Chemical characterization and agronomic effectiveness of phosphorus applied as a polyphosphate-chitosan complex

This work was undertaken to characterize a chitosan-polyphosphate complex (CH-PP) and to evaluate its agronomic effectiveness as a source of phosphorus for ryegrass (Lolium perenne) grown on loamy and clayey soils. High resolution solid state³¹P and¹³C nuclear magnetic resonance were used to characterize this complex and to monitor the structural changes occurring to it during an 8-week incubation period in a loamy soil. A pot experiment was conducted on the two soils after labelling the available P with³²PO₄ ions. This experiment allowed for the determination of the agronomic effectiveness of the chitosan-polyphosphate complex compared to polyphosphate and to monocalcium phosphate. Results showed that chitosan immobilized up to 147 mg P kg^–1 as pyrophosphate and hexametaphosphate. This reaction did not involve major structural changes in the pyrophosphate or hexametaphosphate groups nor in the chitosan. The chitosan-polyphosphate complex was as efficient as the polyphosphate alone to sustain the P nutrition of ryegrass. The relative agronomic effectiveness of these P sources was slightly lower compared to that of monocalcium phosphate. The high P fertilizing value of the chitosan-polyphosphate complex was attributed to its gradual hydrolysis in the soil. The potential interest of chitosan to remove polyphosphates from waste waters while preserving the high P fertilizing value of polyphosphates was addressed.     

On the Quantification of Lignin Hydroxyl Groups With 31P and 13C NMR Spectroscopy

Factors affecting the accuracy of the analysis of lignin hydroxyl and carboxyl groups with ³¹P NMR have been further elucidated. Two modifications of ³¹P NMR analysis of lignin, namely the protocols using 1,3,2-dioxaphospholane (PR-I) and 2-chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphospholane (PR-II) as phosphorylation reagents with different internal standards, were studied. The previous ³¹P NMR standard protocol with PR-II underestimated OH groups by about 30%, whereas the ³¹P NMR standard protocol with PR-I tended to produce overestimated data. It has been shown that cholesterol is not an appropriate internal standard, resulting in underestimated values for OH groups due to incomplete baseline resolution. The best internal standard has been found to be endo-N-hydroxy-5-norbornene-2,3-dicarboximide. Strong care should be taken related to the stability of the internal standards to avoid inflated results due to IS degradation. Under modified optimized conditions, both methods show a good correlation with the ¹³C NMR protocol in the quantification of hydroxyl groups as average, with the variability between the methods in the range of 5–15%. However, the ³¹P NMR protocols report COOH content that is twice as low as that of ¹³C NMR data. Finally, the best approach for the use of the ³¹P and ¹³C NMR methods in lignin analysis is discussed.     

Quantitative Analysis of Dairy Phospholipids by 31P NMR

³¹P NMR analysis of samples prepared in a sodium cholate detergent system was assessed as a method for the quantitative measurement of dairy phospholipids. Major phospholipid (PL) classes measured included: phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS), phosphatidylinositol (PI), sphingomyelin (SM) and dihydrosphingomyelin (DHSM). The ³¹P NMR method was validated by comparison with a quantitative two-dimensional thin-layer chromatography (2D-TLC) technique. The 2D-TLC system was more sensitive, able to detect some minor compounds not observed by ³¹P NMR. However, ³¹P NMR is more suited to routine analysis, with sample analysis taking 36 min. The method was also more versatile and sample analysis was possible on high phospholipid containing materials without prior lipid extraction (e.g. buttermilk protein concentrate, beta serum liquid).     

