SCOT柱色谱峰保留时间与半峰宽间关系的理论探讨

 〕在新建立的SCOT柱色谱理论模型基础上，利用积分变换矩分析及数理统计理论，证明了SCOT柱色谱峰保留时间与半峰宽间的一般关系是一双曲线关系。当双曲线关系中的系数可认为是常数且满足下列条件之一时简化为线性关系：(1)柱外效应可略去且某一个速率过程对峰宽的贡献远远超过其他速率过程时。(2)柱外效应可略去且保留时间远大于死时间时，(3)当死时间的高次项可略去时。理论还给线性关系中的经验常数以一定的物理意义。结果证明在通常色谱条件下简化为线性关系的条件是容易满足的。利用获得的结果还对若干实验事实如负截距的出现，线性关系中的斜率与柱长的平方根成反比等作了圆满的说明，并指出有可能利用改变担体表面积来调整截距值。本文的结果可应用除光滑WCOT柱外的所有类型毛细管柱，既可用于气相毛细管柱，也可用于液相毛细管柱。     

高效液相色谱峰压缩中灵敏度增加值与峰压缩因子的关系研究

以从塔板理论得到的色谱流出曲线为基础,推导了高效液相色谱(HPLC)双流动相分离场中实现峰压缩时,峰压缩因子(峰压缩后的半峰宽与未进行峰压缩时的半峰宽的比值)和峰高表示的灵敏度变化(峰压缩后的峰高与未进行峰压缩时的峰高的比值)的关系,结果表明峰高表示的灵敏度增加值等于峰压缩因子的倒数.并用色氨酸、香豆素、苯和2-硝基酚在不同速率差实现堆积时的相关参数进行了验证.实验结果表明,这些化合物在各个峰压缩条件下的峰压缩因子倒数和实际灵敏度增加值相等,实验结果与理论推导结果一致.考察了该关系式在实际样品测定中的应用,结果表明灵敏度增加值等于峰压缩因子的倒数,这也与理论部分的结果一致.     

化学计量学用于决明子色谱指纹图谱峰纯度的鉴别

应用化学计量学方法鉴别色谱指纹图谱的峰纯度。对背景进行扣除后,用对照组分光谱构建正交投影矩阵对目标色谱峰的光谱进行投影,以目标色谱峰投影后的残余光谱与投影前的原始光谱的夹角余弦为判据鉴别目标色谱峰的峰纯度：用该方法对决明子药材色谱指纹图谱的峰纯度进行识别,鉴别出大黄素、大黄酚和大黄素甲醚三个纯色谱峰。此方法用于色谱指纹图谱峰纯度的鉴别,结果可靠。     

使色谱峰产生拖尾的一个因素--柱出口效应

使用塔板理论证明存在一种使正常色谱峰产生拖尾的因素－柱出口效应。证明符合线性分配的样品组分虽然在色谱内存在3种不同浓度的分布形态,但在流出色谱后却都因柱出口效应的影响而转变成拖尾峰。在不加任何近似处理的情况下,使用塔板理论直接对不同塔板数、容量因子的色谱峰不对称性进行了计算;计算结果同样支持了柱出口效应的存在。     

相对时间法计算凝胶渗透色谱测试大分子分子量和分子量分布

在凝胶渗透色谱(GPC)对大分子的分子量和分子量分布的测试中,本研究利用小分子乙二醇在系统中出峰时间恒定的现象,采用乙二醇的出峰时间作为标识物,将GPC的色谱图转化为相对时间,再以相对时间建立校正曲线,作为计算分子量和分子量分布的依据。此方法解决了在测试色谱图的记录、校准曲线的建立和分子量的计算中以实际时间来表示和计算分子量时,由于GPC泵的重复性不稳定、色谱柱柱效的下降、仪器更换过不同的色谱柱等因素造成的使校正曲线出现偏差、分子量计算结果出现误差等问题。     

尺寸排除色谱扩展因子的保留体积依赖性

尺寸排除色谱扩展函数的方差即尺寸排除色谱柱中单分散高分子峰的扩展因子,以窄分布聚苯乙烯标样用分子量分离和扩展效应同时标准的方法作了测量。简单的理论分析导出了一个方程以表示扩展因子的保留体积依赖性,其中包括四个具有明确物理意义并可实验测量的参数。该方程与实验数据符合得相当好,并解释了扩展因子极值出现的条件。     

