Abstract: A micellar microextraction technique has been developed for the preconcentration and spectrophotometric determination of phosphate ions in aqueous media. This method is based on the formation of a reduced form of molybdophosphoric heteropolyacid and its extraction from the aqueous phase into a supramolecular solvent. The supramolecular solvent phase is formed in situ by introducing an amphiphile and a coacervation agent into the acidic aqueous phase. The feasibility of using biodegradable alkyl polyglucoside (C8–C10) as an amphiphile and carboxylic acids as coacervation agents has been investigated. In the acidic medium required for the formation of the reduced form of molybdophosphoric heteropolyacid, the phase of the supramolecular solvent is separated. The maximum absorbance of the extract is achieved using pivalic acid as the coacervation agent. The procedure is characterized by the limit of detection (3σ) for phosphate ions 5 µg/L. The technique is environmentally friendly and does not require the use of expensive equipment. © Pleiades Publishing, Ltd. 2024. ISSN 1061-9348, Journal of Analytical Chemistry, 2024, Vol. 79, No. 10, pp. 1408–1414. Pleiades Publishing, Ltd., 2024.