Journal Article

Automated Extraction for the Analysis of 11-nor-Δ<sup>9</sup>-Tetrahydrocannabinol-9-Carboxylic Acid (THCCOOH) in Urine Using a Six-Head Probe Hamilton Microlab 2200 System and Gas Chromatography-Mass Spectrometry

Paul D. Whitter, Paul L. Cary, John I. Leaton and Jim E. Johnson

in Journal of Analytical Toxicology

Volume 23, issue 4, pages 286-289
Published in print July 1999 | ISSN: 0146-4760
Published online July 1999 | e-ISSN: 1945-2403 | DOI:
Automated Extraction for the Analysis of 11-nor-Δ9-Tetrahydrocannabinol-9-Carboxylic Acid (THCCOOH) in Urine Using a Six-Head Probe Hamilton Microlab 2200 System and Gas Chromatography-Mass Spectrometry

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An automated extraction scheme for the analysis of 11-nor-Δ9-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 rain, 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.

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Subjects: Medical Toxicology ; Toxicology (Non-medical)

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