基于无基底扣除的数据趋势累积谱峰检测算法

谱峰的检测分析在色谱技术研究中具有十分重要的作用,但在色谱数据采集、传输的过程中,不同程度的噪声干扰给谱峰检测带来了极大的困难。目前传统的谱峰检测算法普遍通过基底扣除的方式对谱峰的形态进行预定义,将谱峰分为单峰、重叠峰等多个种类。针对不同种类的谱峰采用不同的检测方法,这就导致了传统的谱峰检测算法具有高复杂度、低自动化程度以及容易失真等缺点。因此,该文从另一个角度出发提出了一种新型的谱峰检测算法。该算法取消基底扣除以及谱峰分类这一步骤,直接在源数据曲线的基础上进行谱峰检测,主要分为离散差分、趋势累积以及遍历寻峰3个步骤。首先通过信号量表征数据升降趋势;然后进行数据趋势累积,根据累积总和定位谱峰,采用三点定位的方式,即峰起点、极值点和峰终点描述一个谱峰的位置;最后根据遍历排序的方式进行谱峰的筛选。此外,通过谱峰扣除的方式得到曲线基底部分。采用C语言设计编写了算法程序,并对多个动态比表面积分析仪测定的色谱图进行了检测分析,结果显示使用该算法可以精准区分谱峰部分与基底部分,受数据曲线毛刺、震荡等噪声干扰很小,谱峰的三点定位十分准确,且不受其复杂形态的影响,具有很强的普适性。与其他算法相比,该算法定位准确,结构清晰,具有较好的稳定性以及可靠性。该文报道了无基底扣除以及趋势累积等新型谱峰检测思想在吸脱附色谱曲线中的应用,证明了其在吸脱附色谱峰检测中的有效性和良好的应用前景。     

小波变换用于重叠色谱峰组分信息的提取

提出了一个小波变换用于提取重叠色谱中组分信息的理论公式，并将它应用于三组分和五组分重叠色谱实验数据的解析。结果表明：在定定分离度范围内，当相邻色谱峰峰宽相近时，根据此公式的计算结果，可以将各组分的信息从重叠色谱峰信号中提取出来。洒工作对小波变换用于重叠峰的解析具有重要意义。     

色谱图拟合及重叠峰快速分离解析

]本文以EMG分布函数作为色谱峰的数学模型,提出由柱系统的半峰宽规律与峰态偏斜度D计算EMG参数的连环公式,用于快速谱图拟合和重叠峰分解。实验表明校正后的峰面积和拟合精度令人满意;不用半峰宽规律,直接采用优化方法解谱也取得好的结果。     

凝胶色谱中宽、窄分子量分布的峰加宽改正问题

本文用宽分布(M_w/M_n=6.3)及窄分布(M_w/M_n=1.22)两种模型函数,改变一系列加宽因子,“合成”了具有不同加宽程度的GPC谱图,然后计算平均分子量并与原模型分子量进行比较,考察分子量分布对峰加宽改正程度的影响.结果表明:分子量分布宽、窄在峰形改正上有着明显差异,窄分布要比宽分布改正得多.但对于分子量平均值来说,宽分布与窄分布的峰加宽改正程度是相同的.因此,通常认为宽分布试样在平均分子量计算时可以忽略峰加宽改正的说法是一种误解。     

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.     

Determination of water by flow injection analysis with the karl fischer reagent: Minization of effects caused by differences in physical properties of the samples

In the previously described flow-injection method for the spectrophotometric determination of water with the Karl Fischer reagent, problems can arise from the rather large variation between the calibration curves for different types of samples. Different combinations of flow-injection arrangements and detector types are described here, to establish a system which levels out this undesirable spreading between the calibration curves. One necessary condition for attaining a low spread is shown to be the use of a spectrophotometric detector especially constructed to minimize refractive index effects. The best results, including samples with large differences in refractive indices and viscosities, were obtained by a combination of peak area measurements and the use of this detector. For example, the relative mean deviation for a sample containing 0.1% water was about 2%.     

On-line viscometry combined with gel permeation chromatography. I. Instrumental calibration and testing with linear polymers

Gel permeation chromatography (GPC) was combined with flow time measurements on the eluent to provide both the distribution of hydrodynamic volumes and the distribution of intrinsic viscosities in linear polymers. Standard polystyrene samples were used to establish a universal hydrodynamic volume calibration as well as the zone spreading and viscometer transfer line tailing parameters. Viscometry data are particularly helpful in establishing the zone spreading parameters and the calibration curve at very high molecular weights. The results were applied to measurements on samples of linear polybutadiene and polyvinyl acetate. Agreement between values of M _w from GPC with those obtained by light scattering confirmed the universal calibration principle.     

