Multi-residue method for enantioseparation of psychoactive substances and beta blockers by gas chromatography-mass spectrometry.

Currently, consumption of illicit drugs and pharmaceuticals has increased significantly. Many of these substances are chiral and can be available as racemates or enantiomerically pure. Determination of the enantiomeric fraction (EF) in wastewater is useful for: i) distinguishing between the consumption of prescribed and illicit drugs; ii) identification of possible local of illegal synthesis; iii) illegal discharge of sewage and estimation of illicit drugs and pharmaceuticals consumption by a community (wastewater-based epidemiology). This work describes the development of an indirect method by gas chromatography-mass spectrometry (GC-MS) for enantiomeric quantification of chiral substances namely psychoactive drugs and β-blockers based on the formation of diastereomers using (R)-(-)-α-methoxy-α-(trifluoromethyl)phenylacetyl chloride ((R)-MTPA-Cl) as chiral derivatization reagent. The developed method presented linearity (R > 0.99) for 20 compounds, 9 diastereomer pairs and paroxetine (PAR) and sertraline (SER). Recovery ranged from 80.7 to 114.5% (RSD < 9.1%) and accuracy between 84.6 and 118% (RSD < 9.9%). The limits of detection (LOD) varied from 0.03 and 26.0 ngL and limits of quantification (LOQ) from 0.15 and 104 ngL. Results showed the occurrence of amphetamine (AMP), illicit drugs as 3,4-methylenedioxymethamphetamine (MDMA) and methamphetamine (MAMP), alprenolol (ALP), norfluoxetine (NFLX), (SER), metoprolol (MET) and propranolol (PHO) at concentrations ranging from 21.7 ngL (MDMA) to 622 ngL (PHO). Measured concentrations were used to estimate the drug loads of the target chiral substances in a specific population. The EF was determined providing valuable information about the consumption and origin of the target drugs.