Multiple sample light scattering

MCF McFaul, C.A., Alb, A M., Drenski, M.F., and Reed, W.F., Simultaneous multiple sample light scattering detection of LCST during copolymer synthesis, Polymer, 52, 4825, 2011. 

FIGURE 13.16 Second generation ACOMP used to determine how much composition of anionic SS a copolymer with NIPAM can have and still exhibit an LCST (at lOmM ionic strength) fractional conversion of SS and total comonomers and average instantaneous SS composition (top). LS at 90° (log scale) for three detectors at different temperatures increases abruptly at the LCST when there is only about 4% SS in the copolymer (bottom). Adapted with permission from McFaul CA, Alb AM, Drenski MF, Reed WF. Simultaneous multiple sample light scattering detection of LCSTduring copolymer synthesis. Polymer 2011 52 4825 833. 

Drenski MF, Reed WF. Simultaneous multiple sample light scattering for characterization of polymer solutions. J Appl Polym Sci 2004 92 2724-2732. 

FIGURE 14.3 The decrease in light scattering intensity in time as hyaluronate is hydrolyzed by hyaluronidase. Results are shown for various concentrations of hyaluronate. Reprinted with permission from Drenski MF, Reed WF. Simultaneous multiple sample light scattering for characterization of polymer solutions. J Appl Polym Sci 2004 92 2724-2732. 

The latest trend is to smaller beads in smaller columns, as this saves eluent and shortens the time for a chromatographic analysis. This argument can be correct if only one suitable detector is used. However, these modern small columns are not optimal for a combination of detectors. So-called multiple detection is a combination of some detectors with different measurement principles (differential refractometer, spectral photometer, light-scattering detector, on-line viscometer) behind the last column, mostly in series, seldom in a branched ( parallel ) order. In this way, the tedious preparative fractionation of a polymer sample can often be avoided. 

To test the applicability of statistical techniques for determination of the species contributions to the scattering coefficient, a one-year study was conducted in 1979 at China Lake, California. Filter samples of aerosol particles smaller than 2 ym aerodynamic diameter were analyzed for total fine mass, major chemical species, and the time average particle absorption coefficient, bg. At the same time and location, bgp was measured with a sensitive nephelometer. A total of 61 samples were analyzed. Multiple regression analysis was applied to the average particle scattering coefficient and mass concentrations for each filter sample to estimate aj and each species contribution to light scattering, bgn-j. Supplementary measurements of the chemical-size distribution were used for theoretical estimates of each b pj as a test of the effectiveness of the statistical approach. 

Standard static and dynamic light scattering methods assume that there is very little multiple scattering by the particles, that is, the dispersion has to be sufficiently dilute so that the photons are scattered only once as they pass through the sample. Is there a way to look inside a dispersion that is cloudy or milky, such as a foam, and to extract information on the local structure and its kinetics and relaxation Or, is it possible to tailor a dispersion so that... 

Flow cytometry [141, 142] is a technique that allows the measurement of multiple parameters on individual cells. Cells are introduced in a fluid stream to the measuring point in the apparatus. Here, the cell stream intersects a beam of light (usually from a laser). Light scattered from the beam and/or cell-associated fluorescence are collected for each cell that is analysed. Unlike the majority of spectroscopic or bulk biochemical methods it thus allows quantification of the heterogeneity of the cell sample being studied. This approach offers tremendous advantages for the study of cells in industrial processes, since it not only enables the visualisation of the distribution of a property within the population, but also can be used to determine the relationship between properties. As an example, flow cytometry has been used to determine the size, DNA content, and number of bud scars of individual cells in batch and continuous cultures of yeast [143,144]. This approach can thus provide information on the effect of the cell cycle on observed differences between cells that cannot be readily obtained by any other technique. 

One obvious way to reduce the contribution of the multiple light scattering is to use a very thin sample cell of an optical path length below 100 Alternatively, PhiUies suggested... 

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