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Topic: Can dry loading be used on reverse phase silica?  (Read 3511 times)

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Offline Babcock_Hall

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Can dry loading be used on reverse phase silica?
« on: February 28, 2024, 09:23:48 AM »
Dry loading has become our preferred technique for normal phase chromatography.  This week we had a C18-coated silica column to run using methanol/water.  Could this have been dry loaded?  I imagine that the ratio of coated silica to crude product will be higher: I recall a suggestion to have a greater ratio of coated silica to product than would be done in normal phase.

Offline Guitarmaniac86

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Re: Can dry loading be used on reverse phase silica?
« Reply #1 on: February 28, 2024, 04:08:37 PM »
I've dry loaded on RP silica, it can be done.
Don't believe atoms, they make up everything!

Offline rolnor

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Re: Can dry loading be used on reverse phase silica?
« Reply #2 on: February 29, 2024, 02:33:22 AM »

I preferre wet-loading, if your sample does not dissolve in the eluent you should change it, for example use toluene instead of hexane. I think generally you get a more narrow band of the sample if you use wet-load and thus better separation. I have never tried dry-loading a RP column.

Offline kriggy

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Re: Can dry loading be used on reverse phase silica?
« Reply #3 on: March 01, 2024, 06:40:10 AM »
Im assuming we are talking about some kind of preparative flash system ?
Is it because of poor solubility of your mixture ? Have you tried loading in DMSO or DMF? I load all my RP purifications in DMSO with the method being isocratic in high aq. for first 3-5 minutes to wash away the DMSO

Offline Babcock_Hall

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Re: Can dry loading be used on reverse phase silica?
« Reply #4 on: March 01, 2024, 07:43:15 AM »
My department is getting a preparative flash system soon; we just packed a column with C18-coated silica beads.  My student may have used more solvent than was needed, but I am not sure.
« Last Edit: March 01, 2024, 07:55:26 AM by Babcock_Hall »

Offline rolnor

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Re: Can dry loading be used on reverse phase silica?
« Reply #5 on: March 03, 2024, 02:21:17 AM »
Im assuming we are talking about some kind of preparative flash system ?
Is it because of poor solubility of your mixture ? Have you tried loading in DMSO or DMF? I load all my RP purifications in DMSO with the method being isocratic in high aq. for first 3-5 minutes to wash away the DMSO

This method can make everything go with the front, so use as little DMSO or DMF as possible is my tip.

Offline kriggy

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Re: Can dry loading be used on reverse phase silica?
« Reply #6 on: March 05, 2024, 04:00:45 AM »
Yes that is a good point. I never had issues with that but its good idea to dilute in as small volume as possible and then add some water. I think I used 3 ml DMSO for 40 ml/min flow with no issues. On small columns it can be more significant issue. There should be guidlines in the operating manual of the instrument

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