A new approach for the extraction of organic phosphorus (Po) from freshwater sediments, which can be used in solution 31P nuclear magnetic resonance spectroscopy (31P NMR), has been developed and optimized. This approach addresses three important factors for sediment extraction: pH, organic matter (OM), and paramagnetic ions. We classified the sediments according to the pH, OM, and paramagnetic ions (acidic: pH < 7, alkaline: pH > 7; low OM: OM < 100 g·kg-1, high OM: OM > 100 g·kg-1; non-calcareous: Ca/(Fe + Al) < 0.5, calcareous: Ca/(Fe + Al) > 0.5). The 0.25 and 0.5 mol·L-1 NaOH were optimum concentration for acidic and alkaline sediment extracted, respectively. The ratio of sediment to extraction remains at 1:10 (w:v) which exhibited higher extraction efficiency compared with 1:5 and 1:20 for both low and high OM sediments. Use of 25 mmol·L-1 and 50 mmol·L-1 ethylenediaminetetraacetic acid (EDTA) was optimal for Po extraction from non-calcareous and calcareous sediments, respectively. A useful extraction ratio table was developed through systematic orthogonal experiment. This new approach will allow 31P NMR to be more efficiently used for freshwater Po analysis and will help answer questions regarding to the fate and function of Po in freshwater sediments.
Keywords: 31P NMR; Organic matter; Paramagnetic ion; Phosphorus; pH.
© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.