The Determination of THC-COOH (THCA) in Hair using GC-GC-MS. Objective. Marijuana. Literature (continued) Literature

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1 The Determination of THC-COOH (THCA) in Hair using GC-GC-MS Christine Moore, Sumandeep Rana, Fred Feyerherm, Harry Prest Immunalysis Corporation, CA Agilent Technologies, CA Marijuana THC is active ingredient Major urinary metabolite is THCA Parent THC is detected in higher concentrations in hair than THCA However, to avoid environmental contamination concerns in workplace samples, detection of the metabolite THCA is required Objective Proposed Federal Guidelines: Cut-off for THCA in hair: 0.05 pg/mg Aim: To achieve this sensitivity using a single quadrupole mass spectrometric system, producing at least two ions for identification Department of Health and Human Services. Substance Abuse and Mental Health Services Administration. Proposed Revisions to Mandatory Guidelines for Federal Workplace Drug testing Programs. Federal Register 69(7); 004 Author Wilkins et al. J Anal Toxicol. 9(6): 483-9(995) Kintz, et al. J Forensic Sci. 40(4): 69- (995) Literature Methodology NaOH digestion L/L extraction 00 mg sample NaOH digestion L/L extraction Detection Limit 0 pg on column: Unable to detect THCA in hair from users LOD: 5 pg/mg Mean THCA level from users: 0. ng/mg (400 x higher than proposed cut-off) Author Moore, et al. J Anal Toxicol. 5(7): (00) Sachs and Dressler. Forens Sci Int 07(-3): (000) M. Uhl. Forens Sci Int 07(-3): (000) Literature (continued) Methodology NaOH digestion SPE extraction Large volume injection (5 µl) Clean-up using HPLC GC/MS/MS Detection Limit LOD 0.5 pg/mg (0 x higher than proposed cut-off) LOD 0.3 pg/mg LOD 0.6 pg/mg

2 Approach Small improvements at all stages of the procedure:. Extraction. Gas Chromatography 3. Mass Spectrometry. Extraction A. Sonication: Methanol:EtAc (50:50 v,v; room temp; hrs) 50% recovery, clean B. Digestion: NaOH; Liquid-liquid extraction (hexane:etac) Improved recovery; dirty extract Extraction (continued) Extraction Procedure C. Acetone wash; digestion (NaOH); SPE: strong anion exchange column (SPEWare PolyChrom THC ) Good extraction recovery, dirty extract D. Methylene chloride wash; digestion (NaOH); neutralization, SPE: cation exchange/hydrophobic column Best results, full method described Standards: Tri-deuterated THCA (00 µg/ml) THCA ( mg/ml) Cerrilliant (Round Rock, TX) Internal standard concentration: pg/mg Extraction Procedure (continued) Extraction Procedure (continued) Calibrators, controls, specimens: 0 mg hair Cut, weigh into tapered bottom glass tubes Rinse: methylene chloride (.5 ml) Decant solvent; allow hair to dry Add internal standard ( pg/mg D3-THCA) Calibration curve: Negative, 0.05, 0., 0.5,.0, 5.0 pg/mg Add DI water (0.5 ml); N NaOH (0.5 ml) Heat 75 o C, 5 min Cool; centrifuge (500 rpm; 5 min) Pour supernatant into glass tubes already containing: Acetic acid ( ml) M acetic acid (3 ml) 0. M sodium acetate buffer (ph 4; ml)

