(a) CV at 0.20 V s⁻¹ of: — GCE; - - - Pt reference electrode, in agar gel containing KCl; (b) CV at 100 V s⁻¹ of Pt electrode in agar gel containing 5 mM K₃[Fe(CN)₆]/KCl: — vs. Ag/AgCl (agar saturated KCl) as reference electrode; - - - vs. Pt electrode; (c) CV of Pt electrode (0.02 cm²) in agar gel containing 5 mM K₄[Fe(CN)₆]/KCl at: 0.020, 0.050, 0.10 and 0.150 V s⁻¹ (inner to outer CV traces, respectively); (d) Plot of i_p vs. V^½ (♦ = i_pc, ▪ = i_pa); (e) Plot of i_p vs. V sec⁻¹ (♦ = E_pc, ▪ = E_pa)