A new method is presented to characterize the retention dynamics of membrane processes with a new virus surrogate used as a tracer and developed in our laboratory. This virus surrogate is an enzyme-labeled MS2 bacteriophage whose activity can be directly and rapidly detected and quantified by amperometry, which is a sensitive electrochemical technique. In the first step, the amperometric measurement was developed and validated. Microfiltration and ultrafiltration experiments consisting of injecting tracers into the feed and monitoring the tracer presence in permeate (or in retentate) by amperometry, and then validating the use of the tracer and its detection technique in the field of membrane filtration. In particular, global retention experiments demonstrated the ability of this method to differentiate among membrane behaviors and dynamic experiments showed the ability of the method to characterize dynamics of retention in a reproducible way. (C) 2012 American Institute of Chemical Engineers AIChE J, 59: 68-78, 2013