Spectrophotometric determination of tin in canned fruit samples using sappan wood extract as a natural reagent

This research aimed to develop a green spectrophotometric method for the determination of toxic tin in canned fruit samples. A natural reagent derived from renewable sappan wood (locally known as phang) extract was employed to replace conventional toxic chemical reagents. The results demonstrated that brazilein, the active phytochemical, can be readily extracted from phang powder by heating and stirring in a pH 2 buffer solution at 90 °C for 10 min. The reaction between tin(IV) and brazilein proceeds rapidly at pH 2, forming a red complex within 10 min. The resulting solution exhibits a maximum absorbance at 531 nm with a molar absorptivity of 17,688 L mol^-1 cm^-1. Under the optimized conditions, the developed method achieved a limit of detection of 9.3 μg L^-1 (n = 10, 3s_o'). A wide linear range between 0.03 and 1.0 mg L^-1 was obtained with a coefficient of determination (R²) of 0.9999. The intra-day and inter-day precision were below 2.2% (n = 3) and 6.3% (n = 12) relative standard deviations, respectively, for different fruit matrices containing more than 28 μg g^-1 of tin. Method trueness was validated by flame atomic absorption spectrophotometry and no significant difference was observed between the two methods (p = 0.29). Tin in 15 canned fruit samples was found in a range of 22-209 μg g^-1 using the developed method. This study represents the first application of brazilein extracted from phang for tin determination, offering a lower detection limit and a wider linear range compared with previously reported spectrophotometric methods based on synthetic chemical reagents.