Xref: utzoo can.general:1016 sci.bio:1604 sci.med:7798 sci.misc:2822
Path: utzoo!yunexus!ists!mike
From: mike@ists (Mike Clarkson)
Newsgroups: can.general,sci.bio,sci.med,sci.misc
Subject: Re: Dioxin and Native Communities
Message-ID: <257@ists>
Date: 16 Nov 88 06:16:59 GMT
Article-I.D.: ists.257
References: <544@yunccn.UUCP> <591@apss.apss.ab.ca>
Organization: Institute for Space and Terrestrial Science
Lines: 37

In article <591@apss.apss.ab.ca>, nmm@apss.ab.ca (Neil McCulloch) writes:
> In article <544@yunccn.UUCP>, john@yunccn.UUCP (John Hummel) writes:
> > Keywords: Dioxin Pollution Health
> > 1)"Tests have revealed 210 parts per trillion of 2,3,7,8-TCDD, the most
> > 
> > 1 to 9 parts per trillion." (MOE Press Release July 17,1986)
> > 
> > ces.No 2,3,7,8-TCDD was found at a detection level of 20 parts per quadrillion
> 
> Would someone with experience of testing for trace chemicals care to 
> comment on these levels? 20 parts per quadrillion! Now that's 20 parts in
> 1,000,000,000,000,000. I find it hard to believe that reliable measurements
> can be made at this level from samples taken in the field.

I used to do work doing trace detection of toxic chemicals in air, and
I'd believe their detection limits.  Parts per trillion on something
like dioxin is not hard to do with GC/MS, which is gas chromatography to
seperate the components, followed by mass spectrometry to identify and
quantify them.  If you know what molecule you are looking for, then you
can use MS/MS which is much more sensitive.  20 ppq should be obtainable
with MS/MS from a solid or liquid sample. 

Dioxin is a large and very stable molecule.  That's why it doesn't
break down in the environment.  This means that you can do a lot
of sample work up to isolate the dioxin without worrying about breaking
it up in the process.  It also means that you'll have a very nice
fragmentation pattern to identify it with MS/MS.

These instruments are very sensitive.  People in the Toronto area might
want to ask Ben Johnson just how sensitive they really are.  He knows.

Mike.
-- 
Mike Clarkson					mike@ists.UUCP
Institute for Space and Terrestrial Science	mike@ists.yorku.ca
York University, North York, Ontario,		uunet!mnetor!yunexus!ists!mike
CANADA M3J 1P3					+1 (416) 736-5611