Dispersion phenomena contributing effects

Radial dispersion contributes more significantly to the peak profile (dilution of the sample plug) than does axial dispersion. This type of fluid motion results in a washout effect accounting for the small carry-over between successively injected samples. This advantageous phenomenon in turn is a result of the use of low flow rates and small tubing bores, and leads to decreased peak widths and hence increased sample throughputs. 

There is another effect that should be taken into accoimt when ATR spectra are compared to transmission spectra the variation of the refractive index across an absorption band. This phenomenon is known as dispersion, which affects the spectra for internal reflection, contributing to an increase in band intensity, a slight shift in the band position, and a distortion of the band shape. The ATR spectra reported in this work should not be distorted by dispersion, however, since they were obtained at an incidence angle well above the critical angle. 

One such phenomenon is the low-frequency dielectric dispersion (LFDD) of suspensions. This is the denomination given to the frequency dependence of the permittivity of dispersed systems for applied electric field frequencies close to characteristic frequencies of relaxation (typically in the kHz to MHz range) in the electrical double layer. A significant effect has been reported of the properties of the medium, of the particle, and of their interface on the relaxation pattern of the permittivity, in particular number of relaxations observed, natural frequencies, and amplitudes of those relaxations. This explains the increased interest in the determination of the permittivity of colloidal systems during the last decade or so [19-26]. In this contribution, we will show results that clearly demonstrate that the presence of the SPs affects the amplitude and characteristic frequency of the LFDD far more than could be explained by simple considerations of accumulation of effects. 

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