New approach for measuring antioxidant activity via graphite sensor

An ion selective membrane sensor from dioctyl phthalate as a plasticizer in a polymeric matrix of polyvinyl chloride (PVC) and β-cyclodextrin as an ionophore was constructed and evaluated according to IUPAC recommendations. Linear Nernestian response of 2, 2-diphenyl-1-picrylhydrazyl radical (DPPH•) within the concentration ranges of 10−6 to 10−2 mol L−1 was obtained with average recovery 99.87±0.617. Nernstian slope of 58.5 mV/decade with excellent selectivity over the pH range of 3–8 was observed. The suggested method was standardized using butylated hydroxyl anisole (BHA). The 50% radical scavenging activity (IC50) determined by the proposed sensor correlated well with that of the common colorimetric method based on scavenging of DPPH•. An algorithm implemented in Microsoft Visual Basic® 6.0 was used for calculating (IC50) values which are 7.38 μg/ml ± 0.35, 89.98 μg/ml ± 0.45 and 1.45 mg/ml± 1.50 for BHA, paracetamol and dipyridamole, respectively. The proposed sensor represents a simple and reproducible tool for measuring DPPH• scavenging activity of paracetamol and dipyridamole in bulk powder, pharmaceutical formulations and simulated intestinal fluid (SIF) without sophisticated separation techniques.