Chromatography Forum

Hi,

We have an old PE LC-95 UV detector that is working fine at wavelength of 313 nm. Currently, we are going to use it at 248 nm for a HPLC analysis. However when we changed wavelength, it can not be zeroed. It always showed "-1" under 285 nm when push the A/Z button (ok above 285 nm). We have tried washing of flow cell with string acid but still did not work. Anybody has clue? Thanks.

Dear lu_pharm:

I had used old P-E detectors (not exact model). Perhaps I can offer some tips:

1. Check if it is a variable (wavelength) detector.
2. When changing wavelength, you should go from the ‘low side.’ For example, you should set it at 280, and then increase gradually to 285nm.
3. Passing strong acid may not help. You should run mobile phase through it long enough (may be overnight?).
4. A value of –1 is not really a bad thing. Just inject your standard, to see if you can get a good peak, and if the baseline is acceptable.

Good luck.

Alfred