3 • Operation and Maintenance
Doc. 031644-02 9/03
3-27
In PeakNet 6 or Chromeleon, press F8 to display the Commands dialog box.
Select
UV
, select the
NegativeAbsorptionLevel
command, and select a higher
setting. You may continue increasing the setting if the range is required.
Baseline
noise may increase as the NegativeAbsorptionLevel setting increases.
At the default setting, the detector will become saturated when the light
transmission is 20% above the autozero level. The extent of negative absorbance
is wavelength-dependent, as indicated in the table below (these values are
guidelines only).
After changing the negative absorbance setting, run autozero and then check the
intensity of the deuterium lamp. Press F8 to display the Commands dialog box,
select
UV
, and select
LampIntensity
. The reading should be above 10 million
counts; if it is not, select the
UV_Calibration Intensity
command to calibrate the
lamp. After calibration, check the lamp intensity again. If the reading is still too
low, clean the flow cell (see Section 5.2) or replace the lamp (see Section 5.7).
Negative
Absorbance
Level
Approximate Negative
Absorbance at 210 nm
Approximate Negative
Absorbance at 240 nm
Approximate Negative
Absorbance at 254 nm
0
-2200 mAU
-50 mAU
-300 mAU
1
-2300 mAU
-100 mAU
-350 mAU
2
-2600 mAU
-200 mAU
-450 mAU
3
-2600 mAU
-300 mAU
-550 mAU
4
-2700 mAU*
-400 mAU
-630 mAU
5
-2700 mAU*
-500 mAU
-660 mAU
6
-2700 mAU*
-600 mAU
-760 mAU
* These signals are saturated and will not report a further negative value.
