全二维气相色谱/飞行时间质谱(GC×GC/TOFMS)用于烟叶中挥发、半挥发性碱性化合物的组成研究

建立了烟叶中挥发性、半挥发性碱性化合物组成研究的全二维气相色谱/飞行时间质谱(GC×GC/TOFMS)分析方法, 并用所建立的方法对香料烟中碱性化合物进行了表征. 对比了一维气相色谱和全二维色谱方法用于烟叶碱性组分组成分析的效果. 一维色谱质谱方法共鉴定出45种碱性化合物. 用所建立的全二维气相色谱方法, 采用TOFMS谱图库检索结合全二维特有的包含结构信息的二维谱图, 通过族分离和结构谱图鉴定, 鉴定出了香料烟中挥发性、半挥发性碱性组分共92种. 包括吡咯类化合物6种, 吡啶类化合物39种, 吡嗪类化合物10种, 苯胺类化合物11种, 喹啉类化合物11种, 吲哚类4种和其他类化合物11种. 同时对不同类别的化合物在二维气相色谱上的分布模式进行了研究. 研究结果表明, 全二维色谱飞行时间质谱的高分辨率和特有的定性手段适合于烟叶这类复杂植物体系的化学组成研究.     

全二维气相色谱-飞行时间质谱联用技术分析重馏分油中芳烃组成

通过对升温速度、二维补偿温度、调制周期等关键实验参数的优化,建立了全二维气相色谱-飞行时间质谱(GC×GC-TOF MS)分析重馏分油中芳烃组分的方法,得到了重馏分油芳烃组分按环数分布的二维点阵图。根据谱库检索、标准化合物对照及文献报道,对重馏分油芳烃组分中菲、甲基菲及芘、苯并蒽等常见多环芳烃(PAH)进行了准确定性,并将该方法应用到重馏分油加氢处理工艺研究中,对菲、芘的加氢处理产物进行了定性分析。该研究为重馏分油芳烃组分的准确定性提供了新的技术手段,为加深对油品加氢规律的认识提供了技术支持。全二维气相色谱与普通一维色谱对比,在重馏分油的芳烃组分分析上体现了极大优势。     

应用固态热调制技术的全二维气相色谱-质谱联用法对工业废水中有机污染物的检测

采用新型固态热调制技术的全二维气相色谱-质谱联用法对某工业废水进行分析,定性检出162种主要的有机污染物。结果表明,有机污染物主要由苯系物和萘系物组成;同类化合物在全二维气相色谱谱图上呈规律性排布,可以方便地对性质相近的化合物进行归类分析;全二维气相色谱-质谱法具有更大的峰容量、更高的分辨率和灵敏度,是复杂样品的准确可靠的分析方法。     

全二维气相色谱/飞行时间质谱用于烟叶中酸性成分的分离与分析

建立了烟叶中酸性化合物(挥发性、 半挥发性羧酸类和酚类)组成研究的全二维气相色谱/飞行时间质谱(GC×GC-TOFMS)分析方法, 并用此方法对香料烟中的酸性化合物进行了表征. 用同时蒸馏萃取样品的前处理方法, 采用TOFMS谱图库检索结合全二维特有的包含结构信息的二维谱图, 通过族分离和结构谱图, 鉴定出了香料烟中143种挥发性及半挥发性酸性组分, 包括10种酸酐和呋喃二酮, 43种有机酸和90种酚类化合物. 同时对不同类别的化合物在二维气相色谱上的分布模式进行了研究. 结果表明, 全二维气相色谱飞行时间质谱的高分辨率非常适合于烟叶这类复杂体系的分离分析.     

基于全二维气相色谱-四极杆飞行时间质谱高通量检测独活挥发油化学成分

利用全二维气相色谱-四极杆飞行时间质谱(GC×GC-QTOF MS)建立了一种适用于独活挥发油化学成分的高通量检测方法,样品经水蒸气蒸馏提取后,直接采用全二维气相色谱进行分离,并根据谱库匹配、保留指数及精确质量数进行定性确认.结果表明,共分离鉴定了独活挥发油中207种化学成分,其中正向、反向匹配因子大于800的化合物占...     

