Firstly, the adductome of he protein macrophage migration inhibitory factor (MIF) with different haptens encompassing different reaction mechanisms and potencies was investigated. After incubation of MIF with the different haptens at 5 times molar excess of hapten, an untargeted Full MS/dd-MS2 experimental approach was used with a QExactive Quadrupole-Orbitrap mass spectrometer. The data were processed with Proteome Discoverer and the suggested sites of adductions were confirmed in parallel reaction monitoring mode (PRM) on the same instruments.