Solid-phase extraction based on cation-exchange sorbents followed by liquid chromatography high-resolution mass spectrometry to determine synthetic cathinones in urine

Abstract

Cathinone derivates have become very popular as legal highs and are easily obtained on the market as “bath salts”, getting around the legislation due to their modified structure based on banned substances. The aim of this project is to evaluate two mixed-mode cation-exchange sorbents in solid-phase extraction (SPE) and their efficacy in pretreating urine samples for the determination of synthetic cathinones by liquid chromatography high-resolution mass spectrometry (LC-HRMS). A method for determining a group of eleven trending synthetic cathinones in urine using SPE followed by LC-HRMS using Orbitrap as analyser was developed and validated. In the extraction step, two different cation-exchange sorbents were evaluated and compared, a weak one (Oasis WCX) and a strong one (Oasis MCX). Better results were obtained for Oasis MCX in terms of recoveries and matrix effects (lower, if a clean-up step was applied). Method quantification limits were set at 0.2 ng mL−1 and method detection limits were between 0.04 and 0.16 ng mL−1. The results obtained enabled the studied compounds to be quantified at the usual levels at which they are present in urine samples. Moreover, these limits were lower than the ones found in the literature using similar extraction strategies, which shows that the reported strategy can be a useful tool in forensic and toxicological analyses.