Does anyone know how to replace existing solvents completely in a HPLC pump with a different solvent? Specifically, I need to prepare a pump that has been using normal HPLC solvents to be used with completely deuterated solvents and minimize any residual protonated (or should I say hydrogenated) solvents. I tried flushing with the new solvent, but it takes a lot of deuterated solvent to get reasonable results. I also tried to dry out the pump head and connection lines with N2 gas overnight then refill with the deuterated solvent. This still consumes a significant amount of deuterated solvent because now we have to get the gas out of the system. Anyone has a better idea to do this? Any suggestions will be highly appreciated. Thank you in advance.

How about blowing the pump dry the way you described, then putting a bubble trap in the inlet line and recycling your deuterated solvent back into the inlet? With care, you should be able to get by with only about 5 mL or so more than the pump volume (the bubble trap probably holds a couple of mL all by itself)

Or is 5mL a lot when you're using deuterated solvents?