Plate height preparative

Hsieh and Jorgenson prepared 12-33- 4m HPFC columns packed with 5.44-pm spherical stationary phase particles. To evaluate these columns they measured reduced plate height, h,... 

Pio. 15. Graph illustrating the dependence of the reduced plate height on the carbon load of octadecyl silica uuionary phase, prepared Aom Fsitisil with octadecyltrichloro-silane. Ehieiit. methanol-water eiuite, polyey aromatic hydrocarbons retention foctor, 4. Prom the dM of Henman er of. (7 5). 

Direct comparison of column efficiencies of the continuous separation medium prepared in 4.5 cm long both capillary and linear channel as measured using non retained marker acetone did not reveal any difference and an identical plate height of 4-5 pm was observed for both at flow velocities of 0.5-1.5 mm/s. This indicates that there is again no substantial difference between beds formed in both formats. Obviously, the channel behaves as a capillary although it does not have the circular cross section. 

Partition coefficient, 9, 10 Partition ratio, 11 time optimization of, 57-58 Peak, definition of, 69 Peak capacity, 18, 19 Pellicular supports, 157 Permeability, 63-64 Phase selection diagrams, 218-219 Phase volume ratio, 11 Pinkerton (ISRP) columns, 225-226 Plate height, 17 Plate number, 14-16 Plate theory, 3, 28 Polarity index, 210, 211 Pore size of LC supports, 157 Porosity, 27 Precision, 99-100 Preparative scale ... 

Fig. 5.11. Double logarithmic plot of the reduced plate height (h) versus the linear mobile phase velocity (u) in the chromatography of D,L-PA (100 nmol) on an L-PA MIP prepared using benzene as diluent at two different column temperatures. At 20°C k l a 6, k o 2.5. At 45°C k i 2.1, Ic d LO. Mobile phase MeCN/potassium phosphate buffer 0.05 M, pH 7 70/30 (v/v). From Sellergren and Shea [59].

This equation shows the dependence of the plate height of a column on the mobile phase velocity. The three terms of Eq. 2.31 describe different effects that have to be taken into account when selecting a stationary phase in preparative chromatography. The A term, which is almost constant over the whole velocity range, is mainly gov-... 

The smaller the plate height of a column, that is, the higher the efficiency, the narrower is the peak width and the closer the peak shape approaches to the ideal rectangular injection profile shape. Owing to limited rates of mass transfer and nonidealities of fluid dynamics, real peaks are characterized by limited efficiencies. Narrower peaks result in a good peak resolution, small elution volumes, and thus higher outlet concentrations. All these facts provide favorable conditions for preparative applications of chromatography. 

Finally, it is interesting to mention that capillary monolithic columns have also started to be used in gas adsorption chromatography [425, 426]. Poly-DVB monohth obtained in the presence of l.Svol of dodecanol-toluene mixtures possesses good separating power however, its efficiency (the theoretical plate height) still yields by a factor of 3-10 to that of traditional open capillary columns. On the other hand, the theoretical plate height for a similar monolith prepared for use in liquid chromatography proved to be comparable with that of conventional capillary silica-packed column [427]. 

Wirth et al. [22] prepared a silica colloidal crystal-packed fused-silica capillary column, and 2 cm-long of which was mounted onto a PDMS chip for evaluation of efficiency of capillary electrochromatography. Three fluorophore-labeled proteins, ribonuclease A, cytochrome C, and lysozyme, were well separated over a distance of 1 cm by isocratic electromigration, using acetonitrile/water (40/60) with 0.1 % formic acid. The plate height for lysozyme was... 

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