Question for those using a GCMS with an extractor source (Xtr EI 350, 5977B). Our relative abundance for 502 ion has always been lower using the Etune compared to the Atune. We have been using the Tune Evaluation as a criteria check for our instrument to pass and this number sometimes falls below the 2.4%. I recently learned that the Tune Evaluation only applies to the Atune. I also see that the 502 rel abund is somewhat arbitrary because when the 69/219 abundances vary the 502 relative changes a lot, even though the absolute abundance does not, which makes sense. But I’m wondering what guidelines other labs use to say the instrument passes and is operating properly, since we are in the legal field we need a checkoff like a tune evaluation. Is the 502 always lower with extractor sources using Etune? Is there any parameter to change to boost this up? Agilent, do you have any documentation or recommendation for us to use as passing specs for Etune or something written to say rel abun of 502 is not an important gauge of instrument condition?