing left occasional scratches 1.5 microns deep with a general undulation of 150-250 nm. Monte Carlo simulations of a rough surface of bone using these data predicted that additional contrast levels of 5% could be expected from micromilled surfaces and > 10% for hand polished samples of bone. Thus, micromilling is the best preparation method for bone, since this tissue develops a collagen orientation-related relief on polishing, which may be largely responsible for the (incorrect) supposition that lamellation in bone is related to changes in net degree of mineralisation.     

Monitoring 2-D gel-induced modifications of proteins by MALDI-TOF mass spectrometry.

In addition to more than 200 endogenously produced post-translational modifications, a detailed analysis of 2-D gel-separated proteins must also consider other modifications that a protein can experience during various steps of its separation. This review describes the use of matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry to investigate some of these modifications, which can originate during sample preparation and/or during the separation phase. The analyses described were mostly conducted at pH 9-9.5, and yielded reliable information on stable adduct formation that involved protein-bound amino acids and a number of gel components, including acrylamide derivatives, gel cross-linkers, and Immobiline chemicals. The -SH group of Cys was found to be the prime target of such adducts; however, longer reaction times revealed the involvement of the epsilon-NH2 of Lys. The same analysis revealed that the failure to achieve full reduction/alkylation prior to any electrophoretic step could result in protein-protein interaction, which could lead to a number of spurious spots in the final 2-D map. The implications of these modifications on the MS analysis in particular and on proteome research in general are discussed.     

新鲜蔬菜水果的农药多残留快速检测

介绍了一种农药多残留快速检测方法，此方法样品前处理过程简单，快速，采用固相萃取和氮吹仪实现了样品的净化和浓缩；双柱，双检测器的仪器配置提高了检测结果的准确度和精密度。     

农产品和食品中甲醛次硫酸氢钠(吊白块)现场快速定量测定的研究

介绍用于现场快速测定农产品和食品中吊白块含量的一种新方法和技术，包括现场样品快速前处理装置和通过定量测定样品中甲醛和二氧化硫的比例关系，根据甲醛的含量对吊白块进行定量分析。30分钟完成吊白块现场定性、定量检测。     

A comparative study between AFM and SEM imaging on human scalp hair

A comparative study of AFM and SEM imaging of the same area of a human scalp hair has been carried out to determine the similarity and the differences between the two techniques. Sample preparation for SEM analysis requires a metallization step and vacuum exposure, both of which could potentially induce modifications to the surface details. By contrast, AFM is a suitable technique to evaluate any effect resulting from sample manipulation because it can be applied without any specific treatment. AFM analysis demonstrates that sample metallization is responsible for modifications to the surface details of hair, mainly comprising an increase in height of scale steps and of root mean square roughness together with variation in scale profiles. Sample treatments for SEM imaging are in general potentially responsible for surface modifications to the samples involved.     

食品安全快速分析仪的研制及其应用-食品中亚硝酸盐的现场快速测定

研制出了一种用于农产品和食品中甲醛、吊白块、亚硝酸盐、硝酸盐、二氧化硫现场快速检测的车载式仪器,开发出配套的化学试剂盒和食品现场快速前处理设备。该仪器每个检测项目的分析时间控制在30分钟以内。该仪器主要用于质检和市场管理部门的现场流动检测。