Rapid determination of organic acids in Bayer liquors by high-performance liquid chromatography after solid-phase extraction

A rapid high-performance liquid chromatographic (HPLC) method for determining the organic acids in Bayer liquors is reported. It is the first time that high-performance liquid chromatography was used to separate and determine organic acids in Bayer liquors. Oxalic, tartaric, acetic, succinic, glutaric and butene dicarboxylic acid were identified and quantified in 10 min. First time repeatability, reproducibility and recovery were determined out for these acids in Bayer liquors. The organic acids were removed from Bayer liquors by using a solid-phase extraction procedure with ion-exchange cartridges. Previously, the solution of Bayer liquor was adjusted to pH 7.50 with 8 mol/l HCl. Then, this solution was adjusted to pH 2.00 with 0.1 mol/l HCl. The chromatographic separation was achieved with a Kromasil RP-C18 column and thermo stated at 25 °C. Potassium dihydrogenphosphate buffered at pH 2.10 with orthophosphoric acid and methanol were used as mobile phase at a flow-rate of 1.30 ml/min for the whole run. Organic acids were detected with a UV–vis detector at 215 nm. The precision results showed that the relative standard deviations of the repeatability and reproducibility were <2.80% and <3.74%, respectively. The accuracy of the method was confirmed with an average recovery ranging between 85.2% and 114.7%. Under optimum conditions the detection limits ranged from 0.0023 to 10.36 mg/l.