复杂色谱信号自动解析中的化学计量学方法

色谱及其联用技术日趋完善,并向自动化、高通量和快速的方向发展。化学计量学利用"数学分离"手段,可以实现色谱信号的自动化解析,已成为现代色谱分析中非常活跃的研究领域。但以往的化学计量学方法并不能完全有效地实现复杂色谱信号自动化解析。为此,自动化色谱解析算法成为科研工作者关心的重点,众多新型的自动化解析算法被提出。针对复杂一维色谱数据以及联用仪器得到的二维和更高维数据的自动化分析,化学计量学研究主要集中在自动色谱峰识别、背景以及基线漂移校正、色谱谱峰漂移校正以及重叠色谱峰的解析。该文对近十年来发展的复杂体系色谱信号自动化解析中化学计量学方法的原理与应用进行了总结与评述,比较了各类方法的优势与不足。在此基础上,针对当前色谱自动化分析过程中的难题对未来该领域的研究方向进行了展望。     

热解析–气相色谱–质谱法测定汽车零部件及内饰材料中挥发性有机化合物

将待测材料直接放在热解析管中,用热脱附–气相色谱–质谱法对挥发性有机化合物的含量进行检测。经试验优化,热解析时间选择为30 min。在10~500μg/m L范围内,7种苯系物的质量浓度与对应色谱峰面积线性相关,相关系数为0.998 3~0.999 6。方法的加标回收率为80.3%~98.1%,测定结果的相对标准偏差为3.37%~5.42%(n=7)。该方法具有操作简便、提取效率高和全自动化等优点,适用于汽车零部件及内饰材料中挥发性有机化合物的检测。     

遗传算法在色谱谱图解析中的应用

将遗传算法引入色谱峰解析程序 ,结合色谱峰EMG模型及峰形经验公式 ,实现了恒温色谱谱图的全自动解析。对模拟谱图和实验谱图进行了解析 ,取得了满意的结果。本文对遗传算法的运算控制及运算效率进行了研究和讨论     

非对称色谱峰的拟合与重叠峰的拟合解析

 ]利用色谱保留时间tR与色谱峰形模型参数tG、σ、τ间的线性关系、预测了气相色谱填充柱上非对称的和重迭的色谱峰的有关参数，并据此对这两类色谱峰进行了拟合和解析。与常用重叠峰解析方法如中垂线法，三角形法和切线法解析结果的对比证明，曲线拟合法在这些方法中具有最好的准确度。用曲线拟合法进行实际定量的结果表明，对于非对称峰，其定量的相对误差小于0.5％，而对于重叠峰的定量误差则在10％以内。     

免疫算法用于多组分二维色谱数据的解析

通过对免疫系统抗体对抗原消除作用及其记忆功能的模拟,提出了解析二维数据矩阵的新方法。采用模拟的EMG公式作为抗体输入,对二维信号逐行进行迭代消除,从重叠峰中提取单一组分的色谱信息和光谱信息。通过对二维色谱数据的解析,结果表明,该方法可方便地用于多组分重叠二维色谱的解析。     

径向基函数神经网络用于重叠色谱峰解析

 在高斯基径向基函数神经网络 (RBFNN)学习算法中引入了鲁棒性和随机全局寻优的两阶段遗传算法 :结构学习和参数优化。通过两阶段学习算法的交替使用 ,使网络具有结构自学习和参数优化的能力 ,而后将网络应用于组分数未知的重叠色谱峰解析。该方法具有不需人为干预 ,可自动确定网络结构即组分数的优点 ;并且解析精度较高 ,适用于多组分重叠色谱峰的解析 ;对完全重叠色谱峰也具有良好的解析能力。     

