Silicone SPE cartridges become transparent? Is there precipitation?Anpel take you into the truth.

Question 1: The silicone becomes transparent?

First, repeat the experiment process, randomly select 5 small silica gel columns, then add 5mL of dichloromethane, open the flow control valve, so that the dichloromethane infiltrate the silica gel packing, observe the experimental phenomenon. Sure enough, the silica gel really became transparent. Mark the scale on the upper layer of the silica gel with a marker, and then use the glass rod to press down the sieve plate. It can't be pressed. After removing methylene chloride, the transparency disappeared and the silica gel returned to its original white color.

In order to verify the accuracy of this theory, organic reagents such as dichloromethane, chloroform, benzene, toluene, n-hexane, ethyl acetate, methanol, and acetone, which are commonly used in silica gel columns, were selected for verification. Add 5mL of the corresponding organic reagent to the silica gel column to allow it to infiltrate the silica gel packing. After the solvent flows naturally, squeeze the solvent out of the small column and observe the change of the silica gel packing during the entire experiment. Silica gel columns of chloroform, benzene, toluene, and n-hexane really have transparency, but silica gel columns added with ethyl acetate, methanol, and acetone are not obvious. It turns out that solvents with a refractive index close to silica gel can indeed appear transparent.


Question 2: The problem of small column precipitation
Regarding the problem of white unidentified matter at the entrance of the small silica gel column, when the editor deliberately studied, I always couldn't meet it. Finally, in a rainy and rainy weather, I caught the entire crystal formation and disappearance. process.

The reason is that the boiling point of dichloromethane is 40 ℃, and it can volatilize rapidly at normal temperature. When dichloromethane flows out of the outlet of the small silica gel column, the contact area suddenly becomes larger, and the dichloromethane at the outlet of the small column evaporates and takes away a lot of heat. (At this time, touching the small column with your hands will feel ice cold), causing the water vapor in the environment near the column to condense into ice and adhere to the column. Because the rate of volatilization is affected by many factors such as the contact area and the speed of air flow above the liquid surface, the degree of condensation at each column is different.
Interested friends can also experiment. Tips: If you want to see the formation of beautiful crystals, please conduct the experiment in rainy weather or high humidity conditions. The crystal formation is not visible in hot and dry environments.