the particles are not transparent) – both assumptions are not true, but in in most cases the model has shown to give valid results. In the Fraunhofer model it is assumed that the particles interacting with the laser beam are spherical and that the laser light does not “enter” the particles (i.e. The translation of the laser scattering pattern is based on either Fraunhofer or Mie theory. Models for determination of particle size distribution This subject will be discussed in more detail under the section about method validation. – thus during validation, it should be very carefully studied that this mechanical treatment does not alter the particles. Laser diffraction is known to be a very robust method – but some dangerous pitfalls exist: By laser diffraction you do not obtain a direct measurement of the particles: The signals from the measurement is “translated” into a particle size by different calculation methods, assuming that the particles are spherical which might be far from true.įurther, the particles are mechanically affected during measurement: The particles will be exposed to pressure, stirring etc. It should be highlighted that the results from different equipment cannot be directly compared, as variations in the measurement principles will lead to different results. The diffracted light is detected and translated into a particle size distribution. For all laser diffraction instruments the overall principle is to disperse the powder sample in either air or a suitable liquid media and expose it to a laser beam. By laser diffraction analysis it is possible to measure particles size distribution for particles in the size region between <1 µm to around 3 mm for a very large number of particles.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |