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Quantification of organic P and low-molecular-weight organic acids in soil extracts by high performance ion chromatograph

Waithaisong K., Robin A., Martin A., Clairotte M., Villeneuve M., Plassard C.. 2015. Geoderma, 257-258 : p. 94-101.

DOI: 10.1016/j.geoderma.2014.12.024

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.

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