A green chemistry system that utilizes natural extract as an alternative reagent for determination of metal ions has been
investigated. The extract of green tea, a common beverage, is used for quantification of iron. The green tea extract was
prepared in acetate buffer pH 4.8 and could be used without further purification with a simple flow injection (FI) system.
The intensity of iron-green tea extract complexes was monitored using a green LED photometer. The use of natural
reagent combined with the simple FI-LED photometer set up offers an alternative low cost and rapid system for the
determination of metal ions. Detection limit of 0.05 ppm of Fe(III) ion and sampling rate of 180 injections h–1 were
achieved. Application of this system to the analysis of iron in pharmaceutical samples was demonstrated, and the results
agreed well with those from the AOAC method.