Eco-friendly pectin/BCG film sensor: a smartphone-compatible platform for gamma-aminobutyric acid detection

Abstract

This work introduces a biodegradable pectin–bromocresol green (BCG) film integrated into a microplate platform for the colorimetric determination of gamma-aminobutyric acid (GABA). The sensing mechanism relies on electrostatic ion-pair formation between the protonated amine group of GABA (-NH₃+) and the sulfonate group of BCG, producing a distinct color transition from yellow to green. The resulting colorimetric response was quantitatively analyzed using a smartphone-assisted RGB system coupled with ImageJ software. Molecular modelling provided insight into the interaction mechanism and indicated that the GABA-BCG association is dominated by electrostatic interactions. Under optimized conditions, the developed assay exhibited a wide linear range (0.1–1000 mg L−1) with detection and quantification limits of 0.07 mg L−1 and 0.22 mg L−1, respectively. Good analytical precision was achieved (%RSD ≤ 5%), while negligible interference from common amino acids, vitamins and food additives was observed. The method was successfully applied to beverage and dietary supplement samples, demonstrating good agreement with HPLC analysis. The biodegradable BCG–pectin film platform provides a rapid, low-cost, and portable approach for GABA determination and represents a promising sensing strategy aligned with the principles of green analytical chemistry.