一种基于光谱分析的二元不完全重叠色谱峰的分离解析方法

基于二极管阵列检测器获得的色谱-光谱数据,建立了一种二元不完全重叠液相色谱峰的解析方法: 色谱数据经过去噪、归一化处理后,计算各时间点的光谱差异并进行系统聚类分析,提取特征光谱后,利用非负最小二乘法对色谱-光谱矩阵进行解析,得到基于特征光谱的流出曲线,进而得到分离后的色谱峰。将解析结果和纯标样的色谱峰进行比较,解析后的光谱图和纯标样的光谱图无显著差异,保留时间相差小于0.01 min。实验结果表明,该方法在二元不完全重叠液相色谱峰的解析方面能取得良好的效果。     

香港大气颗粒物中多环芳烃的 HELP 法解析

利用新近发展的直观推导式演进特征投影法(HELP),成功地对香港大气颗粒物样本中的多环芳烃化合物进行了定性定量解析.解析结果表明:在样本中存在47种化学成分,其中有18种为多环芳烃化合物及其衍生物.分辨结果与标准光谱吻合很好,并与GC-MS的定性分析结果相一致.在定性分析的基础上,还进行了定量分析.HELP方法大大降低了对色谱分离条件的要求,为今后快速、准确解析色谱光谱联用仪器产生的二维数据提供了崭新途径.     

GC-MS法测定油漆行业废气化学成分及化学计量学解析

采用GU/MS法分离测定油漆行业废气污染物化学成分,利用化学计量学解析法(CRM)对重叠的色谱峰进行解析,得到各成分的纯色谱曲线和质谱,通过质谱库对解析的纯组分进行定性,用解析色谱曲线积分法进行定量.从25个色谱峰中解析出了49个组分,按检索相似度大于90%的原则,鉴定出了其中40个化合物,占总含量的92.3%.废气污染物的主要成分为苯系物和烷烃,分别占总含量的46.8%和27.2%.     

小波分析和人工神经网络方法用于重叠色谱峰的解析

将神经网络与小波分析相结合,提出一种利用小波变换提取重叠色谱峰信息,再用人工神经网络解析的方法,为色谱峰重叠难于分开的物质的测定提供一种方法,提高了色谱分析的准确度,并将此方法应用于高效液相色谱中,建立了混合体系中3.4-二甲酚和2.5-二甲酚同时测定的新化学计量学方法.     

Selection of high-performance liquid chromatographic methods in pharmaceutical analysis. III. Method validation

The most important steps in the validation of high-performance liquid chromatographic (HPLC) methods are discussed. The establishment of system suitability data and the assessment of peak purity are demonstrated on the example of bisquaternary amino steroids. For the recognition of incomplete resolution of adjacent peak pairs, the absorbance-ratio method in which the ratio of absorbances at two preselected wavelengths are plotted as a function of time in combination with the separation of sample components subjected to various chemical and physico-chemical treatments (stress conditions) is applied. The separation power and performance of the HPLC systems are characterized by the system resolution (SR) and system selectivity (SS). The special demands of stability-indicating methods are summarized.     

Correction of retention time shifts for chromatographic fingerprints of herbal medicines

In this study, the combination of chemometric resolution and cubic spline data interpolation was investigated as a method to correct the retention time shifts for chromatographic fingerprints of herbal medicines obtained by high-performance liquid chromatography-diode array detection (HPLC-DAD). With the help of the resolution approaches in chemometrics, it was easy to identify the purity of chromatographic peak clusters and then resolve the two-dimensional response matrix into chromatograms and spectra of pure chemical components so as to select multiple mark compounds involved in chromatographic fingerprints. With these mark components determined, the retention time shifts of chromatographic fingerprints might be then corrected effectively. After this correction, the cubic spline interpolation technique was then used to reconstruct new chromatographic fingerprints. The results in this work showed that, the purity identification of the chromatographic peak clusters together with the resolution of overlapping peaks into pure chromatograms and spectra by means of chemometric approaches could provide the sufficient chromatographic and spectral information for selecting multiple mark compounds to correct the retention time shifts. The cubic spline data interpolation technique was user-friendly to the reconstruction of new chromatographic fingerprints with correction. The successful application to the simulated and real chromatographic fingerprints of two Cortex cinnamomi, fifty Rhizoma chuanxiong, ten Radix angelicae and seventeen Herba menthae samples from different sources demonstrated the reliability and applicability of the approach investigated in this work. Pattern recognition based on principal component analysis for identifying inhomogenity in chromatographic fingerprints from real herbal medicines could further interpret it.     

