Procedure: Changing Equilibration Time; Turning Hydrogen Off During A Solvent Peak; Turning Hydrogen Off Between Runs; Bead Voltage - Agilent Technologies 6890 Series Operating Manual

The Nitrogen-Phosphorus Detector
The bead

Procedure: Changing equilibration time

1. Press [Config][Front Det] or [Config][Back Det]:

Turning hydrogen off during a solvent peak

When using the NPD, the baseline shifts after a solvent peak and can take some
time to stabilize, especially with chlorinated solvents. To minimize this effect,
turn off the hydrogen flow during the solvent peak and turn it back on after the
solvent elutes. With this technique, the baseline recovers to its original value in
less than 30 seconds. This also extends the life of the bead. The hydrogen can
be turned on and off automatically as part of a Run Table. See chapter 7,
"Instrument Automation", in the General Information volume.

Turning hydrogen off between runs

To extend bead life, turn off the hydrogen flow between runs. Leave all other
flows and the detector temperature on. Turn on the hydrogen flow for the next
run; the bead will ignite almost immediately. The process can be automated with
Run Table entries.

Bead voltage

Bead voltage shows the voltage used to heat the bead. It can be an actual
value, dependent on the Adjust offset value, or can be entered as a setpoint.
Equilibration time is not used when you enter a setpoint for Bead voltage,
so you cannot estimate your baseline stability. Use the Bead voltage setpoint
when the automatic startup does not work.
Bead voltage is also useful for small adjustments between runs. If you
observe a baseline drift, you can enter a small, one-time change to compensate
for the drift without having to wait for the Equib time.
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2. Enter a value (in minutes). Long
3
equilibration time reduce bead
lifetime.
Part 1. General Information