离线全二维逆流色谱-液相色谱分离莪术油成分

中药挥发油成分复杂,一维色谱分离由于有限的峰容量难以完全分离中药挥发油成分,全二维气相色谱为分离挥发油成分提供了有力的方法,然而气相色谱一般无法用于天然活性成分的筛选。为建立挥发油成分全二维色谱分析新方法,研究建立以液相色谱为基础的全二维色谱分离分析方法。本文主要研究全二维逆流色谱-液相色谱分离莪术油成分的方法,并探讨两种色谱技术之间的正交性,为活性成分筛选提供新的技术支持。通过优化离线全二维逆流色谱-液相色谱分离方法,对全二维色谱峰容量、正交性和空间覆盖率进行度量。优化液相色谱分析条件并筛选逆流色谱分离两相溶剂体系,通过比色法筛选了逆流色谱两相溶剂体系并采用下相为流动相进行梯度洗脱。在290～375 min采用推挤洗脱,莪术油在第一维逆流色谱分离中达到了良好的分离。第二维反相高效液相色谱的流动相组成为乙腈(A)和水(B)。梯度洗脱程序为0～10 min, 50%A～65%A; 10～14 min, 65%A; 14～21 min, 65%A～85%A; 21～25 min, 85%A～95%A; 25～30 min, 95%A～55%A; 30～40 min, 55%A。在上述条件下...     

全二维气相色谱/飞行时间质谱对赤松松针挥发油化学成分的分析

选取产于小兴安岭的新鲜赤松松针,采用水蒸气蒸馏法提取其中的挥发油,并通过全二维气相色谱/飞行时间质谱(GC×GC/TOF MS)对松针挥发油进行分析和鉴定。对色谱条件进行了优化,确定调制周期为6 s,二维色谱柱长为3 m,二维柱箱相对一维柱箱温度高20℃为最佳色谱条件。通过分析,鉴定出217种物质,其中萜类124种,包含单萜48种、倍半萜64种、二萜12种,共占总含量约69%,酯类33种,占总含量约12%,有机酸类6种,醇类15种,醛类15种,酮类11种和其他类化合物13种。相比于传统一维色谱(1DGC),全二维气相色谱(GC×GC)能提供数倍的峰容量,并对一些天然产物的异构体有着很好的分离,因此其在复杂天然产物分析方面具有独特优势。     

气相色谱灰色分析体系中未知组分保留指数的预测

提出在部分组分已知的气相色谱灰色体系中,利用已知组分的保留指数和保留时间推算死时间和正构烷烃的保留时间,再计算未知组分保留时间的方法,结果显示,在已知组分不是太少的情况下,该方法计算的死时间和正构烷烃的保留时间与实验值吻合,预测的保留指数也有较高的精度.     

基于SPME/GC×GC-QTOF MS法测定回收PET中的挥发性有机物

建立了顶空-固相微萃取（HS-SPME）结合全二维气相色谱－串联四极杆飞行时间高分辨质谱（GC × GC－QTOF MS）测定回收聚对苯二甲酸乙二醇酯（rPET）中挥发性有机物的方法。比较了不同固相微萃取纤维头、萃取温度、顶空平衡时间、调制周期和升温速率对测定效果的影响,用NIST谱库结合色谱保留指数对物质进行定性,并对高频检出物质进行半定量。结果表明,最佳检测条件为：80 μm DVB/C-WR/PDMS萃取纤维头、萃取温度110 ℃、平衡时间30 min、二维调制周期4 s、色谱升温速率8 ℃/min。9个回收PET样品中共检出209种挥发性有机物,包括苯系物、烷烃类、醇类、醛酮类、酯类、烯烃类、萘类、羧酸类和酚类等。高频物质的最高含量为2.13 mg/kg（十四烷）,未发现浓度极高的误用物质。该研究为回收PET中的挥发性有机物调查提供了科学和可靠的方法依据,并为回收PET的利用和安全评估提供了基础数据。     

全二维气相色谱-氢火焰离子化检测器定性定量分析柴油中的多环芳烃

提出了全二维气相色谱-氢火焰离子化检测器(GC×GC-FID)定性定量分析柴油中多环芳烃的方法。利用全二维气相色谱-飞行时间质谱法(GC×GC-TOF MS)确定柴油芳烃的4个族组成,分别为非芳烃、一环芳烃、二环芳烃和三环⁺芳烃,获得37种定性化合物;采用峰面积归一化法对多环芳烃进行定量。结果表明：柴油质控样中多环芳烃测定值的相对误差绝对值不大于5.0%;对柴油样品进行回收试验,回收率为95.7%～104%,测定值的相对标准偏差(n=6)为1.7%～4.3%。方法用于7种实际柴油样品分析,并与NB/SH/T 0806-2022进行比对,结果显示两种方法测定值的相对误差绝对值均不大于5.0%。     

Resolution prediction and optimization of temperature programme in comprehensive two-dimensional gas chromatography

A model is developed for predicting the resolution of interested component pair and calculating the optimum temperature programming condition in the comprehensive two-dimensional gas chromatography (GC x GC). Based on at least three isothermal runs, retention times and the peak widths at half-height on both dimensions are predicted for any kind of linear temperature-programmed run on the first dimension and isothermal runs on the second dimension. The calculation of the optimum temperature programming condition is based on the prediction of the resolution of "difficult-to-separate components" in a given mixture. The resolution of all the neighboring peaks on the first dimension is obtained by the predicted retention time and peak width on the first dimension, the resolution on the second dimension is calculated only for the adjacent components with un-enough resolution on the first dimension and eluted within a same modulation period on the second dimension. The optimum temperature programming condition is acquired when the resolutions of all components of interest by GC x GC separation meet the analytical requirement and the analysis time is the shortest. The validity of the model has been proven by using it to predict and optimize GC x GC temperature programming condition of an alkylpyridine mixture.     

