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Aloha Erika I agree with all Robert's points made in regards to H3+. The term “H3+ correction” describes the algorithm applied to measured d2H data to correct for the contribution of H3+ species formed by ion/molecule reactions in the ion source at increasing gas pressures. (FIRMS 2011) I would however check the position of the “newly” installed filament. It appears you have voltage leakage which is resulting in the large difference between your box and trap. Check that the two “posts” on the filament are equally spaced from any support structure on the source assembly (i.e. the springs). Cheers Bill William Hiscock, Ph.D. Technical Service Engineer Thermo Fisher Scientific Mobile: +61 (0)4 6600 4540 eMail: [log in to unmask] Australian Customer Support 5 Caribbean Drive | (P.O. Box 9092) | Scoresby VIC 3179 Phone:1300 736 767 eMail: [log in to unmask] Web: www.thermofisher.com.au On Oct 22, 2014, at 5:00, Freimuth, Erika (freimuej) <[log in to unmask]> wrote: > Dear Isogeochem, > > I wonder if others have experienced low H3 factors on a Delta V. The H3 factor on this instrument used to range from 5-7, but is now around 3. The filament was recently changed, and the box/trap is 0.91/0.59. The reactor was just replaced and conditioned and backgrounds don’t suggest a leak. We see good reproducibility between runs with the alkane standard Mix A5, but the difference between expected and measured values ranges over ~40 permil. > > If others have insight into the cause of a low H3 factor, any help would be much appreciated. > > Thank you, > Erika > > ____________________ > Erika Freimuth > Graduate Assistant > Department of Geology > University of Cincinnati