3D-printed chemiluminescence flow cells with customized cross-section geometry for enhanced analytical performance

Low force stereolithography is exploited for the first time for one-step facile fabrication of chemiluminescence (CL) flow-through cells that bear unrivalled features as compared to those available through milling or blowing procedures or alternative 3D printing technologies. A variety of bespoke cross-section geometries with polyhedral features (namely, triangular, square, and five-side polygon) as well as semicircular cross-section are herein critically evaluated in terms of analytical performance against the standardcircular cross-section in a flat spirally-shape format. The idea behind is to maximize capture of elicited light by the new designs while leveraging 3D printing further for fabrication of (i) customized gaskets that enable reliable attaching of the active mixing zone of the CL cell to the detection window, (ii) in-line 3D-printed serpentine reactors, and (iii) flow confluences with tailorable shapes for enhancing mixing of samples with CL reagents. Up to twenty transparent functional cells were simultaneously fabricated without inner supports following post-curing and surface treatment protocols lasting less than 5 h. In fact, previous attempts to print spirally-shaped cells in one-step by resorting to less cost effective photopolymer inkjet printing technologies were unsuccessful because of the requirement of lengthy procedures (>15 days) for quantitative removal of the support material. By exploiting the phthalazinedione-hydrogen peroxide chemistry as a model reaction, the five-side irregular pentagon cell exhibited superior analytical figures of merit in terms of LOD, dynamic range and intermediate precision as compared to alternative designs. Computational fluid dynamic simulations for mapping velocities at the entry region of the spiral cell corroborated the fact that the 5-side polygon cross-section flow-cell with Y-type confluence permitted the most efficient mixing of reagents and sample while enabling larger flow velocities near the inlet that contribute to a more efficient capture of the photons from the flash-type reaction. The applicability of the 3D-printed 5-side polygon CL cell for automatic determination of hydrogen peroxide using a computerized hybrid flow system was demonstrated for the analysis of high matrix samples, viz., seawater and saliva, with relative recoveries ranging from 83 to 103%.