Enantiodetermination of R,S-3,4-methylenedioxypyrovalerone in urine samples by high pressure in-line solid-phase extraction capillary electrophoresis-mass spectrometry.

This study presents for the first time an in-line solid-phase extraction capillary electrophoresis-mass spectrometry (SPE-CE-MS) method for the enantiodetermination of drugs of abuse in urine samples. The enantioseparation of R,S-3,4-methylenedioxypyrovalerone (R,S-MDPV) was achieved with a 10 mM ammonium acetate BGE (pH 7) that contained 0.5% (m/v) of sulphated-α-CD as chiral selector. At these pH conditions, this CD was negatively charged, which prevented its entrance into the mass spectrometer since it migrates in the opposite direction. To improve sensitivity, an in-line SPE-CE-MS method using high pressure for sample introduction (i.e. 20 min at 3 bars) was developed. Furthermore, the conditioning procedure and the first part of the electrophoretic separation were performed by switching off the nebulizer gas and the ionization source voltage to avoid non-volatile contaminant arrival into the mass spectrometer. The developed methodology was validated by analyzing urine samples, which required a very simple liquid-liquid extraction (LLE) sample pretreatment. Linearity ranged from 30 to 250 ng mL, limit of detection (LOD) was 10 ng mL, relative standard deviation (RSD) values were below 10.5% in terms of intra-day and inter-day precision and the relative error values were below 9% for peak areas accuracy.