用θ-2θ型衍射仪测定溶液结构的新方法

叙述了θ－２θ型Ｘ射线衍射仪精确测定电解质溶液的结构的新实验技术。设计制作了具有慢温功能的最液体样品池，并建立了样品池窗口强度的校正方法，优化了液体Ｘ射线衍射数据和结构参数精细化的计算机程序，获得了非常令人满意的实验结果，由θ－２θ型Ｘ射线衍射仪精确测定的径向分布函数与θ－θ型衍射仪自由散射比较，表明ＤＲＦ分辨率有所提高。     

用全反射X荧光技术分析釉药粉末

１引言在微量痕量元素分析方面，全反射Ｘ荧光（ＴＸＲＦ）分析技术被认为是八十年代发展起来的最有竞争能力的分析手段，在原子谱仪中处于领先地位。我们从八十年代开始从事ＴＸＲＦ的研究，并于１９９３年自制出一台双激发源双光路全反射Ｘ荧光分析装置。几年来我们在许多领域里开展了应用研究。对水、油、头发、动物、古铜器、矿石粉、高纯材料、人工晶体等进行了分析实验。釉药是生产陶瓷的重要原料，需要好的配方并进行质量控制。但是，釉药粉末是多种原料的混合物，含有Ｓｂ、Ｚｒ、Ｔｉ、Ａｓ等多种元素，难以消解，不易配成均匀的溶…     

X射线荧光光谱分析

本文是“分析试验室”定期评述中“Ｘ射线荧光光谱分析”学科的第五篇评述。它收集了国内学者１９９２年７月到１９９４年６月期间发表在国内外刊物上的１７１篇文章，并对此期间我国Ｘ射线荧光光谱分析的概况和发展进行评述。内容包括ＸＲＦ仪器，同步辐射ＸＲＦ，全反射ＸＲＦ，粒子激发Ｘ线发射光谱，定量分析方法，制样技术，以及在各个科学烽戒严领域中的应用。     

Li2SO4水溶液结构X射线衍射测量条件的优化和数据校正

采用Ｄ／ＭＡＸ－３Ｂθ／２θ型Ｘ射线粉末衍射仪反射法,探索溶液结构研究的新方法。以Ｌｉ２ＳＯ４溶液的衍射实验为例,从狭缝和波长选择、步长及固定时间确定、峰背分离、溶液吸收校正、极化校正和荧光辐射校正等几个方面,重点讨论了Ｘ射线粉末法精确测量液体结构实验数据采集对策,给出了数据校正结果,即Ｌｉ２ＳＯ４溶液的衍射强度。     

半导体硅材料中掺杂元素锗的SRXRF微区分析研究

本文研究了同步辐射Ｘ射线微荧光分析法对半导体材料硅单晶中掺杂元素Ｇｅ的微区分析。利用同步辐射光源的优越性和微区扫描装置获得了清晰的掺杂元素Ｇｅ的二维分布图。实验结果表明，同步辐射Ｘ射线微荧光分析法对样品无导电性要求，可以成为对半导体材料硅单晶样品准确地进行大面积扫描微区测定的手段。对掺杂元素Ｇｅ在硅单晶生长过程中的分布行为和均匀性研究表明，在硅单晶生长的初始阶段由于小平面效应导致了掺杂元素径向分布     

流动注射—冷蒸气原子吸收法测定垃圾样品中泵

研究了反应介质浓度及其流速，反应管道长度，共存元素等对使用ＬＺ－１２００型流动注射氢化物发生器和ＷＦＸ－１０型原子有收分光光度计测定垃圾样品中汞的影响。方法准确度，精密均匀好，且操作简单，试剂用量少，分析速度快。经实验应用，结果满意。     

用θ-2θ型衍射仪测定溶液结构的新方法

叙述了用θ－２θ型Ｘ射线衍射仪精确测定电解质溶液结构的新实验技术。设计制作了具有恒温功能的超厚液体样品池，并建立了样品池窗口强度的校正方法。优化了液体Ｘ射线衍射数据和结构参数精细化的计算机程序，获得了非常令人满意的实验结果。由θ－２θ型Ｘ射线衍射仪精确测定的径向分布函数与θ－θ型衍射仪自由散射比较，表明ＤＲＦ分辨率有所提高。     

煤中形态硫分析及脱除能力研究

在实验室自动定硫仪上采用形态硫直接测定法，测定了７种煤样的脂肪硫、黄铁矿硫与噻吩硫的含量及它们脱除难易程度（能力），结果表明采用本实验方法测得的形态硫结果与Ｘ－射线吸收精细结构能谱（ＸＡＦＳ）所分析的结果一致。煤中形态硫在加热条件下脱除能力为：脂肪硫＞黄铁矿硫＞噻吩硫＞硫酸盐硫，而在弱碱性氧化脱硫条件下各形态硫脱除能力为：黄铁矿硫＞脂肪硫＞噻吩硫＞硫酸盐硫。     

