Chromatography Forum

Hello,

We have been using Waters PDA 2998 with alliance e2695, and Qda detector for about a year now.
Last month there was a malfunction : (probably) something stucked in tube which caused cell optical window to pop out.
There was very noisy baseline for 214-225 nm wavelength, but signal for >230 was ok (we analyse peptides so we mainly use 214 nm) and of course there was a leakage in detector cell.

The waters service man came, he changed detector cell and everything was ok.

The month past away and we have got similar problem again : signal for 214-225 is very noisy, but this time there is no leakage in detector cell (pressure also seems ok)

As mobile phases we use : A) H2O + 0.1% Formic Acid B) ACN + 0.1% Formic Acid C) Metanol (to clean everything before shutdown)

Have anybody got any ideas?

Regards,

Dorian

Provide more details -
How old/how many hours on the 2998's lamp?
What flow rate are you typically using?
What's the back pressure at that rate if you leave the column out?

Are water, MeOH, Formic acid the only things you make mobile phases from?

Is there any derivatization going on?

How old : about 250 hours (the 'loading bar' is half full)

Flow : typically we are using 0,5 ml/min and 1 ml/min

Backpressure without collumn : i will check that

We use only ACN Water (with 0,1% FA) and Methanol (no buffer was used ever on this hplc)

No derivatisation

The problem occured when i injected sample afrer peptide purification (peptide in ACN/Water 0,1% TFA)

Thanks for response.

Edit :

I changed both eluents and intensively purged whole system. It seems ok now (but i injected other samples - peptide dissolved in pure water). Still i've got no idea what was the cause of noise (The sample, or the eluents)