Procedure for running a flash column

2 Procedure for running a flash column Safety note  

Silica dust is very toxic if inhaled, you should therefore take precautions to avoid breathing it in and always handle it in a fume cupboard. Large volumes of solvent are also used for chromatography and you should take precautions to avoid breathing in the vapours or exposing them to sparks. 

For some very non-polar compounds, even small quantities of dichloromethane may cause elution problems and an alternative method of loading can be used. Thus, a solution of the sample is added to a small amount of silica in a round bottom flask and the mixture is evaporated to dryness. The dry impregnated silica is then added to the top of the pre-packed column. 

A pressure of 7psi is recommended in Sfill s original p er, but we tend to rely on flow rate, rather than pressure. 

When all the compounds you are interested in have eluted, and you have identified in which fractions they are, combine the fractions as appropriate (keeping fractions that contain mixtures separate from those containing pure materials). Remove the solvent from the combined fractions on a rotary evaporator, and finally remove the last traces of solvent under high vacuum. 

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