Electrocatalytic determination of hydroxylamine with alizarin red S as a homogenous mediator on the glassy carbon electrode

The anodic oxidation of hydroxylamine has been studied on a glassy carbon electrode by electrocatalytic effect of Alizarine red S (ARS) as a homogenous mediator in 0.1 M the phosphate buffer (pH 6), using the diagnostic techniques of cyclic voltammetry, linear sweep voltammetry and chronoamperometry. Anodic oxidation of hydroxylamine by cyclic voltammetry showed that the catalytic current of the system depends on the hydroxylamine concentration. The magnitude of the peak current for ARS increased sharply in the presence of hydroxylamine and was proportional to its concentration. Hydroxylamine was detected over a linear concentration range of 10–800 μM with low detection limits, which was 7.2 μM with linear sweep voltammetric method. The diffusion coefficient of hydroxylamine was also estimated using chronoamperometry ( D = 2.16 × 10 −6 cm 2 s −1). The chronoamperometric studies were also used to determine the catalytic rate constant for catalytic reaction of ARS with hydroxylamine ( k = 1.86 × 10 3 M −1 s −1). The experimental results showed that the peak current varied in the presence of different metal cations but these effects were omitted in the presence of EDTA, while almost all of the anions had no effect on the peak current of hydroxylamine. This new voltammetric method of hydroxylamine determination is very rapid, reproducible, selective and sensitive, and can be used for the real sample analysis. The importance of the technique is because of its ability to electrocatalytically determine the hydroxylamine with ARS as homogenous electrocatalyst, while it does not need to be prepared as for the modified electrodes. The independency of the system from the interferences and its ability of easily removing the effect of most cationic interferences are the important features of the technique.