Multiangle measurement

USCT IT. The US block forms beam data by the mirror-shadow method and ensures simultaneously precise measurement of coordinates of sensors. It consists of two multichannel blocks, namely tomographic (USTB) for multiangle collection of projection data and coordinate (USCB) on surfaces waves for coordinates measurement of US sensors. 

Correlator hardware and linearly-spaced sample time limitations are discussed. Data transformation from an intensity-weighted to a mass-weighted size distribution is demonstrated. The artificial width of broad distributions is discussed. The use of multiangle measurements is considered, and the effect of baseline error is shown using computer simulated data. 

Multiangle Measurements. More information is potentially available from multiangle measurements. Zero-angle extrapolated data are more amenable to proper data transformation. Separation of translational and rotational motion of highly acicular particles is possible. Verification of peaks at more than one angle lends credence to their existence. Simultaneous deconvolution of angular data may provide a useful constraint. 

Beside of the progress in the theory of a particle movement in the zetameter measurement cell, there was progress in particle measurement techniques. New models of zetameters enable automatic measurement of electrophoretic mobility on the basis of the shift of light wave scattered on the particle that moves in the electric field [82]. This technique is called photon correlation spectroscopy (PCS). To increase the sensitivity of the measurement, it is supported by multiangle electrophoretic light scattering (ELS). This combination, allows one also to measure the particle size distribution of the dispersed phase [83]. 

Korgel, B. A., van Zanten, J. H., and Monbouquette, H. G. (1998), Vesicle size distributions measured by flow field-flow fractionation coupled with multiangle light scattering, Biophys. J., 74, 3264-3272. 

Finally, proper alignment to ensure correct positioning of the laser beam, sample, and photodetector are critical for accurate particle size measurements 185 ]. This is especially important for multiangle measurements because misalignment will produce large systematic errors that are difficult to detect and do not average out. In his review, Stepanek [49] discusses the additional experimental complications of wide correlation functions, square root bias, other sources of systematic error, and resolution of <5 function or sharp peaked PSDs. 

With its multiangle capability, MALLS can be used to measure the size as well as the absolute MW of polymers. The multiangle capability seems to be particularly important for the determination of MW and RMS radius of ultrahigh MW polymers as the Debye plot deviates from the linearity. It is also important for the analysis of ultrahigh MW polymers to use accurate A2 value as well as dn/dc as the resulting MW and RMS radius tend to vary with those values. 

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