Novel optical sensors for the assessment of uranium and thorium in rock samples

Abstract

Herein, we report simple, sensitive, selective and low-cost filter paper strips as uranium(VI) and thorium(IV) optical sensors, wherein different ionophores were incorporated as selective color forming reagents with subsequent measurement of the micellar sensitized color change using a simple desktop scanner as an imaging device. Captured digital images of the filter paper strips carrying the colored complex were cropped and analyzed based on the standard RGB color mode to give RGB intensities that were converted to the corresponding color absorbance values that are directly related to the concentration of U(VI) and Th(IV) in complex certified rock samples. The simplicity, affordability, sensitivity and cost-effectiveness are common features for this approach for the in-situ uranium and thorium analysis. Morin (2′,3,4′,5,7-Pentahydroxyflavone), was applied as a non-leachable chromogenic reagent for the highly sensitive and selective determination of thorium and uranium. On the other hand, Arsenazo III and 4-(2-Thiazolylazo)-resorcinol (TAR) were also incorporated as chromogenic reagents in the filter paper-based strips that were specially prepared for the assessment of uranium.