Electrochemical determination of nitrites and sulfites by using waste-derived nanobiochar

•Electrochemical sensor the simultaneous detection of sulfites and nitrites.•Synthesis of nanobiochar derived from orange waste.•Fabrication of a screen-printed carbon electrode (SPCE) using nanobiochar.•Electrochemical determination of sulfites and nitrites by differential pulse voltammetry (DPV) method.•Detection of sulfites and nitrites in a real sample of white wine and mineral water.