Agilent Technologies 1100 Series Manuál s instrukcemi stáhnout pdf (Strana 73)

1100 Series Capillary LC System Manual 63

Basic System Troubleshooting 4

Wandering Detector Baseline

Critical Decision Determine if the problem is in the DAD, or coming from the LC system:

Remove the flow cell from the DAD. Close the cell cover, and see if the baseline

performance improves.

1 If baseline performance has not improved:

a Replace the lamp(s).

b Evaluate the environment for excessive drafts, temperature changes, etc.

2 If baseline performance has improved, focus attention on the possible

causes and suggested actions below.

Wandering Detector Baseline Possible Causes and Suggested Actions

Possible Causes Suggested Actions Notes

Dirty or defective flow cell • Clean or replace the flow cell

The analytical column • Bypass the column. Pump directly into the flow

cell. If performance improves, try a new column.

Running with the pump mixer

removed

• Reinstall the mixer, and evaluate the

performance of the baseline. If the baseline

performance improves, a solution must be found

which is a compromise between mixing volume

and other chromatographic requirements.

The mixer may have been removed in

an attempt to reduce gradient delay

volume.

"Mixing Noise" when

pumping a binary mobile

phase from two channels.

• Try premixing the mobile phase in one bottle,

and pumping 100% from that one solvent

channel.

If baseline performance improves, a solution

must be found which is a compromise between

mixing volume and other chromatographic

requirements. For an isocratic analysis,

premixing and pumping 100% one channel is the

best solution.

This problem occurs when one (or

both) of the solvents has a high

background absorbance at the

detection wavelength. In this case,

the pump’s mixing efficiency may

not be good enough to produce a

sufficiently homogeneous mobile

phase.

The detector reacts to gluts of the

more detectable parts of the solvent

mixture, and baseline disturbances

result.

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