Biotage
®
ELSD-A120 User Manual 9
Introduction to the Detector
1
Detector Overview
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.
Operational Parameters
ELSD-A120 responds to all compounds that are less volatile than the
mobile phase and is independent of a compound’s optical properties.
It therefore provides advantages over other spectroscopic detectors
for detecting compounds that are deficient in a UV chromophore or
fluorophore.
The removal of aqueous mobile phase within an ELSD is typically
achieved by setting the evaporator temperature to the eluent’s boiling
point in order to remove the solvent. For non-volatile compounds,
operating at these high temperatures maximizes the signal response.
However, at these temperatures volatile and semi-volatile compounds
are destroyed and are therefore not detected. This is problematic for
small molecules, such as pharmaceuticals and drug candidates.
ELSD-A120 is specifically designed to evaporate difficult solvents at
ambient temperatures in order to maximize detection of semi-volatile
compounds.
ELSD-A120 has patented technology that reduces the evaporation
time of highly aqueous solvents at low temperature, and also prevents
the evaporation tube becoming saturated, which would otherwise
prevent further evaporation occurring.
Using this patented evaporation gas technology, a 20 µm droplet of
water at 30 °C can be dried ca. 3x faster than just temperature alone.
For maximum sensitivity of non-volatile compounds the evaporation
gas can be turned off at higher evaporation temperatures.
Therefore, unlike other ELS detectors, where the evaporator
temperature is set according to the type of mobile phase, the
ELSD-A120 evaporator temperature is independent of the mobile
phase. Consequently, ELSD-A120 can be set at 30 °C for all types of
mobile phase provided the evaporator gas flow is adjusted
accordingly. This method of operation ensures that the detector’s
sensitivity is maximized even for low molecular weight compounds.
To prevent against unnecessary gas usage, a controlled gas shut off
valve is integrated into the detector gas manifold. This will only allow
gas to pass into the detector when in RUN mode. Should the detector
default to STANDBY mode, the gas will reduce to a default value of
1.2 SLM for 15 min before closing.
To Next Page
Loading...
