Indirect colorimetric determination of trace hydrogen peroxide by its oxidizing power on chromium(III) oxide nanoparticles

Although enzymes are excellent catalysts in vivo, they are difficult to use in vitro. Therefore, enzyme-mimetic nanoparticles (NPs) or nanozymes, having the properties of certain enzymes but being much more resistant to chemicals and atmospheric conditions, offer a good alternative to biological enzymes. In the present study, Cr 2 O 3 NPs were used as redox catalysts for determination of H 2 O 2, a key compound for biochemistry, food industry and environmental engineering. This method proved to be more selective for H 2 O 2 than other similar nanosensing methods based on Au/Ag NPs formation. This simple method had high selectivity toward H 2 O 2 due to the high redox potential of Cr(VI)/Cr(III) couple, which could not be overcome by mild oxidants. Unlike most studies in the literature using peroxidase-like nanozymes for colorimetric H 2 O 2 determination, a peroxidase substrate is not required in this study. Here, when H 2 O 2 in the real samples (or in case of triacetone triperoxide (TATP) samples, H 2 O 2 released by hydrolysis) were contacted with Cr 2 O 3 NPs at pH 10, Cr(III) was oxidized to Cr(VI). At optimal temperature and time, there was a clear reaction with a net stoichiometry between the probe and analyte. Finally, the generated Cr(VI) was reacted by diphenylcarbazide (DPC) in acidic medium to form a pink colored compound, the color intensity of which was directly related to H 2 O 2 concentration. This method yielded a linear calibration range of 4.0–58 µM for H 2 O 2. For the tested real samples and TATP hydrolyzate, the results obtained by the proposed procedure were compatible with those of the standard TiOSO 4 colorimetric method. Finally, H 2 O 2 scavenging effects of certain antioxidants (AOX) were successfully measured by the presented spectrophotometric Cr 2 O 3 NPs method.