mobile phase problem (Millipore water)

[kapangaluc]

Hello,
I am using 90mM NaOH (1 ml/min) as the mobile phase for carbohydrate chromatograpy.The system is a Dionex with ED40 eletrochemical detector.
The problem is that after we bought a new ultrapure water system (Millipore Synergy) we are getting a very high background baseline. We have tried a different water source and the system works fine; so we know that it may be the Millipore water system. Millipore had no explanation and blamed it on the water the Millipore is fed with, and of course they tried to sell me a different system.
Do you guys have any clue on what the problem may be? Has anyone experienced the same? How do you fix it?
Thank you.

[tom jupille]

Ultrapure water systems are often designed to minimize UV-absorbing garbage, and may not be optimized to remove ionic species. The first thing I would do is to check with Dionex and see what they recommend.

Simultaneously, look hard at the performance specs on the Millipore system and check to make sure that it is meeting those specs. If it is *not*, then check to see if Millipore has any specific requirements for the quality of the incoming water, and test your incoming water to be sure that it meets those specs.

If the system is meeting the manufacturer's specs, but isn't working for you, then it *is* your problem and a more appropriate system may be your best option. If the system doesn't meet the manufacturer's specs, but your incoming water meets their requirements, then it is *their* problem, and you should hold their feet to the fire until they make it right. If they do indeed have a spec on incoming water and yours isn't good enough, then again, it's *your* problem.

[kapangaluc]

Tom,

Thank you very much for you input. I' find out about the quality of DI here in the building and doublecheck the the specs.
kapangaluc

[JGK]

At one of the labs I worked at in the past, we used to hav a sporadic issue with unexplained peaks occuring in our chromatography.

In all cases the problem was due to the water obtained from our RO water unit. All maintenace checks indicated the RO unit was functioning well but in each case switching out the deioniser cartridge pack (not due for replacement) for a new one eliminated the problem.

I got the opinion that some deioniser packs leached material into the RO supply.

[Phycal]

The Synergy system needs RO or demineralized water feed and they say 1-20 liter/day production but I always am very conservative with production numbers. You probably do not have the right system for your lab.