Redox-based colorimetric sensing of H₂O₂ after removal of antioxidants with ABTS radical oxidation

Monitoring and determining H₂O₂ in many industries, treatment plants and biochemical media is important because of its harmful effects even at low concentrations. This work proposes a redox-based colorimetric sensor for the determination of hydrogen peroxide in the presence of antioxidants which are known interferents causing positive errors. On the other hand, the widely used peroxidase-based methods are interfered by enzyme inhibitors. The proposed method consists of two stages, namely antioxidant removal and H₂O₂ determination. In the first step, antioxidants were removed simply using ABTS radical (ABTS⁺) oxidant produced by persulfate. After antioxidant elimination, H₂O₂ in samples was determined by using the CUPRAC colorimetric sensor. The CUPRAC reagent, copper (II)-neocuproine (Cu(II)-Nc), immobilized on a Nafion persulfonate membrane was used for sensor preparation. The light blue Cu(II)-Nc was reduced by H₂O₂ to the yellow-orange colored Cu(I)-Nc chelate on the sensor, and the absorbance increase at 450 nm was recorded. The LOD and the LOQ values obtained for H₂O₂ were 0.33 and 1.10 µM, respectively. The proposed assay was validated in terms of linearity, additivity, precision and recovery. The H₂O₂ contents of spiked food extracts, synthetic serum and certain commercial products (i.e. food sterilization solution, whitening toothpaste and hair bleaching solution) were found to be comparable to the results of peroxidase-ABTS and titanyl sulfate reference assays. In addition, peroxide-type explosive triacetone triperoxide (TATP) was successfully determined in the presence of amine-type antioxidants. The proposed simple and low-cost assay is not inhibited by environmental agents (heavy metals, pesticides, sulfhydryl agents, etc.) adversely affecting enzymatic methods. It is additionally insensitive to turbidity and colored components of complex samples.