Development of Eco-Friendly Agarose-Based Sensor for Enhanced Cadmium Determination in Diverse Food, Biological, and Environmental Matrices

Abstract

A highly sensitive and selective optical sensing membrane for Cd²⁺ detection was fabricated via covalent attachment of 2-(2-amino-3-hydroxy-pyridine-4-ylazo)benzoic acid (AHPAB) onto an agarose matrix. Key parameters, including solution pH, AHPAB loading, and immobilization time, were systematically optimized. Upon exposure to Cd²⁺ ions at pH 3.75, a pronounced shift in the peak absorbance of AHPAB was observed. The developed sensor exhibited rapid response, good durability, and no noticeable leaching of the immobilized reagent. It also demonstrated excellent reproducibility, high stability, and an extended operational lifespan. Moreover, strong selectivity and sensitivity toward Cd²⁺ were maintained even in the presence of various alkali, alkaline earth, transition, lanthanide, and other heavy metal ions. The membrane displayed a linear response across the concentration interval of 15–190 ng/mL, with limits of quantification and detection of 15 and 4.5 ng/mL, correspondingly. Regeneration of Cd²⁺ from the membrane was achieved using 0.05 M EDTA, yielding reversible and reproducible signals with a relative standard deviation of 1.95%. The sensor was successfully utilized for Cd²⁺ detection in food, biological, and environmental water samples.