Paul,

Are you using your EA for C/N or S analysis?

Greg

Stable Isotope Geochemistry wrote:

> All EA users:
>
> I thought this might interest you, I would appreciate any comments.  Paul
> Brooks.
>
> >>>Hi Paul:
> >>
> >>When you "vacum" out your EA, are you cooling it down or turning off
> >>the ovens completely?
> >>
> >>I was just wondering if it was better to remove ash with things warm
> >>or completely off?
> >>
> >>thanks,
> >>Bill
> >>
>
> >
> >Bill,
> >
> >We do not turn off the ovens, or even turn them down to standby.  We have
> about a 9.5mm outer diamter copper tube (3/8 of an inch OD) connected with
> thick flexible tubing to an erlenmeyer flask.  The tube happens to be
> copper but that was simply what we had when we put it together.  The flask
> is connected to simple none high vacuum pump that has a high volume
> throughput at about 70 cm mercury vacuum.  This pump has micron sized
> filters on both the inlet and outlet.  The erlenmeyer flask has a glass
> tube that goes through a stopper to a few cm from the bottom of the flask,
> and at the top near the outlet we stuff some glass wool to help stop dust
> going out of the outlet.
> >
> >With 9x5mm tin capsules burning plant material we vacuum the ash every 200
> samples or so, usually at the begining of a run in the morning. We simply
> take the fitting off the combustion tube and insert the copper tube into
> the ash, then twist and move it back and forth.  This usually removes all
> the ash from the prevous run.  If necessary we have a long drill that we
> can insert into the combustion tube to try and loosen ash. Both the copper
> tube and the drill are marked so that we don't dig down  into the chromium
> oxide.  We don't leave the copper tube sucking in the combustion tube for
> more than 10 seconds at a time.
> >
> >For soils we vacuum out the ash immediately (or first thing the next
> morning) after every run of about 60 samples.  Otherwise we find that the
> ash becomes so hard we cannot loosen it.
> >
> >This procedure keeps a combustion tube in good working condition for at
> least 2000 samples.  We usually replace the tube after this as then the
> cost per samples is only on the order of US$0.20 each for the combustion
> tube, and it is not worth the possability of any trouble to save only a few
> cents per sample by trying to make the tube last longer.
> >
> >When it is being vacuumed the temperature of the combustion tube falls and
> it is not red hot anymore, but using the white opaque combustion tubes this
> doesn't seem to damage the tube.
> >
> >We have tried liners to remove the ash but have found them more expensive
> and difficult to use than vacuuming the ash out.
> >
> >Be carfeul to ensure that your vacuum line has good filers on it.  The
> Chromium oxide is bery toxic and its dust must not be allowed into the room.
> >
> >Hope this helps,
> >
> >Paul Brooks.
> >
> >
> >At 06:51 AM 2/15/00 -0800, you wrote:
> >>
> >>
> >>--
>
> Paul D. Brooks.
>
> Dept. ESPM-Ecosystem Sci.,
> 151 Hilgard Hall, MC 3110,
> UC Berkeley, Ca. 94720-3110.
>
> phone (510)642-3155
> FAX   (510)643-5098 (to Att. Paul Brooks)

--
=======================================
Gregory A. Wandless
Chemist
US Geological Survey
MS954
Reston, VA 20192

Email:[log in to unmask]
Phone: (703) 648-6189
=======================================