Page 121 - Advances in Forensic Applications of Mass Spectrometry - Jehuda Yinon

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at two fragmentation voltage values. After subtraction of background noise
mass spectrum, the reconstructed positive and negative spectra were used
for identification. This method was evaluated in real-life conditions in the
following way: 51 serum samples from a toxicological clinic were analyzed
in parallel with ESI/LC/MS, a standard GC/MS, and HPLC/DAD procedures.
The LC/MS procedure identified 75% of the compounds present in the
samples, vs. 71% for HPLC/DAD and 66% for GC/MS; 38% of compounds
were detected by all three techniques, and 36% by two of them. 196
197
Weinmann et al. established databases for ESI-generated mass spectra
for 430 compounds. Haloperidol was used as a tuning compound for con-
trolled fragmentation. The breakdown curves of haloperidol, observed on
three LC/MS instruments from the same manufacturer and taken under
different concentrations and elution conditions, were comparable.
Mass spectra were taken at three fragmentation energy levels. In the next
study, Weinmann et al. used tuning compounds for standardization of in-
source collision-induced fragmentation. Four drugs — haloperidol, parace-
tamol, metronidazole, and metamizole — were selected as tune compounds
for LC/ESI/MS. Comparative experiments were performed using two LC/MS
instruments with different construction of interface (Sciex API 365 and Agi-
198
lent 1100 MSD) or three instruments of the same manufacturer (Sciex API
365, API 2000 and API 3000). 199 Very similar fragmentation patterns were
observed after adjusting of fragmentor voltages of both instruments.
Therefore, the establishment of a general, applicable library of mass
spectra obtained with different LC/MS instruments is possible when the
fragmentation energy will be adjusted using selected tune compounds. Wein-
mann et al. combined the LC/ESI/MS library with UV spectra library. 200
201
Lips et al. performed a study on the applicability of LC/ESI/MS (pos-
itive ions) for the development of mass spectra library based upon in-source
collision-induced fragmentation. The influence of mobile-phase composi-
tion on the reproducibility of mass spectra of drugs was tested, and data
obtained with two instruments of the same brand but different types were
compared. The breakdown curves (i.e., fragmentation profiles related to
fragmentation energy) of selected drugs were compared with the data of
other authors. The authors stated that the concentration of the organic
modifier, pH, and molarity of the buffer exerted negligible influence on the
mass spectra. This observation is in agreement with the previous finding of
187
Bogusz et al. and Weinmann et al. In order to obtain reproducible mass
197
spectra, the fragmentor voltage was dynamically ramped based on the mass
of the substance. The efficiency of identification was tested on over 40 extracts
from plasma containing various acidic and basic drugs. All drugs except
phenobarbital were correctly recognized. Phenobarbital was not detected at
all due to the positive ionization applied. Acidic drugs were properly detected

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