3D-printed stereolithographic fluidic devices for automatic nonsupported microelectromembrane extraction and clean-up of wastewater samples

Background: There is a quest of novel functional and reliable platforms for enhancing the efficiency of microextraction approaches in troublesome matrices, such as industrial wastewaters. 3D printing has been proven superb in the analytical field to act as the springboard of microscale extraction approaches. Results: In this work, low-force stereolithography (SL) was exploited for 3D printing and prototyping bespoke fluidic devices for accommodating nonsupported microelectromembrane extraction (mu EME). The analytical performance of 3D-printed mu EME devices with distinct cross-sections, including square, circle, and obround, and various channel dimensions was explored against that of commonly used circular polytetrafluoroethylene (PTFE) tubing in flow injection systems. A computer-controlled millifluidic system was harnessed for the (i) automatic liquid-handling of minute volumes of donor, acceptor, and organic phases at the low mu L level that spanned from 3 to 44 mu L in this work, (ii) formation of three-phase mu EME, (iii) in-line extraction, (iv) flow-through optical detection of the acceptor phase, and (v) solvent removal and regeneration of the mu EME device and fluidic lines. Using methylene blue (MB) as a model analyte, experimental results evinced that the 3D-printed channels with an obround cross-section (2.5 mm x 2.5 mm) were the most efficient in terms of absolute extraction recovery (59%), as compared to PTFE tubing of 2.5 mm inner diameter (27%). This is attributed to the distinctive convex interface of the organic phase (1-octanol), with a more pronounced laminar pattern, in 3D-printed SL methacrylate-based fluidic channels against that of PTFE tubing on account of the enhanced 1-octanol wettability and lower contact angles for the 3D-printed devices. The devices with obround channels were leveraged for the automatic mu EME and in-line clean-up of MB in high matrix textile dyeing wastewater samples with relative recoveries >= 81%, RSD% <= 17.1% and LOD of 1.3 mg L-1. The 3D-printed nonsupported mu EME device was proven superb for the analysis of wastewater samples with an elevated ionic strength (0.7 mol L-1 NaCl, 5000 mg L-1 Na2CO3, and 0.013 mol L-1 NaOH) with recorded electric currents below 12 mu A. Novelty: The coupling of 3D printing with nonsupported mu EME in automatic flow-based systems is herein proposed for the first time and demonstrated for the clean-up of troublesome samples, such as wastewaters.