Hi Gilles (and everyone),

One of the troubles we have endlessly in our lab 
is that we find that we cannot run an analysis 
set which spans across the time when the building 
experiences its daily HVAC shifts (ca. 6am and 
ca. 8pm). I've noted an approx. 3 degree shift in 
temperatures during the day versus overnight. To 
deal with this, we simply plan our analytic runs 
to start after 6am and end before 8pm.

I've long suspected the troubles we have arise 
from pressure changes (which are obvious in the 
lab and throughout the building) affecting the 
open splits, thus monkeying with everything. But 
if I'm reading this correctly, the associated 
temperature shifts could be affecting gas flow in 
the regulators and could also be screwing things up?

I'd be interested in everyone's thoughts.

Thanks,

~Penny

At 12:32 PM 3/29/2010, you wrote:
>Hi Stephen
>If you have a dual-inlet, you can use small 
>lecture bottles that can last for years by ref 
>injecting from the one of the inlets.  We do this for N2O, CO and SO2.
>
>The temperature effect is not only on liquefied 
>gases.  Temperature will also affect the gas 
>diffusion thru the gas regulators themselves. 
>You can monitor this variation by running a 
>ratio scan over a day, night or both.  This will 
>dramatically vary on days that are sunny, rainy 
>or a mix of both.  Hot during the day and cold 
>during the night etc. etc. etc.  You can see 
>dramatic changes in the reference ratio which, 
>of course, will have a major effect on long 
>sample runs when you try to normalise your data at the end.
>
>Regards
>Gilles
>
>Gilles St-Jean
>Chercheur / Research Scientist
>Université d'Ottawa / University of Ottawa
>Sciences de la Terre / Earth Sciences
>Laboratoire d' isotopes stables- G.G. Hatch- Stable Isotope Laboratory
>140 Louis Pasteur, RM 101
>Ottawa, Ontario, Canada K1N 6N5
>Tel: 1-613-562-5800 xt 6830 (Bureau / Office)
>                                    xt 6839 (Bureau / Office Lab)
>                                    xt 6836 (IRMS lab)
>Téléc. / Fax: 1-613-562-5192
>Courriel / E-mail: [log in to unmask]
>Toile / Web: <http://www.isotope.uottawa.ca>www.isotope.uottawa.ca
>"You can please some of the people all of the 
>time, and all of the people some of the time, 
>but you can not please all of the people all of the time".
>Mod. from Abraham Lincoln (attributed); 16th US president (1809 - 1865)
>
>----------
>De : Stable Isotope Geochemistry 
>[mailto:[log in to unmask]] De la part de Crowley, Stephen
>Envoyé : 29 mars 2010 12:46
>À : [log in to unmask]
>Objet : [ISOGEOCHEM] Nitrous oxide reference gas
>
>
>Hi All,
>
>In a recent reply to a question regarding the 
>location of a new stable isotope lab, Wolfram 
>Meier-Augenstein mentioned the need to store any 
>pressurized gas cylinder supplying CO2 for 
>reference gas purposes at constant temperature 
>(i.e. ideally within the lab). I presume that 
>similar issues arise where any other liquified 
>gas is used as a reference; in this case I’m 
>thinking of N2O. Could someone with the 
>requisite experience confirm that any cylinder 
>of N2O used as a source of reference gas should 
>also be stored inside the lab, and NOT outside 
>in a conventional external cylinder storage area?
>
>Whilst on this subject (and assuming that both 
>N2O and CO2 do need to be stored in the lab), in 
>order to minimise potential health and safety 
>concerns I’m thinking of using relatively small 
>cylinders of CO2 and N2O. It is possible for me 
>to obtain both gases in 50 litre volumes (at 21 
>bars cylinder pressure) that will fit 
>conveniently out of the way under a bench. Can 
>anyone see any problems with this approach (as 
>opposed to buying more conventional large 
>cylinders containing 2000 litres)? Obviously the 
>cylinders would need to be changed more 
>frequently, but are there any other issues that I need to consider?
>
>Regards,
>
>Steve Crowley
>
>Department of Earth & Ocean Sciences
>University of Liverpool
>4 Brownlow Street
>Liverpool
>L69 3GP
>UK
>
>0151 794 5163/5164
>
>____________________

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                       Dr. Pennilyn Higgins
                        Research Associate

                             "SIREAL"
   Stable Isotope Ratios in the Environment Analytical Laboratory

         Department of Earth and Environmental Sciences
         University of Rochester
         227 Hutchison Hall
         Rochester, NY 14627

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