difficulty with BFB check 624 method

[chemdude314159]

Long-time lurker, first-time poster.

We’re running the 624 method on a 5977B GC/MS P&T system and are experiencing issues with achieving passing BFBs, particularly with ions 174 (which is high) and 175 (which is low or non-existent). We are running a BFB.U or BFB_autotune.U tune when operating. As far as tune alterations go, we’ve tried adjusting the peak width during tuning (reducing to 0.45 or 0.5), lowering the scan speed (1.562 to 781 yielding a 2.7 frequency), and adjusting the gain factor, and tuning to ions 69,131, and 219 but we’re still not getting consistent BFB evaluations.

As far as instrument maintenance goes, we’ve cleaned the source, had the quads MeOH cleaned by an Agilent tech, replaced the column and inlet consumables, cleaned the split vent, and replaced the split vent filter, but again nothing has worked so far. We haven't yet filled the PFTBA vial, but just ordered some and will refill the reservoir when it arrives next week. I’ve looked for other posts addressing similar issues but haven’t found much. I’m wondering if anyone has suggestions to help resolve this problem.
TIA

[70 eV]

Have you tried doing a tune restore to a last known good tune and tuning off that file? I usually go off Mark Ferry's manual tune guide, could try going wider to like 0.55 to see if you pick up 175

https://www.spex.com/KnowledgeBase/Optimize

[chemdude314159]

We've redownloaded the original tunes supplied with the system but we're still seeing the same issues. I'll try increasing the PW to see if we can pick up 175. Thank you!