Abstract: An optical system is provided with a laser device for emitting a multiplet laser beam with two types of frequencies F1, F2, and a sample rotator on which a reference sample and a test sample containing substances are set for rotating both the test sample and the reference sample to separate the substances contained in the test sample. The test sample and the reference sample are irradiated with the multiplet laser beam one after another to shift the phase of the laser beam. The optical system is further provided with a polarizer for polarizing the multiplet laser beams transmitting through the test sample and the reference sample to produce both a test sample signal with a frequency .DELTA.F=F1-F2 and a reference sample signal with the frequency .DELTA.F, and a signal analyzer for analyzing a phase difference between the sample signals to determine an index of refraction of the test sample. Therefore, the substances containing in the test sample are specified.

Abstract: A rotor for separation and collection of specimen particles carried by a liquid buffer by continuous centrifugal elutriation, whereby the interior of the rotor itself is employed as a separation chamber. This separation chamber is shaped such that the circumferential cross-sectional area thereof continuously increases from the outer to the inner periphery in a specific manner, so that centrifugal elutriation is accomplished by pumping the liquid buffer from positions at the outer periphery of the separation chamber towards the inner periphery. A transparent cover can be employed to cover the separation chamber, so that the separated material becomes directly visible as a peripheral ring, without the need to employ a stroboflash lamp, and in addition it is possible to separate large amounts of material by a single centrifuging operation.