Efficiency for close geometries and extended sources of a p-type germanium detector with low-energy sensitivity

Typically, germanium detectors designed to have good sensitivity to low-energy photons and good efficiency at high energies are constructed from n-type crystals with a boron-implanted outer contact. These detectors usually exhibit inferior resolution and peak shape compared to ones made from p-type crystals. To overcome the resolution and peak-shape deficiencies, a new method of construction of a germanium detector element was developed. This has resulted in a gamma-ray detector with high sensitivity to photon energies from 14 keV to 2 MeV, while maintaining good resolution and peak shape over this energy range. Efficiency measurements, done according to the draft IEEE 325-2004 standard, show efficiencies typical of a GMX or n-type detector at low energies. The detectors are of large diameter suitable for counting extended samples such as filter papers. The Gaussian peak shape and good resolution typical of a GEM or p-type are maintained for the high count rates and peak separation needed for activation analysis.     

Inner chromatogram projection (ICP) for resolution of GC-MS data with embedded chromatographic peaks

The chromatographic peak located inside another peak in the time direction is called an embedded or inner peak in contradistinction with the embedding peak, which is called an outer peak. The chemical components corresponding to inner and outer peaks are called inner and outer components, respectively. This special case of co-eluting chromatograms was investigated using chemometric approaches taking GC-MS as an example. A novel method, named inner chromatogram projection (ICP), for resolution of GC-MS data with embedded chromatographic peaks is derived. Orthogonal projection resolution is first utilized to obtain the chromatographic profile of the inner component. Projection of the two-way data matrix columnwise-normalized along the time direction to the normalized profile of the inner component found is subsequently performed to find the selective m/z points, if they exist, which represent the chromatogram of the outer component by itself. With the profiles obtained, the mass spectra can easily be found by means of a least-squares procedure. The results for both simulated data and real samples demonstrate that the proposed method is capable of achieving satisfactory resolution performance not affected by the shapes of chromatograms and the relative positions of the components involved.     

Immobilization of a Monolayer of Bovine Serum Albumin on Gold Nanoparticles for Stereo‐specified Recognition of Dansyl‐norvaline

The assembly strategy to prepare a monolayer of bovine serum albumin on the surface of silica gel supported gold nanoparticles is described. The stereo‐specific recognition ability of this material was evaluated by enantioresolution of Dansyl‐norvaline. For enantiomeric separation, the influences of buffer concentration and the concentration of organic modifier on the separation performance were investigated. A better separation in terms of enantioresolution and peak shape was found with the phosphate concentration at 30 mM. Moreover, the peak shape and resolution can be improved by the addition of methanol solution. Enantioresolution of Dansyl‐norvaline was obtained from this material at optimized conditions. It appears that the immobilization of a monolayer of bovine serum albumin on gold nanoparticles as the chiral selector of Dansyl‐derivative amino acid is promising.     

Simultaneous enantioseparation of cyproconazole,bromuconazole, and diniconazole enantiomers by CD‐modified MEKC

An efficient method for the simultaneous enantioseparation of cyproconazole, bromuconazole, and diniconazole enantiomers was developed by CD‐modified MEKC using a dual mixture of neutral CDs as chiral selector. Three neutral CDs namely hydroxypropyl‐β‐CD, hydroxypropyl‐γ‐CD, and γ‐CD were tested as chiral selectors at different concentrations ranging from 10, 20, 30 and 40 mM, but enantiomers of the studied fungicides were not completely separated. The best dual chiral recognition mode for the simultaneous separation of cyproconazole, bromuconazole, and diniconazole enantiomers was achieved with a mixture of 27 mM hydroxypropyl‐β‐CD and 3 mM hydroxypropyl‐γ‐CD in 25 mM phosphate buffer (pH 3.0) containing 40 mM SDS to which methanol‐acetonitrile (10%:5% v/v) was added as organic modifiers. The best separation was based on the appearance of 10 peaks simultaneously, with good resolution (R_s 1.1–15.9), and peak efficiency (N>200 000). Good repeatabilities in the migration time, peak area, and peak height were obtained in terms of RSD ranging from (0.72 to 1.06)%, (0.39 to 3.49)%, and (1.90 to 4.84)%, respectively.     

