Two approaches to the development of a true automated multiparameter analyzer for cells, AMAC, are discussed. The AMAC IV uses a water immersion lens mounted downstream from a Coulter Orifice for optical measurements. Although this type of device has a very high numerical aperture (0.70) and optimum light scattering characteristics, it is very difficult to minimize the distance between the objective and the orifice, and increasing this distance results in trajectory irregularities of the cells, with the possibility of exchange of sequence of cells between the orifice and the optical sensing zone. The other, the AMAC III, which is the optimal solution to this problem, performs the optical and electronic measurements simultaneously. This transducer is a small square orifice fabricated out of quartz, with sensing electrodes located at both ends. This combined electro-optical transducer has been used for fluorescence, electronic cell volume and opacity (AC amplitude divided by DC amplitude) measurements. Diffraction effects due to the orifice appear minimal and should not interfere with the scattering produced by the cells. Previous studies with a round but otherwise electronically similar orifice have indicated that it was possible to determine the shift in phase produced by the presence of a particle in the orifice. The capacity to measure all of these parameters simultaneously will greatly enhance the reliability of flow cell analysis.
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