High performance liquid chromatography (HPLC) was used for the separation and quantification of the low molecular-mass organic acids in the root exudates of Cr-hyperaccumulator Leersia hexandra Swartz. Eight organic acids, oxalic, tartaric, formic, malic, lactic, acetic, maleic and citric acids, were separated on an XSelect HSS T3 column (250 mm×4.6 mm, 5 μm) within 13 min with the mobile phase of 40 mmol/L potassium dihydrogen phosphate-phosphorous acid at pH 2.40, a flow-rate of 1.0 mL/min, a detection wavelength of 205 nm and a column temperature of 25℃. This is a simple and highly sensitive method for the separation of the eight organic acids with well-shaped peaks. The limits of detection (LODs) for the eight acids ranged from 0.12 mg/L to 12.32 mg/L. Under the optimized conditions, tartaric, malic, lactic, maleic and citric acids in the root exudates were detected with high linearities, acceptable recoveries and excellent precisions. The contents of these acids calculated in the root exudates were (130.90±1.44) μg/g (root dry weight (DW)) for tartaric acid, (1031.34±4.38) μg/g (root DW) for malic acid, (65.54±1.01) μg/g (root DW) for lactic acid, (0.96000±0.00367) μg/g (root DW) for maleic acid and (201.50±1.13) μg/g (root DW) for citric acid. The proposed HPLC method is quite suitable for the simultaneous determination of organic acids in the root exudates of Leersia hexandra Swartz, and can be used in other plant root exudates as well.
