The detector was equipped with Au working and Ag/ AgCI reference electrodes, operating with the following working electrode pulse potentials and durations: E1=+0.05 V (10=0.00 s), E2=0.05 V (tl=0.42 s), E3=+0.75 V (t3=0.43 s), E4=+0.75 V (t4=0.60 s), E5=-0.60 V (t5=0.61 s), E6=-0.60 V (t6=0.96 s). The duration of the IPAD integration interval was set at 0.2-0.4 s.