Enhanced pH-mediated stacking of anions for CE incorporating a dynamic pH junction

A technique has been developed to enhance analyte focusing for CE for the analysis of physiological samples. High-ionic-strength samples are titrated to low-ionic-strength on-line using pH-mediated sample stacking in conjunction with a dynamic pH junction. This method concentrates analytes by reducing their electrophoretic mobility during field-amplification. Parameters responsible for enhanced focusing were investigated, and an enhanced pH-mediated stacking method was optimized for anionic nucleosides. The process results in ultra-narrow peak widths, for example, 0.28 s for thymidine with a 10 min analysis time. Peak width and resolution with the enhanced stacking method were also compared to normal base stacking and electrokinetic injection. With this technique, mass-loading capacity can be increased without degradation in peak shape and resolution is dramatically improved.     

基于环糊精功能化介孔材料制备高选择性化学修饰电极

合成了SBA-15有序多孔氧化硅材料并用β-CD对其进行了修饰,制备了功能化介孔修饰碳糊电极（CD-SBA15/CPE）,利用循环伏安法（CV）、示差脉冲伏安法（DPV）等电化学技术,研究了修饰电极对硝基苯酚、硝基氯苯、苯二酚异构体的识别机理。研究表明：该修饰电极不仅能识别o-、m-、p-硝基苯酚、o-、p-硝基氯苯、o-、p-苯二酚异构体,且具有分辨率高、测定灵敏度高的特点。可望用于实际样品中同分异构体快速、灵敏和选择性检测。     

Optimisation of high-performance liquid chromatography with diode array detection using an automatic peak tracking procedure based on augmented iterative target transformation factor analysis

An automated method for the optimisation of high-performance liquid chromatography is developed. First of all, the sample of interest is analysed with various eluent compositions. All obtained data are combined into one augmented data matrix. Subsequently, augmented iterative target transformation factor analysis performs the integrated tasks of curve resolution and peak tracking. Since this type of curve resolution processes all data at once, it can deal with strong peak overlap and reveal the correspondence of compounds between runs, i.e. peak tracking. The retention time and peak width at half height for each component of the sample are determined for every eluent composition. Next, models are built for the retention time and the peak width at half height. These models are used to predict the resolution and the analysis time for each point in factor space. Finally, a multi-criterion decision-making method, Pareto optimality, is used to find the optimum. The method completes all calculations within a few minutes and without user intervention. By means of this procedure, a mixture of three benzodiazepines is successfully separated using a ternary mobile phase. There are two requirements for the automated optimisation method to work correctly. Firstly, all components of the sample must have sufficiently different spectra. Secondly, each compound should have the same spectrum under all experimental conditions.     

Non-intuitive separation of vanilla compounds using rapid resolution high-performance liquid chromatography

A method is presented for modeling the retention peak migration in rapid resolution high-performance liquid chromatography (HPLC) depending on experimental parameter values. It allows time reduction on the determination of the experimental conditions for optimal resolution (especially for untrained chromatographers). Separation for 18 species present in a conventional vanilla formulation was not possible in a single chromatogram, due to a systematic error in defining single peak migration with the usual assumptions. This was achieved by the means of two runs under different experimental conditions. Prediction of the peak inversion for quantitation purposes in a given mixture is now possible and can help to avoid misidentification on set-ups with UV-ELSD or other non-specific detectors.