Hi Joy,


We use silver capsules and have noticed a build-up of tiny silver globules
at the bottom of the furnace if capsules miss the crucible too often (the
latter is supposed to catch them and retain the silver). This leads to peak
broadening and poor analytical results.

Removing the silver grit brings back analytical performance (without having
done anything to the glassy carbon chips). We clean them when they start to
look dull (rather than shiny).

Mechanical treatment (even rubbing them against each other in a cloth bag)
seems to do the trick, which is why we use it.


Cheers,

Wolfram



On Jun 2 2005, Joy Davis wrote:

> Wolfram,
>
> Thanks for the reply. We're using tin capsules and removing the ash as
> necessary. I was anticipating a decrease in flow rate associated with the
> accumulation of ash (if that was the cause of the beam decrease), but
> have not seen that. We're experimenting with temp (from 980C to 1200C)
> and will likely settle near 1200c.
>
> Renewing the surface of the glassy carbon with emory paper makes sense.
> Ideally, it seems like there should be a way to treat it chemically to
> achieve the same effect.
>
> - joy
>
> > -----Original Message-----
> > From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On
> > Behalf Of Dr W Meier-Augenstein
> > Sent: Thursday, June 02, 2005 2:19 AM
> > To: [log in to unmask]
> > Subject: Re: [ISOGEOCHEM] Reuse of glassy carbon grit
> >
> > Hi Joy,
> >
> >
> > What kind of capsules do you use for sample introduction? Does you
> > reactor packing contain a crucible or similar contraption to collect
> > capsule "residue"? Also, at which temperature do you run your reactor?
> >
> > Your peak shape might suffer as a result of "ash" (read; silver granules
> > should you be using silver capsules) build-up at the bottom of the
> > reactor,
> > which disturbs the carrier gas flow and, hence leads to peak broadening
> >
> > Re glassy carbon chips, we got straight from the horse's mouth as it
> > were (HTW GmbH, Thierhaupten, Germany).
> >
> > Yes, it is possible to "refurbish" the chips. Rub them between fine
> > emerald
> > paper and then wash them with dd water a couple of time.
> >
> >
> > Cheers,
> >
> > Wolfram
> >
> >
> >
> > > -----Original Message-----
> > > From: Stable Isotope Geochemistry
> > > [mailto:[log in to unmask]] On Behalf Of Joy Davis
> > > Sent: 01 June 2005 21:18
> > > To: [log in to unmask]
> > > Subject: Reuse of glassy carbon grit
> > >
> > >
> > > We are beginning to run 18-O on solid organics by pyrolysis
> > > to CO.  The (ceramic) pyrolysis column is packed with glassy
> > > carbon grit with ~10% nickelized carbon.  After about 150
> > > samples, the peak shape deteriorates and the signal drops.
> > > The column packing appears (visually) unchanged from the
> > > initial packing.  Can the glassy carbon be
> > > regenerated/cleaned and reused?
> > >
> > > Also, Alfa Aesar has two "types" of glassy carbon that differ
> > > primarily in their "maximum service temperature".  We (by
> > > mistake) are currently using the lower temperature glassy
> > > carbon (1100C).  What does maximum service temperature
> > > specify and what kind of change in behavior am I likely to
> > > see with the higher temperature (3000C) grit?
> > >
> > > Thanks.
> > > - Joy Davis
> > > Old Dominion University
> > > Norfolk, VA, USA
> > >
>