Page 190 - Advances in Forensic Applications of Mass Spectrometry - Jehuda Yinon

1522_C04.fm Page 173 Thursday, November 13, 2003 9:54 AM

for androstanediol to identify unambiguously testosterone abuse for up to 7
d after administration.
In a recently published study, it has been reported that the d C values
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for 4 synthetic epitestosterone samples examined were all –30.3‰, while the
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mean d C value of epitestosterone obtained from 43 healthy male urine
samples was –23.8‰ (SD, 0.93‰). Nine of 10 athletes’ urine samples with
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epitestosterone concentrations >180 mg/l had their d C values within ±3 SD
of the control group. The other athlete’s d C value was found to be –32.6‰
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and the sample suggested the administering of synthetic epitestosterone. 86

4.4.5 Explosives

Samples of TNT from a known country of origin (but unknown date of
manufacturing) were analyzed for carbon isotope composition. The d C
87
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values of these samples were compared with that of coal and crude petro-
leum. Variations of C/ C ratios of these samples were clearly demon-
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strated and may provide information for sample differentiation purposes.
The exact cause of this variation is not obvious. If all toluene is manufac-
tured from coal or petroleum sources, these variations must be due to a
difference in the initial isotopic composition of the parent material or a
difference introduced in the toluene manufacturing process, depending on
the type of hydroforming process, the kind of catalyst, and the reaction
temperature used.

4.5 Stable Isotope Coding as a Tracing Mechanism:
Methamphetamine Example

Isotope ratio measurement of compounds that have been deliberately tagged
with selected stable isotopes can also be used as a mechanism for sample
differentiation purposes. Parallel with the mechanism of labeling medically
important research drugs with radioactive and nonradioactive isotopes, 88
drugs with high potential for being channeled into illicit use could be labeled
with specific amounts of a nonradioactive isotope during the manufacturing
process. A subsequent isotope ratio measurement could then be used to
differentiate samples from different sources and to further identify the source
of the drug and/or its precursors.
To illustrate this concept, an example is made of the frequently abused
methamphetamine. A study from this author's group incorporates varying
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amounts of C-labeled methylamine during the methamphetamine synthesis
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process. The C to C ratios in the resulting products are monitored by an
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electron impact/quadrupole mass spectrometer, with selected ion monitoring
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