Instrumental Broadening Correction in Size Exclusion Chromatography through Fast Fourier Transform Techniques

Abstract

This paper shows the practicability of the use of the fast Fourier transform (FFT), with appropriate filtering in the frequency domain, as a means of deconvoluting Tung's integral formula (1). The method is limited to uniform instrumental spreading functions, but presents several important advantages: it is numerically efficient, no assumptions about the shape of the spreading function are made, it eliminates the highfrequency measurement noise components from the corrected chromatogram without modifying the original data, and provides a means of physically interpreting the results.     

Instrumental Broadening Correction in Size Exclusion Chromatography. Comparison of Several Deconvolution Techniques

Abstract

Several deconvolution techniques (1–7) and a novel method herein presented, are compared in relation to their ability for correcting size exclusion chromatograms for the undesirable effect of instrumental broadening. Such methods are evaluated on the same computer, and through a “synthetic” example of known solution. Methods based on the frequency domain are only applicable to uniform deconvolution problems with stationary statistics. However, in the herein presented heuristic method (based on the Wiener filter in the frequency domain), it is possible to relax this last restriction, and generate solutions that are equivalent to considering signals with time-varying statistics. The evaluated techniques are compared on the basis of quality of results, computational considerations and adjustment facility. Stochastic techniques provide the best (and nearly identical) numerical solutions. This is mainly due to their increased facility to introduce “a priori” information about the expected solution. As a counterpart, stochastic techniques are conceptually more complex, more difficult to implement, and normally inolve more elaborate adjustment procedures.     

Corrections for Instrumental and Secondary Broadening in the Chromatographic Analysis of Linear Copolymers

Abstract

The effects of instrumental broadening and of polymer/solvent/packing interactions (secondary broadening) are separately investigated in the context of chromatography experiments, for the characterization of linear copolymers with two types of repeating units. The problems associated to the estimation of: a) the joint molecular weight distribution - chemical composition distribution (MWD-CCD) through orthogonal chromatography; and of b) the average MWD - average CCD through standard size exclusion chromatography (SEC) with dual detection are considered. The main difficulty with the secondary broadening correction, is the calibration for this effect. In the case of standard SEC with dual detection, a simple solution was found to the instrumental broadening problem, that involves a direct extension of the calibration and deconvolution techniques developed for linear homopolymers and mass detectors.     

大豆异黄酮指纹图谱中保留时间漂移的校正研究

选取5个极性不同的化合物作为标准样品,在不同仪器及不同色谱柱上采用已建立的大豆异黄酮高效液相色谱(HPLC)指纹图谱条件进行测定,以它们在不同色谱仪(或柱)上的保留时间进行线性回归,并用得到的线性方程对相同条件下测得的大豆异黄酮指纹谱中峰面积为总峰面积1.5%以上的色谱峰的保留时间进行校正,通过校正使保留时间的最大绝对误差由5.868 min减小为0.854 min。采用该方法可以校正相同色谱条件但不同实验室间指纹图谱保留时间的漂移,提高HPLC指纹图谱的重现性。     

Calibration of Separation and Instrumental Peak Broadening in Sec Coupled with Light Scattering of Simple Polymers

Abstract

A recently developed procedure for calibration of separation and instrumental peak broadening in SEC was used for a comparative study of separation and axial dispersion of polystyrene, poly(methyl methacrylate) and poly(vinylchloride). The influence of the uncertainty in the volume lag between the concentration and LALLS detectors upon peak broadening was investigated and a new procedure for the determination of the lag was proposed. The applicability of the universal calibration concept was tested; all the polymers have been found to match a single universal calibration function. Polystyrene and poly(methyl methacrylate) also coincided very well with respect to the instrumental spreading, but for poly(vinylchloride) spreading was found to be a function of polymer concentration.     

Inverse Optimal Filtering Method for the Instrumental Spreading Correction in Size Exclusion Chromatography

Abstract

The Kalman filter based techniques are adapted to solve the most general form of Tung's integral formula, i. e. when a non-uniform, non-symmetric calibration model is employed to correct chromatograms obtained in size exclusion chromatography from instrumental broadening errors. Through this method, the inverse smoothing of a chromatogram contaminated with measurement noise of known statistics is optimally performed by minimizing the estimation error variance. The method is numerically very “robust”, improves the signal to noise ratio, provides good validation checks, and does not involve any previous parameter estimation procedure.     

