Does anyone out there run NO for 18O and if so are there any pitfalls I should look out for? I can not seem to find anything recent on the interwebs. Should I convert the NO to something easier like N2O??? I would be analyzing pure gas on an Isoprime dual inlet. Cheers -- Aaron Shultis, Research Scientist Water Center School of Natural Resources University of Nebraska-Lincoln 103 Water Sciences Lab Lincoln, NE 68583-0844 U.S.A.