Simultaneous determination of the mean and standard deviation of quasi-monodisperse size distributions of microspheres by static light scattering

Pinto, P. N.; Fernandes, Paulo; Guerra, Rui Manuel Farinha das Neves

http://hdl.handle.net/10400.1/5077

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Authors

Pinto, P. N.

Fernandes, Paulo

Guerra, Rui Manuel Farinha das Neves

Abstract(s)

The objective of this work is to quantify the accuracy and precision of particle sizing performed through light scattering goniometry. A rigorous characterization of this simple method depends on a complete description of the scattering geometry, and to our knowledge this has not yet been done. We have determined the central diameter (d0) and standard deviation (σ) of samples of polystyrene spheres with a narrow normal distribution of diameters through a χ2 fit to the light scattering phase function. The fit is performed simultaneously in the variables d0 and σ. The model for the fit includes Mie scattering calculations, integration of the phase function over a normal distribution of diameters and a complete description of the scattering geometry. Experimental tests on spheres with diameters between 2 and 7 μm show that this method provides excellent accuracy and precision for the determination of d0 and good accuracy for the determination of σ. The precision in σ is poor in relative terms but in absolute terms it is around 0.05 μm within the range of sizes tested. We calculate the uncertainty limits for the determination of d0 and σ and show that they are consistent with all the supplier values except the value of σ for the 2 μm spheres, where aggregation was detected by optical microscopy. Other topics included in this work are: (i) comparison between our method and the classical simple fit through a pure monodisperse system (σ = 0); and (ii) dependence of the quality of sizing on the angular range of the measurement. Finally, comparison with published results shows that simple goniometry may outperform more complex methods.

Keywords

Mie scattering Light scattering Particle sizing Particle size distributions

URI

http://hdl.handle.net/10400.1/5077

Citation

Pinto, P N; Fernandes, P.; Guerra, R. Simultaneous determination of the mean and standard deviation of quasi-monodisperse size distributions of microspheres by static light scattering, Measurement Science and Technology, 18, 5, 1209-1223, 2007.