Multidimensional liquid column

Multidimensional Column Liquid Chromatography (LC) in Proteomics - Where Are We Now ... 

C. Corradini, Coupled-column liquid chromatography, in Multidimensional Chromatography, L. Mondello, C. Lewis, K.D. Bartle (Eds.) John Wiley Sons, Chichester, U.K., 2001, pp. 109-129. 

R. A. Kenley, S. Chandry, and G. A. Visor, Multidimensional column-switching liquid chromatographic method for dissolution testing of enprostil soft elastic gelatin capsules, J. Pharm. Sci., 75 999 (1986). 

Dimensionality is an important term, which can be used to describe the nature of the sample, or of the multidimensional system. System dimensionality simply refers to the number of coupled separation stages or dimensions used in the multidimensional system. For example, a single column liquid chromatograph would have a dimensionality of 1, whilst a LC-GC system described above has a dimensionality of 2. On the other hand, sample dimensionality, introduced by Giddings in 1995, is used to describe the intrinsic nature of the sample, and can be defined... 

Multidimensional HPLC offers very high separation power when compared to monodimensional LC analysis. Thus, it can be applied to the analysis of very complex mixtures. Applications of on-line MD-HPLC have been developed, using various techniques such as heart-cut, on-column concentration or trace enrichment applications in which liquid phases on both columns are miscible and compatible are frequently reported, but the on-line coupling of columns with incompatible mobile phases have also been studied. 

Figure 12.8 Mia ocolumn size exclusion chromatogram of a styrene-aaylonitrile copolymer sample fractions ti ansfeired to the pyrolysis system are indicated 1-6. Conditions fused-silica column (50 cm X 250 p.m i.d.) packed with Zorbax PSM-1000 (7p.m 4f) eluent, THF flow rate, 2.0 p.L/min detector, Jasco Uvidec V at 220 nm injection size, 20 nL. Reprinted from Analytical Chemistry, 61, H. J. Cortes et al, Multidimensional chromatography using on-line microcolumn liquid chromatography and pyrolysis gas chromatography for polymer characterization , pp. 961 -965, copyright 1989, with peimission from the American Chemical Society.

Figure 12.9 Typical pyrolysis chromatogram of fraction from a styrene-acTylonitiile copolymer sample obtained from a miciocolumn SEC system 1, acrylonitrile 2, styrene. Conditions 5 % Phenylmetliylsilicone (0.33 p.m df) column (50 m X 0.2 mm i.d.) oven temperature, 50 to 240 °C at 10 °C/min carrier, gas, helium at 60 cm/s flame-ionization detection at 320 °C make-up gas, nitrogen at a rate of 20 mL/min. P indicates tlie point at which pyrolysis was made. Reprinted from Analytical Chemistry, 61, H. J. Cortes et ai, Multidimensional cliromatography using on-line microcolumn liquid cliromatography and pyrolysis gas cliromatography for polymer characterization , pp. 961-965, copyright 1989, with permission from tlie American Chemical Society.

Figure 15.5 Separation of Voriconazole and an internal standard by using SEC-HPLC. Adapted from Journal of Chromatography, B 691, D.A. Stopher and R. Gage, Determination of a new antifungal agent, voriconazole, by multidimensional high-perfomiance liquid chromatography with direct plasma injection onto a size exclusion column , pp. 441 -448, copyright 1997, with permission from Elsevier Science.

Multidimensional liquid chromatography encompasses a variety of techniques used for seunple separation, cleanup and trace enrichment [12,279-289]. A characteristic feature of these methods is the use of two or more columns for the separation with either manual or automatic switching by a valve interface of fractions between columns. These techniques require only minor modification to existing equipment, and of equal importance, enable the sample preparation and separation procedures to be completely automated. 

Also, subcritical (hot/liquid) water can be used as a mobile phase for packed-column RPLC with solute detection by means of FID [942]. In the multidimensional on-line PHWE-LC-GC-FTD/MS scheme, the solid sample is extracted with hot pressurised water (without the need for sample pretreatment), and the analytes are trapped in a solid-phase trap [943]. The trap is eluted with a nitrogen flow, and the analytes are carried on to a LC column for cleanup, and separated on a GC column using the on-column interface. The closed PHWE-LC-GC system is suitable for many kinds of sample matrices and analytes. The main benefit of the system is that the concentration step is highly efficient, so that the sensitivity is about 800 times better than that obtained with traditional methods [944]. Because small sample amounts are required (10 mg), special attention has to be paid to the homogeneity of the sample. The system is... 

SEC in combination with multidimensional liquid chromatography (LC-LC) may be used to carry out polymer/additive analysis. In this approach, the sample is dissolved before injection into the SEC system for prefractionation of the polymer fractions. High-MW components are separated from the additives. The additive fraction is collected, concentrated by evaporation, and injected to a multidimensional RPLC system consisting of two columns of different selectivity. The first column is used for sample prefractionation and cleanup, after which the additive fraction is transferred to the analytical column for the final separation. The total method (SEC, LC-LC) has been used for the analysis of the main phenolic compounds in complex pyrolysis oils with minimal sample preparation [974]. The identification is reliable because three analytical steps (SEC, RPLC and RPLC) with different selectivities are employed. The complexity of pyrolysis oils makes their analysis a demanding task, and careful sample preparation is typically required. 

One attempt to overcome these disadvantages has been to use multidimensional liquid chromatography (LC) followed directly by tandem mass spectrometry to separate, fragment and identify proteins (Link et al., 1999). In this process, a denatured and reduced protein mixture is digested with a protease to create a collection of peptides (Fig. 2.6). The peptide mixture is applied to a cation exchange column and a fraction of these peptides are eluted based on charge onto a reverse-phase column. The... 

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