I have developed a tandem mass spectrometry (MS/MS) based approach for the direct determination of antibody heavy and light chain pairing. This approach eliminates the need for costly and invasive genomics approaches (e.g. B cell sequencing and hybridoma) for determining heavy and light chain pairing during therapeutic antibody discovery. IgG antibodies are composed of two copies of a light chain and two copies of a heavy chain covalently linked by intermolecular disulfide bonds. I have demonstrated that ultraviolet photodissociation (UVPD) and electron capture dissociation (ECD) can efficiently cleave the intermolecular disulfide bonds that bind the heavy and light chains together. This yields a MS/MS spectrum that contains the mass of the intact antibody or Fab fragment, intact mass of the light chain, intact mass of the heavy chain or Fd subunit, and product ions that provide confirmation of the (complementarity determining regions) CDR sequences. This information provides unambiguous confirmation of heavy and light chain pairing. These are completely unprecedented results and will have significant impact on therapeutic antibody discovery as well as quality control during production of antibody therapeutics.