electrochemical detector - repetability problem

[djox]

Hy,

Im kind of a rookie when it comes to working with a ECD. So can anyone please help me with the following problem: im analysing azithromycin and I cannot get a good repetability (under 2%) of the main peak area; for example: area is gradually growing and when you finaly think its going to stabilise it starts to descend.

HPLC is working perfectly so I think its more of a ECD problem

(HPLC conditions: mobile phase is a mixture of acetonitrile and phosphate buffer, flow=1 ml/min, T=25 C; ECD conditions: DC method, cell E1=750 mV, E2=820 mV, guard cell 850 mV)

Thank you for your help

[ravenwork]

From what you've said, I cannot pinpoint this as an ECD problem, although that is certainly possible. Do you have another detector in-line that tells you everything else is fine? From what you have described, I would be thinking an autosampler problem.