I've run out of ideas for solving the matter - please give me some idea! :cry:

I've got brand new Shimadzu GC2010 with BID detector and ShinCarbon column mounted. No valves.
Flow line looks like this:

Injector->0.53 capillary->Vici reducing union->ShinCarbon ST 100/120 (2m, 1mm ID)->Vici reducing union->0.53 capillary->BID

I try to run greenhouse gases analysis (CH4, CO2, N2O) on this but I can't get rid of some ghost peak on CH4 retention time (vial with helium 99,9999% purity purged for nearly an hour). BID still gives me signal on CH4 RT - it's always just where CH4 standard peak is, no matter what pressure and temperature I set so it's definitely CH4 in my opinion - but how this gets into the system in the first place?

Tried 120-300kPa pressures and 40-80deg.C temperatures with ramp to 150 to get rid of any water. Column was conditioned overnight at 250deg.C

I've got pretty same set on GCMS (same pressures and temperatures) and there is no CH4 ghost peak anywhere (same vials with pure helium). I also run about a 200 vials with air samples + calibration standards monthly on that GCMS so it works just fine. Checked also on older FID (PoraplotQ). Only BID gives that strange CH4 ghost peak.

I asked serviceman about this - he is 100% sure there are no leaks and this is some mysterious column matter or something I should just ignore. But the thing is, I can't - that ghost peak is about 1/3 height of my calibration peak so lower detection limit goes ridicoulously high because of..."column matter"? Always on same RT? Or maybe it's just a leak? But how can be anything sucked from air into the system with 300kPa pressure?

I tried different syringes and sampler injection, tightening everything, different pressures, temperatures, BID discharge gas flows - all failed. Last resort would be changing every o-ring and ferrule from injector to the column but maybe someone see other option?

Please help!