Hi Rich et al., Have you checked how your peak backgrounds are set? I'm only familiar with Isodat, but depending on your software and its peak background detection settings you might find the cause of your disparity. How much time do you have between your monitoring gas peak injections? The first injection might still be coming down (zoom in a lot on the spectrogram) when the second injection goes in....even a mV or two difference can influence the values. Hope this helps! Travis ________________________________ From: Stable Isotope Geochemistry [[log in to unmask]] on behalf of Dabundo, Richard C [[log in to unmask]] Sent: Thursday, January 26, 2017 5:40 AM To: [log in to unmask] Subject: [ISOGEOCHEM] Elemental Analyzer CO2 reference peaks Hello, I'm having an issue with CO2 reference peak deviation during an Elemental Analyzer N and C run. Two CO2 reference peaks are produced following the C sample peak. Originally, the first peak was consistently ~1.1‰ lighter than the second peak. After creating a new N2 to CO2 jump calibration, the first reference peak became consistently heavier than the second by about 0.6‰. We have sufficient distance between the sample and reference peaks, and the same issue results even if no samples are loaded. CO2 on-offs are fine, with a standard deviation of about 0.04‰. Does anyone know what may be causing our disparity? Thanks, Rich Dabundo This email may be confidential and subject to legal privilege, it may not reflect the views of the University of Canterbury, and it is not guaranteed to be virus free. If you are not an intended recipient, please notify the sender immediately and erase all copies of the message and any attachments. Please refer to http://www.canterbury.ac.nz/emaildisclaimer for more information.