Transfer of ions from an aqueous phase to an immiscible liquid (or solid) phase by adding an ion of complementary charge to the aqueous phase.
Note: Ion-pair extraction can also be done by adding the complementary-charge containing compound to the organic phase before extraction.
Source:
PAC, 2016, 88, 517. 'Glossary of terms used in extraction (IUPAC Recommendations 2016)' on page 520 (https://doi.org/10.1515/pac-2015-0903)