A method of calculating the second dimension retention index in comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry

A method was developed to calculate the second dimension retention index of comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC/TOF-MS) data using n-alkanes as reference compounds. The retention times of the C(7)-C(31) alkanes acquired during 24 isothermal experiments cover the 0-6s retention time area in the second dimension retention time space, which makes it possible to calculate the retention indices of target compounds from the corresponding retention time values without the extension of the retention space of the reference compounds. An empirical function was proposed to show the relationship among the second dimension retention time, the temperature of the second dimension column, and the carbon number of the n-alkanes. The proposed function is able to extend the second dimension retention time beyond the reference n-alkanes by increasing the carbon number. The extension of carbon numbers in reference n-alkanes up to two more carbon atoms introduces <10 retention index units (iu) of deviation. The effectiveness of using the proposed method was demonstrated by analyzing a mixture of compound standards in temperature programmed experiments using 6 different initial column temperatures. The standard deviation of the calculated retention index values of the compound standards fluctuated from 1 to 12 iu with a mean standard deviation of 5 iu.     

Determination of retention indices in constant inlet pressure mode and conversion among different column temperature conditions in comprehensive two-dimensional gas chromatography

A method to determine the second dimensional real retention time, dead times on both dimensions and retention indices in constant inlet pressure mode was developed in comprehensive two-dimensional gas chromatography. At the same time, the conversion of GC x GC retention indices among different column temperature conditions were also conducted based on some thermodynamics parameters. The calculation accuracies are better than 1.0 retention index unit. Furthermore, a retention index database was developed and used to identify the compounds in a cigarette essential oil sample. It showed that identification by the database was of close agreement with by time-of-flight mass spectrometry, and some isomers could also be distinguished based on the retention index database.     

Assessment by monte carlo simulation of thermodynamic correlation of retention times in dual-column temperature programmed comprehensive two-dimensional gas chromatography

The correlation of retention times in comprehensive two-dimensional gas chromatography caused by correlation of enthalpy and entropy changes between two stationary phases, methylsilicone and poly(ethylene glycol), was examined using commercial GC software and in-house Monte Carlo simulation. The enthalpy change, deltaH0, and entropy change, deltaS0, of 93 compounds were predicted from isothermal one-dimensional gas chromatograms predicted by the software. These values then were mimicked by Monte Carlo simulation, which removed the strong correlation of deltaH0 and modest correlation of deltaS0 between the two phases. Retention times in a comprehensive two-dimensional gas chromatogram (GC x GC) and in simulations of it were predicted for typical dual-capillary temperature-programmed conditions using the actual, correlated values of deltaH0 and deltaS0 and their uncorrelated Monte Carlo counterparts, respectively. The uncorrelated deltaH0 and deltaS0 values caused the retention-time range of the simulations' second dimension to expand substantially beyond that in the GC x GC. Other simulations were developed using a restricted range of uncorrelated deltaH0 and deltaS0 values to mimic more closely the retention-time range of the GC x GC's second dimension. The intervals between nearest neighbor retention-time coordinates were calculated in both the latter simulations and the GC x GC. The intervals were larger in the simulations than in the GC x GC because the former contained uncorrelated coordinates and the latter contained correlated ones, which clustered along or near the diagonal. The retention times in the first dimension of the GC x GC were Poisson distributed, as assessed by statistical-overlap theory. In contrast, the two-dimensional reduced retention-time coordinates in the GC x GC were not Poisson distributed, because retention times were correlated. However, the reduced retention-time coordinates in the simulations were Poisson distributed.     

Molecular structure retention relationships in comprehensive two-dimensional gas chromatography

Comprehensive two-dimensional gas chromatography (GC x GC) offers new opportunities to develop relationships between molecular structure and retentions in the two dimensional (2D) separation space defined by the GC x GC retention in each dimension. Whereas single dimension GC provides only one retention property for a solute, and hence the specific relationship between retention and chemical property is not readily apparent or derivable, the 2D presentation of compounds in GC x GC provides a subtle and exquisite correlation of chemical property and retention unlike any other GC experiment. The 'orthogonality' of the two separation dimensions is intimately related to the manner in which different separation mechanisms, available through use of two dissimilar phases, are accessible to the different chemical compounds or classes in a sample mixture, and indeed the specific chemical classes present in the sample. The GC x GC experiment now permits various processes such as chemical decompositions, molecular interconversions, various non-linear chromatography effects, and processes such as slow reversible interactions that may arise with stationary phases or in the injector or column couplings, to be identified and further investigated. Here, we briefly review implementation of the GC x GC method, consider the molecular selectivity of GC x GC, and highlight a selection of molecular processes that can be probed by using GC x GC.     

