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organic, inorganic ion separation by ion chromatography

Posted: Wed Feb 27, 2019 3:39 pm
by minsun30437
hi, i'm working at lab as intern.

I am trying to separate 7 anions using ion chromatography.
The 7 anions are F-, Acetate, Lactate, Formate, Phosphate, Br-, Cl-.
I had difficulty separating F, Acetate, lactate, formate. But, I tried several times, changing the KOH concentration and column temperature.
At 10ºC, [KOH] 30.5mM, 4 anions begun to separate.

So, I want to make [KOH] gradient not isocratic based the method(10ºC, [KOH] 30.5mM).

How can I solve this problem?

ah, and I use AS18(2X250mm) column, AG18 guard column
hele me, please.

Re: organic, inorganic ion separation by ion chromatography

Posted: Thu Feb 28, 2019 5:47 pm
by John Guajardo
Hi minsun30437,

You will have difficulty separating lactate and fluoride on the Dionex IonPac AS18 column. However, please review figure 10 of the specification sheet for gradient conditions to separate the other anions. The example is for a 4mm column, so please use a flow of 0.25 mL/min for your 2mm column.

If you are able to choose a different column, a better choice for these would be either the Dionex IonPac AS11-HC column or the Dionex IonPac AS19 column.

We do offer a useful tool online to help model isocratic and gradient separations on various Dionex IonPac columns. It's free to use, but registration is required. Please check out Virtual Column Online. You may also find our Dionex IonPac Column Selection Guide useful.

Re: organic, inorganic ion separation by ion chromatography

Posted: Fri Mar 01, 2019 6:09 am
by Markus Laeubli, Metrohm
Isocratic separation is possible as well on Metrosep A Supp 16 - 250/2.0 (will work on the 4 mm column as well).

Separation of standard anions and various organic acids on a Metrosep A Supp 16 – 250/2.0. Measuring conditions: 7.5 mmol/L sodium carbonate / 0.75 mmol/L sodium hydroxide, flow 0.2 mL/min, 65°C.

See chromatogram