Non-suppressed conductivity detection of organic acids in plant tissue extracts by ion-exclusion chromatography with aromatic acid eluents

Aromatic acids were evaluated as eluents for ion exclusion chromatography of organic acids with non-suppressed conductivity detection. The separation of organic acids, performed on an Aminex HPX-87H ion-exclusion column, using a variety of aromatic carboxylic acid eluents, is described in detail. Phthalic acid was found to be a suitable eluent for the separation of the organic acid tested, giving reasonable resolution and detection sensitivity. When 1 mM phthalic acid was used as eluent, an excellent separation of eight acids was achieved in 20 min. Calibration plots for the test acids were linear in the range 10(-2) M to 10(-5) M with detection limits of the order of 10(-6) M. Compared to eluent containing sulfuric acid, the proposed method permits a more sensitive detection for the organic acids tested due to the lower background conductance of the eluent used. The proposed method was used for the determination of organic acids in plant tissue extracts with direct injection of sample extract.