Can I use gases other than air and CO2 in the macroIMS system?
At the electrospray source, it is recommended that you use air and CO2 gas rather than nitrogen or any noble gas (helium, neon, argon, krypton, xenon) to avoid corona discharge at the nanospray tip. The gas used in the macroIMS system is chosen to have a significant electron affinity to minimize on HV breakdown. Air has oxygen, which helps a lot, but usually isn’t quite enough to keep the corona threshold safely above the field needed for electrospray. Thus CO2 is added to push the HV breakdown threshold up a little and give the margin needed for stable operation. Alternatively, it is possible that one could use nitrogen and increase the CO2 flow but no experiments have been done to find it out. One known substitute for CO2 in this application is sulfur hexafluoride which is actually better than CO2 but much more expensive than CO2.
