Preparative Chromatography - Packing Preparative Columns > Page 30
Product recovery when using normal phase solvents is best carried out by bulking the fractions and removing the solvent in a rotary evaporator under reduced pressure. For reverse phase solvents that have a high water content, recovery can be best achieved by passing the fraction through a reverse phase, C18, column of high capacity. The solute and solvent is adsorbed, and the solute and solvent content of the fraction can be recovered by displacement with another solvent, and the solute, now concentrated is recovered by evaporation.
Unless solvent recycling can be employed, which is not always possible, the operation of large diameter columns inevitably involves the use of large quantities of solvent. It follows, that there may be a possibility of both fire and toxicity hazards. As a consequence, the solvent should be selected with care and if possible the entire chromatograph, including the solvent supply, electrically grounded, and the apparatus including fraction reservoirs should be located in a walk-in fume hood.
Packing Preparative Columns
A number of packing techniques are available to the chromatographer that can be used to prepare preparative columns. The best and most appropriate method for any particular column system will depend partly on the particle size of the packing, partly the scale of the separation and partly on the nature of the material to be separated. Contrary to popular belief, there is no magic involved in packing a column, but some experimental skill is required together with a considerable amount of patience, in addition some experience also helps.