LC-ICP-MS analysis of inositol phosphate isomers in soil offers improved sensitivity and fine-scale mapping of inositol phosphate distribution

Abstract

Organic forms of phosphorus (P) prevail in soils and their quantification is vital to better understand global biogeochemical cycles. P speciation in soil is commonly assessed by 31P NMR spectroscopy of sodium hydroxide-EDTA (NaOH-EDTA) extracts. A liquid chromatography-inductively coupled plasma-mass spectrometry (LC-ICP-MS) method that employs NaOH-EDTA is described. Comparison with 31P NMR shows that LC-ICP-MS is up to three orders of magnitude more sensitive. It allows measurement in samples as small as 1 mg. We reveal variation of inositol phosphate distribution in Swedish boreal forest soil and identify myo- and scyllo-inositol hexakisphosphates and other isomers including scyllo-inositol pentakisphosphate. Speciation of the major inositol phosphates was not altered by long-term nitrogen fertilization.