3-36 Using the Detector
4. If calibration is not successful, repeat it.
5. If calibration is still not successful, shut down the detector and restart it
(see Chapter 5).
6. Run the detector normalization diagnostic test (see page 3-36).
Requirement: If this test yields a failing result, repeat it.
Normalizing emission units
You can select either emission or energy units in the Output field of page 2
(see page 3-19). If you select emission units, normalize to a standard water
reference on a monthly basis to ensure that measured signal strengths are as
consistent as possible with those measured by other 2475 detectors.
Tip: Before you pump solvent or mobile phase through the system, flush the
lines with filtered, degassed, and sparged HPLC-grade water. Then pump the
mobile phase, provided you encounter no miscibility problems, at 1 mL/min for
15 minutes, minimum.
Tip: Normalize emission units weekly.
To normalize emission units:
1. Power-on the detector, and allow it to warm and stabilize for at least 1
hour.
2. Run clean, degassed water through the flow cell at 1 mL/min (or a flow
rate sufficient to prevent the formation of air bubbles).
3. Press DIAG, and then press 1 Normalize Units.
The detector adjusts the PMT gain, and it sets the excitation
monochromator wavelength to 350 nm. The emission monochromator
scans from 390 to 405 nm to find the Raman signal for water (397 nm),
minimizing the occurrence of wavelength accuracy errors from distorting
the normalization constants. After the emission monochromator finds
this signal peak, PMT gain is optimized, and the normalization
constants appear.
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