全二维气相色谱的原理、方法及应用概述

全二维气相色谱(GC×GC)是近几年来发展起来的一个新技术,与传统的多维色谱不同,它提供了一种真正的正交分离系统,其峰容量约等于两根柱各自峰容量的乘积,非常适合于复杂样品的分析。本文主要对GC×GC的原理、仪器、分析方法及其应用进行了评述,并展望了其未来发展趋势。     

色谱最新研究亮点

1 多维分离技术新进展 一维色谱是目前最常用的分离分析方法,然而对于复杂体系如蛋白质组,采用一维分离模式其分离度远远不能满足要求.Giddings理论告诉我们:对于分离机理相互正交的二维分离系统(如色谱),峰的容量应该为两个色谱柱峰容量的乘积.因此,多维分离系统是解决复杂分离体系的一个最佳选择.在多维色谱中二维气相色谱发展较快,目前全二维气相色谱仪业已商品化,其峰的容量达到104以上.而二维液相色谱,尤其是正相/反相二维液相色谱技术发展较为缓慢,其主要的技术瓶颈在于第一维色谱(正相)分离后的流动相严重干扰第二维色谱(反相)的分离.     

全二维气相色谱在食品风味化学成分分析中的应用

食品风味是评价食品品质特征的重要指标。食品风味物质分析通常采用一维气相色谱或气相色谱-质谱联用法,但由于某些食品风味成分组成和基质复杂,无法用一维气相色谱将其完全分离。全二维气相色谱将分离机理不同而又相互独立的两根色谱柱以正交方式组合,显著提升了色谱分离能力和分析速度,可满足食品中风味化学成分的二次分离。该文综述了全二维气相色谱技术在未经二次加工的食用农产品(如水果、蔬菜和肉类)和经过二次加工的食品(如乳制品、饮品和调味品)中风味化学成分分析中的应用,展现了全二维气相色谱技术的特点,并为食品风味的解析提供参考。     

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...     

全二维液相色谱的初步构建及其在山羊血清分离中的应用

以GFC/RP模式构建全二维液相色谱系统,第一维凝胶过滤色谱柱使用ShodexProteinKW 802. 5(300mm×8mmi.d. ),以0. 2mol/LNaH2PO4 (pH7. 0)的流动相在0. 15mL/min的流速下等度洗脱,第二维反相色谱柱使用HypersilBDSC18 (35mm×4. 6mmi.d. ),在3mL/min的流速下梯度洗脱。采用平行柱交替分析的形式作切换接口, 2. 5min切换一次,两个反相柱交替富集、分析第一维洗脱产物。以5个标准蛋白混合物的分离评价该系统,在单独一维模式中不能分离的样品在全二维液相色谱中得到了较好的分离,二维系统的总峰容量为225。与一维色谱相比,系统的总峰容量、分辨率得到较大提高。并用于山羊血清的纯化分析,对一维分离中的重合谱峰进行验证,对制备纯化有一定的实际意义。     

六味地黄丸组分的二维液相色谱分离

以1个常规六通阀直接连接两支常规尺寸的色谱柱(250 mm×4.6 mm i.d.),构建简单的SCX/RP在线二维液相色谱系统,对中成药六味地黄丸组分进行了优化分离。样品经过第一维阳离子交换色谱(Hypersil SCX),洗脱产物分离后通过六通阀直接富集到反相分析柱(C18)顶端,被转移到第二维色谱柱上继续进行分离。经过11步不连续的线性梯度洗脱,二维分离系统出峰数量达到550多个,峰容量达到2266。构建的二维液相色谱系统结构简单,与一维色谱相比,具有分辨率高、峰容量大的特点。     

六昧地黄丸组分的二维液相色谱分离

以1个常规六通阀直接连接两支常规尺寸的色谱柱(250 mm×4.6 mm i.d.),构建简单的SCX/RP在线二维液相色谱系统,对中成药六味地黄丸组分进行了优化分离.样品经过第一维阳离子交换色谱(Hypersil SCX),洗脱产物分离后通过六通阀直接富集到反相分析柱(C18)顶端,被转移到第二维色谱柱上继续进行分离.经过11步不连续的线性梯度洗脱,二维分离系统出峰数量达到550多个,峰容量达到2266.构建的二维液相色谱系统结构简单,与一维色谱相比,具有分辨率高、峰容量大的特点.     

