改进计时电流法的数学模型和电路实现

当采用电化学计时电流法对样品进行检测时,由于检测系统的延迟,采集到的电化学信号会产生偏差,这种现象在多通道电化学信号快速采集时尤为明显.为克服该问题,我们提出一种新的电化学方法来快速产生电流峰值,通过测量峰值快速准确地测出被测物浓度.本文首先为该方法建立理论模型,推导出电流峰值与被测物的浓度关系;再引入经典控制理论中的控制环节来改进传统电化学电路以实现该方法,并加入峰值检测电路来准确获取电流峰值信号;最后,利用该方法研究K3[Fe(CN)6]和3,3′,5,5′-四甲基联苯胺(TMB)溶液的电化学反应,证明了本方法相比传统计时电流法具有更高的信噪比和灵敏度,电流峰值与浓度呈线性关系,并且检测结果不受采样时间延迟的影响,克服了计时电流法的不足.

Mathematical Model and Circuit Realization to Improve Chronoamperometry

To overcome the disadvantages of chronoamperometry we report a novel electrochemical method where a peak current is quickly generated for the current vs time curve by changing the waveform of voltage excitation in the working electrode. In particular, we derived a mathematical model to illustrate the principle of this method and it can also be used to demonstrate that the peak current is linear with regards to the concentration of the target substance. Moreover, we developed a device with an improved electrochemical circuit using a control element from control theory to change the waveform of voltage excitation. The improved circuit can detect the peak automatically without a precise sample time. Finally, the device was used to study the electrochemical behavior of K₃[Fe(CN)₆] and 3,3',5,5'- tetramethylbenzidine (TMB). We show that the method has a better signal to noise ratio and higher sensitivity than chronoamperometry. The obtained peak current is linear with regards to the concentration of the target substance and can be quickly detected without a precise sample time.