Colorimetric sensing for ascorbic acid based on peroxidase-like of GoldMag nanocomposites

A new scheme for sensitive and rapid colorimetric detection of ascorbic acid (AA) has been developed by the GoldMag-ABTS free radical scavenging system. The well-dispersed Gold and magnetic particles (GoldMag) was successfully prepared by self-assembly method and characterized by Fourier transform infrared (FTIR), X-Ray Photoelectron Spectroscopic (XPS) techniques. Nanocomposites combine the advantages of superparamagnetic, biocompatibility and high catalytic activity of Fe₃O₄ and gold nanoparticles (AuNPs) and exhibit enhanced the intrinsic peroxidase-like activity, which can be used to catalyze the oxidation of the peroxidase substrates 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) produce a green-colored product in presence of hydrogen peroxide. Ascorbic acid as an effective antioxidant have scavenging effects on ABTS radicals and induce the reduction of green ABTS.⁺ to colorless ABTS^2-, resulting in a significant green color fading. On this basis, a rapid, sensitive and selective colorimetric assay for ascorbic acid has been developed. Under optimal conditions, ascorbic acid has a linear response range from 0.01 mmol/L to 1 mmol/L with a detection limit of 0.12 μmol/L and a short assay time of the 30 s. Furthermore, the colorimetric system showed good sensitivity, stability, selectivity, and repeatability. It also successfully applied to the determination of ascorbic acid in real samples.