A prototype microfluidic paper-based chromatic device for simultaneous determination of copper(II) and zinc(II) in urine

abstract

© 2022The present work proposes the development of a simple and easy-to-make microfluidic paper-based analytical device (µPAD) as a prototype chromatic device for the simultaneous determination of copper and zinc in urine. The µPAD comprises a main circular sampling zone with two identical arms, each containing a circular pretreatment zone and a circular detection zone. Copper(II) and zinc(II) react with 1-(2-pyridylazo)-2-naphthol (PAN) reagent, at pH 6.0 and room temperature, to form chelates colored red and pink, respectively, that can be quantified by digital imaging analysis. The colorimetric reaction sensitivity significantly improved by coating the paper substrate surface with 5% 3-aminopropyltriethoxysilane (APTES) and applying three successive additions of standard or sample onto the sampling zone, without any prior sample preparation step. These combined analytical strategies increased the color intensity of the metal chelates formed on µPAD surface, allowing to detect the desired elements at trace level concentrations. The reaction interferences associated with the presence of foreign elements were eliminated or reduced through the addition of masking agents at different concentrations for each case. Under optimized conditions, excellent linear relationships were obtained in the range 0.1¿10 µg mL¿1, with determination coefficients (R2) greater than 0.9957. The limits of detection (LOD) and quantification (LOQ), respectively, were 27.1 µg L¿1 and 90.3 µg L¿1 for copper and 35.9 µg L¿1 and 119.7 µg L¿1 for zinc. The developed prototype device was validated by analyzing urine certified material samples, obtaining a good concordance without significant difference between the certified values and the measured values. Its application for clinical analysis offers simple, quick, cheap, noninvasive, and environmentally friendly measurements, which are desirable analytical features for point-of-care testing.