Features of Cross-Correlation Spectroscopy for the Study of Liquid Dispersed Media

The method of laser correlation spectroscopy is currently widely used in a number of branches of science and medicine for analysis of variance in liquid media, such as waste water samples, protein solutions, suspensions, or emulsions. Since the classical method of laser correlation spectroscopy gives reliable results only for dilute, non-turbid samples, for turbid media, its modification, the cross-correlation method, is used. The paper describes the principle of operation of the previously developed cross-correlation spectrometer. On the basis of a series of measurements carried out on this spectrometer for various aqueous monodisperse suspensions with particles of known size, the distance was chosen at which the light scattered from the sample should be recorded in order to ensure the maximum signal quality with minimum errors. To demonstrate the results of the device operation, the numerical values of the particle size estimation by the methods of classical laser correlation spectroscopy and cross-correlation are given. The results obtained showed that, first, there is such a distance of scattering registration at which the signal-to-noise ratio of the optical signal has a maximum. Second, as the turbidity of the sample increases, the laser correlation spectroscopy method gives an ever greater underestimation of the calculated particle size, while the cross-correlation method is less sensitive to the concentration of scatterers. To reduce the spread of values obtained by the cross-correlation method, further refinement of the spectrometer is planned.