title: Improvement of (31)P NMR spectral resolution by 8-hydroxyquinoline precipitation of paramagnetic Fe and Mn in environmental samples.
abstract: Solution (31)P nuclear magnetic resonance (NMR) spectroscopy is currently the main method for the characterization of phosphorus (P) forms in environment samples. However, identification and quantification of P compounds may be hampered by poor resolution of spectra caused by paramagnetic Fe and Mn. In this study, a novel technique was developed to improve spectral resolution by removing paramagnetic Fe and Mn from alkaline extracts via 8-hydroxyquinoline (8-HOQ) precipitation. Batch experiments showed that both Fe and Mn were effectively removed by the precipitation at pH 9.0, with the removal efficiencies of 83-91% for Fe and 67-78% for Mn from the extracts of five different environmental samples, while little effect was found on concentration of total P. The (31)P NMR analysis of a model P solution showed that addition of 8-HOQ and its precipitation with metal ions did not alter P forms. Further analyses of the five extracts with (31)P NMR spectroscopy demonstrated that the 8-HOQ precipitation was an ideal method compared with the present postextraction techniques, such as bicarbonate dithionate (BD), EDTA and Chelex-100 treatments, by improving spectral resolution to a large extent with no detrimental effects on P forms.
authors.affiliation: State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, China. smding@niglas.ac.cn
authors.forename: Shiming
authors.initials: S
authors.lastname: Ding
authors.forename: Di
authors.initials: D
authors.lastname: Xu
authors.forename: Bin
authors.initials: B
authors.lastname: Li
authors.forename: Chengxin
authors.initials: C
authors.lastname: Fan
authors.forename: Chaosheng
authors.initials: C
authors.lastname: Zhang
mesh_terms: D011232:Chemical Precipitation; D002681:China; D004777:Environment; D005618:Fresh Water / Q000737:chemistry; D019015:Geologic Sediments / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008345:Manganese / Q000737:chemistry*; D008956:Models, Chemical; D015125:Oxyquinoline / Q000737:chemistry*
chemical_list: D008345:Manganese; D015125:Oxyquinoline; D007501:Iron