Application of structure-based LC/MS database management for forensic analysis

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Cozette M. Cuppett, Michael P. Balogh, Antony Williams, Vitaly Lashin, Ilya Troisky2
TIAFT 2001, The International Society of Forensic Toxicologists; Prague, Czech Republic
Content Type:
Content Subtype:
Benzodiazepines; Clonazepam; Diazepam; Flunitrazepam; Lorazepam; Oxazepam; Temazepam; Triazolam
XTerra C18 3 µm Steel 2.1 mm 100 mm
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Mass spectrometry is used to deduce chemical structures of unknowns or target compounds in mixtures. The analyst is required to determine the identity by one of two means: accepting the results of a library match as determined by a search engine or, with sufficient expertise, making an identification from a ‘first principles‘ basis. We have employed and evaluated spectral management software in our laboratories that facilitates automated identification and incorporates auto-assignment algorithms to assist the analyst with difficult and unknown samples. Beyond simply matching spectral features, chemical structures are used as the basis for fragment assignments. Structure-based assessments allow further characterization of libraries, and searching of those libraries, by common chemical structural or sub-structural features. Confidence in the assignment of an unknown is greatly increased when more than one independent evaluation is made. LC/UV/MS alone produces at least three such determinations: retention time, UV response and MS spectra. Since many labs generate data from a variety of analytical platforms and data formats, this approach unifies the valuable data into a common accessible library. The ability to use the substructure search is demonstrated in our experiments with toxicologically relevant compounds. Instrument control and data acquisition of a Waters Alliance 2690 HPLC, Waters 996 PDA, and Waters Micromass ZQ (ESI-MS) was performed using Micromass MassLynx software. A direct link from the Micromass software to ACD Labs SpecManager software allows for easy transfer of data between software platforms. Within ACD Lab’s SpecManager software, spectra were searched against MS libraries and the auto-assignment function was used to facilitate the identification of the compound and its fragment ions. By providing search results as well as annotated fragment ions, this method allows for greater confidence in results.

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