Forms and exchangeability of inorganic phosphate in composted solid organic wastes

Switzerland yearly produces more than 260,000 Mg of compost, two thirds of which is recycled in agriculture and horticulture. This research was undertaken to examine the forms and availability of inorganic P (Pi) in Swiss composts made from solid kitchen and garden wastes using the isotopic exchange kinetic technique, a sequential Pi extraction and magic angle spinning (MAS) solid-state ³¹P nuclear magnetic resonance (NMR) spectroscopy. The different approaches described in this paper demonstrate the presence of a complex mixture of Pi species in the studied composts. Isotopic exchange experiments and sequential extraction showed that these composts contained relatively large concentrations of rapidly available Pi. Significant correlations were observed between the concentration of water-soluble Pi (Cp), and the total N, C and P content of composts suggesting that organic substances partly controlled the amount of rapidly available Pi. Significant correlations were observed in alkaline composts between the amount of Pi which can not be exchanged within 3 months and the total P and Ca content. In alkaline composts solid-state MAS ³¹P NMR results suggested the presence of a range of slightly soluble and poorly crystallized Ca-P compounds such as apatites or octacalcium phosphates and of organic P compounds. The slowly or non-exchangeable Pi present in these composts could therefore be bound to Ca in the form of apatites or octacalcium phosphates.     

Synthesis and structure of Mu-33, a new layered aluminophosphate

Mu-33, a new layered aluminophosphate with an Al/P ratio of 0.66, was obtained from a quasi non-aqueous synthesis in which tert-butylformamide (tBF) was the main solvent and only limited amounts of water were present. During the synthesis, tBF decomposed and the resulting protonated tert-butylamine is occluded in the as-synthesized material. The approximate structure was determined from data collected on a microcrystal (200 × 25 × 5 μm³) at the European Synchrotron Radiation Facility (ESRF) in Grenoble, but the quality of these data did not allow satisfactory refinement. Therefore the structure was refined using high-resolution powder diffraction data, also collected at the ESRF. The structure (P2₁/c, a = 9.8922(6) Å, b = 26.180(2) Å, c = 16.729(1) Å and β = 90.4(1)°) consists of anionic aluminophosphate layers that can be described as a six-ring honeycomb of alternating corner-sharing AlO₄ and PO₄ tetrahedra with additional P-atoms above and below the honeycomb layer bridging between Al-atoms. The tert-butylammonium ions and water molecules located in the interlayer spacing interact via hydrogen-bonds with the terminal oxygens of the P-atoms. The characterization of this new aluminophosphate by ¹³C, ³¹P, ¹H–³¹P heteronuclear correlation (HETCOR) and ²⁷Al 3QMAS solid state NMR spectroscopy is also reported.     

Characterization of fish oil-in-water emulsions using light-scattering,nuclear magnetic resonance,and gas chromatography-headspace analyses

The effect of the molecular environment on the physical and oxidative properties of homogenized or microfluidized fish oil-in-water emulsions (5% w/w tuna oil in pH 7 phosphate buffer) stabilized by whey protein isolate (WPI, 1 or 5% w/w) or lecithin (2.5% w/w) was examined. Laser light-scattering measurements showed that WPI-stabilized emulsions had smaller particle sizes than lecithin-stabilized emulsions, and that higher pressures reduced the particle size. WPI afforded more protection against oil oxidation than did lecithin, as evidenced by the lower headspace propanal of emulsions as measured by GC-headspace analysis, despite the larger interface in WPI-stabilized emulsions. Reducing the concentration of WPI in emulsions from 5 to 1% decreased the oxidative stability of WPI-stabilized emulsions. The ¹H NMR transverse relaxation times (T ₂) of FA chains in emulsion droplets stabilized by the same surfactants made by homogenization or microfluidization were different and not always related to particle size. The higher mobility (i.e., longer T ₂) of the unsaturated parts of the FA chains within an oil droplet, compared with the saturated parts, suggests that the unsaturated components tended to stay in the core of the oil droplets. This experimental result supports the hypothesis reported in other literature that the more unsaturated FA are buried in the oil core of oil-in-water emulsions. The lack of a universal correlation between particle size and oxidation suggests that the mobility of particles in an emulsion has an influence on the rate of oxidation.     

