Dear All

We`ve been testing waters for del13C of DIC that are preserved with sodium
azide, a common bactericide that is used in water samples. As N2O is
produced during acidification, and which follows the CO2, it was normally
trapped at -130?C. However, we`ve done some tests, which show that even at
-130, there is a minor isotope effect. This may not be a concern for large
samples, but the problem increases with decreasing sample size. Hence, HgCl
is still a better anti-bacterial agent to prevent reaction during storage
of water samples for DIC. Note that NaAz was recommended in Clark and
Fritz`s isotope textbook (Table 10-1), but we have put a note on the book`s
website (http://www.science.uottawa.ca/~eih) with this new recommendation.

Gilles and Ian

Gilles St-Jean
Technologue / Technologist
Laboratoires d'isotopes- G.G. Hatch -Isotope Laboratories
U d'Ottawa / U of Ottawa
Dept des Sciences de la Terre / Dept of Earth Sciences
140 Louis Pasteur, Ottawa, Ontario, Canada, K1N 6N5
Bureau / Office: (613) 562-5800 ext. 6839
Labo / Lab                                    ext. 6836
Fax:                   (613) 562-5192
Courriel / E-mail: [log in to unmask]
Web:                  http://137.122.61.99