![laser diffraction laser diffraction](https://images.fineartamerica.com/images-medium-large-5/2-diffraction-patterns-from-a-helium-neon-laser-sheila-terryscience-photo-library.jpg)
Thus, irregular particles must have a non-zero component of the imaginary RI for light scattering purposes and a robustness check will normally look at values of 0.001, 0.01, 0.1, and 1.0. This causes diffuse light scattering at the boundary and loss of light due to random scattering, which often has an influence similar to absorption of light within the particle.” Thus, we can state that an effective imaginary component of 0 will only be possible for a homogeneous transparent sphere (latex or glass bead standard usually).
LASER DIFFRACTION ISO
For an irregular particle, then ISO 13320:2009 states: “The particle surface may be rough instead of smooth. The real part is typically needed to only two decimal places and the imaginary component to an order of magnitude (factor of 10). In practice, the real part of the RI is determined by other tests and the only requirement is to estimate the imaginary part. In practice, for many materials, it appears that the imaginary part of the RI has more effect on the generated result (a robustness test is mandatory during method development) than the real part and it becomes important to be able to determine the imaginary part of the RI for either a powder or a suspension. Indeed, ISO 13320:2009 indicates that this is likely to be important when the particle size reduces below 40 λ (or 25 μm for a He–Ne laser). In light scattering, especially laser diffraction, there is often a marked dependence of the calculated particle size distribution (from the raw angular scattering information) on the optical properties. This testing can also be used during formulation development to assess the impact of different ingredients and their concentrations (e.g., thickeners, muco-adhesives, surfactants). Neither of these situations is the intended route of administration and will, therefore, have an impact on the effectiveness of the delivered dose.ĭroplet size distribution testing is performed on the finished product as a quality control release test, and on storage to determine any changes within the product throughout its lifetime-for example, changes that will affect the ease of atomization of the formulation (viscosity, surface tension). The value for %<10 μm provides a risk estimate of small droplets that may be deposited into the lung. % 300 μm) will have a tendency to either drip out of the nose, or hit the back of the throat and be swallowed. Span-the span quantifies the spread of the droplet size distribution and is calculated by the following equation: (Dv 90 − Dv 10)/Dv 50
![laser diffraction laser diffraction](https://images.fineartamerica.com/images-medium-large-5/diffraction-patterns-from-a-helium-neon-laser-sheila-terryscience-photo-library.jpg)
Similarly, the Dv 10 and Dv 90 values indicate that 10 and 90%, respectively, of the spray volume is contained in droplets that are smaller than these values
![laser diffraction laser diffraction](https://www.hpcimedia.com/images/website/OldManChem/DIR_06/F_144.jpg)
This testing is performed using laser diffraction, and characterizes the droplet size within the plume in terms of cumulative volume distributions: