Adsorption column, formation

Particle Size and Shape. The polymerization process for producing macroporous synthetic polymers (539) leads to the formation of spherical particles whose size can be controlled within certain limits. The popular XAD polymers are usually sold with approximately 90 of the total weight encompassing smooth beads with 20-50-mesh sizes. Most users incorporate a suspension step to remove the fines in their purification of the polymer, but they do not remove the small number of particles larger than 20 mesh. The particle size and distribution vary with different polymer batches, and it is advisable to mechanically sieve polymer beads and choose only those within the 20-50-mesh size for preparation of the adsorption columns. 

Adsorption column preparation and loading. In order to obtain satisfactory results, the tube must be uniformly packed with the adsorbent uneven distribution may lead to the formation of cracks and channels and to considerable distortion of adsorption band shapes. If there is any doubt concerning the uniformity of particle size of the adsorbent powder it should be sifted before use to remove the larger particles fines are removed from the adsorbent using a sedimentation procedure immediately prior to column packing. In this the alumina or silica gel adsorbent is stirred into between five to ten times its volume of the selected solvent or solvent system, allowed to settle for five minutes and the supernatant liquor decanted off the procedure is repeated until the supernatant liquid is clear. 

They varied only the values of the adsorption and desorption rate constants of the reaction intermediate B, and by using the simplest Langmuir kinetics, they calculated time-concentration curves of compounds A, B, and C shown in Fig. 5. Also from this example, which does not consider any step as clearly rate determining, it is evident how very different concentration versus time plots can be obtained for the same sequence of surface reactions if adsorption and desorption of the intermediate B proceed by different rates, which are, however, comparable with the rate of surface reactions. In particular, the curves in the first and second columns of Fig. 5 simulate the parallel formation of substances B and C, at least... 

Membranes offer a format for interaction of an analyte with a stationary phase alternative to the familiar column. For certain kinds of separations, particularly preparative separations involving strong adsorption, the membrane format is extremely useful. A 5 x 4 mm hollow-fiber membrane layered with the protein bovine serum albumin was used for the chiral separation of the amino acid tryptophan, with a separation factor of up to 6.6.62 Diethey-laminoethyl-derivatized membrane disks were used for high-speed ion exchange separations of oligonucleotides.63 Sulfonated membranes were used for peptide separations, and reversed-phase separations of peptides, steroids, and aromatic hydrocarbons were accomplished on C18-derivatized membranes. 

Dasler, W. et al., Ind. Eng. Chem. (Anal. Ed.), 1946,18, 52 Like other monofunctional ethers but more so because of the four susceptible hydrogen atoms, dioxane exposed to air is susceptible to autoxidation with formation of peroxides which may be hazardous if distillation (causing concentration) is attempted. Because it is water-miscible, treatment by shaking with aqueous reducants (iron(II) sulfate, sodium sulfide, etc.) is impracticable. Peroxides may be removed, however, under anhydrous conditions by passing dioxane (or any other ether) down a column of activated alumina. The peroxides (and any water) are removed by adsorption onto the alumina, which must then be washed with methanol or water to remove them before the column material is discarded [1], The heat of decomposition of dioxane has been determined (130-200°C) as 0.165 kJ/g. 

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