Multidimensional chromatography switching valves

Figure 39. Arrangements for column switching technique A) Heart-, front-, and end-cut techniques B) Backflush technique C) Multidimensional chromatography a)-0 Column 1 -6 g) Detector h) Injection valve...

Figure 12.24 Schematic diagram of the multidimensional packed capillary to open tubular column SFC-SFC system. Reprinted from Analytical Chemistry, 62, Z. Juvancz et al., Multidimensional packed capillary coupled to open tubular column supercritical fluid chromatography using a valve-switching interface , pp. 1384-1388, copyright 1990, with permission from the American Chemical Society.

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. 

Figure 10.3 Gas chromatograms of a cold-pressed lemon oil obtained (a) with an SE-52 column in the stand-by position and (b) with the same column showing the five heart-cuts (c) shows the GC-GC chiral chromatogram of the transferred components. The asterisks in (b) indicate electric spikes coming from the valve switching. The conditions were as follows SE-52 pre-column, 30 m, 0.32 mm i.d., 0.40-0.45 gm film thickness carrier gas He, 90 KPa (stand-by position) and 170 KPa (cut position) oven temperature, 45 °C (6 min)-240 °C at 2 °C/min diethyl-terf-butyl-/ -cyclodextrin column, 25 m X 0.25 mm i.d., 0.25 p,m film thickness carrier gas He, 110 KPa (stand-by position) and 5 KPa (cut position) oven temperature, 45 °C (6 min), rising to 90 °C (10 min) at 2 °C/min, and then to 230 °C at 2 °C/min. Reprinted from Journal of High Resolution Chromatography, 22, L. Mondello et al., Multidimensional capillary GC-GC for the analysis of real complex samples. Part IV. Enantiomeric distribution of monoterpene hydrocarbons and monoterpene alcohols of lemon oils , pp. 350-356, 1999, with permission from Wiley-VCH.

Figure 12.23 SFC-SFC analysis, involving a rotary valve interface, of a standard coal tar sample (SRM 1597). Two fractions were collected from the first SFC separation (a) and then analyzed simultaneously in the second SFC system (b) cuts a and b are taken between 20.2 and 21.2 min, and 38.7 and 40.2 min, respectively. Peak identification is as follows 1, tri-phenylene 2, chrysene 3, benzo[g/h]perylene 4, anthracene. Reprinted from Analytical Chemistry, 62, Z. Juvancz et al., Multidimensional packed capillary coupled to open tubular column supercritical fluid chromatography using a valve-switching interface , pp. 1384-1388, copyright 1990, with permission from the American Chemical Society.

Figure 5 (A) Schematic description of a multidimensional gas chromatography arrangement, where a switching system or valve (V) is located between the two columns. The process of switching the flow between and or to the monitor detector (det M) is not shown. The auxiliary flow (aux) provides flow to the system to assist in the switching process, and/or to provide make-up flow into the column, which Is not receiving flow from the precolumn. is normally a column of regular dimensions, and may incorporate a cryofocusing step at the head of the column. (B) The comprehensive two-dimensional gas chromatography arrangement essentially only requires a mechanism for modulation between the two columns, which provides a series of narrow peaks (at least four normally) to for each D peak. The modulator (M) is shown near the column connection. is normally a short, fast elution column.

---