Preparation and certification of standard reference material 1507: 11-nor-.DELTA.9-tetrahydrocannabinol-9-carboxylic acid in freeze-dried urine

Abstract

The National Institute of Standards and Technology (NIST) has prepared and certified SRM 1507, a freeze-dried urine fortified with 11-nor-delta 9-tetrahydrocannabinol-9-carboxylic acid (THC-9-COOH), the major urinary metabolite of marijuana. The certified concentration of 20 +/- 1 ng/mL for the analyte was obtained from the concordant results of analyses of the material by gas chromatography/mass spectrometry (GC/MS) and high-performance liquid chromatography with electrochemical detection (HPLC-EC). Solid-phase extraction was used to prepare the sample for GC/MS analyses, and liquid-liquid extraction was used for the HPLC-EC analyses. The multistep HPLC method was developed at NIST to circumvent interferences from urinary constituents. The results of a round robin test on this material among five Department of Defense laboratories involved in drug testing are reported.

Reference materials for analytical toxicology including doping control: freeze-dried urine samples

“…The working standard solutions of 100 mg mL 21 and 10 mg mL 21 were prepared by a 1:10 and a 1:100 dilution respectively of the stock standard solutions with methanol. For caffeine, a stock standard solution of 4 mg mL 21 was prepared using methanol as a solvent. The working standard solution of 400 mg mL 21 was prepared by a 1:10 dilution of the stock standard solutions with methanol.…”

“…The initial acetonitrile content (20%) was maintained for 4.5 min and then increased to 30% in 1 min, maintained there for 2.5 min, decreased to 10% in 0.5 min and stabilized for 0.5 min before the next injection. The flow rate of the mobile phase was maintained at 1 mL min 21 . The detector was set to monitor the signal at 280 nm.…”

“…Calibration samples containing 6, 12, 16, 22 and 30 mg mL 21 of caffeine and a control sample of 14 mg mL 21 were used for caffeine quantification. The results of method validation have been previously reported.…”

“…Separation was carried using a cross-linked 5% phenylmethylsilicone capillary column (12 m 3 0.2 mm id, and 0.33 mm film thickness) (HP, Ultra A). Helium was used as carrier gas at a flow rate of 0.5 mL min 21 and as make up gas at a flow rate of 35 mL min 21 . Air and hydrogen detector flows were set at 85 and 4 mL min 21 , respectively.…”

“…Preparation of certified freeze-dried reference materials for drugs of abuse testing has been reported in the literature. [21][22][23][24] The loss of analytes during the lyophilisation process has been reported for some specific compounds, 21 but no special attention has been paid to this phenomenon. However, this could be a major problem in doping control or drugs of abuse testing when preparing freezedried samples for compounds with threshold concentrations.…”