Operating instructions

Charged Aerosol Detectors
Corona Veo and Corona Veo RS
Page 66 Operating Instructions
5.6.2 Setting a Filter Constant
The filter time constant is used to electronically reduce the noise of the baseline within the
chromatographic run. A small filter value (e.g., 0.2 sec) removes little noise, while a large
filter value (e.g., 10 sec) will smooth the baseline significantly.
For details how to set the filter constant from the display, see section 5.3.3 (→ page 50).
5.6.3 Selecting the Evaporation Temperature
General Notes
The temperature-controlled evaporation tube dries the aerosol that comes from the
nebulizer. Thus, the evaporation tube removes the mobile phase components and leaves an
aerosol with dried analyte. The efficiency of this drying procedure depends upon the
chosen temperature and additional factors, such as the mobile phase composition, liquid
flow rate and sample composition. Use performance metrics such as the detector precision
and sensitivity as guidelines to receive the optimal evaporation temperature. After you
have set the evaporation temperature, wait approximately 30 minutes to ensure that the
evaporation tube comes to equilibrium before you start sample analysis.
Tips: A change in the evaporation temperature can have a dramatic effect to the
response of the detector. Try different temperature settings before you finalize
an analytical method.
Corona Veo RS only
When you decide to use an optimized evaporation temperature, perform three
or more injections of a reference standard for the analytical method. For these
reference injections, use different evaporation temperature settings that range
from low to high temperature. Select the most appropriate starting point
temperature, based upon the performance criteria as mentioned before.
For a starting point for selecting an evaporation temperature, refer to the table below:
Factor
Evap. Temp. Guidelines
Effect
Corona Veo Corona Veo RS
Mobile phase
composition
100 % aqueous 50 °C
Use lower or
higher temperature
settings
Baseline noise,
background
current
100 % organic (e.g.
normal phase HPLC)
50 °C
water/acetonitrile or
methanol gradient
(e.g. reversed-phase or
HILIC HPLC)
35 °C
water/THF gradient 35 °C Baseline noise