Solution Foaming–Treated 3D-Printed monolithic packing for enhanced solid phase extraction of trace metals

Post-printing treatment is a promising means of enhancing the performance of devices manufactured using conventional three-dimensional printing (3DP) technologies. In this study we developed a post-printing solution foaming process—involving respective treatment with formic acid (60%, v/v) and sodium bicarbonate (5%, w/v) solutions to generate CO2 as a foaming agent—to increase the surface roughness and porosity of the polyamide 6 (PA6) monolithic packing in a multimaterial fused deposition modeling 3D-printed solid phase extraction (SPE) column, thereby enhancing the extraction of Mn, Co, Ni, Cu, Zn, Cd, and Pb ions from complicated real samples prior to their determination using inductively coupled plasma mass spectrometry. After optimizing the column fabrication process, the solution foaming treatment process, the extraction conditions, and the automatic analytical system, the 3D-printed SPE column incorporating the solution foaming–treated PA6 monolithic packing extracted these metal ions with 18.9- to 42.0-fold enhancements, relative to those of the as-printed column, with absolute extraction efficiencies all greater than 94.3% and method detection limits ranging from 0.2 to 7.7 ng L−1. We verified the reliability and applicability of this method through analyses of the tested metal ions in several reference materials (CASS-4, SLEW-3, 1643f, and 2670a) and spike analyses of seawater, river water, ground water, and urine samples. We conclude that post-printing treatment can dramatically improve the performance of 3D-printed analytical devices.