Marquet P.^*, Mura P.^**, Lacassie E.^*, Verneuil B.^*, Dupuy J.L.^*, Lachatre G.^*,***
* Department of Pharmacology and Toxicology, University Hospital, Limoges, France
^** Department of Toxicology, University Hospital, Poitiers, France
^*** Laboratory of Toxicology, Faculty of Pharmacy, Limoges, France

A sensitive and highly specific method for the determination of LSD and Nor-LSD in urine using LC-ES-MS has been developed. After addition of LSD-d₃ as I.S. and alkalinization of the sample, exctraction was performed on an Extrelut-3 cartridge using diethylether-toluene (60/40; v/v). Chromatography involved a Nucleosil C₁₈ µm (150 x 1 mm I.D.) column and mixture of pH3, 2 mM ammonium formate and acetonitrile (70/30; v/v) as mobile phase. For each analyte, the pseudo-molecular ion and two fragments were respectively selected as quantitation and confirmatory ions.

Recoveries were 93 and 80%, limits of detection 0.025 and 0.035 ng/mL and limits of quantitation (LOQ) 0.05 and 0.10 ng/mL for LSD and Nor-LSD, respectively. Reproducibility was good and linearity excellent from the LOQ up to 20 ng/mL for both analytes.

A comparative study of the Behring EMIT II^® LSD immunoassay and of the present technique was performed using 191 urine samples from drug addicts, methadone maintained patients and from the routine clinical activity of the Lab. It showed false positive results given by the immunochemical technique but no false negative results. Therefore, EMIT is convenient as a first screening method for LSD in urine as far as all poitive results are confirmed using a specific technique.