Chemiluminescence detection in urethane-acrylate microfluidic devices

This work reports on the use of a urethane-acrylate (UA)-based resin in the construction of micro-flow injection analyzers (μFIA) with integrated chemiluminescence (CL) cells for application in ordinary analytical determinations. The proposed devices, manufactured by a rapid and low-cost prototyping procedure, offered suitable transparency to visible electromagnetic radiation and supported flow rates over 2.0 mL min−1 without leakages or damages to the structures of the CL cell. By using a pair of photodiodes as detectors, the determination of hypochlorite ions (2.0–20 mg L−1) based on its reaction with 3-aminophthalhydrazide (luminol) provided a linear response (R2 = 0.998) with a limit of detection (LOD) of 0.5 mg L−1 and repeatability of 0.4% for successive injections (n = 4) of a 2.0 mg L−1 standard solution. The determination of nitrite ions (10–80 μg L−1), carried out using a photomultiplier to detect the quenching of luminescence for the hypochlorite (ClO−)/luminol reaction in the presence of the analyte, demonstrated an adequate linearity (R2 = 0.998), LOD of 5.0 μg L−1 and precision of 0.6% for successive injections (n = 4) of a 10 μg L−1 solution. The results obtained for the determination of hypochlorite in household bleaches and of nitrite in commercial pâtés did not differ significantly from the reference methods at a confidence level of 95%, demonstrating a suitable accuracy for the miniaturized methods. In addition, only 24 mL of residues were produced per hour in both procedures, so that the proposed analyzer fits one of the green chemistry requirements.