Issue 4, 2020

Quantitative measures of myo-IP6 in soil using solution 31P NMR spectroscopy and spectral deconvolution fitting including a broad signal

Abstract

Inositol phosphates, particularly myo-inositol hexakisphosphate (myo-IP6), are an important pool of soil organic phosphorus (P) in terrestrial ecosystems. To measure concentrations of myo-IP6 in alkaline soil extracts, solution 31P nuclear magnetic resonance (NMR) spectroscopy is commonly used. However, overlap of the NMR peaks of myo-IP6 with several other peaks in the phosphomonoester region requires spectral deconvolution fitting (SDF) to partition the signals and quantify myo-IP6. At present, two main SDF approaches are in use; the first fits a Lorentzian/Gaussian lineshape to the myo-IP6 peaks directly to the baseline without an underlying broad signal, and the second fits a Lorentzian/Gaussian lineshape to the myo-IP6 peaks simultaneously with an underlying broad peak. The aim of this study was to compare the recovery of added myo-IP6 to soil extracts using both SDF procedures for six soil samples of diverse origin and differing concentrations of organic P (112 to 1505 mg P per kgsoil). The average recovery of total added myo-IP6 was 95% (SD 5) and 122% (SD 32) using SDF with and without an underlying broad signal, respectively. The recovery of individual peaks of myo-IP6 differed, most notably, the C5 phosphate peak of myo-IP6 was overestimated by up to 213% when a broad peak was not included in SDF. Based on the SDF procedure that includes a broad peak, concentrations of myo-IP6 ranged from 0.6 to 90.4 mg P per kgsoil, which comprised 1–23% of total phosphomonoesters. Our results demonstrate that the SDF procedure with an underlying broad signal is essential for the accurate quantification of myo-IP6 in soil extracts.

Graphical abstract: Quantitative measures of myo-IP6 in soil using solution 31P NMR spectroscopy and spectral deconvolution fitting including a broad signal

Supplementary files

Article information

Article type
Paper
Submitted
24 Oct 2019
Accepted
04 Mar 2020
First published
05 Mar 2020
This article is Open Access
Creative Commons BY-NC license

Environ. Sci.: Processes Impacts, 2020,22, 1084-1094

Quantitative measures of myo-IP6 in soil using solution 31P NMR spectroscopy and spectral deconvolution fitting including a broad signal

J. E. Reusser, R. Verel, E. Frossard and T. I. McLaren, Environ. Sci.: Processes Impacts, 2020, 22, 1084 DOI: 10.1039/C9EM00485H

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