Chemical Nature and Diversity of Phosphorus in New Zealand Pasture Soils Using <Superscript>31</Superscript>P Nuclear Magnetic Resonance Spectroscopy and Sequential Fractionation

Information on the phosphorus (P) forms of pasture soils is central to agricultural and environmental sustainability. We used a combination of ³¹P nuclear magnetic resonance (NMR) spectroscopy of NaOH–EDTA extracts and sequential fractionation to investigate P forms, with an emphasis on organic P in relation to environmental and biophysical variables, in 24 diverse pasture soils taken from around New Zealand (organic C 19–102 g kg⁻¹, total P 116–2746 mg kg⁻¹, pH 5.2–7.0). Soils were separated by cluster analysis of soil physicochemical properties and sequentially extracted P pools into those either derived from volcanic-ash materials or not. This separation was also evident for organic P species in NaOH–EDTA extracts, which removed about 75% of total soil organic P. The major organic P compound class was monoesters (24–60% of extracted P), made up of 14 to 91% myo-inositol hexakisphosphate. The next largest organic P class was diesters (0–4% of P extracted), which were enriched in volcanic-ash soils (monoester to diester ratio = 14) compared to non volcanic-ash soils (ratio = 30). Correlation analysis indicated that mean annual temperature had a significant negative and positive effect on monoester and diester concentrations, respectively. This was attributed to better physical protection of monoesters (especially inositol phosphates) from mineralization, and increased diesters from microbial activity and biological turnover. The anomalous behaviour of volcanic-ash soils was attributed to slow mineralization and the sampling of soils at different times of year without full knowledge of the large and highly dynamic microbial biomass P pool which is predominantly diesters.     

Phosphitylation and quantitative P NMR analysis of partially substituted biodiesel glycerols

The main step during biodiesel production is the catalytic transesterification of triglycerides. Glycerol and fatty acids are by-products of the biodiesel production and considered as contaminants in the final product. By selectively measuring the amount of fatty acids and glycerol with different substitution levels, the yield of this step and the quality of the final biodiesel can be determined.This study examines the application of phosphitylation of glycerol hydroxyl groups with 2-chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphospholane followed by ³¹P NMR analysis to provide a rapid quantitative analytical technique for the determination of substitution patterns on partially esterified glycerols, alcohols and the detection of fatty acids. ³¹P NMR chemical shift data was established with a series mono and di-substituted esters of glycerol, fatty acids and alcohols, then utilized to characterize commercial glycerol and biodiesel samples.     

Solid-state NMR and FT-IR investigation of 12-tungstophosphoric acid on TiO2

The chemical and dynamic nature of the tungstophosphoric acid (TPA) species adsorbed on pressed, extruded, and powdered TiO₂ support was studied by ³¹P and ¹H solid-state NMR spectroscopy and diffuse reflectance FT-IR. From ³¹P NMR and FT-IR results the TPA appeared to be present in at least five forms on the titania surface: a bulk salt phase, two weakly bound intact Keggin species, a range of partially fragmented clusters such as the 11-“defect” Keggin ion, and a range of species formed by high or complete fragmentation of the Keggin ion. The relative amount of these species varied depending on the form of the support. Adsorption was incomplete on extruded titania resulting in bulk salt formation. There was almost complete adsorption on pressed titania pellets, yielding predominantly fragmented Keggin units, along with a small amount of bulk salt. However, complete adsorption (and fragmentation) without bulk salt formation was attained by impregnation of powdered TiO₂. The acidic nature of the catalysts and the degree of TPA dispersion were investigated by solid-state ¹H high-speed MAS-NMR. Pure TPA salt yielded resonances at about 6.5 ppm. The catalysts yielded acidic proton resonances at about 7–8 and 10–11.5 ppm. The broad resonance observed at 7–8 ppm is due to a dispersion of acidic sites on the surface. The intensity of the acidic resonance at around 11 ppm increased with adsorption effectiveness and could, therefore, be related to the formation of hydroxonium ions upon fragmentation of adsorbed Keggin ions. This revised version was published online in July 2006 with corrections to the Cover Date.     

