Dear Darren,

Here is my tuppence worth contribution re drying agents for CF-IRMS
work.

For the same reasons as yours (plus safety considerations) I was
never particularly happy with MgClO4, and for reasons of practicality
not too fond of cryogenic water trapping.

I found Molecular Sieves 3A (beads, pearl from) to be a very
satisfactory substitute for both (cf. W. Meier-Augenstein et al.,
Isotopes Environ. Health Stud., Vol 30, 349-358, 1994). In fact, I
found that larger volumes of MgClO4 can lead to13C memory effects
between two samples of different 13C enrichment.

Mol. Sieves benefit from also from the fact that they are easily
rejuvenated (wash with water -yeah, I know it sounds a bit weird -
and bake out in a muffle furnace at 450 C). However, it must be
stressed that the exclusion volume of 3 Angstroem is very important.
Do NOT use 4A or 5A (mass discrimination / memory effects).

If you like, I should be happy to send you a copy of the
aforementioned paper.


Cheerio,
                 Wolfram



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

University of Dundee, Dept. of Anatomy & Physiology,
Small's Wynd, DUNDEE  DD1 4HN, United Kingdom

Tel.: +44-(0)1382-34/5124, /4968

Fax:  +44-(0)1382-34/5514

e-mail: [log in to unmask]

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