A laser interferometric differential refractometer for detection of chromatographic effluent and measurement of volume elasticity of liquids

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Abstract
A recording liquid interferometer with a sensing volume of only 4 mu l and a lower detection limit of refractive index of less than 2*10-7 has been developed using the narrow beam of a small helium-neon gas laser. The instrument was originally designed for the detection of liquid chromatographic effluents in small-diameter packed capillary columns. It is suitable for use at high liquid pressures (e.g. 50 kg cm-2), as in the study of volume elasticity, and probably also as a detector in supercritical fluid-phase chromatography, using a separation technique recently developed in our laboratory. A special and more versatile phase-to-voltage converter was devised to record the optical phase shift in the interferometer. The instrument and some experimental results obtained with it are described.