XRD法研究水泥水化反应速度

本实验采用Ｘ射线衍射（ＸＲＤ）的常规物相分析法，以物相的衍射强度与多个主峰峰强和半高宽乘积之和成正比的原理，测定了同种水泥水化反应的速度，并与热导式微热量热法进行比较，证实采用ＸＲＤ法测定水泥水化反应速度具有简单、快速和实用的特点。     

FRS—XRSA表征双轴取向PET的结晶度

全倒易空间Ｘ－射线散射理论分析（ＦＲＳ—ＸＲＳＡ）是研究与表征择优取向高聚物结晶度与取向分布的一种新方案，它可以解决粉沫法测定结晶度时取向试样难以消取向的困难，测定拉伸和回复过程中正在形变的取向试样的结晶度．在以前的工作中，对双轴取向的薄膜，仅进行了幅度β＝０°（ＭＤ）与９０°（ＴＤ）两个轴向，△α＝１０°的ＸＲＳ测定，这样推得的结晶度事实上是ＭＴ双轴ＸＲＳ的结晶度，即ＭＴ－ＸＲＳ结晶度Ｘ，这种处理包含着ＸＲＳ沿ＭＴ方向作均匀分布的近似．本文为了澄清这一问题，作了下述三点改进：第一，利用ＦＲＳ中ＸＲＳ的强度分布，内插计算αｉ；，βｉ＝０°～９０°，△βｉ＝１０°的ＸＲＳ，由此求得较符合理论要求的ＦＲＳ－ＸＲＳ结晶度Ｘ；第二，进行了ＦＲＳ－ＸＲＳ的极角因子ｃｏｓαｉ；校正；第三，合理地处理了当极角αｉ＝９０°时出现奇点的困难．结果较合理．同时亦获得了晶粒度在ＦＲＳ中的分布情况．     

食品中痕量危害物分析过程污染的来源和控制

食品中危害物分析日趋痕量化,痕量化学分析因其敏感而易受外部环境的影响发生过程污染。通过对食品中痕量危害物检测过程污染实际案例的分析,发现污染的发生主要来自于实验环境、器具、试剂和过程控制等。探讨建立人员培训,方法学考查,实验环境和实验全过程控制等预防食品中痕量危害物化学分析过程污染的制度,并以此提高食品安全分析实验室检测过程预防污染的水平。     

Experimental design optimization of the analysis of gasoline by capillary gas chromatography

An optimization procedure for multi-step temperature programmed capillary GC was investigated for the detailed hydrocarbon analysis of gasoline. A set of twelve responses, represented by the value of the resolution of the most difficult separations, was selected from several isothermal analyses. The variation of these responses versus the temperature programming conditions was then modeled using a Doehlert matrix for experimental design. Optimal experimental conditions for the twelve responses were then obtained from a response surface optimization. The predicted and experimental resolutions were in good agreement.     

New aspects of ta application for studies of Ca-Mg carbonate minerals exemplified by upper permian rocks

The paper discusses the influence of variable experimental conditions on the thermal decomposition of carbonate minerals. This study was based on Ca-Mg carbonate minerals from Upper Permian dolomite and zuber rocks as well as on calcite and magnesite samples from geological formations of various ages. X-ray diffraction was applied for comparative purposes. Experimental conditions were chosen based on the authors' experience related to studies of both fossil and contemporary organic matters as well as various materials of geological provenience. Since the main factor in thermal analysis of carbonates is the appropriate choice of experimental conditions for outflow of gaseous reaction products, the thermal analyses were carried out with various sample holders, various sample masses and varied thickness of sample layers in holders, using also a dynamic atmosphere. The results obtained indicated that different experimental conditions produced extremely different TA data, e.g. the traditional analysis in crucible sample holders with a thick sample layer (great sample mass) showed well expressed double thermal effects of dolomite. For thin sample layer both peaks of thermal decomposition of carbonate components occurred in very close or almost identical temperatures. The presented results enabled to devise a detailed procedure referring to the choice of experimental conditions and interpretation possibilities as well as to recommend specific TA instruments design and sample holders types. This revised version was published online in July 2006 with corrections to the Cover Date.     

A numerical study of expected accuracy and precision in Calibration-Free Laser-Induced Breakdown Spectroscopy in the assumption of ideal analytical plasma

Calibration-Free Laser-Induced Breakdown Spectroscopy (CF-LIBS) has been proposed several years ago as an approach for quantitative analysis of Laser-Induced Breakdown Spectroscopy spectra. Recently developed refinement of the spectral processing method is described in the present work. Accurate quantitative results have been demonstrated for several metallic alloys. However, the degree of accuracy that can be achieved with Calibration-Free Laser-Induced Breakdown Spectroscopy analysis of generic samples still needs to be thoroughly investigated. The authors have undertaken a systematic study of errors and biasing factors affecting the calculation in the Calibration-Free Laser-Induced Breakdown Spectroscopy spectra processing. These factors may be classified in three main groups: 1) experimental aberrations (intensity fluctuations and inaccuracy in the correction for spectral efficiency of a detection system), 2) inaccuracy in theoretical parameters used for calculations (Stark broadening coefficients and partition functions) and 3) plasma non-ideality (departure from thermal equilibrium, spatial and temporal inhomogeneities, optical thickness, etc.). In this study, the effects of experimental aberrations and accuracy of spectral data were investigated, assuming that the analytical plasma is ideal. Departure of the plasma conditions from ideality will be the object of future work. The current study was based on numerical simulation. Two kinds of metallic alloys, iron-based and aluminum-based, were studied. The relative weight of the error contributions was found to depend on the sample composition. For the here-investigated samples, the experimental aberrations contribute to the overall uncertainty on the quantitative results more than theoretical parameters. The described simulation method can be applied to the Calibration-Free Laser-Induced Breakdown Spectroscopy analysis of any other kind of sample.     

