光电二极管阵列等离子体原子发射光谱分析背景智能化实…

提出了用于光电二极管阵列等离子体原子发射光谱分析背景智能化实时校正的方法，采用二次微分结合原ＩＣＰ光谱法，在不经微分噪声过滤的基础上，实现快速准确的谱线识别，简单背景采用多项式模型，结构背景及翼展干扰采用概率统计模型，通过对高浓度Ｃａ存在下Ａｌ用Ｌａ的测定，表明本方法能够准确地校正背景干扰。     

近红外分析中的基线漂移及校正方法

基线漂移是光谱测定中极易出现的情况,基线校正是光谱数据处理中不可缺少的关键环节。以乏燃料后处理工艺过程中的2BX料液为对象,研究了近红外光谱基线漂移对料液中各组分分析结果的影响,采用一阶微分、建立混合模型及将两者结合使用的方法对光谱数据进行预处理,建立校正模型,对比了3种方法校正后样品不同时间测定结果的RSD值。结果表明,将一阶微分和建立混合模型结合使用的方法校正效果最佳,尤其对于低浓度样品效果最为显著,校正后测定结果精度大幅提高,模型稳健性增强。     

X-射线荧光光谱法(XRF)测定钼精矿中多种元素

详细论述了压片法及熔融片法测定钼精矿的分析条件。其中压片法通过大量采用同一矿区的生产样品经化学定值后作为校准样品建立校准曲线,因此粒度效应和矿物效应基本上可忽略。详细地讨论了元素之间谱线干扰、背景和脉冲高度选择。使用经验系数法校正基体效应,可准确测定钼精矿中的钼、硫、铁、铜、铅、锌等11种元素。在熔融片法中主要讨论了元素谱线的选择及其相互之间的干扰,经理论α系数校正后,可准确测定不同钼矿中的多种元素,其适用范围更广。     

电感耦合等离子体原子发射光谱法同时测定植物样品中多种元素

本文为环境样品分析建立了准确、灵敏、快速的分析方法,探讨了酸类及酸度对谱线强度的影响,同时对基体元素的谱线干扰进行了校正和背景扣除,测定了环境背景值样品树干和树叶中15种元素,经标样测定结果满意。     

基于近红外光谱技术与优化光谱预处理的陈皮产地鉴别研究

采集不同产地陈皮内侧和外侧的近红外光谱,采用不同光谱预处理方法进行预处理,筛选得到最佳光谱预处理方法,结合主成分分析法建立了陈皮产地的鉴别模型.实验发现,陈皮原始光谱中存在明显的基线漂移与背景干扰.使用单一光谱预处理可在一定程度上消除干扰的影响.经标准正态变量变换、多元散射校正、一阶导数、二阶导数与连续小波变换预处理后...     

五氧化二钒中微量砷和磷的直接同时测定

提出了以数学校正扣除基体四价钒色泽对砷(磷)铋钼蓝色泽干扰的方法和校正磷对砷测定干扰的方法.应用于五氧化二钒中微量砷和磷的测定,结果准确、可靠.     

X-荧光α系数法测定稀土氧化物中15个稀土元素

采用粉末稀释直接压片,在PW1400顺序式X-荧光光谱仪上测定了 15个稀土元素。通过电子计算机采用干扰系数扣除严重的谱线干扰,应用α系数校正复杂的基体效应,取得满意的结果。本文研究重点是选择了最佳仪器测量条件;测量出元素间的干扰系数及校正了背景影响;比较了三种基体校正数学模型的效果。分析精度:当含量小于2％时,优于 5％;含量大于2％时,优于?2％。分析速度较文献[5]提高三倍。     

ICP-AES测定钼铁中杂质元素

研究了用ICP-AES测定钼铁中硅、磷和铜的方法,建立了最佳工作条件,采用基体匹配方法,应用软件中谱线干扰校正程序消除了干扰,检出限小于0．005％,回收率在93％-108%之间,RSD小于1．0％。方法简便、快速、准确。     

电感耦合等离子体质谱准确测定单斜辉石中稀土元素

采用密闭酸溶ICP-MS研究了单斜辉石中稀土元素准确分析方法.以基体匹配的混合标准溶液为外标校正溶液;利用115In-103Rh双内标校正系统;并通过单个稀土元素及钡的氧化物、氢氧化物的测定,计算出等效干扰浓度进行校正,从而有效地抑制了分析信号的漂移、基体效应及多原子离子干扰.通过对4个标准参考物质的分析,测定结果与推荐值一致.该法应用于4个单斜辉石样品分析,方法检出限为0.7～2.5 ng·L-1,RSD≤10%(n=5).     

XRF准确测定钼精矿中多种元素分析方法研究

本文详细论述了压片法及熔融片法测定钼精矿的分析条件。其中压片法通过大量采用同一矿区的生产样品经化学定值后作为校准样品建立校准曲线,因此粒度效应和矿物效应基本上可可忽视。文章详细地讨论了元素之间谱线干扰、背景和脉冲高度选择。使用经验系数法校正基体效应,可准确测定钼精矿中的钼、硫、铁、铜、铅、锌等11个元素。在熔融片法主要讨论了元素谱线的选择及其相互之间的干扰。     

Eine einfache messanordnung zur photoelektrischen spektrometrie möglichst kleiner Konzentratione

A method is described whereby the signal strength at the position of a spectral line and the intensity of a representative part of the background are measured alternately. This method is especially suitable for samples where low concentrations are to be determined. The change from line to background takes place rapidly in comparison with the relative long term changes in the discharge phenomena so that the resultant intensity fluctuations are virtually eliminated. The individual measurements are processed separately and represent the statistical mass for a very precise determination of the standard deviation of the method. In conclusion a technique is described whereby the spectrum may be stabilized to ±0.005 Å by relatively simple means.     

