A system and method to generate a concentration gradient eluent flow are described. The concentration gradient eluent flow can include at least two different generants. A liquid can be pumped to an eluent generating device. A first controlling signal can be applied to a first eluent generator to generate a first generant. A second controlling signal can be applied to a second eluent generator to generate a second generant. Either the first and/or the second controlling signal can be varied as a function of time to generate the concentration gradient eluent flow.