title: Automated extraction for the analysis of 11-nor-delta9-tetrahydrocannabinol-9-carboxylic acid (THCCOOH) in urine using a six-head probe Hamilton Microlab 2200 system and gas chromatography-mass spectrometry.
abstract: An automated extraction scheme for the analysis of 11 -nor-delta9-tetrahydrocannabinol-9-carboxylic acid using the Hamilton Microlab 2200, which was modified for gravity-flow solid-phase extraction, has been evaluated. The Hamilton was fitted with a six-head probe, a modular valve positioner, and a peristaltic pump. The automated method significantly increased sample throughput, improved assay consistency, and reduced the time spent performing the extraction. Extraction recovery for the automated method was > 90%. The limit of detection, limit of quantitation, and upper limit of linearity were equivalent to the manual method: 1.5, 3.0, and 300 ng/mL, respectively. Precision at the 15-ng/mL cut-off was as follows: mean = 14.4, standard deviation = 0.5, coefficient of variation = 3.5%. Comparison of 38 patient samples, extracted by the manual and automated extraction methods, demonstrated the following correlation statistics: r = .991, slope 1.029, and y-intercept -2.895. Carryover was < 0.3% at 1000 ng/mL. Aliquoting/extraction time for the automated method (48 urine samples) was 50 min, and the manual procedure required approximately 2.5 h. The automated aliquoting/extraction method on the Hamilton Microlab 2200 and its use in forensic applications are reviewed.
authors.affiliation: Clinical Reference Laboratory, Lenexa, Kansas, USA.
authors.forename: P D
authors.initials: PD
authors.lastname: Whitter
authors.forename: P L
authors.initials: PL
authors.lastname: Cary
authors.forename: J I
authors.initials: JI
authors.lastname: Leaton
authors.forename: J E
authors.initials: JE
authors.lastname: Johnson
mesh_terms: D001331:Automation; D013759:Dronabinol / Q000032:analysis*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods; D006801:Humans; D011619:Psychotropic Drugs / Q000032:analysis*; D012680:Sensitivity and Specificity; D013048:Specimen Handling
chemical_list: D011619:Psychotropic Drugs; D013759:Dronabinol