Bill it's a big problem.
There is a very good chance that the mercury is not tightly bound and
volatilises under the beam.
The specimen would need to be carbon coated to avoid strange peak-shifts and
greater volatility.
The biggest problem though is sensitivity.
Keith may attain 0.1% detection limits from elements just above sodium (using
EDS), but it will be less for mercury, even when discounting volatility.
Worse still, in SEM the beam can be nice and small, but because the
specimen is
thick, the area of analysis of biological samples (it's average atomic number
dependent), using 15 kV will be close to 15 micrometer diameter, which is
useless for many biological specimen.
What you require is a TEM or STEM with analytical capability, then the area of
analysis will be little larger than the beam.
Section thickness should be about 0.5 micrometer. Its easy to lose or to have
elements move during processing.
Not a simple project and its possibly best to collaborate with experienced p
eople. You do have some of the best equipment for that work available in
Sydney.
Cheers
Jim Darley
ProSciTech                 Microscopy PLUS
PO Box 111, Thuringowa  QLD  4817  Australia
Ph +61 7 4774 0370  Fax:+61 7 4789 2313  service@proscitech.com
Great microscopy catalogue, 500 Links, MSDS, User Notes
                      www.proscitech.com

On Monday, January 17, 2000 6:31 PM, Keith Ryan [SMTP:KPR@wpo.nerc.ac.uk]
wrote:
> Bill
>
> An electron mircroscopy way, if it isn't coverslipped, would be to
> simply put it into an SEM equipped for x-ray microanalysis.  No
> further preparation in case you needed to process it further yourself.
>  It would be exposed to vacuum and the electron beam which might cause
> some "burning" or mass loss.  It would take me about 5 minutes to give
> you an answer of whether it was there at more than about 0.1% in any
> local (dry) mass that you focus the beam on, and it focuses down to
> less than a micron diameter.  Maybe that isn't sensitive enough.
> Given longer, I could ash the slide in an oxygen plasma, this is good
> for tissue granules because the organic tissue is removed.  Not good
> if your mercury is linked to organics! Like metallothionins
> (spelling?).  But I'm in England!
>
> Good luck - Keith
>
>
> _______________________
> Keith Ryan (Dr)
> Marine Biological Association
> Citadel Hill
> Plymouth
> Devon PL1 2PB
> England
>
> Tel. 0044 (0)1752 633279 (with answer machine)
> also 0044 (0)1752 633249
> Fax. 0044 (0)1752 633102
>
> e-mail: kpr@wpo.nerc.ac.uk

Dear all,

One of my pathologists has a very difficult case.  He is almost
certain he has the pigment cinanbar(mercury based), which is used as
the red in tatoos, in macrophages.
We are wondering what is the simplest way to identify this pigment if
it is mercury.  We have only on Cytology smear containing this
material and do not want to destroy the slide!!!!

Thank you.
Bill Sinai
Department Manager
Tissue Pathology
ICPMR Westmead Hospital
WESTMEAD NSW AUSTRALIA
Phone 61+2+9845 7774  Fax 61+2+9687 2330