kruschb at govonca.gov.on.ca
Mon Feb 6 13:19:28 EST 1995
In <jordan-0602950810390001 at mac-burl-16.dfci.harvard.edu> jordan at mbcrr.harvard.edu (Rob Jordan) writes:
>I have frequently run across the term semi-quantitative and I have yet to
>figure out what the true meaning of this term is. I was taught that
>studies are either quantitative or qualitative with no gray areas. What is
>the difference between semi-quantitative and semi-nonquantitative? Is one
>considered an pessimist using the latter :) ? Any comments?
Hi Rob J.,
I (being an analytical chemist for many years) regard semi-quantitative
results to mean that the numbers are rough, as in an order of magnitude.
For example, I analyze some well-water for benzene and in a
semi-quantitative report I would say that there was approximately 5 parts
per million benzene. I could dilute and re-run this sample many times and
get the analysis down to 4,578 parts per billion, but 5 ppm is
semi-quantitative. Also the instruments available now will analyze down
to low ppb or low micrograms per cubic liter or meter (whichever the
matrix), so when we get gross amounts (ie ppm levels) we prefer not to
waste the time doing 6 or 7 dilutions to get an exact number.
Likewise a semiqualitative result would say that the substance is an
simple aldehyde without specifying which one exactly it is.
Hope this helps.
Brian Kruschel, Scientist
Ontario Ministry of Environment & Energy
Science & Technology Branch
The thoughts, opinions and comments contained herein do not necessarily
reflect those of my employer... but they should!
"It may be mandatory to grow old, but growing up is optional!"
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