Parallel columns

Figure 3.1 Two-dimensional gas clnomatography instmmental configurations (a) direct ti ansfer heart-cut configuration (b) multiple parallel ti ap configuration (c) multiple parallel column configuration.

The //PLC system described in this chapter is equipped with 24 parallel columns for liquid chromatography, each with its own sample introduction port and exit port for connection to detectors of choice (UV absorbance and/ or fluorescence). Flow from a binary solvent delivery system is divided evenly across 24 channels and results in 1/24 of the programmed pump flow rate through each column (i.e., total flow of 300 /zL/ min will produce a flow of 12.5 /zL/ min in each column). Samples are introduced to the columns by a multichannel autosampler configured to sample from either 96-or 384-well SBS standard plates. Figure 6.2 depicts a general view of the system. 

To evaluate compound solubility, a /.iPLC system equipped with a cartridge containing 24 parallel columns (80 x 0.5 mm (inner diameter equivalent)) was employed. Sets of calibration standards were prepared for 24 compounds at different concentrations (in a 50 50 CH3CN H20 solvent). A maximum standard concentration of 500 jt/M was selected to maintain the amount of DMSO co-solvent in all samples and standards below 5% v/v to minimize possible solubility enhancements due to the presence of DMSO when working with stock solutions provided at 10 mM in DMSO. Standards were added to the appropriate wells of a 384-well plate. The plate was covered with a heat seal foil and transferred to the /./PI.C system for analysis. Figure 6.26 depicts the process for preparation of standards 95 /./I. of a buffer of desired pH were added to the appropriate wells. An additional 5, uL of each compound at a concentration of lOmM (in DMSO) was added to the corresponding wells. The plate was shaken for 90 min and centrifuged at 4000 rpm for 3 min. 

Egle, H. et al. 2005. Fast, fully automated analysis of voriconazole from serum by LC-LC-ESI-MS-MS with parallel column switching technique. J Chromatogr B. 814 361. 

The duration of the injection is a substantial fraction of the cycle time. An effective technique, therefore, is to run the feed vaporiser continuously and to direct the vapour/carrier mixture to one of, say, 2-5 parallel columns in sequencc(24 26). 

Prazen, B.J. Brackner, C.A. Synovec, R.E. Kowalski, B.R. Enhanced Chemical Analysis Using Parallel Column Gas Chromatography With Single-Detector TOF-MS and Chemometric Analysis. Anal. Chem. 1999, 71,1093-1099. 

Whigan, D. Powell, M. L. Increased throughput in quantitative bioanalysis using parallel-column liquid chromatography with mass spectrometric detection. Rapid Commun Mass Spectrom 2001, 15,... 

In the PSA process, the reformer product gas is passed through an adsorption column, where impurities are preferentially adsorbed. After a set time, the feed gas to the reactor column is diverted to a parallel column. At this stage, the first column is depressurized, allowing the bed regeneration. It is a cyclic process, the two columns being alternately pressurized and depressurized [15]. 

Thesenon-Emeric, G. and F.E. Regnier "Process Monitoring by Parallel Column Gradient Elution Chromatography. . -Statistical (in-on Sit".. 11 ]4 (June I. 1991). Wahl. J.H.. C.G. Eskc. and V.L. McGufTin "Solvent Modulation in Liquid t hru maiography." Analytical Chemistry. 1117 (June I. 1991). 

Parallel column In-series columns Column switching... 

Wood is built up of parallel columns of cells. Around these cells, cellulose embedded in lignin is wrapped. If wood is heated to temperatures above 600 °C (the exact temperature depends on the type of wood) in an inert atmosphere, then the polyaromatic biopolymers are broken down and what remains is a carbon skeleton with the anatomy of wood, both at a microscopic and macroscopic level. This skeleton facilitates the infiltration of, for instance, silicon and the reaction to silicon carbide. 

Billingham (Trans. IChemE. 80, Part A, p. 373, May 2002 Trans. IChemE. 81, Part A, p. 134, January 2003) modeled maldistribution as two parallel columns, one receiving more liquid (1 +f)L, the other receiving less (1 —f)L. The vapor was assumed equally split (Fig. 14-65)... 

FIG. 14-65 Parallel-columns model. (From Lockett and Billingham, Trans. IChemE 80, Part A, p. 373, May 2002 reprinted courtesy of IChemE.)... 

Step 4 Apply Eq. (2,9) to derive equations for the component balance lines for each of the parallel columns. 

In principle, all the six-membered ferric wheels [Fe6CI6(LM l7)6] (39) are isostructural and have idealized S g-molecular symmetry. However, there are fundamental differences concerning their crystal packing. For example, all the disk-like molecules of 39a are arranged in parallel and are piled in cylindrical columns, with all the iron centers superimposed. Each column is surrounded by six parallel columns, which are alternately dislocated by 1/3 c and 2/3 c against the central one (Fig. 13). 

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