Let’s be honest: you hate or you love column chromatography. You cannot be indifferent to it.
Most of the chemists I know hate chromatography, and it’s one of the ten top reasons of blasphemy in the lab. Well, I’m one of the few lover (mostly because I don’t do 3 columns a day 7 days a week…). Usually when I’m in working mode on (different from writing/revising/correcting mode on) I’m rushing from one place to another (fume hood, glovebox, hplc, nmr and so on) without a break. The column is my relax moment.
First of all you should choose the size of the column, and like all the phallic glassware in the lab, also the column is affected by what we chemists call the column envy. It’s not too difficult hear something like “I did a column with 5kg of silica” – “I did one of 25cm diameter” – “once I used a whole water pipe because all the columns in the lab were too small for me” – “in my column super fucking Mario himself was pushing the solvent down”. Do not listen to them. Choose the right size, choose the one that fit you needs.
The cotton float to the bottom like a feather. A cascade of silica gel. Gently packing. The solvent that slowly soak down. Ahhh what a beautiful experience…. and the best still have to come.
In the precise moment you load your crude you know that you are going to spend some hours working on it (if you are lucky). After the loading, it’s usually good praxis that you light a candle to your favorite God(s) and say some prayers for the success of the separation. Some people use to sacrifice one or two cylinders to the God(s) for good auspice. I also heard about blood pacts for separating products with Rf difference of 0.01, but this is black column chromatography (sometimes called voodoo chromatography) and I will not talk about this here.
“the column chromatography is not purifying only your product but it is purifying your soul”
ancient tibetan saying
Now that the crude is loaded and all your wishes done, you can start your column. Remember “flash” chromatography doesn’t mean you should take a picture of every single drops. No, you shouldn’t be dressed like flash for doing it, and no, you should’t listen flash from the Queen all day long. Not counting how many people didn’t do the flash chromatography just because they had IOS (this is nerdy). Flash doesn’t mean that you should go for 100bar and use the column as hydrant. No doesn’t work like this. You should use the pressure only for getting a nice flow. And this is another reason why I love chromatography.
What does it mean having a good flow? Everything in life flows and it’s up to you follow the flow, or even better, surfing it. Now adjust the pressure until the dropping flow is hypnotizing you. Drop after drop after drop after drop after drop after drop. Your brain starts to float. Follow with your eyes the drop coming down. Now you are more relaxed. Every single drop is another worry gone away from your mind into the deep test tube sea. This can be dangerous. I’ve seen so many good guys transformed into zombies hypnotized by the wrong flow. “hey buddy, shall we go for lunch” – ” hhhhmmm chhhroooomaatoooograaaaaphhyyyyy” – “ok, never mind, I’ll go alone”. You can also spot a chromatography zombified guy when he is not changing the test tubes anymore: “hey buddy, you should change the test tube, it’s full” – “hmmmm chhhroooomaatoooograaaaaphhyyyyy i’m cooooolllleeeectiiiiinngg on theeee benchhhhhhhh”, do not try to distract them when they are in this state, just say something like “fair enough” and slowly walk away. Remember: The flow is everything, do not mess up with it!
Naturally you still need to see how the separation is going and check the column periodically. We use a special kind of tarots (also called TLC, Tarots for Liquid Chromatography). This magic oracle paper, after being immersed into the holy solvent for some minutes, will tell you if you achieved the all-desired purification. Here is the blasphemy moment. Some times happen that for unknown reasons the God(s) didn’t reward you with a perfect separation, and most of your test tubes are full of mixed products. When this happen just stay calm, relax, take a deep breath and swear loudly without any problem. Anyone else in the lab will understand your point. Collect everything and you will try tomorrow again, maybe this time sacrificing two cylinder and one round bottom flask.
May the God(s) of the chromatography watch over your column.