we switched from Air Products to BOC a while ago, basically because of lower gas bottle rental charges here in the UK. At the moment we are using CP grade nitrogen (L-size), which was around £170/bottle from BOC. We basically followed Isoprime and Thermo installation requirements for the gas purity. Our nitrogen reference gas is used in an Isoprime100 and a VisION IRMS as well as in a Thermo Delta V.
But I am also curious to know if some people use a lower purity without problems.
Stable Isotope Ratio Mass Spectrometry Laboratory
Ocean and Earth Science
National Oceanography Centre
University of Southampton
Southampton, SO14 3ZH
Phone: +44 (0) 23 8059 - 6573 / 6479