Development of a Tannic Acid-Gelatin Modified Filter Paper Membrane for Trace Lead Detection in Water

Abstract

A novel membrane-based solid-phase extraction (SPE) device was developed using cellulose filter paper modified with a tannic acid–gelatin (TA/GE) composite for the preconcentration of lead (Pb(II)) ions from aqueous samples. The TA/GE sorbent layer was fabricated via cross-linking gelatin with tannic acid at pH 9, forming a stable, partially insoluble network that enhances the membrane’s mechanical strength and ion-binding capability. Characterization by SEM confirmed the successful modification, while micro-XRF analysis demonstrated the membrane’s effective adsorption and elution of Pb(II). After preconcentration, square wave anodic stripping voltammetry (SWASV) was used for quantitative determination. The method exhibited linear range of 10–100 μg·L–1, with a limit of detection (LOD) of 2.7 μg·L–1. Method validation using a certified reference material for trace metals in water produced a combined measurement uncertainty (U) of 9 μg·L–1 at the 95% confidence level for a sample containing 61 μg·L–1 Pb(II), showing no significant deviation from the certified value. The developed method was further applied to drinking water and river water samples, achieving recoveries of 82–110% for spiked samples. These results confirm that the TA/GE-modified membrane provides a simple, low-cost, and environmentally friendly platform for trace Pb(II) analysis, with performance meeting both WHO (10 μg·L–1) and Thailand Pollution Control Department (50 μg·L–1) regulatory standards for drinking and surface water.