Amphiphilic surfactants in analytical sample preparation: A self-assembly perspective on mechanisms, green metrics, emerging systems and applications

Sample preparation governs the speed, cost and environmental footprint of chemical analysis, and amphiphilic surfactants have become central to efforts to make this step greener. This review argues that the diverse surfactant-based methods now in use are best understood not as separate techniques but as related expressions of a single organizing principle: molecular self-assembly. Building on this premise, a unified mechanistic account is developed, linking cloud point extraction, coacervative and micellar methods, supramolecular-solvent microextraction, surfactant-modified solid-phase extraction and energy-assisted variants through common principles of amphiphile self-organization in liquid and interfacial systems. Representative applications across environmental, food, and pharmaceutical and clinical analysis are compared critically, emphasising the capacity of surfactant media to enrich trace analytes from complex matrices with little or no organic solvent. Emerging alternative media, including deep eutectic solvents, surface-active ionic liquids and biosurfactants, are assessed alongside the quantitative greenness metrics increasingly used to substantiate sustainability claims. This review confronts the paradox that surfactants promoted as green may themselves be toxic and poorly biodegradable, and identifies artificial-intelligence-assisted method design, biodegradable extractants and stimulus-responsive systems as the field's most promising directions. Surfactant self-assembly, in conclusion, reshapes sample preparation around the matrix rather than against it.