Carbonization mechanisms resulting from intumescence association with the ammonium polyphosphate-pentaerythritol fire retardant system

In this work we study the thermal behavior of an ammonium polyphosphate-pentaerythritol mixture, fire-retardant additive for polyolefins and most particularly the carbonization process resulting from an intumescent phenomenon. The study has been carried out using Micro-Raman and ¹³C, ¹H, ³¹P NMR of the solid state spectroscopies. It is shown that the structure consists in phoscarbonaceous and polyaromatic species. These latter form an anisotropic structure above 280°C. This structure grows when the temperature increases. Finally, a reactional scheme of the carbonization of the intumescent system is proposed.     

Structure–activity studies of dodecatungstophosphoric acid impregnated bentonite clay catalyst in hydroxyalkylation of p-cresol

Bentonite clay impregnated with dodecatungstophosphoric acid (20% DTP/BNT) showed an excellent activity, selectivity and stability [95% product yield with 94% selectivity to 2, 2′-methylenebis (4-methylphenol), DAM] for the hydroxyalkylation of p-cresol with formaldehyde at 353 K and for a mole ratio of 5. Ammonia-TPD results showed that an increase in total concentration of acid sites from 4.9 of parent bentonite to 11.6 micromoles per surface area NH₃ (μmolS^− 1 NH₃) of 20% DTP/BNT was due to a strong interaction of protons of bulk DTP with surface hydroxyl groups of BNT as evidenced by ³¹P NMR studies.     

Preparation of W1/O/W2 emulsions and droplet size distribution measurements by pulsed‐field gradient nuclear magnetic resonance (PFG‐NMR) technique

Multiple emulsions of W₁/O/W₂ type are of major interest in life sciences, offering possibilities for the encapsulation of water‐soluble active agents. In food science, they are also applied for fat reduction. The droplet size distributions of the inner and outer emulsions are of main importance as they influence the rheological and sensorial properties, the release kinetics, as well as the structural and microbial stability. However, the determination of the inner and outer droplet size distributions is a major challenge, as conventional measurement techniques cannot be applied. Pulsed‐field gradient nuclear magnetic resonance (PFG‐NMR) is well known as a non‐destructive tool for droplet size determination, especially in simple emulsions. In this work, double emulsions of the W₁/O/W₂ type were prepared with polyglycerol‐polyricinoleate (PGPR) and polyoxyethylen‐20‐sorbitan monolaurate (Tween 20) as emulsifiers by means of rotor‐stator emulsification machines. PFG‐NMR was applied for measurements of the inner phase (W₁) droplet size distribution as well as for the characterization of the O phase. The W₁ values were compared with results from laser light diffraction of simple emulsions (W₁/O type) and were found to be consistent within the experimental errors, if restricted diffusion in the outer water phase (W₂) and additional effects are considered.     

NMR determination of crystallinity for poly(?-l-lysine)

Crystallinity of poly(?-l-lysine) (?-PL) was discussed by analyzing the differences in the ¹H spin-spin relaxation times (T₂^H), the ¹³C spin-lattice relaxation times (T₁^C), and the ¹³C NMR signal shapes between the crystalline and the non-crystalline phases. The observed ¹H relaxation curve (free induction decay followed by solid-echo method) showed the sum of Gaussian and exponential decays. Similarly, the observed ¹³C relaxation curves obtained from the Torchia method were double-exponential. The ¹³C NMR spectrum of ?-PL was divided into the narrow and the broad lines by utilizing the intrinsic differences in the ¹H spin-lattice relaxation times in the rotating-frame between them, which are attributed to the crystalline and the non-crystalline phases, respectively. Even though the crystallinity is obtained from the identical NMR measurements, the estimated values are different with each other. The crystallinity estimated from the T₂^H differences was 75.8 ± 0.1% at 333 K and 60.7 ± 0.4% at 353 K. From the T₁^C differences, the value was estimated to be 62 ± 11%. Furthermore, the value estimated from the NMR signal separation was 54 ± 5%. In this study we have explained these discrepancies by the difference in susceptibility among the experiments for the inter-phase, which exists in-between the crystalline and the amorphous phases. Furthermore, the estimated crystallinity was ascertained by the X-ray diffraction experiment.     