Chromatographic quantitation using fractions of the peak areas

Quantitative chromatographic analysis is liable to errors due to peak asymmetry because the uncertainty in the detected position of the end of the peak tail decreases the reliability of the computed peak area. This dependence may be a severe drawback whenever peaks of different areas must be compared, as in the case of calibration curves. A new approach to overcome the uncertainties of area calculation due to peak asymmetry is reported in this paper. The approach consists of calculating only the area included between the start and the maximum of the chromatographic peak. Simulated and experimental chromatographic data were used in this study. Both the peak start-to-peak maximum area (SMA) and the start-to-end or total area (TA) were calculated and the quantitative results were compared. Within the scope of this work it is concluded that the SMA yields calibration curves that are more linear and have intercepts closer to zero than the calibration curves obtained using the TA.     

Simultaneous Calibration of Molecular Weight Separation and Column Dispersion of GPC by Coupling with Lallis

Abstract

It is shown theoretically and experimentally that both the calibration of the molecular weight separation and column dispersion can be evaluated simultaneously by coupling gel chromatograph with low angle light scattering photometer. The experimentally determined variation of the spreading factor with retention volume is quite similar to that obtained by Tung using reverse flow technique. A correction method is given for the lowering of inhomogeneity index printed by the data processor of the on-line GPC-LALLS.     

Quantitative analysis of phosphatidylcholine in rat liver tissue by nanoflow liquid chromatography/tandem mass spectrometry

A quantitative method was developed for the determination of phosphatidylcholine (PC) species concentration using nanoflow LC-ESI-MS/MS. In this study, a calibration method is developed to determine the effect of PC carbon chain length on MS peak intensity. Using the multiple standard addition method, a relationship between the peak intensities of different PC species from nanoflow LC-MS and carbon chain length is established first using different injection amounts of PC standards. From this relationship, a calibration curve for each carbon chain length can be obtained for the concentration calculation. It was found that the MS peak area of PC species analyzed by nanoflow LC-MS linearly decreased with increased acyl carbon numbers, and that the effect of the degree of acyl chain unsaturation on MS peak intensity was minimized when the injection amount was maintained at less than 1 pmol. The method was applied for the quantitative calculation of 34 PC species from rat liver, which were identified from data-dependent MS/MS analysis during nanoflow LC separation.     

SIMULTANEOUS CALIBRATION OF MOLECULAR WEIGHT SEPARATION AND COLUMN DISPERSION OF SEC WITH CHARACTERIZED POLYMER STANDARDS

With the aid of the theoretical relationship between the calibration relation of a SEC column for the monodisperse polymer species under ideal working condition and the effective relations between the molecular weight and the elution volume for characterized polymer samples, a computational procedure for simultaneous calibration of molecular weight separation and column dispersion is proposed. From the experimental chromatograms of narrow MWD polystyrene standards and broad MWD 1,2-polybutadiene fractions the spreading factors of a SEC column was deduced by the proposed method. The variation of the spreading factor with the elution volume is independent upon the polymer sample used.     

Matrix sensitivity of solid sampling AAS. Determination of zinc in geological samples

Direct solid sampling techniques in AAS have several advantages over wet digestion methods such as small sample size requirements and simple calibration procedures. But some disadvantages also exist such as the sample in homogeneity and the matrix sensitivity of calibration. The calibration is commonly carried out by varying the sample mass and evaluating the peak intensity versus absolute analyte amount. It is shown here that this procedure must be considered doubtful when matrix effects are expected. In the case of zinc determination in geological samples it has been shown that calibration functions obtained by different reference materials differ significantly from each other. As an alternative a three-dimensional calibration technique can be applied that evaluates the peak intensity versus both analyte content and sample weight. The resulting calibration planes are expected to be hyperbolically curved. This three-dimensional calibration has been applied to the determination of Zn in geological samples and compared with classical solid sampling AAS calibration procedures.     

Software for Microprocessor Controlled HPLC: Peak Area Integration

Abstract

Programs are described for determination of peak areas and peak retention times from the chromatographic data obtained by a dual-microprocessor data handling microcomputer (DHC). The programs provide the necessary equipment testing and calibration routines for an accurate reproduction of a recorded chromatogram, and they are written to be merged with the data acquisition programs to provide a true “real-time” integrator. The integration is performed with baseline stabilization and automatic peak splitting. These features make the integrator applicable to gradient elution chromatography, as well as for the integration of complex chromatograms with overlapping peaks. The integrated chromatogram can be displayed with the limits of integration for each peak. Results of peak area integration of simple and complex chromatograms demonstrate satisfactorily accurate and consistant results that are independent of chromatographic conditions and shape of the peaks.