Nuclear magnetic resonance soil extraction

Cade-Menun, B.J., Liu, C.W., Nunlist, R. and McColl, J.G. (2002) Soil and litter phosphorus-31 nuclear magnetic resonance spectroscopy extractants, metals and P relaxation times. )our-nal of Environmental Quality 31,457-465. 

SOM, soil organic matter HS, humic substances DH, degree of humification HAC, humic acid C FAC, fulvic acid C TEC, total extractable C HR, humification rate HI, humification index NHC, nonhumified C TOC, total organic C HA, humic acid FA, fulvic acids UV-Vis, ultraviolet-visible FT-IR, Fourier transform infrared NMR, nuclear magnetic resonance ESR, electron spin resonance EEM, excitation-emission matrix. 

LC-NMR. Separations using reverse-phase (RP) liquid chromatography are potentially more powerful because samples can be studied without derivatization. Numerous attempts have been made to separate NOM and while most studies exhibit some degree of separation, to date the complete separation of a NOM sample has not been accomplished. Even only partial separation is possible, and it is worth to hyphenate a separation method with structure information-oriented analytical applications. Liquid chromatography combined with nuclear magnetic resonance and preliminary studies with solid-phase extraction were conducted on NOM isolated from freshwater and soil (Simpson et al., 2004). 

Figure 15.9. 13C CPMAS NMR spectrum of humin extracted from a brown chernozem soil from Western Canada. The characteristic doublet in the unsubstituted aliphatic region is characteristic of methylene carbon (28-34 ppm) and shows the presence of both amorphous (soft) domains at 29 ppm and crystalline (rigid) domains at 33 ppm in soil humin. Reprinted from Simpson, M. I, and Johnson, R C. E. (2006). Identification of mobile aliphatic sorptive domains in soil humin by solid-state 13C nuclear magnetic resonance. Environ. Toxi. Chem. 25, 52-57, with permission from the Society of Environmental Toxicology and Chemistry.

Condron, L.M., Goh, K.M., and Newman, R.H. (1985) Nature and distribution of soil phosphorus as revealed by a sequential extraction method followed by 31P nuclear magnetic resonance analysis. J. Soil Sci. 36, 199-207. 

Hawkes, G.E., Powlson, D.S., Randall, E.W., and Tate, K.R. (1984) A 31P nuclear magnetic resonance study of the phosphorus species in alkali extracts from long-term field experiments. J. Soil Sci. 35, 35—45. 

The study of humic substances by nuclear magnetic resonance of the isotope and the proton suggests that aliphatic structures prevail over aromatic structures for the fulvic acids extracted from marine water, contrary to the case for soil fulvic acids. The high values of the H C ratio in marine fulvic acids also point to an aliphatic nature (Stuermer and Payne, 1976). 

Turner, B.L., Mahieu, N. and Condron, L.M. (2003) Phosphorus-31 nuclear magnetic resonance spectral assignments of phosphorus compounds in soi I NaOH-EDTA extracts. Soil Science Society of America Journal 67, 497-510. 

Fig. 2.5. A comparison of the effect of extractants on solution P nuclear magnetic resonance spectra (Cade-Menun etal., 2002). The samples were a soil and a litter sample collected under stands of cedar in Washington, USA. The NaOH samples were extracted with 0.25 M NaOH, the Chelex samples were extracted with 0.25 M NaOH plus 6 1 Chelex to soil or litter (weight basis) and the EDTA samples were extracted with a 1 1 mix of 0.5 M NaOH plus 0.1 M Na2EDTA. Spectra were collected on a DRX-500 spectrometer with a 10-mm broadband probe, using a 90° pulse, 3.2 s pulse delay and 32°C temperature. See Cade-Menun et al. (2002) for more details.

Table 2.4. Studies of phosphorus in agricultural soils using whole-soil extractions and solution P nuclear magnetic resonance spectroscopy.

Crouse, D.A., Sierzputowska-Cracz, H. and Mikkel-son, R.L. (2000) Optimization of sample pH and temperature for phosphorus-31 nuclear magnetic resonance spectroscopy of poultry manure extracts. Communications in Soil Science and Plant Analysis 31, 229-240. 

Escudey, M., Galindo, G., Forster, J.E., Salazar, I., Page, A.L. and Chang, A. (1997) Phosphorus-nuclear magnetic resonance analysis in extracts of a phosphorus-enriched volcanic soil of Chile. Communications in Soil Science and Plant Analysis28, 121-131. 

Rubsk, C.H., Cuggenberger, C., Zech, W. and Christensen, B.T. (1999) Organic phosphorus in soil size separates characterized by phosphorus-31 nuclear magnetic resonance and resin extraction. Soil Science Society of America Journal 53, 1 123-1 1 32. 

Turner, B.L. and McKelvie, I.D. (2002) A novel technique for the pre-concentration and extraction of inositol hexakisphosphate from soil extracts with determination by phosphorus-31 nuclear magnetic resonance. Journal of Environmental Quality 31,455-470. 

Turner, B. L., N. Mahieu, and L. M. Condron. 2003a. Phosphorus-31 nuclear magnetic resonance spectral assignments of phosphorus compounds in soil NaOH-EDTA extracts. Soil Sci. Soc. Am. J. 67 497-510. Turner, B. L., N. Mahieu, and L. M. Condron. 2003b. The phosphorus composition of temperate pasture soils determined by NaOH-EDTA extraction and solution P NMR spectroscopy. Org. Geochem. 34 1199-1210. 

HS was extracted from the labeled SRS soils with 0.25 M NaOH following our previous procedure (23). The isolated HS was then subjected to multinuclear, one and two dimensional nuclear magnetic resonance... 

An alternative approach to the problem of characterising soil P has been to use P-nuclear magnetic resonance (nmr) to obtain both qualitative and quantitative estimates of the various forms of P in soil alkaline extracts. 

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