Operating instructions

Charged Aerosol Detectors
Corona Veo and Corona Veo RS
Page 68 Operating Instructions
5.6.5 Applying a Power Function Value
The signal of the detector has a wide dynamic range with over four orders of magnitude.
The nature of the response is inherently nonlinear. The Power Function Value (PFV)
applies a power transformation to the data output of the detector. Power transformations
may result in extending the linear range of the detector. As a result, a simple linear
correlation can be applied in place of a polynomial regression that is fit to the detector's
raw data response curve after a PFV has been applied. The transformation is applied real
time to the data stream. The data is raised to the selected power; it is scaled and sent out.
The choice of an optimal Power Function Value will result in an increase in the linear
dynamic range of the detector as compared to the default setting. The appropriate or best
value for the Power Function depends on the individual analyte and analysis conditions.
Tips: Changes to the PFV do not result in improvements to the detector's limit of
detection (LoD) performance.
The default PFV setting of 1.0 provides a good universal setting for most
applications and compounds.
The detector accepts any value between 0.67 and 2.00 in increments of 0.01.
To set the power function value from the detector display:
1. On the detector display, in the Main Menu, select the Run Mode soft key.
2. Set the operating parameters as required by your application.
3. For the Power Function parameter, enter the three digits of the desired PFV without
decimal point.
4. Press Enter. The data stream will now be raised to the selected power.
5.6.6 Minimizing Baseline Noise
Minimizing the baseline noise that is generated for a given LC method depends on many
factors. Consider the following recommendations to optimize the detector performance and
reduce baseline noise:
• Use only mobile phases of the highest quality available and keep impurities and
contaminants to a minimum. Observe all guidelines as described in the 'Mobile Phase'
section (→ section 4.5.1, page 41).
• Flush the LC system periodically in order to remove any non-volatile mobile-phase
residues if applicable.
• Observe the recommended maintenance schedule for the detector and the LC system as
per the manufacturer's guidelines.
• The gas supply should be filtered and free from moisture and hydrocarbons. Observe the
gas requirements in section 3.1 (→ page 23) and the guidelines for gas supply in
section 4.5.3 (→ page 42).