全二维气相色谱分析持久性有机污染物的应用进展

持久性有机污染物（POPs）组分复杂,在自然界中超痕量存在,其分离分析十分困难。全二维气相色谱（GC×GC）作为一种新型色谱技术,与传统的一维气相色谱相比,具有峰容量大、分辨率和灵敏度高等优势,越来越广泛地应用于环境有机污染物的分析。该文综述了近十年来全二维气相色谱在持久性有机污染物分析中的应用进展,主要包括全二维气相色谱在解决一些复杂POPs定性定量分析难题方面的应用,如二恶英、毒杀芬和短链氯化石蜡等;概述了全二维气相色谱对多种POPs同时定性定量分析的应用进展;讨论了全二维气相色谱在非目标有机污染物筛查分析中的应用,并对发展趋势及相关应用前景进行了总结展望。     

全二维气相色谱分析直馏柴油中含硫化合物

采用全二维气相色谱-硫化学发光检测器,以直馏柴油为研究对象,考察了一维色谱柱初始温度、升温速率及两维柱温温差等条件对含硫化合物分离的影响,建立了直馏柴油中含硫化合物的分析方法。本方法对基质复杂的直馏柴油中含硫化合物的分离,并定性分析或归类了直馏柴油中的主要含硫化合物。以苯并噻吩为测试样,以峰面积对浓度作图,硫的浓度在1～100mg/kg范围内,峰面积与硫的浓度呈线性关系,相关系数大于0.999。与传统一维气相色谱相比,全二维气相色谱技术除可检测到苯并噻吩类、二苯并噻吩类等含硫化合物外,还可检测到直馏柴油中的硫醚类化合物;苯并噻吩类和二苯并噻吩类化合物也可得到较好分离。     

强阳离子交换毛细管液相色谱-反相加压毛细管电色谱二维系统的构建及其在中药黄柏提取物分离中的应用

加压毛细管电色谱(pCEC)具有电泳和液相色谱的双重分离机理,其柱效高、选择性强、分辨率高和分离速度快并可进行梯度洗脱。我们在此基础上加入离子交换色谱模式,构建了强阳离子交换-反相加压毛细管液相色谱(micro strong cation exchange liquid chromatography/reversed phase pressurized capillary electrochromatography, μ-SCXLC/RP-pCEC)二维系统,并对中药黄柏的提取物进行了优化分离。第一维μ-SCXLC采用线性盐梯度分离,样品被切割成11个馏分洗脱收集后进入第二维,第二维脱盐后,采用RP-pCEC进行分离分析,梯度洗脱。以中药黄柏提取物为样品,此二维系统的分辨率和峰容量都较一维系统有很大提高,理论峰容量可达900左右,证明构建的二维体系非常适合复杂样品的分离分析。     

Comprehensive two-dimensional gas chromatography: a hyphenated method with strong coupling between the two dimensions.

Comprehensive two-dimensional gas chromatography (GC x GC) provides a true orthogonal separation system. It is explained and demonstrated that it generates a peak capacity that is approximately equal to the product of the peak capacities of the two individual separation systems. The resulting peaks are ordered in a two-dimensional plane in bands of compounds with the same characteristics. Quantitation of the separated (groups of) components is fundamentally not different from one-dimensional gas chromatography, but the sensitivity is far better and true baseline is always available. The two co-ordinates of each peak in the plane make the identification more reliable. Instrumental considerations of GC x GC are discussed. The three designs of contemporary GC x GC systems are presented and compared. Although the technique is still very young, a number of applications on complex samples as petroleum and environmental samples have already been reported. Finally, the future perspectives of GC x GC are discussed.     

Projection of multidimensional GC data into alternative dimensions—exploiting sample dimensionality and structured retention patterns

Comprehensive multidimensional gas chromatography (GC×GC) is a powerful separation technique. One of the features of this technique is that it offers separations with more apparent structure than that offered by conventional one-dimensional GC (1-D GC). While some previous studies have alluded to this structure, and used structured retention patterns for some simple classifications, the topic of structured retention in GC×GC has not been studied in any great detail. Using the separation of fatty acid methyl esters (FAME) on both nonpolar/polar and polar/nonpolar column sets, the interaction between the separation dimensions and the sample dimensions is explored here. The GC×GC separation of a series of compounds is presented as a projection of the sample from sample space, a p-dimensional space with dimensions defined by the dimensionality of the sample, into separation space: for GC×GC, a two-dimensional plane passing through the sample space in an orientation defined by the separation conditions. Using this conceptual model and some a priori knowledge of the sample, it is shown how the image of the sample in the separation space can be used to construct an image of the sample in alternate dimensions, such as second dimension retention factor (²k) vs. chain length in the case of FAME. These projections into alternate dimensions should facilitate the interpretation of the complex patterns found within the GC×GC chromatogram for the identification and classification of compounds.     

