Antibody drug conjugates (ADCs) are potent and specific biopharmaceuticals. These large molecules are typically analyzed using ELISA methods, which may not have the selectivity to accurately quantify the ADC alone. HPLCMS/MS analysis of the digested ADC is an alternative approach that provides better selectivity. In order to increase the selectivity/sensitivity of the method, analysis was conducted using microflow HPLC (MFLC) and immunocapture sample preparation. Typical immunocapture techniques require the use of labor intensive magnetic beads. Thermo Scientific™ MSIA™ sample preparation is simple and can be fully automated, greatly increasing the sample throughput. The resulting MSIA data results in lower limits of quantitation due to the selectivity and extraction efficiency improvements when compared to other non-immunocapture methods such as pellet digestion.