DETERMINATION OF LSD AND N-DEMETHYL-LSD IN URINE BY LIQUID-CHROMATOGRAPHY COUPLED TO ELECTROSPRAY-IONIZATION MASS-SPECTROMETRY

A sensitive and highly specific method for the determination of LSD an d N-demethyl-LSD in urine, using combined liquid chromatography and ma ss spectrometry (LC-MS) with electrospray ionization, has been develop ed. Extrelut-3 extraction cartridges were used for a basic sample clea n-up. Elution was obtained by toluene-diethyl ether (60:40, v/v). A Nu cleosil C-18 (150 x 1 mm LD.) reversed-phase column was used for the c hromatographic separation, together with a mixture of 2 mM ammonium fo rmate buffer (pH 3) and acetonitrile (70:30, v/v) as mobile phase. Rec overies were 93 and 80%, detection limits 0.025 and 0.035 ng/ml for LS D and N-demethyl-LSD, respectively. Intra-assay precision, studied at four concentrations, was better than 9% at the ng/ml range and better than 14% at 0.10 ng/ml for both compounds. Limits of quantitation were 0.05 and 0.10 ng/ml for LSD and N-demethyl-LSD, respectively. Reprodu cibility was good and linearity excellent for LSD in the range from 0. 05 to 20 ng/ml (r>0.9999, n=7).