To extend the applicability of solid phase extraction devices manufactured using 3D printing technologies, a stereolithographic 3D printer and resins incorporating titanium dioxide nanoparticles (TiO2 NPs) were employed to fabricate a demountable minicolumn with TiO2 NP–incorporated packing as a sample pretreatment device for the selective extraction of inorganic As and Se species from high-salt-content samples, and to facilitate their analyses when coupled to an inductively coupled plasma mass spectrometer. After optimization, the automatic system enabled highly sensitive determinations of As and Se species with detection limits as low as 0.004–0.033 μg L−1 for As and 0.061–0.128 μg L−1 for Se. Reliability was confirmed through analyses of the reference materials 1643f, SLEW-3, CASS-4, and 2670a, as well as spike analyses of samples of water and human urine. These 3D-printed minicolumns appear to be very useful for multi-elemental speciation of these elements from high-salt-content samples. Thus, the incorporation of active nanomaterials into raw printing resins can enable 3D printing technologies—not only to fabricate functionalized devices for diverse sample pretreatment applications but also to encourage the future development of multifunctional devices for analytical science. Graphical abstractSchematic presentation of a demountable minicolumn fabricated using a stereolithographic 3D printer and the resins incorporating with TiO2 NPs. They were used to selectively extract As and Se species through controlling the sample acidities.