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October 31, 2004
Well, Sonny, That's Not How We Did It
I don't even want to try to estimate how many chromatography columns I've run over the years. I remember some of my first ones, from the early 1980s, an era that is beginning to sound alarmingly distant. I ran them at a fierce rate for the rest of that decade and most of the 1990s, only tapering off in the last few years.
For those outside the field, organic chemists spend a lot of time purifying compounds by running them through silica gel, which is similar to very pure, very finely ground sand. Usually that's done by dissolving the impure mixture in some solvent and pumping it through a column of the stuff. In the old days (up until the late 1970s/early 1980s) this was often done just by gravity, but then the fashion came in for "flash" chromatography, where you force the solvent through by air pressure. Younger chemists who've never done any other kind don't appreciate the flashy aspects of that method, since they've never sat around all day while a gravity column drips - it's like waiting for a stalactite to form.
The most refined form of column chromatography is HPLC, high pressure liquid chromatography, which uses metal columns, highly refined silica (and other solid supports), and special pumps to ram mixtures through at hundreds or thousands of pounds/sq. inch. But HPLC machines aren't cheap, and neither are the consumables, and they can be finicky to operate, no matter what the sales rep says.
Recent years have seen the advent of various pre-packed flash columns for benchtop use. Back in graduate school, those would have been the equivalent of having your compounds purified by dancing girls while the chef whipped up some appetizers - even if these things had been available, there's no way we would have been allowed to order such degenerate labware. So I went through my peak column-running years doing it the old-fashioned way, and now that I only do one once in a while, there are all these premade gizmos just sitting around. 'Twas ever thus.
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