Characterization of the sensitivity of side scatter in a flow-stream waveguide flow cytometer

Background: We previously reported a new optical configuration, in which bo th the side scatter and the fluorescence are collected using the index-guid ed, total internal reflection of a flow stream in air (the flow-stream wave guide). Methods: Using a mixture of 0.202-mu m and 0.093-mu m diameter polystyrene beads, we have characterized the side scatter (SSC) sensitivity of a custom -built flow cytometer (miniFlo) which incorporates a flow-stream waveguide. Results: The SSC-triggered SSC signal of 0.093-mu m polystyrene beads in wa ter was almost baseline resolved from the background. We also measured the SSC-triggered SSC signal of the same beads in water on our FACScan, which i s a commercial unit with the conventional optical arrangement that uses a c ustom imaging objective to collect light from a sheath flow cuvette in perp endicular direction-the signal from 0.093-mu m beads was not resolved from the background. Conclusions: The SSC sensitivity of miniFlo is one of the best reported in the literature. Cytometry 37:160-165, 1999. Published 1999 Wiley-Liss, Inc.