Toxicological screening of urine for drugs by liquid chromatography/time‐of‐flight mass spectrometry with automated target library search based on elemental formulas

Abstract

The present study describes a novel approach for utilizing liquid chromatography/time-of-flight mass spectrometry (LC/TOFMS) in qualitative screening analysis. An LC/TOFMS method was developed for screening toxicologically relevant substances in urine samples. After solid phase extraction and LC separation, the method included full spectrum acquisition followed by automatic internal calibration, searching against a target library, and reporting positive identifications. The target library, containing 433 toxicologically relevant substances in the mass range of 105-734 Da, was created simply by entering the elemental formulas of substances into the instrument software for the calculation of their respective monoisotopic masses. In addition to parent drugs, the library contained selected urinary drug metabolites, based on their structures available in the literature. Identification was based on the exact masses of the compounds. The LC/TOFMS method provided 5-10 ppm mass accuracy for a majority of identified compounds in authentic urine samples. Compared with established thin-layer and gas chromatographic methods, the LC/TOFMS method produced similar findings in urine with the additional advantage of metabolite identification without actual reference substances.

Fragmentation of toxicologically relevant drugs in positive‐ion liquid chromatography–tandem mass spectrometry

“…Structures and thus formulae of possible metabolites may be taken from literature and also added to the database. Initially, an Applied Biosystems, Carlsbad, CA (www.appliedbiosystems.com) Mariner TOFMS system was applied (Gergov et al, 2001a;Pelander et al, 2003). This approach actually allows screening for drugs and related compounds without the availability of primary reference standards, as is often the case with drug metabolites and with street drugs (Pelander et al, 2003;Laks et al, 2004).…”

Accurate determination of tissue steroid hormones, precursors and conjugates in adult male rat

“…Especially, liquid chromatographyelectrospray ionization time-of-flight mass spectrometry (LC-TOFMS) made possible to perform the accurate mass determination of components containing matrixes. This method could be applied to drug screening using ESI to produce pseudomolecular ions, measuring their mass and comparing the results with a database containing the exact monoisotopic masses of the target analysis (16,17). The difference between the theoretical and measured isotopic patterns provides the evaluation and numerical expression using the SigmaFit algorithm for exact identification.…”

Combined drug screening and confirmation by liquid chromatography time-of-flight mass spectrometry with reverse database search

“…The authors' laboratory was the first to develop an automated procedure involving accurate mass measurement by LC-TOFMS followed by target database search for routine comprehensive urine drug screening [6,15,16]. The approach is based on reverse search with use of a database that includes the molecular formulae and monoisotopic masses of the drugs and metabolites of interest.…”

“…The "TOF revolution" [2] initially emerged from the pharmaceutical industry and drug discovery [3,4], and when combined with LC or gas chromatography (GC), the technique was readily adapted to other application areas of small molecule identification. Forensic [5,6] and clinical toxicology applications [7] together with steroid identification [8] were among the pioneer fields, soon followed by pesticide analysis [9,10]. Since then, numerous papers have been published dealing with identification by accurate mass measurement and often combined with a database or spectrum library search, as recently reviewed within forensic toxicology [11,12], doping control [13], and pesticide analysis [14].…”