Talking About the Experience of “Passing the Flash Column”
For those who learn organic, “passing the flash column” is almost a basic skill that no one knows. You can understand that different substances run at different speeds in the same medium, so they run for a long time. Then there will be one, two, or three, we can separate them according to the order of filtering out, and get our products from them.
The flash column is a very critical thing in the organic laboratory. In many cases, the whole reaction is meaningful only after the flash column is passed and the pure product is obtained. At the same time, it is very time-consuming and energy-consuming work to pass a column: a flash column generally takes several hours or more. For example, up to several hundred milligrams of product, it takes at least one morning to complete a column; if it is a more complicated separation of natural extracts, then a flash column will often happen in a few days.
Even though it takes so long, it doesn’t mean you can leave the pillars there and do other things by yourself-the pillars must be kept staring at. You need to check the board at intervals to see what is coming out of the column: sometimes there is a difference of four or five drops between the first component and the next component. If you miss it, it may be all in vain. This is especially true for laboratories that don’t have many test tubes and are accustomed to using flasks or conical flasks to connect products.
If the flash column is dry, there may be a lot of bubbles in the silica gel, which makes it difficult to separate the product. For some subjects that require high yields, the result of doing a flash column may be that the yield is directly dropped by ten points or halved. Such a blow is very fatal, and in many cases, it may be reworked from scratch.
Although it is possible to use high-polarity solvents to soak out the residual products in the silica gel, the loss is not small. Sometimes it takes a few steps to get a few hundred milligrams of product. If the flash column dries out accidentally when passing the column, and then the soaking doesn’t make much of it, it may be another week if you have to rework from scratch. Even a month has passed.
But dry columns are a problem mainly for methodology and synthesis laboratories. If you just get the product, you don’t need to over-entangle the yield reaction, such as making small molecule functional materials. The yield is not the primary factor to consider. You only need to get something that is enough to test its performance.
After the flash column is passed, it is not the end, and the crude product in the test tube must be rotated or recrystallized to obtain a pure product. If the steamed product is no longer visible, you need to start again.
Flash column chromatography technology is an indispensable separation method in organic chemistry laboratories, but generally, flash column chromatography is very laborious, and Flash Chromatography flash column is fast and simple and has considerable separation effects. It has been used in more and more laboratories at home and abroad. used. Nevertheless, for beginners or laboratories that have not purchased an automatic flash column machine, manual flash column is still necessary.