X射线衍射多谱峰匹配强度比定量相分析方法

提出了1种采用x射线衍射多谱峰匹配强度比进行定量相分析的新方法;该法是利用混合物样品x射线衍射谱图中的多谱峰数据,结合ICDD卡中的各相标准谱峰的相对强度分布数据进行最小二乘法回归分析,求得混合物样品中各相间的多谱峰匹配强度比;以多谱峰匹配强度比取代通常采用的特定单一谱线强度比,用于混合物样品的x射线衍射定量相分析,有利于提高定量相分析的精度;采用多谱峰匹配强度比结合绝热法和基体清洗法X射线衍射定量相分析原理,通过对4组分混合物样品的分析,证实实验结果和理论完全一致。     

基于多尺度小波变换的红外光谱谱峰识别算法

传统的谱峰检测方法一般分为3个步骤:谱线平滑、基线校正和谱峰识别.现有的基于小波变换的峰值检测方法能较好地将基线校正和谱峰识别两个步骤融为一步.在此基础之上,本研究将谱线平滑也很好地融入到小波变换的峰值检测算法中,使整个峰值检测算法成为一个整体.在峰值提取时,原始谱图直接处理,不再是处理加工过的谱图,减小了谱峰检测结果...     

多个(重)强峰压制与白酒的核磁共振分析

利用激发塑型（excitation sculpting）方法,结合多频率选择性激发的形状脉冲（shapedpulse）、13^C CPD去偶和修整脉冲（trimpulse）等手段进行多个（重）强峰的压制,测试了市售白酒的各种1^H核磁共振谱图,并根据样品性质对脉冲序列中的各种参数进行了优化。在压制了其中水和乙醇峰后得到的一维、二维谱图中,清晰地呈现了各个微量组分的谱峰以及反映各组：分化学结构的相关峰,据此对图谱中各个谱峰进行了指认。实验表明这种方法对酒类产品的分析研究非常有效,可以应用于酒类生产和储存过程的质量控制、产品的真假及产地的鉴别等。     

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。     

化学谱图重叠峰检测及基线校正

本文提出一种谱峰曲线与其一个阶差分曲线相结合的算法，经宽松变换处理后，用于区分化学谱图中谱峰的终点是否真正落回到基线上，并由此建立了一种具有健壮性的重叠峰检测方法和及时准确的谱图基线校正方法。由于此算法的阈值参数可以固定，从而保证了重叠峰检测较少地受到人为的影响，进一步提高了化学谱图数据处理的自动化水平。     

二维相关分析中参考谱的选择对分离重叠峰的影响

二维相关光谱是一项将光谱强度看作两个独立的光谱变量的函数的技术, 它是由动态光谱经过数学转化后得到的. 在扰动过程中, 动态光谱等于实际测得的光谱减去参考谱, 参考谱的选择是任意的, 甚至可以为0, 但是在实际应用时, 人们逐渐发现参考谱的选择会对二维相关光谱产生一定的影响. 本篇文章采用模拟的方法, 建立光谱模型, 光谱强度按e指数形式单调变化, 比较以平均谱为参考谱和不设参考谱得到的二维相关光谱图, 分析它们的区别, 在不同参考谱条件下, 利用二维相关光谱分离重叠峰, 得到的结果也不相同, 将两种条件综合利用可以得到更多更正确的信息.     

便携式气相色谱仪中嵌入式谱峰识别算法设计

设计了嵌入式气相色谱谱峰识别算法,用于便携式气相色谱仪的数据分析处理,现场使用时能够不连接计算机就得出分析结果。该算法提出了用于谱峰识别的序列映射方法,减小了对斜率阈值的依赖,增强了谱峰分析的准确性和稳定性。通过实验对比可知,即使对于复杂组分的样本谱图,该嵌入式分析算法也能较好地分析提取出样品的谱峰数据,其分析结果与实验室色谱工作站软件分析结果非常接近,能够满足用户现场使用的分析需求,提高了便携仪器在现场使用的快捷性和便利性。     

X射线衍射测试样品位置对谱线峰位和强度的影响

鉴于X’Pert Pro MRD多晶X射线衍射仪的样品台5维可移动,研究了样品的位置对物相测试中谱线峰强度和峰位的影响.结果表明,样品表面低于或者高于光路中心,都会造成谱图峰位的偏移,对峰强度影响不明显.当样品表面低于光路中心位置时,峰位呈减小趋势.当样品表面高于光路中心位置时,峰位呈增加趋势.当水平位置放置了不同厚度的样品进行批处理测试时,谱线的峰强度会受到最厚的样品的影响,峰位的变化不明显.     

基于分形理论分辨重叠峰的新算法

将分形理论用于仪器分析信号的解析,提出一种面向分析谱图中重叠信号处理的分形分辨算法.通过对信号进行分形分析,采用分形维数可有效地反映信号的特征,准确地得到谱峰个数和位置的信息,避免人为判断的误差,实现重叠复合信号的分辨.实验表明,这种新的重叠谱峰分辨法能用于光谱、电化学、色谱等仪器分析数据的处理     

煤有机硫分析中XPS分峰拟合方法及参数设置

通过对含硫模型化合物和新峪焦精煤中的有机硫含量的分析,对XPS谱图的分峰拟合方法和参数设置进行了探讨。结果表明,用XPS解析煤中不同形态硫含量时,应按2p3/2和2p1/2劈裂峰分峰方法进行,并设置劈裂峰的面积比约为2∶1,裂距为1.18 eV,L-G%相同,FWHM值也相同;限定各有机硫2p3/2峰峰位分别为:硫醇硫醚类硫162.1~163.6 eV;噻吩类硫164.0~164.4 eV;亚砜类硫165.0~166.0 eV,同时对分峰拟合参数在一定范围内进行动态微调,可实现良好的数据重现性和较佳的拟合度。     

Essential peak area normalisation for quantitative impurity content determination by capillary electrophoresis

Summary A number of papers have been published [1–5] which mention that normalisation of CE peak areas (ie division of peak areas by migration time) is necessary to ensure correct quantitation. However, there is a general unawareness of the impact of not performing this simple data manipulation upon impurity results when expressed as % area/area. An exercise has been conducted to exemplify the need for this normalisation using the separation of selected pharmaceuticals as illustrative examples. The impact of normalisation on % area/area results was demonstrated using the pharmaceutical ranitidine, and a synthetic precusor, as test solutes. The UV absorbance of each compound was determined and found to be equivalent. A solution of ranitidine hydrochloride was the spiked with a weighed amount of precursor. The % area/area CE results, when normalised, mateched the known weighed radio. Use of uncorrected peak area data in this instance would have resulted in a severe underestimation of impurity levels. A quantitative analysis of drug related impurities was conducted at three levels of operating voltage whilst keeping all other operating parameters constant. This produced electropherograms having identical peak profiles but each peak having a different retention time and peak area. However, when normalised, the results were identical at each level of operating voltage confirming the validity and necessity of normalisation. A chiral separation of a racemic pharmaceutical was conducted. The uncorrected peak area data indicated the test sample was not racemic whilst the corrected data correctly confirmed that the compound was racemic. The significance and impact upon reported purity data of not normalising peak area data has been clearly demonstrated in this paper.     

New peak broadening parameter for the characterization of separation capability in capillary electrophoresis

The influence of separation conditions on peak broadening is usually estimated by the number of theoretical plates. Using the data available in literature and experimental data, it is shown that in pressure‐assisted capillary electrophoresis the plate number is not directly related to the separation capability of conditions used. The experiments at different electrolyte flow velocities demonstrate that a higher plate number (the best separation efficiency) can be obtained with a lower peak resolution. Since ions are separated by electrophoresis due to the difference in electrophoretic mobilities, the peak width in terms of electrophoretic mobility is suggested as a new peak broadening parameter describing the separation capability of the conditions used. The parameter can be calculated using the tailing factor and the temporal peak width at 5% of the peak height. A simple equation for the resolution calculation is derived using the parameter. The advantage of the peak width in terms of mobility over other parameters is shown. The new parameter is recommended to be used not only in pressure‐assisted capillary electrophoresis but also in general capillary electrophoresis when in a number of runs the virtual separative migration distance and separation capability of the conditions used change widely.     

Characterization of warfarin unusual peak profiles on oligoproline chiral high performance liquid chromatography columns

Unusual peak profiles of warfarin were characterized on two oligoproline chiral stationary phases (CSPs). The pattern of 1st peak (S(−)) broadening and the 2nd peak (R(+)) compression was observed under mobile phase of hexane (0.1% TFA)/2-propanol (IPA) on a triproline CSP 1, and with other alcohol modifier such as ethanol, 1-propanol, 1-butanol, 2-butanol, and tert-butanol as well. Through analyzing system peak of additives, the unusual peak profile was interpreted by perturbation of TFA additive system peak. The unusual peak profile was also found in enantioseparation of coumachlor and on a covalently bonded doubly tethered diproline CSP 2. The pattern of 1st peak (S(−)) broadening and the 2nd peak (R(+)) compression can change to pattern of 1st peak compression and the 2nd peak broadening from 15 to 50 °C. Chiral separation of warfarin created nonlinear van’t Hoff plots on CSP. No peak broadening/compression were observed with methyl tertiary butyl ether or ethyl acetate as the modifier. The peak shapes of the two warfarin enantiomers can thus be tuned by varying alcohol concentration and column temperature. High separation factor and resolution may be carried out to tune the peak profiles into Langmuir/anti-Langmuir band-shape composition. Using none hydrogen donor modifier may avoid interference of the TFA system peak.     

