Microfluidic Paper-based Analytical Device for the Determination of Hexavalent Chromium by Photolithographic Fabrication Using a Photomask Printed with 3D Printer

This article describes a simple and inexpensive microfluidic paper-based analytical device (mu PAD) for the determination of hexavalent chromium (Cr-VI) in water samples. The mu PADs were fabricated on paper by photolithography using a photomask printed with a 3D printer and functionalized with reagents for a colorimetric assay. In the mu PAD, Cr-VI reacts with 1,5-diphenylcarbazide to form a violet-colored complex. Images of mu PADs were captured with a digital camera; then the red, green, and blue color intensity of each detection zone were measured using images processing software. The green intensity analysis was the best sensitive among the RGB color. A linear working range (40 - 400 ppm; R-2 = 0.981) between the Cr-VI and green intensity was obtained with a detection limit of 30 ppm. All of the recoveries were between 94 and 109% in recovery studies on water samples, and good results were obtained.