Magnetic dispersive solid-phase extraction using a zeolite-based composite for direct electrochemical determination of lead(II) in urine using screen-printed electrodes.

Magnetic dispersive solid-phase extraction (MDSPE) is combined with electrochemical detection by using a screen-printed carbon electrode modified with gold nanoparticles to determine lead(II). A zeolite-based magnetic composite was used as sorbent during sample preparation, thus combining the unique properties of zeolites as sorbent materials with the remarkable advantages provided by magnetic materials. Three different zeolite-based magnetic composites were initially investigated and characterized. ZSM-5/Fe2O3 treated with HNO3 (ZSM-5/Fe2O3(tr)) was finally selected as sorbent. Lead was extracted from urine samples using ZSM-5/Fe2O3(tr). After extraction, the phases were separated by using an external magnet. Subsequently, the magnetic composite carrying the analyte was directly deposited onto the working electrode of a modified screen-printed carbon electrode for final electrochemical detection. Thereby, the elution and detection of Pb(II) were carried out in a single step. A multivariate approach was employed to optimize the experimental parameters affecting extraction. Under optimized conditions and at a typical working potential of -0.23 V (vs. Ag pseudo-reference electrode), response is linear in the 0 to 25 μg L-1 Pb(II) concentration range. The empirical limit of detection ranged from 1.0 to 2.0 μg L-1. The method was used to analyze Pb(II)-spiked urine samples, and apparent recoveries ranged between 99 and 107%, with coefficients of variation of <20%. Graphical abstractSchematic presentation of the analytical method to determine lead(II) in urine samples. Magnetic dispersive solid-phase extraction using a zeolite-based composite (ZSM-5/Fe2O3(tr)) is directly combined with electrochemical detection by using a screen-printed carbon electrode modified with gold nanoparticles (SPCnAuE).