After a primary infection protocol of macrophages with Leishmania amazonensis, the percentage of infection drops as infection progresses and the uninfected population of macrophages mask the effects of infection for electrophysiological studies. In order to increase or maintain the infection percentage, we introduce an enrichment process after primary infection, which increases the possibility of following the infection longer times than any known process. A membraneless separation technique, step-SPLITT fractionation, implying flow and transverse gravity field in a ribbon-like channel, was used for enriching samples of macrophages infected with particles and with L. amazonensis. We demonstrate the capability of the s-SPLITT of generating, from a mixture resulting from a primary infection, an enriched and a depleted fraction with infected cells, without using any selective labeling pre-processing. It is also shown that a continuous sorting is possible without damaging cells and the losses of matter into the separation chamber is minimal.