A study on redox reactions of the azo dye Sudan I and its hydroxylated metabolites on pyrolytic graphite and boron doped diamond electrodes to support electrochemical studies of metabolic transformations

•A complex voltammetric study of Sudan I and products of its redox transformations.•The first comparative study of voltammetric behavior of major Sudan I metabolites.•Distinction of Sudan I and its major metabolites by voltammetry is possible.•Adsorption of analytes on basal plane PGE enhances sensitivity compared to BDDE.•Sudan I and its metabolites can be detected in excess of NADPH.