Assessment of systematic errors in measurement of vapor pressures by thermogravimetric analysis

The present study explores the application of the diffusion limited evaporation theory to the estimation of vapor pressure from TG experimental data. A simplified method was developed to calculate the apparent values of the vapor pressure of pure substances from TG data, based on isothermal TG runs with crucibles having different surface areas available for evaporation. Antoine parameters are estimated through a numerical procedure based on a non-linear least square algorithm. The procedure also evaluates the substance diffusivity in nitrogen. The methodology developed might be used for a preliminary screening of the vapor pressure of pure compounds, due to the limited amounts of sample that are necessary and to the limited time frame required for the experimental runs. However, the estimation of diffusivity and vapor pressures values by the TG technique is possible with limited accuracy. Possible sources of error were thoroughly investigated and discussed.     

Stopped-flow injection analysis. The influence of diffusion on dispersion of normal and reverse flow injection

A relationship is derived to enable the comparison of the dispersion heights of normal and reverse flow injection analysis (FIA). A single channel flow system is employed in the absence of a chemical reaction. The stopped-flow injection method is used to probe the influence of molecular diffusion on the overall dispersion of normal and reverse FIA, which appeared to demonstrate fundamentally different diffusion behaviors. Small discrepancies are observed between the dispersion heights, which are enhanced by the stopped-flow period, especially when unmatched matrix ionic compositions of the indicator and counter solutions were involved. For these conditions, the diffusion flux rate is enhanced considerably, displaying a peak, in addition to the transient, for both methods. The influence of diffusion on the dispersion characteristics of normal and reverse FIA is discussed theoretically. Diffusion in the proposed model is postulated to oppose dispersion by convection. The latter initiates concentration gradients in the injection zone and propagates it with flow time over the dispersion zone profile. The diffusion flux then reacts in order to confine the indicator dispersion for normal FIA and to enhance it for reverse FIA. This model is consistent with the experimental results and accounts for most of the phenomena encountered. Probably owing to the influence of secondary flow phenomena, the use of coiled tubes has suppressed the effects of diffusion on the overall dispersion behavior.Part of the experimental work was performed at IMI Institute for Research and Development, Haifa, Israel.     

Thermogravimetry as a screening tool for the estimation of the vapor pressures of pure compounds

A simplified approach was developed to estimate the vapor pressure of pure compounds from experimental data obtained by isothermal thermogravimetric (TG) analysis. A numerical procedure was developed to estimate the Antoine parameters of the substance by the analysis of isothermal TG data. The results of the experimental validations carried out evidenced that at least a preliminary estimation of vapour pressures of pure substances by the analysis of TG data is possible. The limited time and the reduced amounts of sample required for the experimental runs make the technique attractive with respect to the conventional and more accurate techniques for vapor pressure assessment.     

一种基于免疫识别的主因子数判断方法

根据免疫算法的基本思想,提出了一种基于免疫识别(IR)的主因子数判断方法.对模拟数据和HPLC-DAD数据的处理结果表明,IR比嵌入误差(IE)、因子指示函数(IND)和交叉验证(CV)更能有效地克服噪音的影响.当实际数据中的非线性和不等性方差噪音使其它方法失效时,IR仍能得到正确的主因子数.     

第12届全国大学生化学实验邀请赛情况和实验笔试题解析

介绍了第12届全国大学生化学实验邀请赛实验笔试题的命题思路,对参赛选手的答题情况和反映出的问题进行了总结分析。     

Toward automated chromatographic fingerprinting: A non-alignment approach to gas chromatography mass spectrometry data

In contrast to targeted analysis of volatile compounds, non-targeted approaches take information of known and unknown compounds into account, are inherently more comprehensive and give a more holistic representation of the sample composition. Although several non-targeted approaches have been developed, there's still a demand for automated data processing tools, especially for complex multi-way data such as chromatographic data obtained from multichannel detectors. This work was therefore aimed at developing a data processing procedure for gas chromatography mass spectrometry (GC–MS) data obtained from non-targeted analysis of volatile compounds. The developed approach uses basic matrix manipulation of segmented GC–MS chromatograms and PARAFAC multi-way modelling. The approach takes retention time shifts and peak shape deformations between samples into account and can be done with the freely available N-way toolbox for MATLAB. A demonstration of the new fingerprinting approach is presented using an artificial GC–MS data set and an experimental full-scan GC–MS data set obtained for a set of experimental wines.