REKUPIS: Preliminary Spectral Characterization of a Banana Peel Extract-Based Reagent for Urea Colorimetry

Abstract

Reagents for urea and creatinine assays are usually imported, synthetic, and costly for vocational laboratory practicums. This study reports the first-year development of REKUPIS, a reagent formulated from an ethanolic banana peel extract in neutral phosphate buffer, and its preliminary spectral characterization. Ripe peels of four local cultivars (Raja, Susu, Kluthuk, and Kepok) were bought from three traditional markets in Lombok, dried, ground, macerated in ethanol for 48 h, filtered, concentrated on a water bath, and formulated into 3–4 reagent formulas. The absorbance of 16 urea test samples was read in a 96-well plate at 490 nm, 500 nm, and 560–600 nm. Mean absorbance was highest at 490 nm (0.1364 ± 0.0671; range 0.0517–0.3035) and fell to 96.9% of that value at 500 nm and 78.5% at 560–600 nm, while the ranking of samples was nearly identical at all wavelengths (Spearman ρ ≥ 0.97). Because the highest response occurred at the shortest wavelength tested, the absorption maximum probably lies at or below 490 nm and remains to be defined by wider scanning. The banana peel reagent produced a measurable colorimetric response, and about 490 nm is a reasonable starting wavelength for calibration, precision, and stability studies; analytical performance has not yet been demonstrated.