任意多阶梯度场强毛细管凝胶电泳中谱带的迁移和展宽

在自行制备的毛细管凝胶电泳柱上，通过实验考察毛细管凝胶电泳（ＣＧＥ）中场强（Ｅ）和组分迁移率（μ）的关系，发现在一般ＣＧＥ使用的场强范围内，μ随Ｅ增大而成近似线性的增加。并讨论了产生这种现象的原因。以此为基础提供了任意多阶梯度场强毛细管凝胶电泳中组分的迁移时间和距离的计算公式，用于编制计算机程序。     

Methods for Quality Control of Fingerprint Chromatograms in Traditional Chinese Medicines

SometraditionalChinesemedicines (TCM )havealonghistoryofcommontherapeuticuse .Re cently ,anincreasedinterestcanbeobservedinthecharacterizationofthesenaturalsubstancesinordertohaveabettercontrolontheiractioninhealthprotection .However ,duetothecomplexityof…     

凝胶色谱与多角激光光散射联用研究聚氧化乙烯的扩展效应和链构象

采用凝胶色谱与多角激光光散射联用的方法,测定了一系列不同分子量的聚乙二醇(PEG)和聚氧化乙烯(PEO)在色谱柱中的扩展效应.扩展因子随PEG/PEO分子量的增加而增大,经扩展效应改正后得到了样品的准确分子量和分子量分布.同时建立了PEO的Z均回转半径Rgz与重均分子量Mw之间的单分散标度关系:Rgz=0.0272 Mw0.56,结果表明,长链PEO在水溶液中由于排除体积效应采取溶胀的无规线团构象.     

Methods for Quality Control of Fingerprint Chromatograms in Traditional Chinese Medicines

Some traditional Chinese medicines (TCM) have a long history of common therapeutic use. Recently, an increased interest can be observed in the characterization of these natural substances in order to have a better control on their action in health protection. However, due to the complexity of their chemical composition, it is in most ca-     

An Instrumental Correction for the Determination of Mercury in Biological and Sediment Samples Using Cold Vapor Atomic Absorption Spectrophotometry

Low recovery rate and inconsistent measurements were found in the determination of mercury by method of cold vapor atomic absorption spectrophotometry using the hydride formation system (Hitachi HFS-2, Hitachi Ltd., Tokyo). To overcome this problem of insufficient reaction time we developed a simple T-joint device attaching to the commercial HFS-2 system for the determination of mercury in various biological tissues and sediment samples. The T-joint device was designed to combine sample and reductant injection which increased the reaction time of the sample allowing a complete formation of mercury vapor and speeding up the analysis process in comparison to the traditional cold vapor atomic absorption spectrometric method. Recoveries of mercury were in the range 95% - 100%. The corrected procedure gave precise and accurate readings with several certified reference materials: NIES No. 2 from the Japan Environment Agency; IAEA-356 from the International Atomic Energy Association, and DOLT-2, DORM-2, TORT-2, PACS-1 and MESS-2 from the National Research Council of Canada. Simple acid digestion methods were developed based on the sample Hg level and the nature of the sample. The sample detection limits were 0.0125 μg g⁻¹ fresh weight and 0.0625 μg g⁻¹ dry weight for biological samples, and as low as 0.0125 μg g⁻¹ dry weight for sediment samples. These analytical protocols we established met the general requirements in environmental research and monitoring of mercury pollution.     

An On-Line Wavelet Transform for De-Noising of High Performance Liquid Chromatograms

ABSTRACT

A novel algorithm of wavelet transform, called the on-line wavelet transform, which can be used in on-line processing of signals of an instrumental analysis, is proposed. And application of the on-line wavelet transform in denoising of high performance liquid chromatograms was investigated. Results showed that the noise in chromatograms was cleanly removed by the method, peak position after the on-line de-noising dose not change, and the linearity of calibration curves of concentration versus peak area remained and even was improved. Quantitative determination of three mixed samples were investigated with five standard samples; the recoveries were between 94.0-105.0%.     

