Thermo Scientific VH-D20 Operating Manual page 111

Guidelines for selecting the evaporation temperature
Charged Aerosol Detectors (VH-D20, VF-D20)
Operating Manual
The following guidelines are recommended for selecting an optimal
evaporation temperature:
• In general, use the lowest evaporation temperature within the
specified temperature range that provides acceptable limits of
sensitivity.
• As a starting point, use an evaporation temperature of 35 °C.
• Higher evaporation temperature settings can be used when analytes
of interest have low volatility, relative to the background. Since the
volatility of background residue is typically unknown,
experimentation is required for optimizing this parameter for a given
method.
• Perform screening runs at two evaporation temperature settings.
VH-D20 detector: Use a minimum of two evaporation
¨
temperatures. Typically, 35 °C and 40 °C are appropriate if the
temperature range is unknown. If required, perform additional
tests in a maximum of 5 °C increments.
VF-D20 detector: Use two evaporation temperatures, depending
¨
on whether the temperature range is known. If the temperature
range is unknown, 35 °C and 50 °C are an appropriate starting
point for screening runs.
• Consider that higher evaporation temperature settings may
inadvertently reduce response for low-analyte levels, even if they
are considered as non-volatile analytes.
• Remember to check the limits of sensitivity by actual analysis of low-
level standards. Also, check the analyte signal reproducibility at each
evaporation temperature setting.
• For detection of semi-volatile analytes, you can use lower
evaporation temperature settings. However, this may lead to higher
background levels and noise.
NOTICE
Do not use non-volatile modifiers, such as sodium phosphate. Observe
the mobile phase guidelines in this manual. See
for the Detector (} page 96).
6 • Operation
Mobile Phase Guidelines
Page 111