Chronoamperometry differential pulse voltammetry

Electrochemical biosensors have some advantages over other analytical transducing systems, such as the possibility to operate in turbid media, comparable instrumental sensitivity, and possibility of miniaturization. As a consequence of miniaturization, small sample volume can be required. Modern electroanalytical techniques (i.e., square wave voltammetry, chronopotentiometry, chronoamperometry, differential pulse voltammetry) have very low detection limit (1(T7-10 9 M). In-situ or on-line measurements are both allowed. Furthermore, the equipments required for electrochemical analysis are simple and cheap when compared with most other analytical techniques (2). Basically electrochemical biosensor can be based on amperometric and potentiometric transducers, even if some examples of conductimetric as well as impedimetric biosensor are reported in literature (3-5). 

They are applicable to electrodes of any shape and size and are extensively employed in electroanalysis due to their high sensitivity, good definition of signals, and minimization of double layer and background currents. In these techniques, both the theoretical treatments and the interpretation of the experimental results are easier than those corresponding to the multipulse techniques treated in the following chapters. Four double potential pulse techniques are analyzed in this chapter Double Pulse Chronoamperometry (DPC), Reverse Pulse Voltammetry (RPV), Differential Double Pulse Voltammetry (DDPV), and a variant of this called Additive Differential Double Pulse Voltammetry (ADDPV). A brief introduction to two triple pulse techniques (Reverse Differential Pulse Voltammetry, RDPV, and Double Differential Triple Pulse Voltammetry, DDTPV) is also given in Sect. 4.6. 

Differential pulse voltammetry (DPV) is essentially an instrumental manipulation of chronoamperometry. It provides very high sensitivity because charging current is almost wholly eliminated. More important for CNS applications, it often helps to resolve oxidations which overlap in potential. The method combines linear potential sweep and square-wave techniques. The applied signal is shown in Fig. 16A and consists of short-duration square-wave pulses (<100 msec) with constant amplitude (typically 20 or 50 mV) and fixed repetition interval, superimposed on a slow linear potential scan. The Fapp waveform can be generated with a laboratory-built potentiostat, but most DPV work is done with a commercial pulse polarograph (see Appendix). The inset of Fig. 16A shows an enlargement of one pulse. The current is measured just before the pulse... 

The majority of measurements for electroanalysis with microelectrodes are recorded under steady-state conditions by using either chronoamperometry (CA), linear sweep voltammetry (LSV) or cyclic voltammetry (CV) [1,2, 9,10]. Moreover, to solve problems related to the selectivity between species with similar redox potentials, pulsed techniques such as differential pulse voltammetry (DPV) [1, 7, 43 5] and square-wave voltammetry (SWV) [1, 45-49] have been employed. The use of the latter technique also minimizes the influence of oxygen in aerated natural samples [47]. In order to enhance sensitivity in these measurements, fast-scan voltammetry (FSV) [50] or the accumulation of analytes onto an electrode surface has also been performed, in conjunction with stripping analysis (SA) [51]. 

Atomic Force Microscopy Chronoamperometry Chronocoulometry Cyclic Voltammogram Chronovoltabsorptometry Degenerate Four-Wave Mixing Differential Pulse Voltammetry Differential Scanning Calorimetry Electron Energy Loss Spectroscopy Explanation Extended HUckel... 

The influence of CoTSPc and PLL amount in the sensor response was analyzed and best results were obtained when using 0.8 mmol L of CoTSPc and 0.12 mmol L of PLL. The measurements were carried out by differential pulse voltammetry (DPV) and chronoamperometry. With the latter technique a linear response was observed for 0.2-8 mg L DO in solution. 

Although multiple electrochemical techniques exist, those used in freely moving animals are chronoamperometry, differential normal-pulse voltammetry, and fast-scan cyclic voltammetry. Excellent comparisons between these can be found in literature, particularly Troyer et al.[5,7,30] and Robinson el al.[8] and therefore will not be diskussed here. 

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