Page 24 - Advances in Forensic Applications of Mass Spectrometry - Jehuda Yinon

1522_C01.fm Page 11 Tuesday, December 2, 2003 10:05 AM

Figure 1.6 Unknown mass spectrum underlying the peak 4 in Figure 1.5 (upper
part), the reference spectrum (middle part), and the structure and the hit list
found by library search in Reference 92 (lower part).

detecting several thousand compounds is strictly recommended and will be
described in 1.4.2.2, using the urine of the same case.
More or less comprehensive screening procedures for drugs in blood,
serum, or plasma have been described, mainly using HPLC-
DAD. 17,26,33,35,37,38,97–104 HPLC coupled with a single stage or tandem mass
spectrometer (LC/MS, LC/MS/MS) is becoming more and more a routine
apparatus, especially in blood and plasma analysis. 22,25,41,46,105 However, before
establishing LC/MS screening procedures in routine work, several limitations
should be kept in mind, as stated by all experts in this field. 24,26,28,106–108 The
spectral information of electrospray ionization (ESI) and/or atmospheric
pressure chemical ionization (APCI) spectra is limited, compared to EI mass
spectra, and they can vary considerably between the apparatus. Another
important problem for ESI is the reduction of the ionization of a compound
(ion suppression) due to coeluting compounds (e.g., matrix) because in these
109
cases a relevant toxicant might be overlooked, resulting, in the worst case,
in the patient’s death. In the author’s opinion and experience, analytes that
are volatile in GC should be screened for, using full-scan GC/MS. Neverthe-
less, LC/MS is an excellent completion for screening, library-assisted

© 2004 by CRC Press LLC