There has been growing interest in separations-based techniques for the identification and characterization of microorganisms because of the versatility, selectivity, sensitivity, and short analysis times of these methods. A related area of analysis that is scientifically and commercially important is the determination of the presence or complete absence of microbes (in essence, a test for sample sterility). In such a test, it is not of immediate importance to identify a particular microorganism, but rather, to know with a high degree of certainty whether any organism(s) is (are) present. Current regulations require culture-based tests that can take up to 2 weeks to complete. As a rapid alternative, capillary electrophoresis-based methods are examined. Experimental formats are developed that promote the consolidation of all cell types into a single zone (peak) which is separated from the electroosmotic flow front and any other interfering molecular constituents. This process can be accomplished using a segment of dilute cetyltrimethylammonium bromide, which serves to temporarily reverse the migration direction of the cells, and another segment of solution containing a "blocking agent", which serves to stop the cell migration and focus them into a narrow zone. Relatively wide-bore capillaries can be used to increase sample size. This approach appears to be effective for a broad spectrum of bacteria, and analyses times are less than 10 min.