Biotage ELSD-1080, Руководство по эксплуатации

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Biotage ELSD-1080
1.Nebulization 2.Evaporation 3.Detection
Figure 3. Principles of Operation
3.1.1 Theory
There are four main processes by which the path of
electromagnetic radiation or light can change direction, when
passing through a medium containing a suspended particulate
phase. These are shown in Figure 4:
Figure 4. ELSD Scattering Mechanisms
The importance of each of these processes depends on the
radius of the particle (r) compared to the wavelength (
λ ) of the
incident light. Rayleigh scattering is predominant when r/ λ is <
5x10
-2
. When particle dimensions are greater than λ /20 they
no longer behave as point sources, and Mie scattering becomes
predominant. Once particle size approaches the wavelength of
incident light then reflection and refraction begin to prevail.
The relative importance of refraction and reflection can be
understood by examining the effects of the incident light on a
single spherical particle whose equilateral axis lies in the same
plane as the photo-detector and light source. With this
configuration, refraction is of greater significance than
reflection. The majority of organic compounds have refractive
indices between 1.3 and 1.5. Changes in the refractive index
within this range will not greatly affect the quantity of light
reaching the detector. This accounts for similarities in the
sensitivity of the detector to various compounds.
30 Publication date: July 2010