Quantification of organic P and low-molecular-weight organic acids in ferralsol soil extracts by ion chromatography

Kittima Waithaisong (1) , Agnès Robin (1) , Agnès Martin (1) , Michael Clairotte (1) , Manon Villeneuve (1) , Claude Plassard (1)

1 UMR Eco&Sols - Ecologie fonctionnelle et biogéochimie des sols et des agro-écosystèmes

A better understanding of the composition of organic phosphorus (organic P) and low-molecular-weight organic acids (LMWOAs) in soil will make it possible to predict phosphorus cycling, improve biomass production and help phosphorus management in forest plantations. The method for quantifying organic P and LMWOAs in soil extracts was developed using ion chromatography (IC). Sodium hydroxide (0.5 N) was validated as an extractant for both organic P and LMWOAs. A mixture of 200 mM NaOH and ultrapure water was used to create a linear gradient elution. The eluent program separated five different organic P forms (glucose-6-phosphate, AMP, fructose-1,6-bisphosphate, ATP and phytate) as well as pyrophosphate from inorganic P (Pi), and four LMWOAs (malate, malonate, oxalate and citrate) in a 25 minute run through an AS11 column. The variability of the quantification was expressed as the relative standard deviation which was less than 20% for most of the analytes. The recovery rate of organic P assayed by IC to colorimetry was 110 ± 20%. This chromatographic method was shown to be suitable for the quantification of organic P and LMWOAs in soil samples and could be an easier alternative to 31P Nuclear Magnetic Resonance (NMR) measurement.

Mots clés: Organic P forms; Low-molecular-weight organic acids; Soil extract; Single-run separation; IC quantification

Domaines: Géochimie

Kittima Waithaisong, Agnès Robin, Agnès Martin, Michael Clairotte, Manon Villeneuve, et al.. Quantification of organic P and low-molecular-weight organic acids in ferralsol soil extracts by ion chromatography. Geoderma, 2015, 257, pp.94-101. ⟨10.1016/j.geoderma.2014.12.024⟩. ⟨hal-01268814⟩