June 11, 2015, 715004752 Rev. A
Page 24
1.3.2 Dual-wavelength mode
In dual-wavelength mode, the detector can monitor two wavelengths, one on channel
A and one on channel B. The sampling frequency is reduced to 1 or 2 Hz, limiting the
use of this mode to more standard chromatography where peak widths span at least
20 seconds to enable full characterization of a peak. You can use dual-wavelength
mode to obtain additional information about an analyte by running in the RatioPlot or
MaxPlot mode.
You can select any two wavelengths from 190 nm to 700 nm.
In dual-wavelength mode, the following conditions apply:
•
If both selected wavelengths are greater than 370 nm, the detector applies the
second-order filter to block unwanted UV light.
•
If both selected wavelengths are less than or equal to 370 nm, the detector
removes the second-order filter.
•
If the selected wavelengths bracket the 370 nm threshold, the detector does not
apply the second-order filter and issues a warning message that any data
collected for the wavelength above 370 nm can contain inaccuracies because of
possible UV light interference (second-order effects).
1.3.2.1
Chart-out selection modes
When operating in dual-wavelength mode, the detector offers these choices for
analog output in addition to the selections offered in single-wavelength mode and
explained on
. The default selection for dual-wavelength mode is Absorbance.
Table 1–6:
Additional options for analog output in dual-wavelength mode
Mode option
Description of mode
Absorbance (A and B)
Standard LC mode where the current
absorption is scaled and sent directly out
the analog output. The scaling depends
on the AU setting and the absorbance
offset. The absorbance value is scaled for
the 2-V analog output. If a setting of
1 AU/V is desired, you can set an AU of
2.0000 for either the A or B output
channels that can be controlled
independently, even in single-wavelength
mode.
MaxPlot
Results in the output of the larger of the
two absorbance values scaled to the
selected AU setting. Use this mode when
observing, with one data channel,
multiple compounds that exhibit
absorbancies at two separate
wavelengths.
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