Sangin Lee,a, Elisabeth Leere Øiestad a,b and Frederik André Hansen,a
aSeksjon for farmasøytisk kjemi ved farmasøytisk institutt, Universitetet i Oslo, Sem Sælands vei 3, 0371 Oslo
b Oslo Universitetssykehus, Avdeling for rettsmedisinske fag, Seksjon for rusmiddelforskning, Postboks 4950
Nydalen, 0424 Oslo
E-mail: sanginl@farmasi.uio.no
Tetrahydrocannabinol (THC) is one of the most frequently monitored drugs of abuse in forensic analytical chemistry. THC is metabolized to 11-hydroxy-THC (11-OH-THC) and 11-nor-9-carboxy-THC (THC-COOH) by CYP-enzymes(1), and they are monitored together in samples such as blood and urine. These matrices are challenging and making it necessary to develop improved sample cleanup and enrichment.
Supported liquid membrane (SLM)-based extractions have shown promising potential in previous studies. This kind of extraction can be performed under applied voltage (electromembrane extraction – EME), or with another gradients such as pH or solvent (liquid membrane extraction – LME). The challenges that the compounds offer are high hydrophobicity and weak acidity. In this project, different strategies of EME and LME will be investigated in equipment based on conductive vials, and the LC-MS method will be developed by comparing performances of one-factor-at-time (OFAT) optimization with a multivariate response surface methodology (RSM). As far as it is possible, both sample solution (donor) and acceptor solution will be analyzed to measure mass balance of the system.
So far, the LC-MS method has been developed, and different membranes have been tested. The donor and acceptor solution were adjusted to pH 12 to ionize the analytes (pKa = 9.34 for THC and 11-OH-THC), with 50% DMSO in donor and 70% DMSO in acceptor to avoid adsorption of analytes to vials. The initial voltage of 40 V was applied with 900 rpm of agitation in 15 minutes. The conditions of EME were developed from the previous master thesis, where the only THC-COOH has been investigated(2). Both hexadecane and dodecane have shown nearly 100% recovery for THC. The poster will present additional results from the development of the SLM-bsed extraction and LC-MS method.
References
1 Johansson, E., et al. (1989). «Terminal elimination plasma half-life of delta 1-tetrahydrocannabinol (delta 1-THC) in heavy users of marijuana.» Eur J Clin Pharmacol 37(3): 273-277.
2 Vo, K. T. (2020) “Elektromembranekstraksjon av THC-syre“ Seksjon for farmasøytisk kjemi ved Farmasøytisk institutt, Universitetet i Oslo