Agilent 1200 peak area issue

[moonchips]

Greetings,

We have an Agilent 1200 with Empower 2.0 with peak area issue.

it is a gradient run,
waters x-bridge C18 column, 150mm*3.5um
mobile phase A:95/5/0.05% H2O/MeOH/TFA
mobile phase B:95/5/0.05% MeOH/H2O/TFA
injection: 5uL

The peak height was 0.8AU before this issue happened. And then one day, the peak height changed to 1.1, with peak split and 1.5 times peak area. the retention time also shifted slightly.

Agilent engieer has been working on it for a long time with more than 6 visits. He changed some seals, the pump outlet and inlect valve, the board etc. Now with 5uL injection, the peak is 2AU without peak splitting. The issue is still there, why do I get higher intensity?

Could any one tell us the possible cause for this?

Thanks,

[Consumer Products Guy]

What were the results when a new, second column was tried?

[carls]

Please post examples of "good" and "bad" chromatograms. They will be very helpful.

Here's the procedure for embedding chromatograms in a post:

viewtopic.php?t=2617

[moonchips]

the problem was fixed after the electronic board for the UV detector was changed.

Thanks