An investigation of peak-broadening effects arising when combining CE with MS

In this study, peak-broadening effects caused by nebulizing gas flow and lack of temperature control have been investigated for separation capillaries with three different inner diameters. The study was performed with serial UV/ESI-MS detection in an effort to distinguish between peak broadening arising in the separation and peak broadening arising in the ion source. The nebulizing gas was found to significantly affect both migration time and separation efficiency when using capillaries with 50 and 75 microm id. If the nebulizing gas is on during injection, the injection volume increases to such an extent that significant peak broadening is induced. Reducing the id to 25 microm minimizes the parabolic flow induced by the nebulizing gas. Results indicate that the nebulizing gas pressure can be optimized to minimize peak broadening in the ion source. A decrease in detection sensitivity, possibly related to the orthogonal design of the interface, was observed when the nebulizing gas pressure was increased. A tapered capillary tip was found to provide superior separation efficiency as well as sensitivity.     

溴化1-乙烯基-3-十二烷基咪唑硅胶键合固定相制备及其色谱性能

膜脂作为细胞质膜的主要组成部分,在生命活动中扮演着重要的作用,其涉及多种重要疾病的发生和发展过程。发展适用于膜脂分离分析的新型色谱材料对于其后续结构和生物学功能研究具有重要的意义。该文选用具有潜在生物相容性的离子液体溴化1-乙烯基-3-十二烷基咪唑（1-vinyl-3-dodecylimidazole bromide,VDI）为功能单体,通过一步法点击反应将其接枝到巯基功能化硅球表面,制备得到了新型溴化1-乙烯基-3-十二烷基咪唑硅胶键合固定相（Sil-VDI）。利用傅里叶变换红外光谱仪和热重分析仪对Sil-VDI固定相材料的结构进行表征,结果证明Sil-VDI色谱固定相已被成功制备。保留机制研究显示填充Sil-VDI色谱柱具有典型的反相/离子交换混合模式保留特性。基于此,采用不同疏水性物质烷基苯、多环芳烃、苯胺、苯衍生物和无机阴离子BrO₃ ^- 、NO₃ ^- 和IO₃ ^- 为测试物,对所制备固定相的色谱性能进行了研究。结果表明,该固定相对4类疏水性物质和无机阴离子均有较好的分离选择性和良好的峰对称性。进一步研究了所制备的Sil-VDI色谱柱对鸡蛋黄磷脂和肺腺癌细胞提取膜脂的分离效果,结果显示Sil-VDI色谱柱对2种磷脂样品均显示出了良好的分离能力。该文所制备的Sil-VDI色谱固定相合成方法简便,具有良好的分离分析应用潜能,后续工作会进一步研究该固定相在生物样品中的分离分析性能。     

A complementary mobile phase approach based on the peak count concept oriented to the full resolution of complex mixtures

Situations of minimal resolution are often found in liquid chromatography, when samples that contain a large number of compounds, or highly similar in terms of structure and/or polarity, are analysed. This makes full resolution with a single separation condition (e.g., mobile phase, gradient or column) unfeasible. In this work, the optimisation of the resolution of such samples in reversed-phase liquid chromatography is approached using two or more isocratic mobile phases with a complementary resolution behaviour (complementary mobile phases, CMPs). Each mobile phase is dedicated to the separation of a group of compounds. The CMPs are selected in such a way that, when the separation is considered globally, all the compounds in the sample are satisfactorily resolved. The search of optimal CMPs can be carried out through a comprehensive examination of the mobile phases in a selected domain. The computation time of this search has been reported to be substantially reduced by application of a genetic algorithm with local search (LOGA). A much simpler approach is here described, which is accessible to non-experts in programming, and offers solutions of the same quality as LOGA, with a similar computation time. The approach makes a sequential search of CMPs based on the peak count concept, which is the number of peaks exceeding a pre-established resolution threshold. The new approach is described using as test sample a mixture of 30 probe compounds, 23 of them with an ionisable character, and the pH and organic solvent contents as experimental factors.     

