Analytical Sciences

A Green Sequential Injection Spectrophotometric Approach Using Natural Reagent Extracts from Heartwood of Ceasalpinia sappan Linn. for Determination of Aluminium

Watsaka SIRIANGKHAWUT,* Yaowalak KHANHUATHON,** Piyanete CHANTIRATIKUL,* Kraingkrai PONHONG,* and Kate GRUDPAN**

*Creative Chemistry and Innovation Research Unit, Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Mahasarakham University, Maha Sarakham 44150, Thailand
**Department of Chemistry, Faculty of Science, and Chemistry Research Group for Green Innovation, Center of Excellence for Innovation in Analytical Science and Technology, Chiang Mai University, Chiang Mai 50200, Thailand

A cost-effective and environmentally friendly approach using a simple sequential injection spectrophotometric system with a non-synthetic reagent from plant extracts was proposed for a green analytical-chemistry methodology. The crude aqueous extracts from heartwood of Ceasalpinia sappan Linn. in acetate buffer pH 5.5 were utilized as an alternative natural reagent for the quantification of aluminium. The extracts contained homoisoflavonoid compounds, brazilin, and brazilein, which reacted with Al³⁺ to form reddish complexes with the maximum absorption wavelength at 530 nm. The optimum conditions for the sequential injection parameters, such as sequential profile, sample and reagent volumes, and the pH effect, were investigated. Under the optimum conditions, a linear calibration graph in the range of 0.075 – 1.0 mg L⁻¹ Al³⁺ was obtained with limits of detection and quantification of 0.021 and 0.072 mg L⁻¹ Al³⁺, respectively. Relative standard deviations of 3.2 and 2.4% for 0.1 and 0.25 mg L⁻¹ Al³⁺ (n = 11), respectively, and sampling rate of 128 injections h⁻¹ were achieved. The developed system was successfully applied to pharmaceutical preparations, water, and beverage samples. The results agreed well with those obtained from the ICP-AES method. Good recoveries between 87 and 104% were obtained.

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