For size exclusion chromatography, the operating conditions and gel selection depend on the application and the desired resolution, see Figure 1. For instance, the smaller the particle size in the stationary phase, according to the size range from the sample, the better the resolution. Also, a very slow flow is not recommended since it will make all particles go through the column very slowly and decreasing the resolution. A moderate flow rate is preferred instead.
Figure 1. A. Chromatogram with good resolution. B. Chromatogram with bad resolution.