We studied the quantification of silver birch (Betula bendula) triterpenoid, papyriferic acid with high performance liquid chromatography and mass spectrometry (LC/MS) using atmospheric pressure electrospray ionization (API-ES), atmospheric pressure chemical ionization (APCI) and atmospehric pressure photoionization (APPI) techniques, in positive and negative ion modes. The results show that in positive ion mode API-ES exhibited the highest sensitivity compared with the other ionization systems. Ionization process of API-ES under the experimental conditions is soft and only few and small fragment ions were observed. The simple electrospray spectrum of papyriferic acid consisted mainly of [M+Na]+ions, while also [M+K]+ions were found. The detection limit for positive ions of papyriferic acid was 100 pg, 400 pg and 3 ng for API-ES, APCI and APPI, respectively. At negative mode, the detection sensitivity of papyriferic acid was fairly low (for API-ES 200 pg and APCI 20 ng) or it was not detected at all (APPI).