Hi,
We are currently using DMSO/MeOH as our dissolution solvent. 100mg samples in 500µl. We often have dissoluton issues and as DMSO is a pain to dry, we usually add more solvent until we get dissolution. We then inject onto std H2O/ACN gradients. Someone recently suggested the use of DCM/MeOH/H2O. Does anybody use this and in what concentrations.
I'm presuming that the DCM/MeOH is used to dissolve the sample and the H2O is used as a cap to prevent evaporation? How is the DCM received at the injection point as obviously it doesn't like water?

Your choice of solvent will depend a lot on your needed solubility, as you are currently attempting to make a 200 mg/ml sample prep. Do you really need to be that concentrated? I'm wondering why you are drying DMSO if injecting into aqueous system. UV absorbance/detection wavelength may be a factor also, so consider wavelength for alt. solvents - maybe DMF, THF are possibilties, but not at short nm. As far as the earlier suggestion, DCM/methanol/water will mix, just depends on the relative amounts. Same applies to injecting (even neat) DCM; will dissolve, but depends on mobile phase, and also how much you inject.

How much do you plan to inject? It you want to inject a small sample volume onto an analytical column, you may get away with injecting DCM/MeOH/H2O mixtures.