Screening of new psychoactive substances in human plasma by magnetic solid phase extraction and LC-QTOF-MS

The emergence of new psychoactive substances (NPSs) is an increasing challenge in forensic toxicology. There are many extraction methods in use to isolate NPSs in biological fluids, including protein precipitation (PPT), liquid-liquid extraction (LLE), and solid phase extraction (SPE). However, there is a need to develop an effective extraction method with a short extraction time and low consumption of solvent. To meet these requirements, magnetic solid phase extraction (m-SPE) was attempted to isolate 40 NPSs in human plasma in this study. Forty NPSs (13 synthetic cannabinoids, 13 phenethylamines, 4 tryptamines, 4 other substances, 3 aminoindanes, 2 piperazines, 1 phencyclidine-type substance) were spiked in plasma and analyzed by m-SPE using COOH-functionalized multi-walled carbon nanotubes with magnetic nanoparticles (COOH-mMWCNTs). A liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) method was used for screening and identification of 40 target compounds. Method validation including limits of detection, recovery, matrix effect, and precision was performed for all 40 -target compounds. The limits of detection (LOD) of the 40 analytes were between 0.002 and 0.084 mg/L. Extraction recovery ranged from 36.9% to 110.6% (average 87%). Matrix effects ranged from -29.0% (ion suppression) to 9.8% (ion enhancement). Both intra- and inter-day precision values were less than 27.5% (RSD%). The accurate mass of QTOF-MS enabled the identification of analytes by exact monoisotopic mass and isotopic pattern. m-SPE was applied to extract 40 NPSs, and revealed less time-consuming and laborious than conventional SPE. This method proved to be an advantageous procedure to extract NPSs from biological fluids.