Results of the 3D numerical convection–diffusion-reaction model. The reaction involved ascorbic acid H2Asc and ferricyanide reactants and dehydroascorbic acid Asc and ferrocyanide products. (a) Concentration fields of (top row) and (bottom row) in isometric view. (b) (top row) and (bottom row) concentration fields in three y–z planes. Each column of (b) shows an axial position x with corresponding t and depth-averaged, unreacted sample fraction MR. Data in both panels are for Qsa = 30 µl min−1, Qsh = 1 ml min−1, = 40 mM, and [H2Asc]0 = 200 mM, and pH = 10.