Quantification of 11-nor-9-carboxy-THC and panel of 22 drugs in hair using a hybrid triple quadrupole linear ion trap mass spectrometer (QTRAP)

Abstract

The goal of this study was to develop a mass spectrometric method that reproducibly detects and quantifies 11-nor-9-Carboxy-THC levels in hair below 0.2 pg/mg. Using the same QTRAP system, a method was evaluated that allows the identification with simultaneous quantification and confirmation through MS/MS library matching and ion ratio values, for a panel of commonly analyzed forensic drugs in hair. Sample preparation of 11-nor-9-Carboxy-THC consisted of a methanol/water wash followed by a NaOH digest at 75 °C for one hour and then hexane/ethyl acetate liquid extraction. For the other compounds an overnight acetonitrile/formic acid digest was used. HPLC separation used a reverse-phase column at 30 °C, using 8.0 minute gradient. A SCIEX 6500 + QTRAP system in MRM3 mode was used for 11-nor-9-Carboxy-THC detection and MRM (two transitions per analyte) with Information Dependent Acquisition (IDA)-triggering enhanced product ion (MRM-IDA-EPI) scans for analysis of all other analytes. Detection of 11-nor-9-Carboxy-THC in hair by MRM is hampered by the complexity of the matrix and presence of compounds of similar structure and mass. This often leads to high background and interfering peaks in the MRM trace that does not allow the low detection requirements. In order to eliminate these interferences and background to improve the LOQ with good reproducibility, MRM3 fragmentation has the required selectivity to allow for the low level quantification. We will show that at the 0.2 pg/mg cutoff level in MRM mode the 11-nor-9-Carboxy-THC is hardly detectable in the high background and multiple interfering peaks but easily detectable using the MRM3 approach. We were able to quantifiy 11-nor-9-Carboxy-THC levels in hair down to 0.04 pg/mg with 99% accuracy and less than 11% CV. A scheduled MRM-IDA-EPI experiment was developed to detect and confirm the presence of analytes from a targeted 22 compound panel in hair. The experiment allowed the simultaneous confirmation via MS/MS library matching (scores > 75% for all compounds) and ion ratios (<20% CV for all analytes) as well as successful quantification of each compound in the panel with high precision. This was achieved by scheduling the MRM transitions and maximizing the time spent acquiring quality full scan MS/MS data to use in library searching. Linearity was from 5 pg/mg to 2.5 ng/mg for all compounds. We developed a MRM3 method that reproducibly detects and quantifies 11-nor-9-Carboxy-THC levels in hair down to 0.04 pg/mg. We also developed a QTRAP method allowing simultaneous identification quantification and confirmation for a panel of 22 forensic drug compounds. For Research Use Only. Not for use in diagnostic procedures.