ASTM E2490-09 (R2021) pdf free download.Standard Guide for Measurement of Particle Size Distribution of Nanomaterials in Suspension by Photon Correlation Spectroscopy (PCS).
1 .1 This guide deals with the measurement of particle size distribution of suspended particles, which are solely or predominantly sub—100 nrn, using the photon correlation (PCS) technique. It does not provide a complete measurement methodology for any specific nanomaterial, hut provides a general overview and guide as to the methodology that should be followed for good practice, along with potential pitfalls.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
3. Terminology
3. 1 Definitions of Terms Specific to This Standard:
3.1.1 Some of the definitions in 3.1 will differ slightly from those used within other (non-particle sizing) standards (for example, repeatability, reproducibility). For the purposes of this guide only, we utilize the stated definitions, as they enable the isolation of possible errors or differences in the measurement to be assigned to instrumental, dispersion or sampling variation.
3. 1 .2 correlation coefficient, n—measure of the correlation (or similarity/comparison) between 2 signals or a signal and itself at another point in time.
3. 1 .2.1 Discussion—If there is perfect correlation (the signals are identical), then this takes the value 1.00: with no correlation then the value is zero.
3. 1 .3 correlogram or correlation function, n—graphical rep— resentation of the correlation coeflicient over time.
3.1.3. 1 Discussion—This is typically an exponential decay.
3. 1 .4 cuinulants analysis, n—mathematical fitting of the correlation function as a polynomial expansion that produces some estimate of the width of the particle size distribution.
3. 1 .5 diffusion coefficient (self or collective), n—a measure of the Brownian motion movement of a particle(s) in a medium.
3.1.5.1 Discussion—After measurement, the value is be inputted into in the Stokes-Einstein equation (Eq 1, see 7.2.1.2(4)). Diffusion coefficient units in photon correlation spectroscopy (PCS) measurements are typically im2/s.
3.1.6 Mie region, n—in this region (typically where the size of the particle is greater than half the wavelength of incident light), the light scattering behavior is complex and can only be interpreted with a more rigorous and exact (and all- encompassing) theory.
3.1.6.1 Discussion—This more exact theory can be used instead of the Rayleigh and Rayleigh-Gans-Debye approxirnalions described in 3.1.8 and 3.1.9. The differences between the approximations and exact theory are typically small in the size range considered by this standard. Mie theory is needed in order to convert an intensity distribution to one based on volume or mass.
3. 1 .7 polvdispersitv index (P1), n—descriptor of the width of the particle size distribution obtained from the second and third curnulants (see 8.3).ASTM E2490 pdf download.