State of the art of diffusive gradients in thin films for in situ speciation analysis and chemical fractionation of metals and metalloids in water

Diffusive Gradients in Thin Films (DGT) has become an established passive sampling technique because it provides time-integrated, in situ measurements of labile metal(loid) species. Its capacity to support metal(loid) speciation and correlate labile fractions with ecotoxicological thresholds has further increased its relevance in environmental monitoring. Given the growing number of publications and the expanding scope of applications, a critical overview of recent developments is justified. This review comprehensively analyses advances in DGT applications for metal(loid) speciation and fractionation in aquatic systems from 2020 to 2025. Emphasis is given to technical improvements, including the integration of DGT with complementary analytical techniques and the development of customized binding resins targeting specific analytes. Our analysis indicates that DGT is increasingly recognized as a tool for ecological risk assessment and may gain attention in regulatory frameworks if extensive and collaborative validation networks are pursued. Advances in design and data interpretation enhanced DGT specificity and versatility. However, challenges such as the lack of standardized practices, influence of diffusive boundary layers (DBL) and biofilm formation remain critical factors affecting accuracy. In summary, DGT continues to evolve as a powerful tool for environmental monitoring, offering enhanced capabilities for understanding contaminant dynamics, supporting risk assessment, and informing regulatory practices.