Preparation of two functionalized magnetic carboxylated multiwalled carbon nanotubes for the extraction of eleven synthetic cannabinoids in wastewater followed by UPLC-MS/MS

Synthetic cannabinoids (SCs) are new psychoactive substances with an increasingly large number of users and strong addictive properties. The metabolites produced after smoking SCs flow into sewage with urine and feces. Owing to the extremely low concentration of SCs and the complexity of sewage matrix, the development of different adsorbent materials to enrich SCs in sewage and enhance detection sensitivity is essential. However, existing adsorption materials, such as spherical magnetic solid-phase extraction (MSPE) materials, possess drawbacks of easily saturated functional sites, long extraction time, and low sensitivity. To solve these problems, we proposed two novel poly (glycerol methacrylate- co -trimethylolpropane trimethacrylate)/poly (dopamine- co -chitosan)-functionalized magnetic carboxylated multiwalled carbon nanotubes (GTMC/DCMC) as adsorbents and developed two highly sensitive quantitative analytical techniques to detect eleven SCs in wastewater. The magnetic adsorbents were fully characterized using transmission electron microscopy, infrared spectroscopy, vibrating sample magnetometry, and X-ray photoelectron spectroscopy. Additionally, two MSPE-UPLC-MS/MS methods were developed and validated to determine eleven trace analytes in wastewater. The validation results show that the limits of quantification (LOQ) of GTMC is 5.0 ng/L and the LOQ of DCMC is 2.5 ng/L. Additionally, the recoveries of GTMC range from 63.17 % to 86.22 %, and the recoveries of DCMC range from 61.29 % to 97.41 %. The relative standard deviations of intraday and interday precision are less than 10 %. The MSPE-UPLC-MS/MS methods are successfully applied to real wastewater samples, and the entire pretreatment process is completed in 25 min. Therefore, the proposed methods are convenient, rapid, sensitive, and reliable for the determination of trace SCs in wastewater.