What might be the reason for noisy baseline in applications with Electrochemical detection. We passivated everything- pumps, capillaries. What are the requirements for the water for these applications.

Unfortunately, there are many possible reasons for noisy baselines with ECD! Are you experiencing high background currents and if so, are you using ECD grade reagents? If you visit the ESA website, you can request an application note which describes a procedure for 'cleaning' water for use in mobile phases for ECD assays (basically this involves passing deionised water through an SPE cartridge).

If you are experiencing short-term noise this could be caused by your pump - are you using a pulse dampener?

Is your mobile phase sufficiently degassed? Any air bubbles in the flow cell will cause a very unstable baseline.

Depending of the type of ECD detector you have, either the working or reference electrode may need attention (polishing etc).

Best of luck!

In addition to the possibilities mentioned by Anonymous above, there are also possible issues with the cell cabling and the reference electrode. What mode are you operating in (pulsed mode, D.C. mode or scanning mode)? What is your background? Is it significantly higher than normal? High background can be caused by contaminated reagents or contaminated water. For example, deionized water is often contaminated due to poor maintenance of the deionized water system. The resistance meter might indicate greater than 18 megaohms on your deionized water system but if the supply tubing is green due to algae growing in the tubing, your water will not produce low background even when the reagents you use are of good quality. Even if you're deionize water supply tubing looks okay, it might still be contaminated. Has the deionized water system received any routine maintenance in the past year? It would be helpful to know which specific electrochemical application you are attempting.