First, I apologize for the merged words in my previous post about
rhubarb. I cut and pasted from MS Word. It looked fine on my end,
but there were lots of merged words in the Bee-L posting.
Second, regarding the question about plants translocating contaminants
to their leaves - it's well known in pollution chemistry that many
plants will end up with higher levels of contaminants in the margins
of leaves, tips of needles, and sometimes preferentially in floral
parts. We could spend a couple of weeks talking about this topic.
Third, Charles wants to know whether 1 molecule of a metabolite equals
one part, such as a part per billion.
In the US, a part per billion is defined as 1 microgram per
kilogram. As an aside, a ppb in the US is not necessarily the same unit as a
ppb in some other countries.
To compare, you first have to look up (https://www.rsc.org/merck-index)
or calculate the molecular weight of the metabolite chemical.
Molecular mass or molecular weight is the mass of a molecule. It is
calculated as the sum of the mass of each constituent atom
multiplied by the number of atoms of that element in the molecular formula.
You can convert molecular mass to moles. This calculation requires
Avogadro's constant to convert molecular mass to mole of substance.
Avogadro's constant (AC) is fundamental to understanding both the makeup of
molecules and their interactions and combinations. For instance, since
one atom of oxygen will combine with two atoms of hydrogen to create
one molecule of water (H2O), one can similarly see that one mole of
oxygen (AC of Oxygen atoms) will combine with two moles of hydrogen atoms
(2 × AC of H atoms) to make one mole of H2O.
A mole means 6.02214179×10 to the 23 of anything. Although often associated with
the number of atoms, a mole is like the use of the term dozen: a dozen eggs, a
dozen books, a dozen pair of socks.
FYI, Bee-L didn't support my use of superscripts. If you want
to see Avogadro's Constant as usually written, Google it.
Now, there are three steps to converting moles of a substance to
grams (http://www.chemteam.info/Mole/Moles-to-Grams.html )
1 Determine how many moles are given in the problem.
2 Calculate the molar mass of the substance.
3 Multiply step one by step two.
The URL link given above has a flow chart that helps understand all of this.
So, Charles, you have to either look up the weight of one molecule of
the metabolite or calculate it. Then you need to convert it to grams,
and then to ppbs. Let us know what you find out.
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