Paul-

For about a year now we have been making our own H-isotope standard gas
using a commercial H2-generator. By mixing D2O and H2O, we can virtually
pick the delta-D value of our standard gas (within about 50 permil or so).
This system works beautifully, and we can fill a 20L tank to 80 psi
overnight, enough standard gas to last us a month or more using the
continuous-flow inlet.

The drawbacks of the system are 1) the gas does not have a 'certified'
delta-D value, we have to determine it relative to other standards; 2) H2
generators are very expensive (~$4,000), so we borrow one on campus which is
being used to produce carrier gas for a GC; 3) there is a large (~600-800
permil) depletion from water to H2 in these generators, so you will have to
spend some time calibrating your particular H-generator before you can get
the right delta-D value every time.

I'll be happy to supply more details about the system if anyone is
interested.

Alex

________________________________
Alex Sessions
Mail Stop 4
Woods Hole Oceanographic Institute
Woods Hole, MA 02346

office: Fye 116
phone: (508) 289-2570
email: [log in to unmask] <mailto:[log in to unmask]>



Paul Brooks wrote:

> I am just setting up to begin H/D analysis, and have been told
> that regular
> bulk tank H2 is always so depleted that it is useless to use as a
> reference
> gas.  What do other users do for a H2 reference gas here in N.
> America?  Is
> there a supplier of a bulk gas in a reasonable range?  I already have a
> small tank of calibrated H2 but it is much too expensive to use
> as a day to
> day reference gas.