Paper-Based Colorimetric Biosensor Derived from Gnetum gnemon Peel Tannic Acid for Sensitive Cadmium Detection in Environmental Monitoring Ninik Triayu Susparini*, Fahri Rozanno Putra, Syaddam, Siti Nasiro, Boima Situmeang
Chemistry, Sekolah Tinggi Analis Kimia Cilegon
Abstract
Sustainable and low-cost sensing platforms for heavy metal detection are urgently needed for environmental monitoring. This study reports the fabrication of a paper-based colorimetric biosensor utilizing tannic acid, a naturally occurring polyphenol extracted from the peel of Indonesian Gnetum gnemon L. (melinjo), as a novel biorecognition element for the rapid detection of Cd2+. The total phenolic content was determined to be 191.003 +/- 3.945 ppm, expressed as tannic acid equivalents. The bioactive extract was immobilized onto cellulose paper via a simple immersion method. Upon exposure to Cd2+, the fabricated strips exhibited a distinct color transition from pink to yellowish-brown, a phenomenon attributed to the coordination complex formation between tannic acid and the target ion. The biosensor demonstrated a low detection limit as low as 1.75 x 10 ^-4 ppm, excellent linearity (R2= 0-9965), and good repeatability (RSD = 2.39%). High selectivity toward Cd2+ was achieved over other metal ions, including Hg2+, Pb2+, Cr2+, Fe3+ and Mn2+. Stability test incicated that the extract remained stable at 25-50 C and under light exposure for up to 6 h, but showed degradation under oxidative conditions. Energy dispersive X-ray analysis confirmed Cd adsorption with a characteristic signal of 1.78% elemental composition. This work present a robust, eco-friendly, and low-cost analytical platform that holds significant promise for the point of need monitoring of cadmium contamination in environmental water system.
Keywords: Cadmium detection, Colorimetric sensing,Environmental monitoring,Paper based biosensor,Tannic acid
