Square-Wave Voltammetry and Dissolved Oxygen

4 Square-Wave Voltammetry and Dissolved Oxygen Problem 

Through the use of SWV, how is it possible to selectively minimise some Faradaic currents In particular, how is it possible to reduce the size of an oxygen signal from an SWV voltammogram recorded in aqueous solution, without degassing  

As described in Problem 9.3 part (ii) the increased sensitivity of SWV arises due to the possibility that the analyte of interest can be reoxidised (or re-reduced) on the reverse pulse. Ckjnsequently, not only is there an increase in net current, but the reoxidised analyte may then undergo further reduction on the next pulse. This is only possible for analytes which exhibit chemically and electrochemicaUy reversible electron transfer. Consequently, SWV is more sensitive to such species. 

The reduction of oxygen in aqueous solutions is irreversible in nature in terms of both the chemical and electrochemical processes involved, and hence it is not reoxidised on the reverse pulse, such that the voltammetric wave as measured is not enhanced. Thus in a solution containing a reversible species of interest and oxygen (where both react electrochemicaUy at similar potentials), the use of SWV may allow analytically useftil voltammetric data to be obtained without degassing of the solution. As a caveat, it should be noted that although it is possible to measure an analytically useftil voltammetric response in the presence of oxygen, the chemistry occurring within the solution may be altered by its presence. 

---