Hi Simon, Mr. Robert Dekner Analytical Quality Control Services Laboratories Seibersdorf IAEA PO Box 100 A-1400 Vienna Austria tel: +43-1-2060-28226 fax: +43-1-20607-28222 eml: [log in to unmask] has these standards (among others) which might be of interest.. 302a 2H water 508.4 per mil VSMOW 302b 2H water 996.0 per mil vs VSMOW 304a 18O water 251.7 per mil vs VSMOW 304b 18O water 502.5 per mil vs VSMOW See Europa Scientific Webpage: (Suppliers of Certified Reference Materials) for a complete listing! Cheers, Neil S. Summer Stable Isotope Laboratory Department of Geology 1112 Turlington Hall, University of Florida, PO Box 117340 Gainesville, FL 32611-7340 email: [log in to unmask] Phone: (352) 392-2296/31 FAX: (352) 392-9294