Biotage ELSD-1080, Operation Manual

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Biotage ELSD-1080
3. System Description and
General Operation
3.1 Basic Principles of Operation
Nebulization
The eluent inlet is connected to the nebulizer via a short length
of stainless steel capillary tube. The incoming eluent stream
passes through the heated nebulizer and is mixed with the
incoming nebulizer gas stream. The mixed gas and eluent
stream form an aerosol plume containing a uniform dispersion
of droplets that then passes as a continuous flow into the
evaporator section. Any larger droplets or the inefficiently
nebulized droplets collect in the nebulizer chamber waste trap
and then drain off via the waste outlet into a collection bottle.
Evaporation
After nebulization the atomized spray is propelled through the
evaporation tube assisted by the carrier gas. In the evaporator
section the solvent is removed leaving a stream of dry particles
of the analyte. A diffuser located in the evaporator assists in
the drying of the particles, acting as an efficient heat
exchanger, prevents ballistic particles reaching the scattering
chamber and randomizes the particle plume. The Biotage ELSD-
1080 detector uses patented gas flow technology in the
evaporation zone to aid evaporation at low temperatures. By
adding a stream of dry nitrogen (evaporation gas) at the
entrance of the evaporator tube less volatile solvents (e.g.
water) are easily evaporated. This evaporation gas is controlled
by the user and facilitates sub-ambient operation.
Detection
Light from an LED is passed through the detector at right
angles to the direction of particle flow. A light trap is located
opposite the source of light to capture the transmitted incident
beam eliminating internal reflections within the detector body.
When pure solvent is being evaporated, only its vapor passes
through the light path and the amount of light scattered to the
photomultiplier is small and gives a constant baseline response.
When a non-volatile solute is present a particle cloud passes
through the light path, causing light to be scattered. This
scattered light enters the optical aperture of the detection
system and generates a signal response from the photodiode in
real time. The quantity of light detected is dependent on the
solute concentration and solute particle size distribution.
Publication date: July 2010 29