You can try Messer-Griesheim IR reference gasses. They have references at about -200 and -400 permil in 1 litre (200 bar) containers you can fit with a 3/8 Swagelock directly on your D.I. =46or further information, contact with: Miss Schmidt Messer Griesheim GmbH W=F6rthstrasse 170 D-47009 Duisburg- Germany I dont know if they have a 3W page, but they may offer me a free IR-tank for advertising!! Bests Pat > >I am currently studying D/H in atmospheric methane. I require a supplier o= f >a D/H isotopic reference gas with a value of circa -300 per mil (SMOW). >Can anyone help? __________________________________________________________ Patrick DAUBY Universite de Li=E8ge Laboratoire d'Oc=E9anologie Unit=E9 de Recherche en Biog=E9ochimie des Isotopes Stables (URBIS) B6 Sart Tilman B-4000 Li=E8ge, Belgium Phone: +32.4.3663322 - 3663307 =46ax: +32.4.3663325 Beep: 0454.700.671 (inside Benelux only) WWW: http://www.ulg.ac.be/oceanbio/urbis.htm __________________________________________________________