A method for the rapid and robust confirmation of 11-nor- 9-tetrahydrocannabinol-9-carboxylic acid (THCA) in urine involving basic hydrolysis with NaOH and direct injection of the hydrolysate in a column-switching LC-MS-MS system was developed and validated. THCA-d3 was used as internal standard. Detection was performed in negative-ion mode bymonitoring the tran-sitions from the [M-CO2]- ionm/z299.2!245.2 and andm/z299.2!191.1 that were found to provide a better signal-to-noise ratio than the transition from the pseudomolecular ion atm/z343. The high sensitivity of detection enabled the injection of a small volume (10ml) of the NaOH hydrolysate which, together with the applied column switching system, proved to confer ruggedness to themethod and to avoid the deterioration of the instrumental apparatus despite the large amount of inorganic ions in the hydrolysate. The LLOQ was established at 5ng/ml, and the LLOD was calculated as 0.2ng/ml (S/N =3). The method was submitted to thorough validation including evaluation of the calibration range (5–500ng/ml), accuracy and precision, ma-trix effects, overall process efficiency, autosampler stability, carryover and cross-talk, and 10-times reduction of sample vol-ume (0.1ml). Proof of applicability was obtained by direct comparison with the reference GC-MS method in use in the lab (the R2 between the two methods was 0.9951).
Rapid and robust confirmation and quantification of 11-nor-Δ9-tetrahydrocannabinol-9-carboxylic acid (THC-COOH) in urine by column switching LC-MS-MS analysis
POLETTINI, ALDO ELIANO
2012-01-01
Abstract
A method for the rapid and robust confirmation of 11-nor- 9-tetrahydrocannabinol-9-carboxylic acid (THCA) in urine involving basic hydrolysis with NaOH and direct injection of the hydrolysate in a column-switching LC-MS-MS system was developed and validated. THCA-d3 was used as internal standard. Detection was performed in negative-ion mode bymonitoring the tran-sitions from the [M-CO2]- ionm/z299.2!245.2 and andm/z299.2!191.1 that were found to provide a better signal-to-noise ratio than the transition from the pseudomolecular ion atm/z343. The high sensitivity of detection enabled the injection of a small volume (10ml) of the NaOH hydrolysate which, together with the applied column switching system, proved to confer ruggedness to themethod and to avoid the deterioration of the instrumental apparatus despite the large amount of inorganic ions in the hydrolysate. The LLOQ was established at 5ng/ml, and the LLOD was calculated as 0.2ng/ml (S/N =3). The method was submitted to thorough validation including evaluation of the calibration range (5–500ng/ml), accuracy and precision, ma-trix effects, overall process efficiency, autosampler stability, carryover and cross-talk, and 10-times reduction of sample vol-ume (0.1ml). Proof of applicability was obtained by direct comparison with the reference GC-MS method in use in the lab (the R2 between the two methods was 0.9951).
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