Speciation of trace iron in environmental water using 3D-printed minicolumns coupled with inductively coupled plasma mass spectrometry

To demonstrate that three-dimensional (3D) printing technologies can be used to manufacture sophisticated solid phase extraction devices for speciation of trace iron in samples of environmental water, in this study we used a stereolithographic 3D printer and non-functionalized acrylate resin to fabricate minicolumns capable of extracting Fe(II) and Fe(III) selectively from high-salt-content samples and facilitating their analyses when coupled with an inductively coupled plasma mass spectrometer. After optimization of the experimental conditions, a facile strategy was developed for the quantitative iron speciation through determination of the total iron concentration [Fe(II) and Fe(III), at pH 5 with evacuation by air] and then the Fe(III) concentration (at pH 4 with evacuation by water) with an external calibration scheme. Our automatic, lab-on-valve, flow-injection-analysis system allowed the determination of these two iron species with limits of detection of 1-2 ng L-1 for Fe(III) and 1 ng L-1 for Fe(II). To verify the method's reliability and applicability, we determined the levels of Fe(II) and Fe (III) quantitatively in several reference materials (SLEW-3, 1640a, 1643e) and performed spike analyses of these two iron species in various water samples (tap water, ground water, river water, seawater). Our proposed dual 3D-printed minicolumn speciation system appears to be highly applicable to reliable and sensitive iron speciation in environmental water samples; such devices would also be suitable alternatives to commercial devices.