Dave, there's another publication dealing with the measurement of d18O-values in organic substances from J. Koziet: J. Mass Spectrom. 32 (1997), pp 103-108. He is working with a glassy carbon pyrolysis tube at a relatively high temperature (1200°C, if I remember correctly) and so he has to protect this tube from contact with air. This means that his system is a little bit more complicated to build up, but might offer a higher variability as compared to our system (Werner et al., 1996), which is quite easy to construct. It works perfectly well for most organic substances. If you have any more questions or if you find some unexpected problems you can also contact me directly via e-mail: [log in to unmask] (I'm no subscriber to the Isogeochem, but can use the mailbox of my collegue M. Gehre for this purpose) Best regards Barbara Kornexl Barbara Kornexl UFZ Umweltforschungszentrum Leipzig-Halle GmbH Permoserstr. 15 D-04318 Leipzig Tel.: 0049/341/235-2252