Determination of Phenolic Acids in Root Exudates of Allelopathic Rice by Solid Phase Extraction-Ion Chromatography with Conductivity Detection

A simple, effective, and green ion chromatography method with conductivity detection was developed for the determination of benzoic acid, cinnamic acid, syringic acid, and p-hydroxybenzoic acid in the root exudates of allelopathic rice. The analytes were well separated within 25 min in an anion exchange column (150 mm × 4.0 mm i.d., 5 µm particle size) with mixtures of 6.4 m mol L−1 Na2CO3 and 2.0 m mol L−1 NaHCO3 as the mobile phase at a flow-rate of 0.7 mL min−1. Detection limits of benzoic acid, cinnamic acid, syringic acid, and p-hydroxybenzoic acid were 0.05, 0.20, 0.50, and 0.05 µg mL−1, respectively. Intra- and inter-day precision was ≤4.0% and 3.2%, respectively, and the intra- and inter-day accuracy, indicated by relative error, ranged from −8.0% to 9.0%. The developed method was successfully used to determine phenolic acids in the root exudates of allelopathic rice. The average recoveries of the analytes were between 90.7% and 103.0%.