A novel and simple fluorescence enhancement method is introduced for selective pyrophosphate (PPi) sensing in an aqueous solution. The method is based on a 1:1 metal complex formation between tris(8-hydroxyquinoline-5-sulphonate) thulium(III) [Tm(QS)3] and PPi ion. The linear response covers a concentration range of 1.6 × 10−7–1.0 × 10−5 mol/L PPi and the detection limit is 2.3 × 10−8 mol/L. The association constant of Tm(QS)3–PPi complex was calculated as 2.6 × 105 mol/L. Tm(QS)3 shows a selective and sensitive fluorescence enhancement toward PPi ion in comparion with I3−, NO3−, CN−, CO32−, Br−, Cl−, F−, H2PO4− and SO42−, which is attributed to higher stability of the inorganic complex between pyrophosphate ion and Tm(QS)3. Copyright © 2011 John Wiley & Sons, Ltd.