Dear Listmembers We are currently experiencing problems with our Finnigan Delta PlusXL. Since Monday the 45/44 ratio for the CO2 reference gas has changed from 1.157812 to 1.169340 and consequently all measured values are incorrect. The 45/44 ratio of an injected C19 n-alkane standard has remained constant over the same period of time. We have checked the reference gas inlet assembly and everything is working as it should. The 45/44 value measued on our DeltaS, for the same cylinder of gas has remained constant at 1.1500. If anybody else has experienced this problem and can shed any light on it we would be most grateful. Regards Ian ------------------------------------- Dr Ian D Bull School of Chemistry University of Bristol Cantock's Close Bristol BS8 1TS UK Tel. +44-(0)117-9289934 Fax. +44-(0)117-9251295 Email: [log in to unmask] "Laugh and the world laughs with you. Cry and the world laughs louder." -------------------------------------