Changing nitrogen gas supply for collision cell

Question

Hello, 
 I'm about to replace the nitrogen tank that feeds the collision cell on our 6545 QTOF. I just have a simple question, can I change the nitrogen tank while the MS is in stand-by mode or does it need to be vented ? 
 This brings me to a second question : What is the use of nitrogen for CC if no MS/MS analysis is performed ? 
 Have a nice day

philebel · Answer

HI Catechol 
 The nitrogen cylinder 99.999% purity can be change while the system is on standbye without the need to vent. 
 If you look at your vacuum for the Quad vac when the collision cell gas is turn off, it will become too good (E-6 Torr) which can impact your transmission of ions (compare to past results and give you different results). We also use (as you know) the nitrogen in the collision cell to perform MSMS analysis on your compounds of interest. 
 I would recommend you keep using high purity nitrogen for the collision cell and if you want to remove the replacement of cylinder in the future, some nitrogen generator companies have an add-on to your nitrogen generator that can supply sufficient flow for the collision cell at 99.999%. We usually see this with IM-QTOF as the flow for the drift tube is higher, but this would be more expensive than replacing the cylinder every 9months-12months. 
 I hope this helps.