AbstractThe commercial gel electrophoresis apparatus with intermittent scanning of the migration path and preparative capacity (HPGE‐1000, LabIntelligence) is applicable to polymer solutions as well as gels. Unresolved rat liver microsomes can be isolated from 11–15% polyvinylpyrrolidone (PVP) solution by means of a syringe. The automated band isolation technique applied under resolving conditions in dilute polymer solutions allowed for the sequential isolation of three microsome components with 85, 76 and 75% recovery, respectively, under strict control of the dimensions of the volumetric collection module of the HPGE‐1000 apparatus. Separations of unlabeled microsomes and sea urchin egg components in dilute polymer solutions have been performed, using detection by “fluorescence reduction”. The unlabeled major component of a sea urchin egg homogenate has been isolated from electrophoresis in 1.5% PVP (Mr= 106) solution in 25–50% yield (0.24–4 μg/8 lanes of the HPGE‐1000 apparatus). However, since separations of both microsomes and sea urchin egg granules in dilute polymer solutions are restricted to a narrow range of polymer concentrations, their retardation coefficients,KR= d(log mobility)/d(polymer concentration), are