Comprehensive two-dimensional gas chromatography in stop-flow mode

The theory and proof of concept of a new mode of operation for comprehensive two-dimensional gas chromatography (GC x GC) is presented. In current GC x GC interface designs, the modulation period defines the separation time allowed in the second dimension. In the stop-flow GC x GC mode, flow in the primary column is periodically stopped for brief periods of time. Consequently, the modulation period for the primary column and the amount of time available for second dimension separation become independent variables. This allows the separations in both the primary and secondary dimensions of the GC x GC system to be carried out under more optimised conditions, allowing extended periods of time for second dimension separations without sacrificing the separation in the primary dimension. This new technique has the potential to offer increased separation power and overall resolution as it is further developed.     

Fast Temperature Programming in Gas Chromatography using Resistive Heating

The features of a resistive-heated capillary column for fast temperature-programmed gas chromatography (GC) have been evaluated. Experiments were carried out using a commercial available EZ Flash GC, an assembly which can be used to upgrade existing gas chromatographs. The capillary column is placed inside a metal tube which can be heated, and cooled, much more rapidly than any conventional GC oven. The EZ Flash assembly can generate temperature ramps up to 1200°/min and can be cooled down from 300 to 50°C in 30 s. Samples were injected via a conventional split/splitless injector and transferred to the GC column. The combination of a short column (5 m×0.25 mm i. d.), a high gas flow rate (up to 10 mL/min), and fast temperature programmes typically decreased analysis times from 30 min to about 2.5 min. Both the split and splitless injection mode could be used. With n-alkanes as test analytes, the standard deviations of the retention times with respect to the peak width were less than 15% (n = 7). First results on RSDs of peak areas of less than 3% for all but one n-alkane indicate that the technique can also be used for quantification. The combined use of a short GC column and fast temperature gradients does cause some loss of separation efficiency, but the approach is ideally suited for fast screening as illustrated for polycyclic aromatic hydrocarbons, organophosphorus pesticides, and triazine herbicides as test compounds. Total analysis times – which included injection, separation, and equilibration to initial conditions – were typically less than 3 min.     

Flow regime at ambient outlet pressure and its influence in comprehensive two-dimensional gas chromatography

With method development in one-dimensional GC already being a tedious task, developing GC x GC methods is even more laborious. The majority of the present GC x GC applications are derived from previously optimised 1D-GC methods, from which especially the carrier gas flow settings are copied. However, in view of the high pressure inside the first-dimension column (high flow resistance of the narrow-bore second-dimension column), diffusion in the first column is much slower than in 1D-GC. Proper optimisation of the column combination and the carrier gas flow can considerably improve separations in GC x GC. To assist in the process of selecting column dimensions and flow rate optimization, we have developed a computer programme, based on Excel, that enables quick and simple calculation for all types of column combinations. The programme merely needs column dimensions and carrier gas type as input parameters and calculates all resolution and velocity parameters of the GC x GC separation by using flow rate and plate height equations. From the calculations a number of interesting conclusions can be drawn. As an example, the calculations clearly show that the majority of column combinations reported up till now have been operated at a far from optimal flow -- and, consequently, a far from optimal resolution. Probably even more important is the conclusion that the majority of column combinations used so far, i.e. those with 100 microm I.D. second-dimension columns, are not necessarily the best choice for GC x GC.     

