Most lab's can accomplish detection of neonics and metabolites in the low
ppb range, with 1 ppb often the LOD (limit of detection). Broad spectrum
pesticides analyses usually give up some sensitivity, so the LOD is often in
the 1-5 ppb range, sometimes a bit higher. If you can afford the price,
chemical specific methods can lower the LOD.
As a side note (and I'm now talking about instrument detection limits, not
neonics), for volatile and semi-volatile chemicals, traps are often used
that accumulate a sample over a period of time (say 30 minutes). Using this
approach, LODs may be in the low Parts Per Trillion (U.S. definition of
PPTr).
We've proven that bees can search out and detect some chemicals at levels
as low as 5-15 PPTr. There are only a few field portable instruments that
can go that low, and then only for very specific chemicals.
We've some interesting video of bees. With a buried target leaking a
vapor to the air where the chemical concentration in the air is measured at
~5PPTr at 1 ft height above the ground, using the 30 minute sample
concentration method, we see bees yards away turning towards the chemical source
and flying upwind to it. According to experts at Sandia Labs who model vapor
plumes, a low PPTr source would rapidly disperse and dilute, so that many
yards away, the vapor concentration would be very small, certainly in the
Parts Per Quadrillion range. How low? Don't know, we don't have any
instruments that can detect and measure a plume at that level, yet the bees
immediately recognize its presence.
Now, a caution, Parts Per Billion, Parts Per Trillion are not the same in
the U.S. and Europe.
According to Webster's, PPB is:
1. In the United States and France, a thousand millions
(1,000,000,000) - 9 zeroes
2. In Great Britain and Germany, a million millions (1,000,000,000,000)
-12 zeroes
So there is more than one definition for PPB, PPTr
Jerry
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