"k.papai" wrote in message
oups.com...
wrote:
wrote:

The difference is small (~3 parts per thousand PDB), but readily
measurable if you've got good technique. It arise from the fact that
synthetic testosterone is produced from plant sterols, which are lower
in 13C than animal hormones/tissues/etc. due to isotopic
discrimination.

Andy Coggan

This isotope test are very difficult. The manufacturer of the testing
equiptment says "quite regularly there are errors."

Exactly my point from yesterday.
I don't see how isotopic tests of C12/C13 could hold any value with
WADA or UCI.

The amounts being tested are phenomonally miniscule.

You need hard evidence and so far there is NONE.

There's more to this than meets the eye - the amount of testosterone in
urine is VERY small. The amount used to TEST is a great deal smaller. That
means that the differential analysis can have large errors simply from
chance.

Think of it this way - if you have three molecules of C12 and one of C13
NORMALLY all it takes if for an addition C13 to be in a test sample to
demonstrate a change of from 4/1 to 4/2 - 25% vs 50%. A 100% increase.

Here's another source of error - the idea is to filter out everything BUT
testosterone using a column of some sort and then to break the testosterone
down into its components molecules and then use a mass spectrometer to
measure the weight.

Columns are far from perfect and since the absolute quantities are low, it
is fairly easy for the technician to catch more than the testosterone in the
mix and to break down other components of the urine as well. Yet another
source of error.

What's more - unless the observer is a specifically and highly trained
individual in the art of GC/Mass Spec, it would be highly unlikely that he
could even detect a faulty separation process. And believe me, it IS and art
and not a science.