Anion analysis by IC- carbonate contamination

[Annemarie]

I am running anion analysis on a Dionex IC using a AS19 column, AG19 guard and a ASRS 300 suppressor. I use an eluant generator for KOH. I use DI water to run the generator. I am getting a carbonate peak eluding in front of my sulfate peak. It is making integration a pain. In the blank runs, I also see a second peak after the carbonate. The RT is just a few seconds before sulfate so it is screwing up the calibration curve. It started small a couple of weeks ago but the peak has been getting bigger and bigger. I haven’t changed anything on the IC or the DI system. Can someone tell me where the carbonate is coming from (I'm assuming the water?)and how to get rid of it?
Thanks,
Annemarie

[chromodoom]

Hi Annemarie

the Carbonate in your samples comes from the limestone solved in the Water (Water hardness, Drinking Water) or from the Carbodioxide in the Air (DI Water). You can remove the Carbonate in your Eluent DI Water by using an CR-ATC Continuously-Regenerated Anion Trap Column (http://www.dionex.com/en-us/products/co ... 86259.html). But this doesn't solve your Problem with the Carbonate in your samples.
Think about to change your method to an Carbonate Eluent with an Carbonate Eluent Anion Exchange Column (http://www.dionex.com/en-us/products/co ... 73214.html)

regards

chromodoom

[Annemarie]

Hi chromodoom,

Thanks for the information. I am new to anion analysis and it turns out that I have the CR-ATC installed. I’m assuming that since I didn’t have this problem before, the CR-ATC has failed? I went to the Dionex web page and saw they had a CR-ATC regeneration kit. Have you ever tried to regenerate the unit or should I just buy a new one? I have only been running the instrument for about 4 months- do CR-ATC get contaminated that fast?
Thanks for your help!

Annemarie

[Markus Laeubli, Metrohm]

Dear chromodoom

Carbonate eluents are usually more flecible tha hydroxide eluents. But this does not reall solve the problem with sample carbonate.
Whatever eluent you use CO2 removal after chemical suppression will improve the situation.

[chromodoom]

Hi Annemarie

My CR-ATC works since 1.5 Years without any problems. What kind of samples do you have?

Get sure that the CR-ATC starts/stopps automaticly by starting/stopping the Pump. Set it up on your ICS System in Direct Mode (Disconnected from your Computer, or computer off)

chromodoom

[Annemarie]

I ran a bunch of water blanks and only the carbonate and the unknown peak next to it show up. I don’t see the peaks in the samples. Of course, the samples with SO4, I’m not sure of. So, has anyone tried to regenerate a CR-ATC?