Flow injection spectrophotometry using natural reagent from Morinda citrifolia root for determination of aluminium in tea

A flow injection (FI) spectrophotometric method with using natural reagent extracted from Morinda citrifolia root has been developed for determination of aluminium. The extract contained anthraquinone compounds which could react with Al3+ to form reddish complexes which had maximum absorption wavelength at 499.0 nm. The extract could be used as a reagent in FI system without further purification to obtain pure compound. A sensitive method for determination of aluminium in concentration range of 0.1–1.0 mg L−1, with detection limit of 0.05 mg L−1 was achieved. Relative standard deviations of 1.2% and 1.7% were obtained for the determination of 0.1 and 0.6 mg L−1 Al3+ (n = 11). Sample throughput of 35 h−1 was achieved with the consumption of 3 mL each of carrier and reagent solutions per injection. The developed method was successfully applied to tea samples, validated by the FAAS standard method. The method is simple, fast, economical and could be classified as a greener analytical method.