Immobilization zones through which a sample flows before reaching the proteolytic agents and/or active enzyme and associated electrode/s of an electrochemical test sensor may be used to trap or chemically deactivate active enzyme and/or proteolytic agent deactivating agents. Through either trapping or chemical deactivation, the immobilization zones substantially prevent the enzyme deactivating agents from reaching, and thus reducing the activity of the active enzyme or enzymes. Similarly, trapping or chemical deactivation may be used to prevent or substantially reduce the incidence of the proteolytic deactivating agent or agents from reaching the proteolytic agent.