Retention time reproducibility in comprehensive two-dimensional gas chromatography using cryogenic modulation an intralaboratory study

A survey was conducted to determine the reproducibility of retention times in both the first (D1) and second dimension (D2) axes of the two-dimensional separation space, in the comprehensive two-dimensional gas chromatographic analysis of an essential oil sample using cryogenic modulation. The retention times in the two dimensions for a number of individual components comprising hydrocarbon, alcohol, ester and ketone chemical classes in a Melaleuca alternifolia essential oil were recorded from replicate analyses using four separate column sets and two identical gas chromatographs. Run-to-run, day-to-day, instrument-to-instrument, and column set-to-column set reproducibility were demonstrated from the experimental design. A total of 60 GC x GC analyses were conducted. The longitudinally modulated cryogenic system produced reproducible modulation start times and consistent modulation phase profiles for individual components in all experiments, and retention time variations in both dimensions were negligible. The average run-to-run reproducibility of 43 components for six replicate injections was found to be 0.12% RSD in the first dimension, and 0.74% RSD in the second dimension. Day-to-day reproducibility showed statistically "significant" difference (F-test), but this was partly ascribable to the excellent within-day reproducibility that led to apparent day-to-day differences. Confidence in absolute retention times (hence component positions) in the two-dimensional separation space is critical to component identification.     

气相色谱中测定死时间的Grobler－Balizs法和Ambrus法的比较

经理论推导和实验数据验证，证明测定死时间的Ｇｒｏｂｌｅｒ－Ｂａｌｉｚｓ法和Ａｍｂｒｕｓ法是同一的。     

A convenient method for routine estimation of dead time in gas chromatography

A set of retention times (tR) of n-alkanes at different temperatures and the primary dead times (tM) are used to determine the 4 numerical constants (a, b, c, and d) of an equation. This equation is rearranged into a second equation, used in turn for routine calculation of the secondary dead time (tMS) of each chromatogram from any member of the n-alkane series. Equation 2 can be used to calculate the tMS of both packed and capillary columns. The calculated tMS values are in good agreement with those of the tM values. The greatest difference is 3.38%, but it is speculated that the percent difference would be lower when more tR data are collected for the determination of the 4 numerical constants of Equation 1. Error in measurement of retention time undoubtedly would affect the accuracy of the estimated dead time, but it is attenuated by a factor of 1 + e(a + bN + c/T + dN/T).     

Overloading of the second-dimension column in comprehensive two-dimensional gas chromatography

Comprehensive two-dimensional gas chromatography (GC x GC) is based on a coupling of two GC columns of different characteristics by means of a device that allows portions of the effluent from the primary column to be injected onto the second dimension column for an additional separation. The time available for the separation in the second-dimension column is very short. Thus, this separation should be very efficient. The vast majority of GC x GC practitioners use very narrow bore columns for the second dimension. While this approach is justified in principle, if peaks in the second dimension overload this column, its peak capacity is severely reduced. A series of second-dimension columns of varying internal diameters, but similar phase ratios, were used to study these effects. The results indicate that 250 microm columns often provide comparable second dimension peak widths to 100 microm columns, while at the same time being less prone to overloading, indicating that they may often be a better choice than smaller diameter columns in the second dimension of GC x GC systems.     

Pulsed flow modulation comprehensive two-dimensional gas chromatography

Pulsed flow modulation (PFM) is based on higher flow rate time compression of the first GC column effluent, which prior to the injection into the second column is stored for a few seconds in a standard fused silica wide bore transfer line. We constructed the PFM device with two standard 1/16 in. brass compression fittings with the insertion of the two columns inside the wide bore 0.53 mm i.d. fused silica storage transfer line for the elimination of dead volumes. This simple arrangement provides a combination of flexibility in the length of the sample storage transfer line hence comprehensive two-dimensional gas chromatography (GC x GC) cycle time, inert sample path and full elimination of cooling gas consumption. A record short second column injection time of 20 ms is demonstrated. Practical injection times are the sample collection time (such as 4s) divided by the second to first column flow rate ratio (such as 20/0.7), which is typically around 150 ms. Due to the low cost of the device it can also be considered for use with non comprehensive time segmented GC x GC to remove a few accidental coelutions. PFM-GCxGC excels with high second column capacity due to the use of 0.32 mm i.d. columns with high flow rates as the second dimension GC x GC column. As a result, PFM-GCxGC can have up to two orders of magnitude higher second column sample capacity and linear dynamic range for improved reduction of adverse matrix interference effects due to column overloading.