How to separate fluoride, lactate, acetate and formate

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I could use some advice. I am currently running anions (AS19 Dionex column). I am having trouble separating the fluoride, lactate, acetate and formate. The fluoride, lactate and acetate are all shoulders on each other. The retention times are- Fluoride-5.39, Lactate-5.60, acetate-5.9, formate-6.8. My method is gradient KOH. Time zero is 10 mM increasing concentration to 15mM at 10 minutes. What would help the separation? Longer time to get to the 15mM? Or increasing to 15mM sooner? I don’t have a lot of experience in method development. Thank you in advance!
Hi Annemarie
In IC, using a gentler concentration gradient is a way to increase the retention time of peaks and hopefully resolve them better. So you could try going from 10 mM at zero time to 15 mM at 15 minutes instead of 10 minutes to see if that helped
We did this separation isocratically on an Metrosep A Supp 16 - 250/2.0 column (2mm). Carb/bicarb eluent (7.5/0.75 mmol/L at 0.2 mL/min).

Dr. Markus Laeubli
Manager Marketing Support IC
Metrohm AG
9101 Herisau
Thank you. I will give it a try!
The AS15 does a really good job separating fluoride from those other peaks. I think it will separate all of these peaks pretty well.
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