Hi Sheila,

Glycerol ethoxylate is a cryoprotectant and can be commercially purchased from molecular dimensions as a stock solution of 50 or 100%.

Since you have it in your mother liquor you can test for cryo suitability by fishing the crystals and subject it under the cryostream to check for ice build-up with time - with this you can increase the Glycerol ethoxylate percentage (> 30%) or just make up a cryo-solution (cryoprotectant) by supplementing the the mother liquor with 25-30 % glycerol or ethylene glycol before fishing and cooling.

https://www.moleculardimensions.com/products/c436-Cryoprotectant-Reagents/

All the best!

It seems like your well solution can act as a good cryoprotectant, take 2 ul of the well solution and drop into the liquid nitrogen. If the droplet can survive for 5-6 sec, then go with it. Usually, poor cryoprotectant vanished within 2 sec.

Here is a simple way to find out whether the crystallisation condition is a good cryoprotectant: use a crystal harvesting loop to take such solution, snap freeze it in liquid nitrogen, and then check it on a X-ray diffractometer. If you don't see ice rings on the diffraction image, it means the solution can serve as a good cryoprotectant. Well, in case you don't have easy access to a diffractometer, you may use another simpler but less reliable trick - use a large loop (0.5-2mm) to take a bit of your crystallisation solution, dip the loop quickly into liquid nitrogen, then take the loop slightly out of nitrogen, which is to both keep the drop frozen and make it easy to observe, and finally check whether the frozen drop in the loop is clear or milky - milky meaning there is ice formed during the freezing process and the solution is thus not a good cryoprotectant.