Novel photochemical voltammetric method for the determination of traces of iron in tea

In dilute sulphuric acid, brilliant green (BG) exhibits a sensitive 2.5 order differential polarographic wave at −0.5 V vs. SCE. Trace Fe(III) has a strong catalytic effect on the slow photochemical reaction of BG under ultraviolet irradiation in the presence of oxalic acid as activator. The changes in concentration of BG can be monitored by polarography. On those grounds, a novel photochemical voltammetric method for the determination of 10–4000 ng ml−1 Fe is described by the fixed irradiation time procedure, with a 3σ detection limit of 3 ng ml−1. Iron in tea samples has been analysed with satisfactory results. The photochemical reaction mechanism is discussed.