Evaluation of strong acid properties of layered HNbMoO6 and catalytic activity for Friedel–Crafts alkylation

The acid properties and catalytic activity of layered HNbMoO₆ for liquid-phase Friedel–Crafts alkylation are examined. ³¹P MAS NMR spectroscopy using trimethylphosphine oxide as a probe molecule reveals that HNbMoO₆ possesses strong acid sites in the interlayer region. Layered HNbMoO₆ is demonstrated to display remarkable catalytic performance for this reaction, substantially exceeding the activities of niobic acid, niobium–molybdenum mixed oxide, ion-exchange resins, and zeolites. It is determined that benzyl alcohol is intercalated into the HNbMoO₆ interlayer during alkylation to form a monolayer configuration, allowing the strong interlayer acid sites to participate in the reaction.     

31P and119Sn high resolution solid state CP/MAS NMR study of Al2O3-SnO2 systems

A series of Al₂O₃-SnO₂ catalysts with the mole ratio of Al₂O₃ to SnO₂ equal to 1:1, 1 0.5, 1 0.1, 1 0.05 and 1 0.01 were characterized by³¹P NMR of adsorbed trimethyl phosphine (TMP) and¹¹⁹Sn MAS NMR spectroscopy. It was found from³¹P NMR that no Brønsted acid sites exist in these samples. Pure SnO₂ shows two different types of Lewis acid sites; in the mixed oxide samples a Lewis peak characteristic of pure Al₂O₃ is always seen, together with either one or two other Lewis peaks, depending on the Sn concentration.¹¹⁹Sn CP/MAS NMR spectra of the highest Sn-content sample show one narrow line at –603 ppm superimposed on a very broad line, indicating a strong interaction between Al and Sn oxides.     

The application of isotopic (32P and 15N) dilution techniques to evaluate the interactive effect of phosphate-solubilizing rhizobacteria, mycorrhizal fungi and Rhizobium to improve the agronomic efficiency of rock phosphate for legume crops

A pot experiment was designed to evaluate the interactive effects of multifunctional microbial inoculation treatments and rock phosphate (RP) application on N and P uptake by alfalfa through the use of ¹⁵N and ³²P isotopic dilution approaches. The microbial inocula consisted of a wild type (WT) Rhizobium meliloti strain, the arbuscular mycorrhizal (AM) fungus Glomus mosseae (Nicol. and Gerd.) Gerd. and Trappe, and a phosphate solubilizing rhizobacterium (Enterobacter sp.). Inoculated microorganisms were established in the root tissues and/or in the rhizosphere soil of alfalfa plants (Medicago sativa L.). Improvements in N and P accumulation in alfalfa corroborate beneficial effects of Rhizobium and AM interactions. Inoculation with selected rhizobacteria improved the AM effect on N or P accumulation in both the RP-added soil and in the non RP-amended controls. Measurements of the ¹⁵N/¹⁴N ratio in plant shoots indicate an enhancement of the N₂ fixation rates in Rhizobium-inoculated AM-plants, over that achieved by Rhizobium in non-mycorrhizal plants. Whether or not RP was added, AM-inoculated plants showed a lower specific activity (³²P/³¹P) than did their comparable non-mycorrhizal controls, suggesting that the plant was using otherwise unavailable P sources. The phosphate-solubilizing, AM-associated, microbiota could in fact release phosphate ions, either from the added RP or from the indigenous ``less-available' soil phosphate. A low Ca concentrations in the test soil may have benefited P solubilization. Under field conditions, the inoculation with AM fungi significantly increased plant biomass and N and P accumulation in plant tissues. Phosphate-solubilizing rhizobacteria improved mycorrhizal responses in soil dually receiving RP and organic matter amendments. Organic matter addition favoured RP solubilization. This, together with a tailored microbial inoculation, increased the agronomic efficiency of RP in the test soil that was Ca deficient at neutral pH.     

