A novel profuse color card for convenient visual determination of iodide in human urine based on catalytic oxidation reaction

In this work, we reported a novel and convenient profuse color card for naked eye determination of iodide (I − ) in urine using chromogenic substrate 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). I − catalyzed the oxidation of ABTS by peroxyacetic acid causing ABTS to yield cyan product ABTS + with a new absorption peak at 730 nm. The addition of rose-red dye rhodamine B (RhB) changes the overall color of the solution from pink to purple and finally to blue, which makes the solution multicolor and easy to distinguish. A good linear relationship for I − was obtained ranging from 10.0 to 500.0 μg/L with the detection limit of 9.2 μg/L. Importantly, the sensor can semi-quantitatively estimate the concentration of I − in human urine with naked eye through the standard color card and assess the deficiency or excess of iodine in human body. The proposed profuse color card opens up a new colorimetric method for the rapid, simple and reliable determination of I − in clinic, and has promising applications in developing assay kit for the clinical diagnosis of I − in urine.