Waters 2489, Overview And Maintenance Manual

Page: 71 / 150

June 11, 2015, 715004752 Rev. A
Page 71
Recommendation:
In dual-wavelength mode, select a wavelength pair below or
above 370-nm. If one or both of the selected wavelengths spans the 370 nm
threshold, the detector beeps three times, and the warning message shown below
appears. Because of possible UV light interference (second-order effects), you can
observe additional peaks and inaccurate peak areas.
Figure 3–16: Dual-wavelength, 370-nm, threshold warning message
3.2.10.1 Obtaining a RatioPlot
The RatioPlot output, on one channel only (channel A), depends on the values you
specify on absorbance screen 5 for minimum and maximum ratios. You must be
operating the detector in dual-wavelength mode to obtain a ratio plot. The RatioPlot
provides a plot of the ratio of the absorbances of two wavelengths from 0 V to 2 V.
The minimum and maximum ratio parameters are measured ratio units, not
absorbances. (See page 57 .)
To obtain a RatioPlot:
1. Be sure the detector is operating in dual-wavelength mode (see the previous
discussion).
2. From the absorbance screen, press Next to reach screen 3 of 5.
3. In the Data out field, press 8, ratio A/B.
4. Press Enter to select the ratio plot.
5. Press Next until screen 5 of 5 appears.
6. Enter the minimum AU, and then press Enter.
Tip:
The minimum AU field contains a threshold value. The RatioPlot function is
not plotted if either wavelength does not exceed the minimum AU threshold.
7. Enter the minimum ratio for the RatioPlot, and then press Enter.
8. Enter the maximum ratio for the RatioPlot, and then press Enter.
9. Return to the absorbance screen by pressing the HOME key.
3.2.10.2 Obtaining a MaxPlot
The detector obtains a MaxPlot by monitoring absorbance at two selected
wavelengths while plotting the maximum absorbance for each sample component.
To run a scan using the MaxPlot function:
1. Be sure the detector is operating in dual-wavelength mode (see “Operating the
detector in dual-wavelength mode” on page 70 ).
2. From the absorbance screen, press Next to reach screen 3 of 5.