Packed column preparation filling columns

Tang et al. used columns packed with a slurry of beads suspended in supercritical C02. This packed column was filled with a dilute sol solution prepared by hydrolysis and polycondensation of tetramethoxysilane and ethyltri-methoxysilane precursors. The column was dried using supercritical C02 and heated first to 120 °C for 5 h followed by another 5 h at a temperature of 250 °C [108-110]. Column efficiencies of 127,000 and 410,000 plates/m were reported... 

Slurry packing techniques are required for the preparation of efficient columns with rigid particles of less than 20 micrometers in diameter. The same general packing apparatus. Figure 4.8, can be used to pack columns by the balanced-density slurry, liquid slurry, or the viscous slurry techniques. Down-fill slurry packing is the method of choice for small bore columns and packed capillary columns. 

Two types of columns are used. A packed column is one filled with inert, solid particles coated with a liquid stationary phase. Standard tubing is about 0.5 cm in diameter, with lengths ranging from 1 m to 20 m however, columns for large-scale preparative work may be up to 5 cm in diameter and several meters long. Commonly used solid supports are diatomaceous earth, Teflon powder, and glass beads. The stationary liquid must be chosen on the basis of the compounds to be analyzed. A more recently developed and more widely used type of column is the open-tubular or capillary column. This is prepared by coating the inner wall of the column with the stationary liquid phase. The inside diameter of a typical capillary tube is 0.25 mm, and... 

The ratio between the through-pore size (ca. 8 pm) and the skeleton size (ca. 2.2 pm) shown in Fig. 5.2a is much greater than in a packed bed of a particle-filled column. Figure 5.3 shows the plots of skeleton size against the through-pore size in a column for a silica monolith prepared in a capillary or in a mould, as well as in a particle-packed column. The through-pore size/skeleton size ratios observed with the... 

The crude product is dissolved in the minimum quantity of benzene and is placed on an alumina-filled column about 60 cm. in length and 5.5 cm. in diameter prepared by packing it, under benzene, with 60 g. of Merck alumina per gram of crude crystalline product. Elution with 1 1 (by volume) methylene chloride (dichloromethane)-benzene mixture removes a red band a second band is eluted from the column by methanol. Evaporation of the solvent from each of these fractions affords the red crystalline isomers, t... 

Column preparation is the most difficult task within the IGC-experiment. In the case of packed columns, the preparation technique developed by Munk and coworkers is preferred, where the solid support is continuously soaked wifli a predetermined concentration of a polymer solution. In the case of capillary IGC, columns arc made by filling a small silica capillary with a predetermined concentration of a degassed polymer solution. The one end is then sealed and vacuum is applied to the other end. As the solvent evaporates, a thin layer of the polymer is laid down on the walls. With carefully prepared capillary surfaces, the right solvent in terms of volatility and wetting characteristics, and an acceptable viscosity in the solution, a very uniform polymer film can be formed, typically 3 to 10 xm thick. Column preparation is the most time-consuming part of an IGC-experiment. In the case of packed columns, two, three or even more columns must be prepared to test the reproducibility of the experimental results and to check any dependence on polymer loading and sometimes to filter out effects caused by the solid support. Next to that, various tests regarding solvent sample size and carrier gas flow rate have to be done to find out correct experimental conditions. 

---