Page 25 - Advances in Forensic Applications of Mass Spectrometry - Jehuda Yinon

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identification, and quantification of unstable, low-dosed, and/or rather polar
compounds, especially in plasma. 22–31

1.3 Screening for Drugs in Alternative Matrices
by GC/MS

There are several advantages of alternative matrices over urine and blood for
drugs of abuse testing. They can be collected rather easily and noninvasively
with low risk of adulteration. In addition, using hair, the window of drug
19
detection is dramatically extended to weeks, months, or even years. The
great advances in analytical techniques today allow us to monitor drugs in
such matrices. Several reviews on drug testing in alternative matrices have
been published in the last years. 7,8,10,12–15,19,53,110 Most procedures published in
last 2 years are still based on GC/MS; for example, see References 75, 76, 78,
111–120. However, as already mentioned above, it must be kept in mind that,
until now, no really comprehensive screening procedure has been described
for alternative matrices as would be necessary in general unknown cases, and
that the pharmacokinetic interpretation is often difficult.

1.4 Screening for Drugs in Urine by GC/MS

1.4.1 Screening Procedures for Detection of Particular
Drug Classes in Urine by GC/MS

As already discussed above, urine still remains the standard for comprehen-
sive screening, especially in general unknown cases in clinical and forensic
toxicology and doping control. Procedures are described not for single drugs
but for all, or at least several, drugs of a pharmacological or chemical class.
For toxicological screening procedures in urine, the detectability of the parent
compound is of minor value if the concentrations of the metabolites are
much higher in urine than those of the parent drug and if the metabolites
can be detected by the procedure. Most of the toxicologically relevant drugs
are rather lipophilic substances that undergo extensive metabolism. As pure
substances of the metabolites are usually not available, it is necessary to
control the quality of the screening procedures using urine samples of vol-
unteers or in-patients treated with a known dose of the drug. The procedure
should be sufficiently sensitive to detect therapeutic concentrations at least
over a 12 to 24 h period after ingestion. Papers on the detection time of drugs
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of abuse in urine have recently been reviewed. An interesting experimental
approach for the validation of qualitative chromatographic methods and its
application in an antidoping control laboratory was recently described. 122

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