Hi Bill,

The short answer is yes. I do find it rather beneficial to use research
grade He for all my IRMS work.

In Europe, the three high-end He grades are 4.8, 5.0 and 6.0 which
stands for 99.998%, 99.999% and 99.9999 % purity, respectively.
The 6.0 stuff is pretty expensive so I usually go for 5.0 in
combination with a Supelco high-capacity gas purifier.

In my experience, this is the only system that actually works, most of
the stuff on the market introduces c*@#p rather than removing it.
The system consists basically of a wee furnace a cartridge that
looks a bit like an HPLC column (no, I don't know what's in it,
Supelco won't tell). Ever the pessimist, never working without
backup, I have another Supelco product behind the purifier (an OMI
tube) which serves both as an indicator for cartridge exhaustion and
purifier while I'm replacing the cartridge.

Feeding 5.0 He in this system, you get 6.0+ out. Of course, it is
possible to use the cheaper 4.8 and still get something between 5.0
and 6.0 out but that reduces the life span of the cartridge. You have
to calculate for yourself which is the more economical option.

Hope this helps.


All the best,
                            Wolfram



*****************************************************
Dr. W. Meier-Augenstein, CChem MRSC
Senior Research Fellow

University of Dundee, Dept. of Anatomy & Physiology,
OMS, DUNDEE  DD1 4HN, United Kingdom

Tel. (B): +44-(0)1382-34/5124 or /4574
Fax  (B): +44-(0)1382-34/5514

e-mail (B): [log in to unmask]
e-mail (H): [log in to unmask]

URL: http://www.dundee.ac.uk/anatphys/wma/wolfram.htm
*****************************************************