A fiber-optic probe for particle sizing in concentrated suspensions

Abstract

A fiber-optic probe employing two monomode optical fibers, one for transmitting a Gaussian laser beam to the scattering volume and the second, positioned at some backscatter angle, for receiving the scattered light is described. Performance and suitability of the system for a process control environment is assessed by studying a suspension of polystyrene latex particles over a wide range of sizes and concentrations. The results show that the probe is ideal for a process control environment in industrial and laboratory applications. Particle size is recovered, without any additional corrections for multiple light scattering, in concentrations containing up to 10% solids of 39-nm polystyrene latex spheres.

Characterization of Submicron Systems via Optical Methods

“…Such dilutions have the potential to profoundly perturb any colloidal system, but microemulsions, defined as systems at thermodynamic equilibrium, are particularly susceptible. 29 Novel approaches, such as use of fiber optic probes, 30 have been implemented to reduce the need for such dilutions, and at least one such system is commercially available.…”

Diffusing-wave spectroscopy

“…Primarily, it provides, without the need for index matching, quantitative information about particle displacements <<>,2(t» up to high concentrations-well in the regime of high order multiple scauering. Ir works best when single and low order scattering are negligible, and therefore ideally complements other recently developed techniques such as t\m-color cross-correlation spectroscopy [11] and single-mode fiber-optic dynamic light scattering [12][13][14] Oespite discussions about the accuracy of current OWS theories [15] and difficulties with the proper description of incident and diffusing light near the sampIe surface [16][17][18][19], it seems fair to say that OWS is by now weil established to provide quantitative information, to within a few % accuracy, about <o,2(t» , 0,. particle sizes, flow rates, ultrasonic amplitudes, and so on, for homogeneous multiple scattering media, if the few relevant experimental parameters (sampIe geometry, L, 1·, .... ) are weil controlled. Recent illustrations for this are given in the section entitled DurS on homogeneolls colloidal systems, whereas the two sections following on from this deal with novel developments into more complex inhomogeneous systems and multiple scattering imaging of objects in motion.…”

<title>Laser light scattering: from an advanced technology development program to experiments in a reduced gravity environment</title>

“…The study of milky concentrations of polystyrene standards in water ranging up to 10% weight concentration without multiple scattering problems was enabled through the use of these backscatter probes. 29 Work with high concentration protein solutions without the multiple scattering problems was successfully accomplished by using LLS and backscatter fiber optic probes. The probes have proved to be of great importance when LLS is applied to protein crystal growth experiments 30 • Reference 30 discusses the detection of the size of BSA and Lysozyme proteins in solutions of varying concentration.…”