3 Solid Phase Extraction Procedure Condition SPE columns (hydrophobic/cation exchange): Hexane:EtAc (75:5 v,v ml) Methanol (3 ml) DI water ( 3 ml) 0.M hydrochloric acid ( ml) Load samples Wash DI water ( x 3 ml) 0. M HCl:acetonitrile (70:30 v,v, 3 ml) Extraction Procedure (continued) Elute THCA: Hexane:EtAc (75:5, v,v 3mL) Evaporate eluent to dryness (N ; 40 o C) Reconstitute: Trifluoroacetic anhydride (TFAA, 50 µl),,,3,3,3-hexafluoro--propanol (HFIP, 30 µl) Cap, heat (70 o C/5 min) Leave at room temp for 0 min Evaporate to dryness (vacuum oven) Reconstitute in toluene (5 µl). Gas Chromatography Deans Switch system: Used to divert analyte of interest from to A. Two-dimensional GC (GC:GC) Serial columns As different in polarity as possible Dean s switch allows flow to be diverted from primary column to analytical column Restrictor tubing m 40m x 0.8 mm x 0.8 µm solenoid valve 5m x 0.5 mm x 0.5 µm Switch off: effluent goes to (no cut) Switch on: effluent is cut to restrictor solenoid valve (off) restrictor solenoid valve (on) 55.4 psi 8 psi 55.4 psi 8 psi --- clean helium --- He + effluent --- clean helium --- He + effluent 3

4 Injection: GC Parameters Pulsed splitless mode 00 o C; 55.4 psi Purge flow: 50 ml/min; Purge Time: min Volume: µl Oven: 00 o C for 0.5 min; ramped at 50 o C to 00 o C; ramped at 0 o C to 60 o C; held for.9 min cooled at 0 o C to 00 o C Post run: Oven temp raised to 30 o C; held for 3 min Total run time: 5.3 min. Gas Chromatography (continued) B. Cryogenic focusing Used to cold trap the analyte as it passes through analytical column Operated through Back software of system Cooled using compressed air JAS Cryotrap re-focuses THCA on analytical column Cryogenic focusing restrictor solenoid valve (on) 55.4 psi 8 psi Cryo Focuser cooled from oven temp at 0 min (80 o C) to 00 o C as fast as possible: 777 o C/min Held at 00 o C for.5 min allows THCA to cold trap Re-heat focuser at 777 o C/min to 80 o C releases THCA to Cryogenic Effect 3. Mass Spectrometry Derivatization: Maximize number of electronegative, volatile groups on molecule because of selected mode Tried various combinations: HFIP/PFPA; PFPOH/PFPA; HFBA/PFPOH; TFAA/PFPOH; TFAA/HFIP Trifluoroacetic anhydride adds COCF 3 (97 mass units),,,3,3,3-hexafluoro--propanol adds CH(CF 3 ) (5 mass units) 4

5 Structure of THCA Derivatization (continued) TFAA and HFIP add 9 fluorine groups to the molecule (addition 48 mass units) Two sites of derivatization Molecular weight of THCA: 344 amu Total resultant mass= 59 H = 590 (593) Loss of [M-OCH(CF 3 ) ] = m/z 4 (45) 3. Mass Spectrometry (continued) Instrument parameters: Reagent gas: Ammonia (~7 x more sensitive than methane) Purity % with max impurities: CO ppm; Methane ppm; N ppm; O ppm; H 0 5 ppm Stainless steel regulator Mode: Negative ion chemical ionization (NCI) Electron Capture Chemical Ionization (ECCI) 3. Mass Spectrometry (continued) Instrument parameters: Collision gas flow: 8 x Torr MS Source: 50 o C MS Quadrupole: 06 o C Transfer line: 80 o C SIM ions: 590 (593); 4 (45) Retention Time: 3.9 min Calibration Curve Hair specimen: Negative 5

6 Sample ID GC/MS/MS GC/GC/MS Self-reported Frequency Hair specimen:. pg/mg THCA No use x week x week x week x week x week x week x week MEAN pg/mg 0.9 pg/mg THCA detected in hair (pg/mg) THCA detected in hair of self-reported marijuana users GC/MS/MS 3 7 (mean) GC/GC/MS 8 (mean) Frequency of reported use (times/week) 56 Summary Procedure makes use of minor modifications in methodology: Cleaner extraction Efficient derivatization Minimal background from the matrix diverted to analytical column Cryogenic focusing NCI mode using ammonia as reagent gas improves sensitivity Conclusion Described method uses single quadrupole mass spectrometer to routinely achieve Federally proposed concentrations for THCA in hair 6