Transfer-volume effects in two-dimensional chromatography: adsorption-phenomena in second-dimension size-exclusion chromatography

Gradient-elution LC × LC is a valuable technique for the characterization of complex biological samples as well as for synthetic polymers. Breakthrough and viscous fingering may yield misleading information on the sample characteristics or deteriorate separation. In LC × SEC another phenomenon may jeopardize the separation. If the analytes adsorb on the SEC column under the injection-plug conditions, peak splitting may occur. In LC × LC the effluent from the first column is the sample solvent for the analytes injected into the second dimension. If a gradient-elution LC × SEC setup is used (i.e. if reversed-phase gradient-elution LC is coupled to organic SEC and if normal-phase gradient-elution LC is coupled to SEC with a polar solvent), the percentage of weak solvent may be significant, especially at short analysis times. In this case adsorption in the first-dimension-effluent zone on the second-dimension SEC column can become an issue and two peaks--the first eluting in size-exclusion mode and the second undergoing adsorption--can be obtained. The work presented in this paper documents peak splitting in LC × SEC of polymers. The adsorption of the polymer on the size-exclusion column was proven in one-dimensional isocratic runs. The observed effects were modeled and visualized through simulation. Studies on the influence of the transfer volume were carried out. Keeping the transfer volume as small as possible helped to minimize peak splitting due to adsorption.     

Potential of long capillary monolithic columns for the analysis of protein digests

The gain in separation efficiency for protein digests using long monolithic columns has been evaluated for a LC‐MS system with capillary monolithic columns of different lengths (150 and 750 mm). A mixture of BSA, α‐casein and β‐casein tryptic digests was used as a test sample. Peak capacity and productivity (peak capacity per unit time) were determined from base peak chromatograms and MS/MS data were used for protein identification by MASCOT database searching. Peak capacity and protein identification scores were higher for the long column. Analyses with similar gradient slope for the two columns produced ratios of the peak capacities that were slightly higher than the expected value of the square root of the column length ratio. Peak capacity ratios varied from 2.7 to 4.0 for four different gradient slopes, while protein identification scores were 2–4 times higher for the long column. Similar values were obtained for the productivity of both columns and the highest productivity was obtained at gradient times of 45 and 75 min for the short and long column, respectively. The use of long monolithic columns improves peptide separation and increases reliability of protein identification for complex digests, especially if longer gradients are chosen.     

Metrics of separation performance in chromatography. Part 1. Definitions and application to static analyses

Earlier introduced metrics of separation performance are described in a systematic way. After providing the definitions of the metrics suitable for a broad variety of applications, the study focuses on static analyses (isothermal GC, isocratic LC, etc.) and their general separation performance. Statistically expected number of resolved (adequately separated) single-component peaks is treated as the ultimate metric of general separation performance of chromatographic analysis. That number depends on the peak capacity of the analysis and the number of components in a test mixture. The peak capacity, in turn, depends on the separation capacity of a column and the lowest separation required by the data-analysis system for resolving poorly separated peaks. The separation capacity is a special case of a broader metric of the separation measure which is a function of column efficiency, solute separability, and the level of the solute interaction with a column stationary phase. The formulae for theoretical prediction of all these metrics for arbitrary pairs of peaks in static analyses are derived. To provide a better insight into the basic metrics of the separation performance, additional metrics such as the solute discrimination (relative difference in solute velocities), utilization of separability (solute discrimination per unit of their separability), specific separation (the separation per unit of separability), and others are defined and found for static analyses.     

Separation analysis of macrolide antibiotics with good performance on a positively charged C18HCE column

The separation of basic macrolide antibiotics suffers from peak tailing and poor efficiency on traditional silica‐based reversed‐phase liquid chromatography columns. In this work, a C18HCE column with positively charged surface was applied to the separation of macrolides. Compared with an Acquity BEH C18 column, the C18HCE column exhibited superior performance in the aspect of peak shape and separation efficiency. The screening of mobile phase additives including formic acid, acetic acid and ammonium formate indicated that formic acid was preferable for providing symmetrical peak shapes. Moreover, the influence of formic acid content was investigated. Analysis speed and mass spectrometry compatibility were also taken into account when optimizing the separation conditions for liquid chromatography coupled with tandem mass spectrometry. The developed method was successfully utilized for the determination of macrolide residues in a honey sample. Azithromycin was chosen as the internal standard for the quantitation of spiramycin and tilmicosin, while roxithromycin was used for erythromycin, tylosin, clarithromycin, josamycin and acetylisovaleryltylosin. Good correlation coefficients (r² > 0.9938) for all macrolides were obtained. The intra‐day and inter‐day recoveries were 73.7–134.7% and 80.7–119.7% with relative standard deviations of 2.5–8.0% and 3.9–16.1%, respectively. Outstanding sensitivity with limits of quantitation (S/N ≥ 10) of 0.02–1 μg/kg and limits of detection (S/N ≥ 3) of 0.01–0.5 μg/kg were achieved.