Recently, we found that the Raman optical activity (ROA) technique can be used to monitor even a weak lanthanide luminescence including circular polarization. In the present study we compare circularly polarized luminescence (CPL) spectra of Eu(III), Sm(III), and Er(III) induced by aqueous solution of sialic acid. For Eu providing the strongest signal a chelation model was proposed where the carboxyl adopts the axial conformation and carboxyl oxygen is attached to Eu(III).