A 4D-printed, magnetically actuated automated solid-phase extraction device coupled with ICP-MS for multiple trace metal analysis.

Abstract

Four-dimensional printing technologies are accelerating the development and fabrication of stimuli-responsive devices for analytical applications. Herein, we employed the multi-material fused deposition modeling printing technique, iron(II,III) oxide nanoparticle-incorporated polylactic acid filaments, and acrylonitrile butadiene styrene filaments to fabricate an all-in-one solid-phase extraction (SPE) device, which featured the flow manifolds connecting a monolithic packing and four temperature-controlled and magnetically actuated switching valves that were actuated by a hammer-shaped cantilever. When the inner chamber of the cantilever was filled with warm water (above the glass transition temperature of the polylactic acid), the applied external magnetic field induced the bending of the cantilever to switch the flow direction. When removing the external magnetic field, the cantilever returned to its original position, allowing recovery of the flow direction for magnetically actuated fluid control. The optimized SPE device manipulated the sample and eluent streams to pass through the monolithic packing and enabled an automated SPE scheme coupled with inductively coupled plasma mass spectrometry for determination of Mn, Co, Ni, Cu, Zn, Cd, and Pb ions, with the method's detection limits ranging from 0.3 to 2.8 ng L^-1. We validated the reliability and applicability of this analytical method through determining the metal ions in reference materials (CASS-4, SLRS-5, 1643f, and Seronorm™ Trace Elements Urine L-2) and real samples (seawater, river water, ground water, and human urine). Our results suggest that four-dimensional printing technologies can effectively fabricate thermo-magneto-responsive analytical devices and enhance the practical applicability of conventional SPE schemes for multiple trace metal analysis.