We have a new Agilent 7010 GC/QQQ with a purged ultimate union that we’d like to use for back-flushing and quick column swaps without venting, but I’m not getting good guidance from Agilent on the correct length/size of restrictor to use between the PUU and the MSD. What I’ve found online has been all over the place. Do those with a similar setup have recommendations on what they’ve tried, or what works/doesn’t work? Any help would be great. Current analytical column is 0.25um with a flow around 1.2ml/min.