page_title: Multiangle light scattering
section_title: The Zimm plot and batch collection
hierarchical_section_title: Multiangle light scattering / Applications / The Zimm plot and batch collection
caption_attribution_description: English: This file is an explanation of how a Zimm Plot is used to determine molar mass and size
context_page_description: Multiangle light scattering describes a technique for measuring the light scattered by a sample into a plurality of angles. It is used for determining both the absolute molar mass and the average size of molecules in solution, by detecting how they scatter light. Collimated light from a laser source is most often used, in which case the technique can be referred to as multiangle laser light scattering. The insertion of the word “laser” was intended to reassure those used to making light scattering measurements with conventional light sources such as Hg-arc lamps that low angle measurements could now be made. Until the advent of lasers and their associated fine beams of narrow width, the width of conventional light beams used to make such measurements prevented data collection at smaller scattering angles. In recent years, since all commercial light scattering instrumentation use laser sources, this need to mention the light source has been dropped and the term MALS used throughout.
context_section_description: MALS is most commonly used for the characterization of mass and size of molecules in solution. Early implementations of MALS such as those discussed by Bruno H. Zimm in his paper “Apparatus and Methods for Measurement and Interpretation of the Angular Variation of Light Scattering; Preliminary Results on Polystyrene Solutions” involved utilizing a single detector rotated about a sample contained within a transparent vessel. MALS measurements from non-flowing samples such as this are commonly referred to as a “batch measurements.” By creating samples at several known low concentrations and detecting scattered light about the sample at varying angles, one can create a Zimm plot by plotting : vs  where c is the concentration of the sample and k is a stretch factor used to put kc and  into the same numerical range.
  When plotted one can extrapolate to both zero angle and zero concentration, and analysis of the plot will give the mean square radius of the sample molecules from the initial slope of the c=0 line and the molar mass of the molecule at the point where both concentration and angle equal zero. Improvements to the Zimm plot, which incorporate all collected data, commonly referred to as a “global fit” have largely replaced the Zimm plot in modern batch analyses.
caption: Zimm plot
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