Dionex ion cromatography system for cations

[krista]

Hallo!
Is there somebody using ics-1000 for cations in waters. I'd have some questions. I am a new users, and have encountered some difficulties.Thanks.

[Mark Tracy]

There are several Dionex people (users and employees) that participate in this forum and are willing to answer your questions. So what is the problem?

[krista]

To start with: I am trying to calibrate the analizer, but i cannot figure out why sodium standard solution gives me jumping graph. Even i use the same solution, it gives me always different concentration. Problem is especially well seen with small concentrations, but difference is with higher concentations as well. Rest of the cations give good calibration results. I use MSA as an eluant, have tried different concentrations, still the same. I have prepared several sodiumnitrate solutions, but no change.
Krista

[Mark Tracy]

Since the other ions give good calibration it means that the pump, injector and detector are working correctly.

The most likely problem is contamination; sodium is everywhere. Do you see sodium in any of your blanks? In other cation standards?

Another possibility is bad integration. Are the integration baselines flat and drawn consistently?

[krista]

Baseline is flat and steady.
I do have some tracies of other cations in separate solutions, but as i use stock solution of 5 cations, and it does not affect other cations.
At the beginning we were thinking that maybe there is cross interference between sodium and ammonium, but ammonium has nice calibration curve. What should be optimal MSA concentration at flowrate 1. I use 5 mM. I did not notice big difference at 4, and i did not want to have longer analization time. Maybe i should.

[Mark Tracy]

I'm not really the IC expert, but my colleagues who are tell me that TRIS buffer coelutes with sodium. Any chance of that?

What happens when you analyze DI water? Just to check your process, try taking a sample of DI water through all the steps as if it were a standard.

The MSA oncentration depends on the column you are using. I would recommend you get the method working as described in the column manual before you try to optimize the runtime.

[krista]

I cannot believe it, but my DI water shows all the cations. So my column must be contaminated, because i was ensured it is not water.
I have used that column only a month and with standard solutions. IC was first dested a year ago, and then it was not in use. First I try to wash it with stronger eluent and water. Hopefully it will help.

[Mark Tracy]

Your column is probably not the contaminated part; column contamination causes a lumpy, wavy baseline. Given its history, a good cleaning with strong eluent is a good idea anyway. Since you are seeing peaks, the contamination is coming in with the injection. Are you doing manual injections or using an autosampler? Finding the problem will take time, patience and maybe a bit of humility. Best of luck.

[krista]

I just wanted to thank you Mark for advice.
I had a vacation. I am still having the problem. It seems that it is going and coming. It is not deffenitely the water. Peaks vary in size with every injection. I tryed just in case water from other laboratory. I have those peaks with autosampler as well as with mannual acq. It seams that i am washing it out from somewhere, peaks are larger when i use manual acq. I am hoping i can wash it out continuously injesting water. Could it help?

[Mark Tracy]

A couple possibilities:

* Your injection valve may be contaminated. One by one, disconnect each tube, wash it, the fitting and the port with clean water and reconnect. Be sure to seat the tube and ferrule properly. In a really serious case, you may need to disassemble and clean the valve itself; you may prefer to let the Dionex service representative do this.

* Your autosampler syringe may be dirty. (I've had this problem myself with an AS50.) The flush function may not be enough. Dismount the syringe and manually wash it with clean water, then reinstall it.

Good luck