2D chromatography comprehensive

Such a system has been used for the comprehensive 2D chromatography of proteins [9,14], synthetic polymers [16], oxygen heterocyclic fraction of cold-pressed citrus oils [22,29], carotenoids [39], triglycerides in fats and oils [18-21], pharmaceuticals [29], and acidic and phenolic compounds [27,28]. 

If we can (1) find a way to join two gas chromatography systems with differing stationary phases, (2) separately and repeatedly trap everything eluting from the first phase (column), (3) then repeatedly separate each trapped fraction on a second column, and (4) store and manipulate the data signals from a detector at the end of the second column, we can produce a comprehensive 2D chromatography system (e.g., 2D GC cf. Section 11.3). 

Many chromatographic method combinations are possible and have indeed been used e.g. SEC, LAC, LC-CAP, GC, SEC, CE, TREE [2]. Obviously, techniques such as GC and SEC, which destroy the mobile phase, can only be used as the final dimension. Most popular to date have been HPLCxGPC combinations, because comprehensive 2D chromatography was first established in synthetic polymer work. Details on the methodology and experimental implementation can be foimd in the literature [3]. 

Most developments in the past two decades, however, have involved coupled column systems which are much more amenable to automation and more readily permit quantitative measurements, and such systems form the subject of this present book. A review on two-dimensional GC was published (43) in 1978 (and recently updated (29)), and the development by Liu and Phillips in 1991 of comprehensive 2D GC marked a particular advance (33). The fundamentals of HPLC-GC coupling have been set out (37) with great thoroughness by Grob. Other work on a number of other aspects of multidimensional chromatography have also been extensively reviewed (44,45). 

A comprehensive 2D HPLC can be carried out with two very similar columns in reversed-phase liquid chromatography (Ikegami et al., 2005). A mixture of water and tetrahydrofuran was used as a mobile phase in the lst-D separation, and a mixture of water and methanol (CH3OH) in the 2nd-D separation with a common Ci8 stationary phase. 

It was in this context that the first true comprehensive online LC x LC separation was reported (Bushey and Jorgenson, 1990). Mixtures of intact proteins were analyzed using cation-exchange chromatography (CEX) as the first dimension and size exclusion chromatography (SEC) as the second. This research demonstrated that the practical difficulties of coupling two dissimilar LC modes for a comprehensive 2D separation are relatively easy to overcome when instrumentation is properly configured. 

Holland and Jorgenson reported separating amines using anion exchange and reversed-phase columns in 1995 and since then, there have been numerous reports of combining two LC columns (2D-LC) to achieve efficient sample separation. In addition to the few references mentioned in this section, see Chapter 4 in this handbook on two-dimensional comprehensive liquid chromatography. 

Comprehensive 2D liquid chromatography is emerging as a new powerfnl technique for the separation of complex samples because of increased peak capacity, selectivity, and resolution in comparison to single-dimensional HPLC. 2D LC x LC systems essentially represent programming of stationary phases. Comprehensive LC x LC techniqne represents specific 2D mode, where all sample componnds eluting from the first dimension are snbjected to separation in the second dimension [167]. The whole effluent from the first dimension is transferred into the second-dimension... 

Harju, M. Bergman, A. Olsson, M. Roos, A. Haglund, P, Determination of atropisomeric and planar polychlorinated biphenyls, their enantiomeric fractions and tissue distribution in grey seals using comprehensive 2D gas chromatography J. Chromatogr. A 2003,1019, 127-142. 

The high resolution of LC-SEC separations and the full automation using 2D-CHROM software enable the reliable and comprehensive characterization and deformulation of complex analytes like copolymers, polymer blends, and additives. 2D chromatography will become a powerful tool with flexible and easy-to-use software. Basically, all types of LC methods can be combined to give superior resolution and reproducibility. 

In liquid chromatography, two dimensional separations in the vast majority of cases are not comprehensive. While comprehensive 2D-LC separations (LC X LC) can be accomplished and have been demonstrated (e.g., Refs. 30 and 31), the technique is not very popular. Probably one of the main reasons for this is the inability to perform very fast separations in liquid chromatography. In GC X GC, a typical second dimension separation can be completed in a few seconds. In LC, the separation time required is much longer. The problem can be overcome by stopping the flow in the first dimension column while the second dimension separation proceeds, but this causes the overall analysis times to be very long. 

Comprehensive two-dimensional (2D) chromatography is a very powerful tool for the separation of complex samples because it offers a significant increase of peak capacity as a result of the expansion of the available separation space. Co-eluting peaks in one-dimensional (ID) chromatography might be separated in the second dimension, meaning that more peaks can be individually detected in comprehensively interfaced two-dimensional chromatography. 

Although relatively unknown, the instrumentation for 2DLC was conceived and implemented by Emi and Frei (1978). They reported the valve configuration presently used in most comprehensive 2DLC systems. However, they automated neither the valve nor the data conversion process to obtain a contour map or 2D peak display. They used a gel permeation chromatography (GPC) column in the first dimension and a reversed-phase liquid chromatography (RPLC) column in the second dimension and studied complex plant extracts. 

In many cases, data can be obtained offline and analyzed in a comprehensive manner from a fraction collector. For example, LC and gas chromatography (GC) can be utilized to form a 2D experiment — LC/GC. This is quite useful as the retention... 

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