SOFT 2004 Meeting Abstracts - Society of Forensic Toxicologists

A31
ANALYSIS OF TETRAHYDROCANNABINOL (THC) AND CARBOXY·
TETRAHYDROCANNABINOL (CTHC) IN WHOLE BLOOD
Amy Kinkennon*, Tim Robert, David Black, Peter Stout
Aegis Sciences Corporation, Nashville, TN, USA
THC and CTHC were isolated from I mL of whole blood using SPEWare Cerex PolyChrom THC SPE
cartridges (35 mg beds). Analytes were eluted, and then derivatized with PFPA. Samples were
reconstituted in 50 ul of ethyl acetate, and 2 uL injected on an HP 5890 GC interfaced to a Finnigan TSQ
7000 MSIMS.
The MSIMS was used in the positive CI mode for THC, and negative CI mode for the CTHC, with methane
as the reagent gas. The THC molecular ion at 461 mlz was selected in Ql, collided with Ar in Q2, and two
daughter ions monitored in Q3. The CTHC did not generate a strong molecular ion (622 m/z), so a 602 m/z
fragment was selected in Q L This fragment was collided with Ar in Q2, and two daughter ions monitored
in Q3. D3·THC and D3-CTHC were used as internal standards, and appropriate ions were monitored for
these compounds. Analysis time was -15 min per sample.
The method was shown to have a linear range of I-50 nglml for THC and 5-50 ng/ml for CTHC. Precision
and accuracy studies were conducted using known control materials manufactured in drug free blood with
good accuracy and precision over the linear range. Interference studies indicated that neither ibuprofen
(110 uglml), acetaminophen (110 ug/ml), salicylate (700 uglml), nor ethanol (63 uglml) affected the
analysis. Forty authentic blood samples from previous casework were analyzed using this method. Twenty
had screened positive, and had been confirmed by an outside laboratory. Nine had screened positive, were
sent for confirmation, and were returned negative. Eleven had screened negative and had not been
previously confirmed.
Keywords: Blood analysis, Carboxy-THC, Tandem mass spectrometry
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