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340CF ELSD
Section 2 Introduction
2.3.1 Nebulization
Figure 2-1 Thermo-Split chamber: Cooling
Figure 2-2 Thermo-Split chamber: Heating
2-2
Nebulization transforms the liquid phase leaving the column into
an aerosol cloud of fine droplets. The size and uniformity of the
droplets are extremely important in achieving sensitivity and
reproducibility. The ELSD uses a special concentric flow nebu-
lizer and a constant flow of an inert gas to ensure a narrow
droplet size distribution. Our nebulizer is constructed entirely
from PTFE, which accumulates deposits less than either glass or
stainless steel.
To handle flow rates and mobile phases common in HPLC, all
ELSDs need a way to divert part of the aerosol cloud to waste.
The ELSD uses a patent pending Thermo-Split technology.
Our Thermo-Split chamber combines a gentle bend with tem-
perature controlled walls. When the aerosol exiting the nebulizer
encounters a cool environment, it partially condenses into larger
particles whose momentum carries them into the wall and down
the drain.
With cooling, the particles con-
dense and increase in size. They
are carried into the walls of the
bend and exit via the drain.
With heat, the particles decrease
in size and all pass the bend in
the Thermo-Split chamber.
With the Temperature control option installed, the temperature
of the Spray Chamber may be elevated. As the aerosol traverses
the chamber, it partially evaporates, shifting the particle size dis-
tribution low enough for essentially all the particles to negotiate
the bend. These operating conditions may be useful for special
applications. Under these conditions a majority of the aerosol
particles pass through the chamber and are carried into the
evaporative zone.
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