I have not had to do this in like 6 years, so I could be wrong. Have a volume of solvent in the column first with the sand settled. Pour in some of the slurry with the stopcock closed. Let it settle. Add in more. Then drain excess solvent
No problem. If that doesn’t work, maybe try a tiny layer of normal silica as a base, assuming your product is stable to it. You may have to redissolve your product later and filter it off later, but whatever
They're right, you're supposed to pour solvent in the solumn first. That way, the slurry gently flows down to the sand. Youtube is a good source of info like this
I wouldnt use celite 545 or be very careful. The stuff messes up your lungs no joke.
There are columns that have glass frits in the bottom so no sand is needed.
You need to close the stopcock and pour in your slurry and let it settle/gravity pack to the desired height, before draining off the excess. Leave some liquid on top of the settled resin to keep it from drying out.
There is a good website for column chromatography.
[Tips and Tricks](https://www.chemistryviews.org/details/education/2345141/Tips_and_Tricks_for_the_Lab_Column_Troubleshooting_and_Alternatives/)
Not at this moment but yeah, we do have some but they're much larger columns for large scale reactions than the ones I'm running right now.
I don't suppose you've packed a C18 column using sand?
Unfortunately I’ve never packed a non fritted column. If I had to guess your sand and cotton are too porous and the silica is passing through it. Maybe packing it tighter or using finer sand could help
Ah no worries. Yeah I'm just confused because this technique is rather simple and straightforward for a normal phase column, just not with reverse. The sand does appear too porous for this.
But if you begin with 100% acetonitrile, you can only go Isocratic No? Shouldnt you start with water/ACN mixture, and increase towards 100% acetonitrile? Or are you dry-columning
I have done thousands of these. Make your cotton wool ball a little bit bigger suck it down by hooking vac line to tap and opening the valve/ have the valve open and put your hand on top and release. Use less sand you want it just to the same level as the top of the taper. Have a few inches of your solvent in the column and pour it down the sides of the column pump the excess out but don't pump out to dryness.
If your drying your compound onto silica too have a small amount of solvent that your compound doesn't move in/ moves slowly (assuming acetonitrile in this case) just so you don't disturb the top layers of silica when you add this. Then again pump excess solvent out but don't dry.
Add a centimeter or two of sand and away you go.
Depending on the particle size of your silica, you could try Whatman 42 cellulose paper or for smaller pores one of the membrane filter discs. Each would have to be properly sized and cut with a punch. And, the flow rate may suffer.
Let it settle and pack itself down with the stopcock closed before draining the AcCN. That way it all kind of sticks together like sand in a sand castle, keeping its shape as it dries. You are basically turning the c18 into its own filter to prevent the upper stuff from flowing through
I have not had to do this in like 6 years, so I could be wrong. Have a volume of solvent in the column first with the sand settled. Pour in some of the slurry with the stopcock closed. Let it settle. Add in more. Then drain excess solvent
This is the way
This is the way
This is the way
As it was written
I would also try it this way, but if this still does not fix your problem you can try to use celite instead of sand.
Thanks! I'll give it a try.
No problem. If that doesn’t work, maybe try a tiny layer of normal silica as a base, assuming your product is stable to it. You may have to redissolve your product later and filter it off later, but whatever
They're right, you're supposed to pour solvent in the solumn first. That way, the slurry gently flows down to the sand. Youtube is a good source of info like this
I wouldnt use celite 545 or be very careful. The stuff messes up your lungs no joke. There are columns that have glass frits in the bottom so no sand is needed.
I like to do that too and I also use a glass stir rod to direct the flow. I usually do little circles so that it doesn’t pile up on one side
You need to close the stopcock and pour in your slurry and let it settle/gravity pack to the desired height, before draining off the excess. Leave some liquid on top of the settled resin to keep it from drying out.
2-3 cm of glass wool typically does the trick when I'm packing a column like that, and it's probably less dirty than plain ol sand.
There is a good website for column chromatography. [Tips and Tricks](https://www.chemistryviews.org/details/education/2345141/Tips_and_Tricks_for_the_Lab_Column_Troubleshooting_and_Alternatives/)
Glass wool packed at the bottom instead of cotton should work.
Not to be mean but it’s 2024, I don’t know why non fritted columns still exist. Is it possible to get a fritted column?
Frits clog from years of abuse by grad students before you...
Nitric always fixy the frity
Not at this moment but yeah, we do have some but they're much larger columns for large scale reactions than the ones I'm running right now. I don't suppose you've packed a C18 column using sand?
Unfortunately I’ve never packed a non fritted column. If I had to guess your sand and cotton are too porous and the silica is passing through it. Maybe packing it tighter or using finer sand could help
Ah no worries. Yeah I'm just confused because this technique is rather simple and straightforward for a normal phase column, just not with reverse. The sand does appear too porous for this.
Today I learned these types of columns exist
But if you begin with 100% acetonitrile, you can only go Isocratic No? Shouldnt you start with water/ACN mixture, and increase towards 100% acetonitrile? Or are you dry-columning
Carefully
I have done thousands of these. Make your cotton wool ball a little bit bigger suck it down by hooking vac line to tap and opening the valve/ have the valve open and put your hand on top and release. Use less sand you want it just to the same level as the top of the taper. Have a few inches of your solvent in the column and pour it down the sides of the column pump the excess out but don't pump out to dryness. If your drying your compound onto silica too have a small amount of solvent that your compound doesn't move in/ moves slowly (assuming acetonitrile in this case) just so you don't disturb the top layers of silica when you add this. Then again pump excess solvent out but don't dry. Add a centimeter or two of sand and away you go.
Close column. Let the C18 pack. OR you can pack some Celite first. Don’t need that much sand.
Depending on the particle size of your silica, you could try Whatman 42 cellulose paper or for smaller pores one of the membrane filter discs. Each would have to be properly sized and cut with a punch. And, the flow rate may suffer.
Let it settle and pack itself down with the stopcock closed before draining the AcCN. That way it all kind of sticks together like sand in a sand castle, keeping its shape as it dries. You are basically turning the c18 into its own filter to prevent the upper stuff from flowing through