H-devicers,

I use the same Nelson-Dettman recipie.  Cr lifespan, of course, depends on 
the injection volume your using.  Injecting 1.5uL gets me to almost 1000 
before the precision drops off but I can get through 98 vials in about eight 
hours on just half the reference-side volume.  Oh, inlet capillary crimp 
position is key to this as well.

The protocol you set up also involves several inter-connected variables, 
inj. volume, bellows' mV level in the method, number of COV cycles, PAL 
protocol duration, etc, all of which affect run time, thus how long the 
reference last (unless you have auto-refill) due to the time required for 
the sample bellows to close sufficiently with each injection in order to 
reach the selected mV threshold.  In other words, adjustments to injection 
volume to affect the reactor's lifespan is tied to other variables.

There also seems to be differing effects on the reactor life with heating 
and cooling (say for septa changes), and what temperature and vacuum 
condition (valves) you leave it at when it's idle.
This H-device isn't 'plug-n-play'.  :)

Bob

------------------------------------------------
Robert Brander, Lab Manager
Idaho Stable Isotopes Laboratory
  www.cnr.uidaho.edu/isil
Department of Forest Resources
College of Natural Resources, Room 214
P.O. Box 441133, University of Idaho
Moscow, ID 83844-1133, U.S.A.
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lab: (208) 885-6512
fax: (208) 885-6226
cell: (509) 338-2814
------------------------------------------------





>From: "Geldern, Robert" <[log in to unmask]>
>Reply-To: Stable Isotope Geochemistry <[log in to unmask]>
>To: [log in to unmask]
>Subject: Re: [ISOGEOCHEM] H-dev chromium
>Date: Thu, 18 Aug 2005 19:42:24 +0200
>
>Hi Gerry,
>we use the "recipe" given in Nelson and Dettman (2001, RCM 15, p.2301).
>This is a 50:50 mix of -100mesh and -325mesh chromium powder (Alfa
>Aesar Items #:10147 and #10148).
>I mixed the two powders in a 1l glass bottle on a pulley block. Works
>fine.
>On top and bottom of the reactor make sure to fill in app. 1cm of
>pure 100mesh powder (see ref given above).
>
> > Does size matter?
>
>Always. :-)
>Finnigan recomended the -100mesh, but the reactor is "used" after
>250-300 injections. The mix mentioned above is good for more than
>3000 injections due to the larger surface.
>My reactor is now near the end and injects no. 3211
>right know.
>
>greetings,
>Robert
>
>
>--
>Dr. Robert van Geldern
>Leibniz Institute for Applied Geosciences (GGA)
>S3: Geochronology and Isotopehydrology
>Stilleweg 2, 30655 Hannover, Germany
>phone: +49-(0)511-643-2313 (office), -2539 (lab)
>fax: +49-(0)511-643-3665
>mailto:[log in to unmask]