Software note: using probe secondary structure information to enhance Affymetrix GeneChip background estimates

High-density short oligonucleotide microarrays are a primary research tool for assessing global gene expression. Background noise on microarrays comprises a significant portion of the measured raw data. A number of statistical techniques have been developed to correct for this background noise. Here, we demonstrate that probe minimum folding energy and structure can be used to enhance a previously existing model for background noise correction. We estimate that probe secondary structure accounts for up to 3% of all variation on Affymetrix microarrays.     

Statistical mechanical treatment of protein conformation. I. Conformational properties of amino acids in proteins.

A statistical mechanical (one-dimensional Ising model) treatment, based on the dominance of short-range interactions, is developed in this series of papers; it is intended as an improvement over empirical prediction schemes for obtaining approximate initial conformations of proteins (to be used to try to deduce the native conformation by subsequent energy minimization). In the present paper, the statistical weights for a two-state model (alpha-helical and other conformations) and for a three-state model (alpha-helical, extended, and other conformations) are evaluated from x-ray data on 16 native proteins. The method for evaluating the statistical weights is presented. Asymmetric alpha-helical nucleation parameters are also evaluated for the 20 naturally occurring amino acids. On the basis of these statistical weights, the conformational properties of the twenty naturally occurring amino acids are discussed. The statistical weights evaluated from x-ray data are also discussed in comparison with experimental results on the helix--coil transition in polyamino acids in solution. The predominant role of short-range interactions, and some possible long-range effects in determining the statistical weights, are discussed in conjunction with the mechanism of protein folding.     

Quantitative analysis of trace levels of surface contamination by X‐ray photoelectron spectroscopy. Part I: Statistical uncertainty near the detection limit

We discuss the problem of quantifying common sources of statistical uncertainties for analyses of trace levels of surface contamination by using X‐ray photoelectron spectroscopy. We examine the propagation of error for peak‐area measurements by using common forms of linear and polynomial background subtraction including the correlation of points used to determine both background and peak areas. This correlation has been neglected in previous analyses, but we show that it contributes significantly to the peak‐area uncertainty near the detection limit. We introduce the concept of relative background subtraction variance (RBSV) that quantifies the uncertainty introduced by the method of background determination relative to the uncertainty of the background area itself. The uncertainties of the peak area and atomic concentration and of the detection limit are expressed using the RBSV, which separates the contributions from the acquisition parameters, the background‐determination method, and the properties of the measured spectrum. These results are then combined to find acquisition strategies that minimize the total measurement time needed to achieve a desired detection limit or atomic‐percentage uncertainty for a particular trace element. Minimization of data‐acquisition time is important for samples that are sensitive to X‐ray dose and also for laboratories that need to optimize throughput.     

Probability of Detection (POD) as a statistical model for the validation of qualitative methods

A statistical model is presented for use in validation of qualitative methods. This model, termed Probability of Detection (POD), harmonizes the statistical concepts and parameters between quantitative and qualitative method validation. POD characterizes method response with respect to concentration as a continuous variable. The POD model provides a tool for graphical representation of response curves for qualitative methods. In addition, the model allows comparisons between candidate and reference methods, and provides calculations of repeatability, reproducibility, and laboratory effects from collaborative study data. Single laboratory study and collaborative study examples are given.     

A fast and simple method for background removal in Auger electron spectroscopy

A purely formal method for background removal in electron beam induced Auger electron spectroscopy is presented. The method has been developed for practical purposes. It is typically used to remove the background of a complete recorded spectrum, no fit is necessary to remove the backscattered electrons background. An overcompensation of the background, resulting in negative values of the background removed spectrum is not possible, all values of the background removed spectrum are positive or zero. Since the Auger peaks are separated by zeros after background removal, the method is well suited for peak finding and identification.     

Quantitative Auger electron spectroscopic analysis of carbides,nitrides and carbonitrides

A novel method for the quantitative evaluation of Auger electron spectra based on peak areas is presented. Sample and reference spectra in integral mode are filtered by an area conserving digital filter. This transforms the peak shapes influenced by chemical effects into standard peak shapes. After filtering a linear combination of reference spectra, differentiated spectra accounting for peak shifts and some low order polynomials to account for variations in the background is fitted to the sample spectrum by a least squares method. The need to approximate the spectrum of the secondary electron background explicitly for direct calculation of peak areas is thus eliminated. Filters of different widths are applied to reduce errors by chemical effects. The composition of the sample is computed from the composition of the reference samples and the coefficients obtained from the fit.To demonstrate the validity of this technique it has been applied to both, Gaussian model peaks and spectra of titanium carbonitrides. A further test on an alloy series is under investigation. The results show that the method works as predicted and gives accurate quantification.     

A fast and simple method for background removal in Auger electron spectroscopy

A purely formal method for background removal in electron beam induced Auger electron spectroscopy is presented. The method has been developed for practical purposes. It is typically used to remove the background of a complete recorded spectrum, no fit is necessary to remove the backscattered electrons background. An overcompensation of the background, resulting in negative values of the background removed spectrum is not possible, all values of the background removed spectrum are positive or zero. Since the Auger peaks are separated by zeros after background removal, the method is well suited for peak finding and identification.Dedicated to Professor Dr. H. Seiler on the occasion of his 65th birthday