Mobility measurements by phase analysis.

A new instrument, based on the principle of phase analysis light scattering (PALS) for the measurement of electrophoretic mobilities, has been produced. Such measurements are particularly useful in the study of dispersions in nonpolar and highly conducting media. The current PALS configuration can be used to measure mobilities up to 3 orders of magnitude lower than with the conventional Doppler mode. The device has a number of new features; in particular, all the signal processing is digital and the optical system features a reference beam configuration. Data are presented to show that on suitable samples both the PALS technique and conventional laser Doppler electrophoresis can be performed on the same instrument and the techniques are in good agreement.