Increasing recovery in washing and lyophilizing - (Aug/15/2014 )

I’m looking for some general lab technique tips on recovering the most possible mass from my fractions collected by preparative HPLC.

The solvent I’m collecting from the HPLC is ~95:5 ethanol:water. The sample has fairly low solubility in ethanol and very low solubility in water.

I pool the collected solution in several 16x100mm glass tubes, then dry away most/all of the solvent under nitrogen blow, vortexing occasionally to help concentrate the compound at the bottom and not on the walls. Next I wash with ~10mL ice cold water, centrifuge for 10 mins, and remove supernatant.Considering the solubility of this compound and the color of the supernatant, I believe very little mass is lost here.

I then add ~5ml water, vortex and sonicate until everything is dissolved, then combine all the collected fractions into 40mL glass vials (filling each about halfway), then freeze and lyophilize.

The final step is painstakingly scraping the compound from each vial into a small container for massing and storage. Most of the compound seems to get stuck in a very fine powder all around the bottom of the vial and is very difficult to collect. I end up redissolving in ethanol to be added to the next run.

Just looking for any tips to improve this process. I’m sure there are obvious improvements I am overlooking.

Thanks!

Is there a good solvent? Ideally one that is dissolves poorly in water (chloroform, 1-butanol, 1-octanol?) If so, then you can layer the solvent on top, vortex, and recover the top layer. Then concentrate and recover.