Problem with HPAEC-PAD baseline???

[rick1112]

Hi

I have started using HPAEC-PAD (dionex ICS-3000) for estimation of carbohydrate..
I am using a method for quantification of sialic acid (Ref. Dionex TN 41)..but I discovered that my baseline is very unstable and noisy..? could any one suggest me the possible reason for this..???

What all parameters can I control or optimize to get a steady baseline..??

Thank you all

[bartjoosen]

PAD=Pulsed amperometric detection?

We have had a lot of trouble with HPLC/PAD, the only things that were really helpfull: passivate the system with HNO3 and then stabilise, stabilise and.... wait while the system is getting stable.

Bart

[Chris Pohl]

rick1112,

Before trying things like nitric acid treatment (this should pretty much be your last resort), try solving your baseline problems by looking for possible issues with your eluent components. First off, your hydroxide should be prepared using a relatively fresh bottle of 50% sodium hydroxide (preferably from Thermo Fisher). Secondly, baseline problems are often connected to the quality of your sodium acetate. Fluka makes the best high purity sodium acetate for this application but not all batches are ideal so you might need to sample another lot if you're already using Fluka sodium acetate. Finally, baseline problems can be caused by contamination of your deionized water system. If your deionized water system hasn't been recently serviced, this might be the cause of your problem. Often, over time lifeforms coat the interior of the delivery system downstream from the final filter and contaminate the deionized water with glucose. Sometimes the problem is bad enough that you can see discoloration of the delivery tubing (in extreme cases the tubing will turn green) which can indicate a contamination problem. The easiest way to troubleshoot this possible cause is to try obtaining clean water from another lab to see if this helps your baseline problem.

Chris