HPLC separation of organic acids

[CIL]

I want to separate organic acids using Rezex Organic acid column. Mobile phase is 0.005N H2SO4. Individual injection gives very good results. However, when acid mixture is injected, we are not getting separated peaks. I need help to separate mixture of organic acids.

[Blazer]

Hi welcome. As a general rule, the more information you provide, the more help you can get. Posting chromatograms is very helpful; a picture worth a thousand words, and all that.

Your separation issue sounds fairly straightforward. Without knowing which organic acids you're trying to separate and which ones aren't separating, we can't offer a ton of specifics. Let's start with this, however. Separation of organic acids is a simple enough separation that many vendors often include an application note or sales brochure. You can probably find your solution on your column vendor's website.

[Consumer Products Guy]

Call Restek tech help.

I used some organic acid columns from at least 2 vendors with 0.025N H2SO4 and was satisfied with the results, conductivity detector. I was only interested in formic, malic, and citric acids at the time.

[CIL]

Thanks for responding. I want to separate organic acids like formic acid, fumaric, malic, acetic acid, lactic acid, citric acid, tarteric acid, oxalic acid, formic acid, succinic acid. I am using UV detector (210 nm). Individual acids are elluting at different retention time, however, problem is after mixing, all are elluting together.

[Andy Alpert]

FYI: Some food analysis labs analyze most of these isocratically with a cheap silica-based C-18 and a C-8 column connected in series, using a simple phosphate buffer. If the sample is expected to contain quinic acid (e.g., cranberry juice), then it is necessary to use a non-endcapped column if you want to separate tartaric and quinic acids. Note that the advertisements for endcapped reversed-phase columns' use for organic acids never show samples containing quinic and tartaric acid together...

[Markus Laeubli, Metrohm]

Dear CIL

What are the concentrations you are injecting?
What are the retention times of the acids?