Observation of [Al(OH) n (H2O)6-n ] n (MoO4) in hydrotreating catalyst precursors by solid-state27 Al NMR

A previously unobserved octahedral²⁷Al MAS NMR resonance has been detected in rehydrated calcined Mo/Al₂O₃ hydrotreating catalyst precursors. This resonance is attributed to the presence of hydrated forms of aluminum molybdate such as [Al(OH) _n (H₂O)_6-n ] _n (MoO₄) (n = 1 or 2). The cross-polarization relaxation parameters, obtained from variable contact time experiments, yielded information on the relative sizes of the [Al(OH) _n (H₂O)_6-n ] _n (MoO₄) domains in the catalysts with different molybdenum loadings. Analysis of the²⁷A1 MAS NMR spectra of P-Mo(8)/Al₂O₃ and P-Mo(12)/Al₂O₃ (wt%P = 0.0–12.0) shows that a function of the phosphate in the 12 wt% Mo catalyst is to prevent the re-hydration of the molybdate phases on the calcined catalysts.     

Rapid Identification and Relative Quantification of the Phospholipid Composition in Commercial Lecithins by <Superscript>31</Superscript>P NMR

³¹P NMR analysis of samples prepared in a sodium cholate detergent system was used as a method for the identification and quantification of enzymatic hydrolysis products of lecithin. To precisely characterize all of the hydrolysis products from commercial lecithin, a series of enzymatic reactions of each phospholipid with phospholipase PLA1 were conducted and monitored by ³¹P NMR at different times. Twenty-six phosphorus-containing hydrolysis products from six classes of phospholipids (PC, PI, PS, PE, PG, PA) were found and determined by ³¹P NMR measurement. The impact of pH on the chemical shift values for these hydrolysis products was observed and reported. To the best of our knowledge, this is the first report of ³¹P-NMR chemical shift values for entire lyso-phospholipids hydrolyzed from 6 classes of phospholipids. Rapid and routine analysis of phospholipid composition in commercial lecithins by ³¹P NMR was achieved without the need of phospholipid standards.     

Sunflower Lecithin: Application of a Fractionation Process with Absolute Ethanol

Native or modified lecithins are widely used as a multifunctional ingredient in the food industry. A fractionation process of sunflower lecithin (a non GMO product) with absolute ethanol was used for obtaining enriched fractions in certain phospholipids under different experimental conditions (temperature 35–65 °C, time of fractionation 30–90 min, ethanol/lecithin ratio 2:1, 3:1). Phospholipid enrichment in PC and PI fractions was obtained and analyzed by ³¹P NMR determinations. The percent extraction coefficients for different phospholipids (%E_PC, %E_PE and %E_PI) in both fractions were calculated. Values of %E_PC in PC fractions significantly increased (p < 0.05) from 12.8 (35 °C, 30 min, 2:1) to 57.7 (65 °C, 90 min, 3:1) at increasing temperature and incubation time. %E_PE varied from 3.0 to 18.3 in the same fraction while %E_PI presented lower values (<3%) under all the conditions assayed. The study of the effect of the operating conditions on the fractionation process evidenced a relevant influence of temperature, incubation time and to a minor extent of the ethanol/lecithin ratio on the enriched fraction yield% and selectivity of the main phospholipids (PC, PI, PE) estimated by %E_PL. Response surface methodology (RSM) was utilized to explain the influence of the different parameters to optimize this process.     

Reinforcement of model filled elastomers: characterization of the cross-linking density at the filler-elastomer interface by H NMR measurements

The cross-linking density at the filler-elastomer interface is analyzed by ¹H NMR measurements in model reinforced elastomers composed by grafted nanosilica particles and cross-linked ethylacrylate chains. We have focused our attention on the effect of introducing fillers on the relaxation of the bulk polymer matrix which is observed at long times (t>100 μs). Measurements performed at high temperature (T>T_g+120 K) have revealed that its relaxation is affected by the topological constraints existing at the particle surface. We deduce that the effect of particles in the bulk matrix can be interpreted as that of an homogeneous additional constraint density which increases proportionally to the surface area introduced in the matrix.