SOFT 2004 Meeting Abstracts - Society of Forensic Toxicologists

M27
DETERMINA TION OF THC IN ORAL FLUID SAMPLES USING LC-MS
Manuel Rivadulla*, Oscar Quintela, Marta Concheiro, Ana Rios, and Angelines Cruz.: Forensic
Toxicology Service, Institute of Legal Medicine, University of Santiago de Compostela, Galicia, Spain,
15782
Analysis of THC and its metabolites in biological samples is of great relevance for forensic purposes. In the
case of oral fluid the analysis should determine THC, whereas in urine, it detects the inactive metabolite
THC-COOH. Most laboratories analyze THC in such samples using GC-MS methods, but these
procedures are time-consuming and involve unavoidable previous extraction and derivatization. In this
paper we report a validation method in which the THC is isolated from oral fluid by a simple liquid-liquid
extraction with hexane. The separation and quantitation was done on a positive ion electrospray (BSI
positive) high performance liquid chromatography-mass spectrometry (LC-MS) in the selected ion
monitoring (SIR) mode. Calibration curves for ,1.9-THC were performed in oral fluid, achieving linearity
between 2 nglmL and 100 ng/mL. The procedure was validated in terms de linearity (coefficient of
correlation: 0,9956±0,0035), repeatability (5.33-10.02 %, n=6), reproducibility (2.58-14.7 %, n=6). The
limit of quantification (LOQ) was defined as the lowest concentration of analyte that could be measured
reproducibly and accurately (CV < 20% and bias> 80%), which was 2 ngimL. The LOD was estimated on
the criteria of the lowest concentration of an analyte that the bioanalytical procedure can reliably
differenciate from the backgroud noise, which was 1 ng/mL. The mean recovery was 86.62%. The method
requires only 200 ilL of oral fluid, and has been used to analyze oral fluid samples collected from drivers,
by spitting, salivette and intercept@ modes.
Keywords: LC-MS, Oral Fluid, THC
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