Synthesis of a novel polydopamine and C18 dual-functionalized magnetic core-shell mesoporous nanocomposite for enrichment and analysis of widely abused illegal drugs in urine samples on site and in the laboratory

In this study, a novel polydopamine and C18 dual-functionalized magnetic core-shell mesoporous silica (Fe3O4@nSiO2@mSiO2@PDA-C18) nanocomposite was designed and synthesized, which was employed as an adsorbent to extract illegal drugs from urine samples by magnetic solid-phase extraction (MSPE) procedures. The as-prepared nanocomposite was fully characterized and combined with ultrahigh performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) to monitor 12 trace illegal drugs and metabolites, including 6-monoacetylmorphine (6-MAM), morphine (MOR), codeine (COD), amphetamine (AMP), methamphetamine (MAMP), 3,4-methylenedioxymethamphetamine (MDMA), 3,4-methylenedioxyamphetamine (MDA), ketamine (KET), norketamine (NK), cocaine (COC), benzoylecgonine (BZE) and methcathinone (MC). Optimal MSPE procedures were achieved by fully investigating parameters of activation, adsorption, washing and desorption steps. The MSPE-UHPLC-MS/MS method offered high sensitivity with limit of detection (LOD) range of 0.005-0.05 ng mL-1 and good linearity with the concentration of 0.01-1000 ng mL-1. Also, the intra- and inter-day recovery respectively ranged in 90.2-105.0% and 89.8-107.4%, and the intra- and inter-day precision was in the range of 0.5-14.0% and 1.2-10.0%, respectively. By application to real urine samples, the proposed method could not only be equally sensitive for quantifying 12 illegal drugs in urine but also significantly reduce the pretreatment time when comparing with methods based on solid-phase extraction. Furthermore, the designed dual-functionalized adsorbents could also be applied for on-site determination of MAMP in urine coupled with urine test kit, and the detection threshold of MAMP urine test kit remarkably reduced from 1000 ng mL-1 to 50 ng mL-1. Therefore, the present method was a convenient, economic and sensitive approach for determining illegal drugs in urine samples both on site and in the laboratory.