SOFT 2004 Meeting Abstracts - Society of Forensic Toxicologists

A82
AN IDA MEDIATED LC-MSIMS SCREENING PROCEDURE WITH SEMI-QUANTITATIVE
POTENTIAL
Tineke N. Decaestecker l , Pierre E. Wallemacq2, Carlos H. Van Peteghem 3 , and Jan F. Van Bocxlaer" I
1Laboratory of Medical Biochemistry and Clinical Analysis, Ghent University, Harelbekestraat 72, B-9000
Ghent, Belgium, 2Laboratory of Toxicology and Special Chemistry, Clinical Hospital St.-Luc, Hippocrate
Avenue, B-1200 Brussels, Belgium, lLaboratory of Toxicology, Ghent University, Harelbekestraat 72, B­
9000 Ghent, Belgium
Systematic toxicological analysis (STA) in forensic toxicology comprises general unknown screening
(GUS) procedures, whether or not restricted to well-defined subgroups, as well as specific confirmation and
quantitation of individual compounds. Even though in some forensic cases, the substance involved is
known or strongly suspected, the possibility that other toxic compounds may have contributed to the
observed biological effect cannot be excluded. Efficient and extensive screening strategies are therefore
indispensable. This study evaluated an IDA-mediated LC-MSIMS screening methodology, qualitatively as
well as quantitatively, and shows its scope and limitations in a forensic setting. After all, an LC-MS
screening strategy could on the one hand reduce the off-line sample preparation mandatory in GC-MS,
because relatively non-volatile compounds can be analyzed as such, and on the other hand increase the
range of compounds amenable to MS. IDA is an artificial intelligence based product-ion scan mode
providing automatic "on-the-fly" MS to MS/MS switching. This laboratory introduced in a preliminary
communication, as first, the concept ofIDA-based LC-MSIMS screening using a Q-TOFI. By performing
information dependent scanning at two different fragmentation energies, two collision-induced dissociation
(CID) spectra for each of the detected compounds are generated. As the MSIMS spectra derive from a
single precursor ion, a very selective and very specific method was devised. Additionally, advance
knowledge about the xenobiotics that could be responsible for a certain intoxication is not necessary.
Limitation of the MSIMS acquisition time to an acceptable minimum resulted in an almost instant switch
back to the MS mode. As such, this approach provided MS chromatograms that still could be of use for
semi-quantitative purposes. Since former studies revealed that the IDA intensity threshold, unequivocally
related to the background noise, seemed to be a critical parameter, the solid phase extraction procedure, the
liquid chromatographic conditions and the mass spectrometric parameters all were optimized in advantage
to IDA Optimization of the SPE procedure was performed by means of experimental design. Whole blood
was preferred as biological matrix because of its relevant toxicological characteristics, although this did not
facilitate the analysis since the drug concentration in whole blood are relatively low compared to urine
samples. The influence of two different threshold values, Le. 100eV and 400eV, on the qualitative and
quantitative results was examined. Finally, the screening procedure we developed was benchmarked on the
one hand qualitatively against the results obtained from traditional GUS approaches in a number of routine
toxicological laboratories (37 samples). To that end, immunochemical techniques (EMIT, RIA), HPLC­
DAD, GC-MS and GC-NPD techniques were applied to screen the whole blood samples. On the other hand
the IDA-mediated screening strategy was compared semi-quantitatively against established LC-MSIMS
methods (7 samples). From a qualitative point of view the procedure performed exceptionally well: when
applying a threshold of 100eV, mostly all of the drugs detected by the conventional techniques were
identified, as well as additional drugs that were not previously reported. The procedure proved well-suited
for an initial semi-quantitative assessment, as is customary in e.g. forensic toxicology before accurate
intoxication levels are determined using targeted analytical analysis.
[l] Decaestecker et aI. Rapid Commun. Mass Spectrom. 2000, 14, 1787-1792.
Keywords: LC-MSIMS, STA, IDA
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