organic, inorganic ion separation by ion chromatography

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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.
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.
Best regards,

John Guajardo
Product Manager, IC Columns
Thermo Fisher Scientific
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
Dr. Markus Laeubli
Manager Marketing Support IC
Metrohm AG
9101 Herisau
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