Use of Monoclonal Delta-9-Tetrahydrocannabinol Antibodies Chemically Bound to a Polystyrene Surface Using Glutaraldehyde for the Purpose of Extracting Delta-9-Tetrahydrocannabinol and Delta-9-Tetrahydrocannabinol carboxylic acid from postmortem whole blood samples for analysis by gas chromatography mass spectrometry
Quantitations of drugs and their respective metabolites in postmortem blood samples using gas chromatographic instrumentation is a primary analytical practice used to determine if drugs played a role in or were the cause of a victim's death. Postmortem blood samples often prove difficult to work with due to interfering substances formed during the putrefaction process. Attempts to eliminate interfering substances with present day extraction methods can be time consuming, costly and often ineffective when dealing with drugs that exhibit toxicity or impairment at very low concentrations. This study was conducted using monoclonal antibodies chemically bound to a polystyrene surface to extract Δ-9-Tetrahydrocannabinol and its major carboxylic acid metabolite from postmortem blood samples. The device was a Falcon® cell culture flask with 12.5 cm 2 of surface area. To each flask was added a 5% solution of glutaraldehyde followed by 5 μg/ml of antibody. Binding studies for THC and THCA using ELISA reagents resulted in an average binding capacity of ≥ 200 ng/ml for individual analytes. When both analytes were added at equal concentrations, binding capacity for THCA fell as the concentration for THC was increased. Percent yield studies demonstrated an average 54% yield for THC and an average of 49% yield for THCA. Paired t test for THC demonstrated a significant difference in two runs where t 0.1(8) = 3.355 and paired t values were 4.384 and 6.034. Two runs for THCA were t .01(27) = 2.771 had paired t values of 9.596 and 8.827 which also demonstrate a significant difference. All samples reported as "None Detected" for THC or THCA by MCL were found to contain no THC or THCA by this extraction method. Ten samples reported by MCL as "unable to report due to interfering substances" for THC were run twice with two samples showing no THC detected and eight of the samples showed no interferences present when using this extraction device.