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

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.