Page 19 - Advances in Forensic Applications of Mass Spectrometry - Jehuda Yinon

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immunoassay prescreening, e.g., in DUID cases. 21,90 An automated screening
procedure for barbiturates, benzodiazepines, antidepressants, morphine, and
cocaine in blood after SPE and TMS has been developed. 9,48 The sample
preparation consists of SPE and TMS derivatization, both automated using
an HP PrepStation. The samples are directly injected by the PrepStation and
analyzed by full-scan GC/MS. Using macros, peak identification, and the
reporting of results are also automated. This fully automated procedure takes
about 2 h, which is acceptable for forensic drug testing or doping control but
not for emergency toxicology. Automation of the data evaluation is a com-
promise between selectivity and universality. If the exclusion criteria are cho-
sen too narrowly, peaks may be overlooked. If the window is too large, a series
of proposals is given by the computer, which have to be revised by the toxi-
cologist. In order to extend this limited blood screening, one working group
recommended to combine it with a urine screening using the REMEDI black
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box system. Maurer has described a rather comprehensive plasma screen-
ing procedure based on a standard LLE after addition of the universal internal
standard trimipamine-d . This universal extract can be used for GC/MS as
3
25
well as for LC/MS screening, identification, and quantification. The GC/MS
screening is based on mass chromatography 24,46 using macros for selection of
91
suspected drugs, followed by identification of the unknown spectra by
library search. The selected ions for screening in plasma (and gastric con-
92
tent) have recently been updated by the author’s coworkers using experiences
from their daily routine work with this procedure, and they are summarized
in Table 1.1. The drugs or poisons which can be detected in plasma after
therapeutic or toxic dosage are listed in the author’s handbook. Of course,
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further compounds can be detected, if they are present in the extract, volatile
in GC, and their mass spectra are contained in the reference libraries. 92,94–96
The plasma screening procedure is illustrated in Figure 1.1 to Figure 1.6.
Figure 1.1 shows mass chromatograms corresponding to fragment ions typ-
ical for analgesics of a plasma extract. Generation of the mass chromatograms
can be started by clicking the corresponding pull-down menu which executes
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the user-defined macros. Three major peaks appear, the identity of which
is confirmed by comparison of the underlying full mass spectrum with ref-
erence spectra. Figure 1.2 shows the unknown mass spectrum underlying
peak 1 (upper part), the reference spectrum (biomolecule linoleic acid, mid-
dle part), and the structure and the hit list found by library search in Refer-
ence 92 (lower part). Figure 1.3 and Figure 1.4 show the same for peaks 2
(oxycodone) and 3 (biomolecule cholesterol). Figure 1.5 shows mass chro-
matograms corresponding to fragment ions typical for sedative–hypnotics
generated from the same data file. The peaks 1 and 3 indicate the same
compounds as indicated in Figure 1.1. Figure 1.6 shows the mass spectrum
underlying peak 4 (upper part), the reference spectrum (meprobamate,

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