31P FT-NMR spectroscopy

Because the application of NMR spectroscopy to environmental samples is relatively new, we focused our studies on the identification and characterization of DOP by 31P FT-NMR spectroscopy. Ultrafiltration and reverse osmosis concentration techniques were employed to increase the dissolved organic phosphorus concentrations to the detection level of 31P FT-NMR techniques (approximately 10-20 mg of P/L). With these concentration methods a DOP concentration factor of up to 2000 is obtainable. This chapter reports the use of 31P FT-NMR spectroscopy in the analysis of DOP. In... 

Figure 15. Seasonal changes in dissolved organic phosphorus detected by 31P FT-NMR spectroscopy. The peak height ratio was 4.0-5.0 ppm 0.0-2.0 ppm.

These techniques may further enhance the ability of 31P FT-NMR spectroscopy to be used for the identification of hydrosphere DOP. We have demonstrated already that 31P NMR spectroscopy is a viable technique for DOP identification and characterization. 31P NMR spectroscopy may eventually be useful through several of the techniques mentioned in this chapter for studying interactions of DOP with dissolved humic substances, colloids, and seston and particulate adsorption. Hence, 31P FT-NMR spectroscopy... 

Because NMR spectroscopy is a nuclei-specific technique and has the ability to distinguish between similar compounds, it is an excellent method for identifying similar species in complex matrices. Thus, 31P FT-NMR spectroscopy is ideal for the identification and characterization of the hydrosphere DOP. Even so, NMR spectroscopy is fairly insensitive and requires high sample concentrations. Low DOP concentrations are increased to 31P FT-NMR detection limits by using ultrafiltration and reverse osmosis membranes. Not only is the DOP concentrated, but it is fractionated according to its molecular size. Compared to other concentration and molecular size fractionation techniques for DOP, ultrafiltration and reverse osmosis are relatively rapid and easy. 

The initial observation is that PMMA is essentially completely degraded to monomer by heating to 375°C in a sealed tube while heating a mixture of red phosphorus and PMMA under identical conditions yields a solid, non-deqraded, product as well as a lower yield of monomer. One may observe, by 3C NMR spectroscopy, that the methoxy resonance is greatly decreased in intensity and methyl, methoxy phosphonium ions are observed by 31P NMR. Additional carbonyl resonances are also seen in the carbon spectrum, this correlates with a new carbonyl vibration near 1800 cm 1 in the infrared spectrum and may be assigned to the formation of anhydride. The formation of anhydride was also confirmed by assignment of mass spectra obtained by laser desorption Fourier transform mass spectroscopy, LD-FT-MS. 

Copper(I) complexes [Cu(L)(Tpx)] (L = 4-(diphenylphosphane) benzoic acid, Tpx = Tp, pzTp, or Tp ) have been synthesized and characterized by FT-IR in the solid state, and by NMR (3H and 31P 1H ) spectroscopy, ESI MS, and conductivity measurements in solution. The solution data are in accordance with partial dissociation of the sterically hindered complexes due to breaking of Cu-P and Cu-N... 

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