Guinier Plot


The Guinier Plot allows the determination of the Radius of Gyration \(R_g\) from the measured scattered intensity \(I_s(q)\) as a function of the scattering angle \(\theta\). It is used in X-Ray, neutron and static light scattering (SLS). Using a logarithmic plot of the Guinier equation


\begin{gather}\ln{I_s(q)} = \ln{I_i} - \frac{q^2 R^2_g}{3}\end{gather}


one obtains \(R_g\)  from a simple linear fit.


This is however only true for small scattering angles and within RGD limits:


Related products:


Performs advanced DLS & SLS to obtain hydrodynamic radius, radius of gyration, molecular weight, form and structure factor as well as second virial coefficient. Offers unmatched range and precision of scattering angles.

LS Spectrometer


Image presents LS Spectrometer which is an advanced instrument for DLS and SLS measurements. It enables measurement of hydrodynamic radius, radius of gyration, 2nd viral coefficient, molecular weight, form factor and structure factor.

3D LS Spectrometer

  • Either scattering angle should be sufficiently small or the wavelength of the scattered wave (\(q R_g \ll 1\)). 
  • The difference in refractive index n of solvent and scattering unit should not be very large (\(m -1 < 0.3\)).
  • As is the case for all SLS measurements multiple scattering must be suppressed or the sample must be sufficiently dilute.


So for colloidal science the RDG limits should be considered more carefully than for polymer science, because the difference in relative refractive index is typically small between a polymer chain and the surrounding solvent.



Learn more about static light scattering by following our online technology section step by step.

It is advisable to read the different sections in the suggested order if you want to understand all the details. For a quick reference you can also jump to each section individually.



A very detailed source of information is the slide show "Light Scattering Fundamentals".