title: LC-MS analysis of low molecular weight organic acids derived from root exudation.
abstract: A sensitive method for quantification of citric, fumaric, malic, malonic, oxalic, trans aconitic, and succinic acid in soil- and root-related samples is presented. The method is based on a novel, fast, and simple esterification procedure and subsequent analysis via liquid chromatography-mass spectrometry. Derivatization comprises in situ generation of HCl, which catalyzes the Fischer esterification with benzyl alcohol. As a key advance, the esterification with the aromate allows reversed-phase separation and improves electrospray ionization efficiency. The method provided procedural detection limits of 1 nM for citric, 47 nM for fumaric, 10 nM for malic, 10 nM for malonic, 16 nM for oxalic, 15 nM for succinic, and 2 nM for aconitic acid utilizing 500 μL of liquid sample. The working range was 3 nM to 10 μM for citric acid, 158 nM to 10 μM for fumaric acid, 34 nM to 10 μM for malic acid, 33 nM to 10 μM for malonic acid, 53 nM to 10 μM for oxalic acid, 48 nM to 10 μM for succinic acid, and 6 nM to 10 μM for aconitic acid. Quantification of the analytes in soil-related samples was performed via external calibration of the entire procedure utilizing (13)C-labeled oxalic and citric acid as internal standards. The robustness of the method was tested with soil extracts and samples from hydroponic experiments. The latter concerned the regulation of phosphorus solubilization via plant root exudation of citric, malic, and oxalic acid.
authors: Department of Chemistry, University of Natural Resources and Applied Life Sciences-BOKU Vienna, Vienna, Austria.
authors: Leonhard
authors: L
authors: Jaitz
authors: Bernhard
authors: B
authors: Mueller
authors: Gunda
authors: G
authors: Koellensperger
authors: Daniela
authors: D
authors: Huber
authors: Eva
authors: E
authors: Oburger
authors: Markus
authors: M
authors: Puschenreiter
authors: Stephan
authors: S
authors: Hann
mesh_terms: D029688:Brassica napus / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D019343:Citric Acid / Q000032:analysis*; D008293:Malates / Q000032:analysis*; D015394:Molecular Structure; D008970:Molecular Weight; D019815:Oxalic Acid / Q000032:analysis*; D018517:Plant Roots / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization; D053719:Tandem Mass Spectrometry
chemical_list: D008293:Malates; D019343:Citric Acid; C030298:malic acid; D019815:Oxalic Acid