Hello Andrew, equilibrating at 120 °C overnight in an evacuated stainless steel equilibration vessel with two waters (−268 ± 1 and +113 ± 1‰, respectively), I measured exchangeable H fractions varying between 0.18 and 0.24 for leaf litter samples from a climate transect across the Argentinean Pampas and Patagonia (page 62 in the below GCA paper). Temperature conditions, equilibration time and thorough drying, as pointed out already by Len, play a big role. E.g. time to reach equilibrium is longer for these kinds of samples compared to more defined matrices like cellulose. - Geochimica et Cosmochimica Acta 152 (2015) 54–71 - Environ. Sci. Technol. 2013, 47, 949−957 + supporting information (for more method details about the used equipment) Best regards, Marc Ruppenthal -----Ursprüngliche Nachricht----- Von: Stable Isotope Geochemistry <[log in to unmask]> Im Auftrag von Wolfram Meier-Augenstein (pals) Gesendet: Donnerstag, 20. Dezember 2018 10:05 An: [log in to unmask] Betreff: Re: [ISOGEOCHEM] help interpreting 2H exchange exp't Let's say the exchange fraction of 0.000475 would have been incorrectly determined (for whatever reasons). Let's also say the actual exchange fraction is 0.05 (as it is more or less for raw cotton; see RCM 2014, 28, 545-552). With a d2H(non-ex) of -177.8 the choice of equilibration waters would have yielded d2H(total) of -178.7 and -168.2 for water A (-196.1) and water B (+14.5) respectively. The difference between d2H(A) and d2(B) for equilibrated samples would thus be 10.5. -----Original Message----- From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On Behalf Of WASSENAAR, Leonard Irwin Sent: 20 December 2018 08:06 To: [log in to unmask] Subject: Re: [ISOGEOCHEM] help interpreting 2H exchange exp't Hi Andrew - the devil is always in the prep and analysis details. Something seems wrong to me with such a low exch-H fraction. What is the residual moisture content (gravimetrically)? How did you treat / dry the sample, etc. It's also possible - by a fluke - that the H isotope fractionations of the 2 waters you used landed you right on the identical value of the non-exch H. I would go far outside the natural range - i.e. very positive on one of the waters (like +500). Len -----Original Message----- From: Stable Isotope Geochemistry <[log in to unmask]> On Behalf Of A.J. Tanentzap Sent: Wednesday, 19 December 2018 20:35 To: [log in to unmask] Subject: [ISOGEOCHEM] help interpreting 2H exchange exp't Dear all I've run an exchange experiment on a solid organic as described in Meier-Augenstein et al. 2011. Rapid Commun Mass Spectrom. I estimated the non-exchangeable 2H ratio to be -178. The estimated fraction of exchangeable H in the sample was 0.0005. When I re-run the sample in a bulk analysis, the total (i.e. exchangeable + non-exchangeable) ratio was -190. Would someone be so kind as to explain how this is possible with a near-zero fraction of exchangeable H? Many thanks! Andrew This email message is intended only for the use of the named recipient. Information contained in this email message and its attachments may be privileged, confidential and protected from disclosure. If you are not the intended recipient, please do not read, copy, use or disclose this communication to others. Also please notify the sender by replying to this message and then delete it from your system. ---------- This email has been scanned for spam and viruses by Proofpoint Essentials. Visit the following link to report this email as spam: https://eu1.proofpointessentials.com/index01.php?mod_id=11&mod_option=logitem&mail_id=1545293198-undAjfiyMfJ1&r_address=w.meier-augenstein%40rgu.ac.uk&report=1 ________________________________ Robert Gordon University has been awarded a TEF Gold award for the quality of its undergraduate teaching and learning, placing it in the top 20% of Universities in the UK Robert Gordon University, a Scottish charity registered under charity number SC 013781. This e-mail and any attachment is for authorised use by the intended recipient(s) only. It may contain proprietary material, confidential information and/or be subject to legal privilege. It should not be copied, disclosed to, retained or used by, any other party. If you are not an intended recipient then please promptly delete this e-mail and any attachment and all copies and inform the sender. Please note that any views or opinions presented in this email are solely those of the author and do not necessarily represent those of Robert Gordon University. Thank you.