Determination of Organic Acids Exuded from Plant Roots by High Performance Liquid Chromatography

A simple and highly sensitive method was developed for the determination of organic acids exuded from plant roots by high performance liquid chromatography with ultraviolet (UV) detection. The root exudate was passed through cation and anion exchange resin columns subsequently. The eluant was then concentrated in a rotary evaporator. The residue was dissolved in dilute HClO4 solution at pH 2.1. The separation was performed on a Bio-Rad Aminex HPX-87H sulfonic column at 50 degrees C with an eluent containing 5 mmol/L H2SO4 at a flow-rate of 0.5 mL/min, and the organic acids were detected at a wavelength of 210 nm by a UV detector. Average recoveries for the root exudates were in the range of 82.0%-96.2% and the detection limits were 1-120 microg/L, and the relative standard deviations (RSD) were 0.67%-3.31% for the seven organic acids. The intra-day precisions were 1.2%-4.7%, and inter-day precisions were 3.3%-10.6%. These results demonstrated that the proposed method is simple, sensitive and reliable for the determination of organic acids in plant root exudates, despite the presence of the particularly complex matrix.