Accurate identification and quantification of 11-nor-Delta(9)-tetrahydrocannabinol-9-carboxylic acid in urine drug testing: Evaluation of a direct high efficiency liquid chromatographic-mass spectrometric method

• A direct liquid chromatographic-tandem mass spectrometric (LC-MS/MS) method for measurement of urinary Delta(9)-tetrahydrocannabinol carboxylic acid (THCA) was developed. The method involved dilution of the urine sample with water containing H-2(9)-deuterated analogue as internal standard, hydrolysis with ammonia, reversed phase chromatography using a Waters ultra-performance liquid chromatography (UPLC (TM)) equipment with gradient elution, negative electrospray ionization, and monitoring of two product ions in selected reaction monitoring mode. The measuring range was 2-1000 ng/mL for THCA, and the intra- and inter-assay imprecision, expressed as the coefficient of variation, was below 5%. Influence from urine matrix on ionization efficiency was noted in infusion experiments, but was compensated for by the internal standard. Comparison with established gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry methods in authentic patient samples demonstrated accuracy in both qualitative and quantitative results. A small difference in mean ratios (similar to 15%) may be explained by the use of different hydrolysis procedures between methods. In conclusion, the high efficiency LC-MS/MS method was capable of accurately identify and quantify THCA in urine with a capacity of 14 samples per hour.

Nyckelord

urine; drug testing; (+/-)-11-nor-9-carboxy-Delta(9)-tetrahydrocannabinol; LC-MS/MS

MEDICINE

MEDICIN

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