Hi Wolfram
The "higher" water background is usually seen on the Delta V PLUS not on the Delta V Advantage or previous generation instruments. For example, on CO2 (mass 44) in dual-inlet you get:
Delta V Advantage and older Delta Plus generations: 1200 molecules per ion
Delta V Plus: 800 molecules per ion

The water background (mass 18) looks worse because it has almost 10 times better transmission to the collectors with the V Plus's refined optics. To compare to the other instruments you divide by ~10 the water signal.  So there isn't more water in the source; it is just the transmission to the collectors that falsely indicates worse.

Regards
Gilles 

Gilles St-Jean
Chercheur / Research Scientist
Université d'Ottawa / University of Ottawa
Sciences de la Terre / Earth Sciences
140 Louis Pasteur, Ottawa, Ontario, Canada K1N 6N5
Tel: 1-613-562-5800 xt 6830 (Bureau / Office)
                    xt 6839 (Bureau / Office Lab)
                    xt 6836 (IRMS lab)
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-----Message d'origine-----
De : Stable Isotope Geochemistry [mailto:[log in to unmask]] De la part de Wolfram Meier-Augenstein
Envoyé : 18 décembre 2007 08:04
À : [log in to unmask]
Objet : Re: [ISOGEOCHEM] SS analyzer vs Al analyzer

<http://www.qub.ac.uk/eerc/people/academic_staff/wma/wm_a/efnhh.htm>
Dear Sarthak,


You are not alone with these questions. I too would be interested to learn what Delta-V users experiences are in this respect.

Some Delta-V users have mentioned to me seeing rather high water background readings (higher than on other instruments in the same lab), something that may or may not be related to the source seal material.

Another question would be if long-term use (> 3 years) would result in noticeable ion burn effects on the analyzer material?


Best,

Wolfram


________________________________
From: Stable Isotope Geochemistry [[log in to unmask]] On Behalf Of Sarthak Chakraborty [[log in to unmask]]
Sent: 18 December 2007 04:45
To: [log in to unmask]
Subject: [ISOGEOCHEM] SS analyzer vs Al analyzer

Dear All,

I have a technical query which I like to get an answer from the users rather than from the manufacturer.

The Thermo Fisher has introduced an aluminum alloy based analyzer instead of stainless steel in their Delta V Plus CF IRMS. I would like to know if it may affect the vacuum in general and particularly the long term performance of the machine.

Regards,
Sarthak