RP chromatography works sufficiently using gradient elution for resolution, but which detector you selected..

Glycerol does not adsorb UV, therefore you need a RI (refractive index) detector, which requires an isocratic elution (it is not possible to use two pomps or a system with valves and one pump >>> no stable baseline), thus use a premixed solvent as eluent.

Retention of glycerol will be low on a C18 column, I expect that diglycerol dicarbonate shall have a much higher retention. Eluent composition water/acetonitril range 100 to 95/5. Start with the latter one and decrease the ACN concentration if there is insufficient retention of glycerol.

Alternative is to use a Pb-carbohydrate column at 80°C. The eluent is than 100% water in combination with RI-detection. You can add UV-detection for selective detection of the diglycerol dicarbonate,

Hello Ioannis Papaioannou,

another method to analyze your two components diglycerol and diglycerol dicarbonate with GC or GC-MS would be derivative GC. Both components are very polar, so they cannot be chromatographed well with a semi-polar phase like DB5. Underivatized, a WAX phase would have to be used. To use a phase like DB5, both can be easily silylated with hexamethyldisilazane. However, a prerequisite for derivatization would be a hydroxyl-free sample; solvents such as methanol or other alcohols as well as water cannot be used.

I am currently analyzing butanediol, glycerol and hexanol in an aqueous reaction solution. My approach is to first dilute the solution 1:20 with acetone (acetonitrile would be an alternative) and then add 200µl hexamethyldisilazane/ml sample. The reaction proceeds completely at 70°C in 30 minutes. I then analyze with GC-MS on a factor four 5MS phase. I get well separated peaks, without tailing or fronting, see figure.

Good luck with your work and best regards

Joachim Horst