Smartphone readable three dimensional printed analytical kit for on-site detection of Cr(VI)

A rapid and easy-used colorimetric method was developed for on-site and rapid analysis of Cr(VI). Under acidic condition, Cr(VI) was reacted with 1, 5-diphenylcarbazide (DPC) and a purple-red complex was formed subsequently, inducing the color changed from colorless to purple-red, this color variance can be detected by ultraviolet–visible spectrophotometer (UV–Vis), smartphone and even naked-eye. For realizing the goal of on-site analysis, this method was integrated in a three dimensional (3D) printed analytical kit, smartphone was used as a portable detector. Under the optimized conditions, limit of detections (LODs) of 0.0014 μg/mL and 0.0016 μg/mL were obtained by smartphone and UV–Vis, respectively. Concentration of Cr(VI) as low as 0.05 μg/mL was still visible by naked-eye. This colorimetric system was further applied to the analysis of several environmental water samples, recoveries of 90–107 % were obtained. It is a promising portable analytical device/system for Cr(VI) on-site and rapid analysis.