小波变换用于色谱重叠峰的解析

利用小波变换的时频局部化性质，通过对色谱重叠峰信号小波变换后的某些频率段进行放大，使重叠谱峰得到了分离，并将此方法用于苯和甲苯二组分色谱体系的定量分析，重叠峰中各组分均得到了良好的线性关系及令人满意的定量分析。本文还讨论了不同小波基、分解的次数及放大系数在解析结果的影响。     

Enzymatic Detection of Urinary Steroids on Thin-Layer Chromatograms

Abstract

Enzymatic detection of urinary steroids on thin-layer chromatograms (TLC) is described. Steroids in urine such as neutral 3α-hydroxysteroids, 3β-hydroxysteroids, acidic 3α-hydroxysteroids and 17β-hydroxysteroids are detected on thin-layer plate using enzyme reactions.

Combination of chromatographic techniques and enzyme reactions give more specific analysis of the compounds in a body fluid. Some clinical application by the use of these enzymatic methods is also described and these enzymatic detection methods are shown to be useful for the diagnosis of some disease of abnormal steroid metabolism.     

Quasi-Continuous Videodensitometric Recording of Chromatograms in Circular TLC

JPC – Journal of Planar Chromatography – Modern TLC - A new method of quasi-continuous videodensitometric recording of circular thin-layer chromatography (TLC) is proposed. It is based...     

Optimization of Peak Separation and Broadening in Aqueous Gel Permeation Chromatography (GPC) -Poly (Sodium Styrene Sulfonates)

Abstract

An experimental study of the gel permeation chromatography of a series of poly (sodium styrene sulfonates) in aqueous media has been undertaken. The objective of this study was to develop a set of operating conditions that would maximize peak separation and minimize peak broadening. Using CPG-10 porous glass packing, it has been found optimal to work at pH near 6 and ionic strength near 0.05. Under those conditions, ion exclusion is eliminated and the optimum balance between resolution and reproducibility is obtained. Addition of a few ppm neutral surfactant to the mobile phase prevents adsorption to the packing surface, and improves resolution.     

傅立叶变换-主成份分析方法用于二维色谱数据的压缩和重构

结合傅立叶变换（ＦＴ）和主成份分析（ＰＣＡ）技术,实现了二维高效液相色谱数据的压缩和重构,并对不同信噪比的二维色谱测量数据进行了处理,即使对原始数据的压缩比高达２００倍,仍能很好地重构原始数据,当原始数据的信噪比较低时,阈值的选择受大振幅噪音的影响,使压缩比略有下降,但仍然能够保持信号基本不失真。     

建设高效的公共仪器实验室

随着微电子技术的进步 ,仪器分析相关的技术和方法在最近几十年的发展非常迅速 ,不仅更多的物化性质得到利用 ,而且仪器的自动化程度越来越高 ,日常操作使用不断简化 ,使分析测试、分离等方法在化学、生物及相关材料科学研究中的应用越来越广泛。仪器分析技术的迅速发展 ,对化学类学生的基础理论和实验课教学提出了更高的要求 ,对学生有关仪器原理、操作方法及实际应用等方面的培训也提出了新的要求和目标。为适应形势发展的需要 ,北京大学化学学院将仪器设备合理配置 ,对教学实验内容和学生培养目标进行改革 ,于 1 996年筹建了北京大学化学…     

Spray Reagents for the Visualization and Detection of Sesame Oil Unsaponifiables on Thin-Layer Chromatograms

Anisaldehyde and crotonaldehyde have been tested as spray reagents for the visualization of major components of sesame oil unsaponifiable matter. Colours produced using anisaldehyde were shades of the spectrum, which are characteristic of the lignans and sterols inherented in the Sesamum indicum in relatively higher coverage, sensitivity and selectivity. However, crotonaldehyde could detect four of the eleven unsaponifiable matters in relatively more stable and bright colour spots.     

The Initial Stage of the Development of Planar Chromatograms

JPC – Journal of Planar Chromatography – Modern TLC - The aim of the work discussed in this paper was to re-investigate the initial stage of the retention process in TLC, namely the...