在线高效液相色谱-毛细管气相色谱联用方法的建立

建立了一种以保留间隙柱技术和阀切换以及定量管样品转移为接口并具有早期溶剂蒸气出口的在线液相色谱与毛细管气相色谱联用方法。考察了主要实验条件,如溶剂蒸发温度、载气压力等对联机系统性能的影响,并用萘和联苯对该系统的线性范围进行了测定。利用联机系统对一种轻柴油样品进行了分析。     

In situ fabrication of microporous organic network coated capillary column for high resolution gas chromatographic separation of hydrocarbons

Microporous organic networks (MONs) are a new class of porous materials synthesized via Sonogashira coupling reactions between organic building blocks. Here we report an in situ synthesis approach to fabricate MONs coated capillary column for high resolution GC separation of hydrocarbons. The McReynolds constant evaluation reveals the MONs coated capillary is a non‐polar column. The MONs coated capillary column shows good resolution for GC separation of diverse important industrial hydrocarbons such as linear and branched alkanes, alkylbenzenes, pinene isomers, ethylbenzene and styrene, cyclohexane and benzene. The MONs coated capillary column gave a high column efficiency of 1542 plates per meter for hexane and good precision for replicate separations of the selected hydrocarbons with the RSDs of 0.2–0.3, 1.5–3.1, and 1.9–3.3% for retention time, peak height and peak area, respectively. The MONs coated capillary also offered better resolution than commercial Inert Cap‐1 and Inert Cap‐5 capillary columns for hexane and heptane isomers. These results reveal the potential of MONs as novel stationary phases in GC.     

Study of Monolithic Integrated Micro Gas Chromatography Chip

A monolithic micro gas chromatography (μGC) chip which integrated the micro separation column (μSC) and the micro thermal conductivity detector (μTCD) based on MEMS (Micro-electro-mechanical systems) technique was fabricated. Compared to the state of the art, the μSC with high depth-to-width ratio channels that was coated with mesoporous silica nanoparticles as stationary phase could effectively improve the column capacity and separation performance. Besides, the stable suspending μTCD, which was designed and fabricated in two ports of the μGC chip, could availably enhance the thermal isolation and reliability of the device. The mixture of light hydrocarbons (methane, ethane, propane and butane) could be separated from each other and detected by this monolithic integrated μGC chip, in which the overall analysis and detection time was only 33 seconds, the separation resolution of ethane and propane was 8.34, and the number of theoretical plate was as high as 11420. The monolithic integrated μGC chip has many advantages such as good separation resolution, high column efficiency and short analysis time, and is suitable for portable gas chromatographic field and onsite detection.     

Comparative study of differential flow and cryogenic modulators comprehensive two-dimensional gas chromatography systems for the detailed analysis of light cycle oil

The modulator is the key point of comprehensive two-dimensional gas chromatography (GC×GC). This interface ensures the sampling and transfer of the sample from the first to the second dimension. Many systems based on different principles have been developed. However, to our knowledge, almost only cryogenic modulators are used in the petroleum industry. Nevertheless cryogenic fluids represent some disadvantages in term of safety, cost and time consuming. This paper reports a comparative study between differential flow and cryogenic liquid modulators for the detailed analysis of hydrocarbons in middle distillates type light cycle oil (LCO). Optimization of geometrical dimensions of a set of columns was carried out on the differential flow modulator system in order to reproduce the quality of separation of cryogenic modulation. Then a comparative study was investigated on sensibility and resolution (separation space and peak capacity) between the two systems.     

Enantiomeric separation of chiral polychlorinated biphenyls on beta-cyclodextrin capillary columns by means of heart-cut multidimensional gas chromatography and comprehensive two-dimensional gas chromatography. Application to food samples

Three commercially available chiral capillary columns, Chirasil-Dex, BGB-176SE, and BGB-172, have been evaluated for the separation into enantiomers of the 19 chiral polychlorinated biphenyls (PCB) congeners stable at room temperature. The enantiomers of 15 chiral PCBs were, at least to some extent, separated using these beta-cyclodextrin based columns. Multidimensional techniques, such as heart-cut multi-dimensional gas chromatography (heart-cut MDGC) and comprehensive two-dimensional gas chromatography (GC x GC), were investigated for their ability to solve coelution problems with other PCBs present in commercial mixtures and real-life samples. Heart-cut MDGC improved the separation as compared to one-dimensional GC, and enantiomeric fractions of the investigated chiral PCBs could be determined free from interferences. However, limitations on the number of target compounds that can be transferred to the second column in a single run and, therefore, the time consumption, have led to the evaluation of GC x GC as an alternative for this type of analysis. With GC x GC, two column set-ups were tested, both having a chiral column as first-dimension column, and two different polar stationary phase columns in the second dimension. On using both column combinations, congeners 84, 91, 95, 132, 135, 136, 149, 174, and 176 could be determined free from coelutions with other PCBs. Results on the application of heart-cut MDGC to food samples such as milk and cheese are given, as well as the first results on the application of GC x GC to this type of samples.