This article describes a simple exercise using a free, easy-to-use, established online program. The exercise helps to reinforce protein purification concepts and introduces undergraduates to pH as a parameter that affects anion-exchange chromatography. The exercise was tested with biochemistry majors at California State University-Chico. Given the versatility of the program, this work is also a model for instructors that wish to develop their own exercise to help teach other protein purification techniques.