Re: Anal. Chem. Nomenclature: Trace & Ultratrace Analysis


Dr_Dickie wrote:
> "Henry Boyter" <hboyter@xxxxxxxxx> wrote in message
> news:g%W3e.16226$QB6.1008996@xxxxxxxxxxxxxxxxxxxxxxxxxxx
> > There is none. It is based on who is talking and what
> > analyte you are talking about.
> >
> >
> > --
> >
> > Henry Boyter, Jr.
> > PhD Chemist
> >
> > http://www.itt.edu/staff/boyter/links/index.html
> > The opinions expressed are those of Dr. Boyter and
> > are provided for informational purposes only and
> > should not be used as advice. No warranty or
> > expression of professionalism is implied.
> >
> >
> > "Farooq W" <farooq.w@xxxxxxxxx> wrote in message
> > news:1112548063.656668.149820@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> > > What is the proper definition of trace and ultratrace analysis in
terms
> > > of analyte concentration?
> > >
> >
> >
>
> My favorite is the way folks switch from molarity to ppm or ppb when
talking
> about LOD or LOQ. It depends on what the MW of the compound detected
is.
> The heavier the MW, the more likely it is to be expressed as
molarity, the
> lighter the MW the more likely it is to be expressed as ppb.
> Single molecule detection:
> See that plastic Pepsi bottle?
> > Yes.
> Congratulations, you just got single molecule detection.

"Single molecule detection" is a misnomer.
The method I am aware of uses photometric
methods to irradiate a flow cell through
which there is a likelyhood of finding
a single molecule of analyte, based on the
concentration of the solution, and volume and
flow rate through the cell. The cell is
laser fried, reradiates, that radiation
is captured and amplified while the
molecule just zapped moves on. Then
another blast from the laser, a new
sucker shakes off the xs energy, etc.
This goes on until enough data has been
collected to present on a screen or chart.


Mark (Next contestant, please :-)

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