THEORY OF OPTICAL CHROMATOGRAPHY

To evaluate the performance of optical chromatography, a number of equ ations are theoretically derived using a ray-optics model. These mathe matical formalisms are experimentally verified by determining the rela tionship between the velocity of motion of a polystyrene bead with res pect to the intensity of an applied radiation force under the conditio n where there exists no applied fluid now. The force is confirmed to b e at a maximum at the focal point and to decrease with increasing dist ance from this position. The radiation force is verified to be proport ional to the square of the particle size when the particle diameter is much smaller than the beam diameter. In addition, the radiation force is ascertained to be proportional to the laser power. These results a re in excellent agreement with the proposed theoretical model, which i s based on ray optics. Furthermore, by analogy with conventional chrom atography, fundamental parameters such as retention distance, selectiv ity, theoretical plate number, and resolution are calculated, and opti mum conditions for chromatographic separation are discussed. Based on the results obtained, the dynamic range can be extended by increasing laser power and decreasing now rate. Peak broadening is primarily caus ed by variations in laser power and now rate of the medium for large p articles (> 1 mu m). It is possible, in theory, to distinguish particl es whose diameters differ by less than 1% for particles with a diamete r larger than 1 mu m. Three sizes of polystyrene beads are well separa ted at a now rate of 20 mu m s(-1) and a laser power of 700 mW. This t echnique is also applied to the separation of human erythrocytes. Two fractions, one consisting of cells ranging from 1.5 to 2.4 mu m in dia meter and another consisting of cells ranging from 3.5 to 5.7 mu m in diameter, are observed. Optical chromatography is useful for separatio n and size measurement of particles and biological cells.