Heering H A, Mondal M S, Armstrong F A
Department of Chemistry, Inorganic Chemistry Laboratory, Oxford University, South Parks Road, Oxford OX1 3QR, England.
Anal Chem. 1999 Jan 1;71(1):174-82. doi: 10.1021/ac980844p.
Staircase cyclic voltammetry (SCV) is the digital counterpart of analog cyclic voltammetry (CV). However, when the redox-active species is adsorbed at the electrode surface, the voltammetric peak shapes (width, height, area, and to a lesser extent the reduction potentials) obtained with SCV can be very different from those of CV, even when small potential steps are used. Like analog CV, SCV provides a straightforward method to estimate and subtract the background and charging currents from the desired Faradaic current, while the pulsed nature of SCV provides the time-dependent decay of the Faradaic current, similar to chronoamperometry. Thus, electron-transfer rate constants can be directly measured as a function of applied potential, and no a priori model is required. An SCV equivalent of the square wave "quasi-reversible maximum" of observed peak height versus sampling moment and step size is predicted. The SCV response can only become independent of potential step size and similar to CV at high scan rates (ν > 10 k(0)E(step)), if the current is sampled at half the step interval. The applicability of SCV to studies of redox centers in proteins is illustrated for the two-electron oxidation/reduction of yeast cytochrome c peroxidase, adsorbed at a pyrolytic graphite edge-plane electrode.
阶梯循环伏安法（SCV）是模拟循环伏安法（CV）的数字对应方法。然而，当氧化还原活性物质吸附在电极表面时，即使使用小的电位步长，SCV获得的伏安峰形状（宽度、高度、面积，以及在较小程度上还原电位）也可能与CV的伏安峰形状有很大不同。与模拟CV一样，SCV提供了一种直接的方法来估计并从所需的法拉第电流中减去背景电流和充电电流，而SCV的脉冲性质提供了法拉第电流随时间的衰减，类似于计时电流法。因此，可以直接测量电子转移速率常数作为施加电位的函数，并且不需要先验模型。预测了观察到的峰高与采样时刻和步长的方波“准可逆最大值”的SCV等效值。如果在步长间隔的一半处采样电流，SCV响应仅在高扫描速率（ν>10k(0)E(步长)）下才与电位步长无关且类似于CV。以吸附在热解石墨边缘平面电极上的酵母细胞色素c过氧化物酶的双电子氧化/还原为例，说明了SCV在蛋白质中氧化还原中心研究中的适用性。
