Statistical comparative study between the conventional DPPH spectrophotometric and dropping DPPH analytical method without spectrophotometer: Evaluation for the advancement of antioxidant activity analysis.

Recently, new approaches for measuring antioxidant activity have been developed to eliminate or reduce the use of a spectrophotometer. All analytical methods must provide consistent and reliable results, which should be compared with statistical models. Therefore, we compared the conventional and dropping DPPH methods with three widely used standards. We employed and compared with three statistical methods. Good R-squared (R2 = ≥0.96) confirmed the similarity in comparison of using dropping DPPH method compared with the conventional DPPH method and reported lower deviations (ARD = -0.32 to 0.13; RMSD = 0.10 to 1.15). Bland-Altman method (95% CI) demonstrated a good agreement between the two methods using standards and grape extracts (skin and seed). These findings suggested that the dropping DPPH method proved cheaper (without spectrophotometer) and correlated well with the conventional DPPH method. Therefore, this method could be affordably conducted in research laboratories in developing and less developed countries.