CHEM 2312H Lecture Notes - Lecture 1: Aston Martin Db5, Elution, Column Chromatography
Document Summary
Can look at how to do lab techniques on youtube. Rf = 0. 25 spot really lightly if 2 component mixture, then get multiple spots in a verticle line. Column volume of solvent (how much solvent corresponds to 1 column) Silica gel particles packed randomly and also take up space. Many open spots and pores in the sio2 ~50% volume of silica bed occupied by the other 50% is open/void volume. 1/rf =~ # column volumes it will take to elute the sample. For tlc, if use aggressively polar solvent (pure ethyl acetate), compounds will run too close to solvent front. Or if use very nonpolar solvent (hexanes)won"t elute at all --> rf = 0 --> it will take forever in flash chromatography. Collect fractions (collect from flash column in test tube) of 5-10 ml. If rf >= 0. 3 0. 2 0. 1, then ratio can be 10, 20, and 30 respectively. Density of silica gel = 0. 5 g/ml (dry weightincludes porosity)
