General unknown screening procedure for the characterization of human drug metabolites in forensic toxicology: applications and constraints.

LC coupled to single (LC-MS) and tandem (LC-MS/MS) mass spectrometry is recognized as the most powerful analytical tools for metabolic studies in drug discovery. In this article, we describe five cases illustrating the utility of screening xenobiotic metabolites in routine analysis of forensic samples using LC-MS/MS. Analyses were performed using a previously published LC-MS/MS general unknown screening (GUS) procedure developed using a hybrid linear IT-tandem mass spectrometer. In each of the cases presented, the presence of metabolites of xenobiotics was suspected after analyzing urine samples. In two cases, the parent drug was also detected and the metabolites were merely useful to confirm drug intake, but in three other cases, metabolite detection was of actual forensic interest. The presented results indicate that: (i) the GUS procedure developed is useful to detect a large variety of drug metabolites, which would have been hardly detected using targeted methods in the context of clinical or forensic toxicology; (ii) metabolite structure can generally be inferred from their "enhanced" product ion scan spectra; and (iii) structure confirmation can be achieved through in vitro metabolic experiments or through the analysis of urine samples from individuals taking the parent drug.

Application of Empore C-8 extraction disks for screening urine in systematic toxicological analysis.

Solid-phase extraction (SPE) by means of disposable columns has become a widely accepted technique for sample pretreatment in toxicology, both for directed analyses and for screening analyses. However, the sample capacity in SPE is usually limited to a few millilitres. Therefore, we have investigated to what extent these problems can be overcome by using Empore extraction disks, consisting of chemically modified C-8 reversed-phase silica, embedded in an inert polytetrafluoroethylene (PTFE) matrix. Human urine was selected as the matrix and dexetimide and mepyramine were initially used as test drugs because these drugs were available in tritiated form. Additional drugs investigated included codeine, hexobarbital, imipramine, methamphetamine, and nitrazepam. In these investigations, the sample capacity for untreated urine was at least 25 mL, and analyte quantities up to 250 micrograms could be retained by these filters. Washing with water/methanol mixtures was successful in removing substantial amounts of endogenous interferences, and methanol proved to be an acceptable eluent. Thus, these disks seem to have interesting potential for toxicological analysis in that sample concentration and cleanup can be achieved at the same time.