I am currently working on a method for the assay of Citrate and EDTA. The method as I inherited it uses a Copper(II) Sulfate solution to chelate and then anion exchange. UV detection at 240nm.
Current chromatography gives a split peak shape for Citrate and small response for EDTA. Does anyone know of a better methodology to use or possibly why the citrate peak splits. I am leaning toward the divalent state of Citrate but not definite.
Thanks in advance.

A couple of questions in regards to your problem.
what pH are you using?
is the split peak in standards, samples or both?
it could be that you're seeing both citrate and isocitrate.
just a thought...

We've assayed for both, routinely, but never simultaneously. Is there a definite business need to do simultaneously?

First, citrate is readily analyzed by ion chromatography using conductivity detection. Generally, hydroxide eluent are preferred for this application. EDTA can also be analyzed by ion chromatography but it's analysis is complicated by the tendency of this analyte to form complexes with metals presence in the sample or the metals commonly contaminating the stationary phase, resulting in multiple peaks. Generally, it's better to analyze EDTA as a complex (as in your method) or to perform the separation at low pH (pH in the 2-3 range) where complexes are insufficiently stable to maintain their integrity during the separation process. This should be possible, although I haven't tried it, with direct UV detection using a UV transparent acid eluent system such as phosphoric acid. With an anion exchange column under such conditions you should be able to separate and detect both EDTA and citrate.

FYI: the double peak of observed for citrate is unlikely to be connected to the trivalent character of the anion. More likely, your complex is falling apart during the chromatography. To improve matters, you need to have copper in both the mobile phase and spiked into in the sample.

Thanks Chris. The copper in teh mobile phase is not something I had thought of.