Chromatography Forum

Hi, I'm looking for a way to extract both citric and oxalic acids from the urine. Urine organic acids (I guessed) are interfering the separation of oxalic acid using a RP column with UV detector

thanks

Anion exchange SPE will extract the acids from urine; however, if the problem is being caused by other acids in the sample they will also be extracted. What RP column are you using, what is the mobile phase, and what is the retention time. You may be able to fix the problem by adjusting the chromatography to seperate the interferences from your analyte. Maybe you can try an ion-pairing reagent?

If you search Pubmed, you should find details of methods.

One example..

Simultaneous determination of oxalic and citric acids in urine by high-performance liquid chromatography.

Khaskhali MH, Bhanger MI, Khand FD.

J Chromatogr B Biomed Appl. 1996 Jan 12 ; 675(1):147-51.

A simple method for the simultaneous determination of oxalic and citric acids had been developed using reversed-phase HPLC. An aqueous solution containing potassium dihydrogen phosphate (0.25%) and tetrabutylammonium hydrogen sulphate (2.5 mmol) at pH 2.0 was used as mobile phase. Under these conditions both the components were well resolved and detected at 210 nm. The recovery for oxalic and citric acids was 97% and 102%, respectively. The method presented here was applied to urine specimens of a large number of urolithic patients and control subjects. Because of the simplicity of the method its application provides better means of monitoring the concentration of oxalic and citric acids in the formation of renal calculi.

Bruce Hamilton

Below is an oxalic acid injected on to Unison UK-C18:

http://www.imtakt.com/TecInfo/TI257E.pdf