Basic Phosphate Research Articles

Neopentyl Esters as Robust Linkers for Introducing Functionality to Bis-MPA Dendrimers

A series of neopentyl carboxylic acids bearing functionality amenable to click chemistry were prepared and then appended to high-generation bis-MPA dendrons via fluoride-promoted esterification. The nucleophilic stability of neopentyl and non-neopentyl dendrons in acidic to basic phosphate buffers was compared by monitoring degradation via quantitative 1H nuclear magnetic resonance (NMR). The neopentyl periphery dendrons were found to be highly resistant to hydrolysis under all experimental conditions. The neopentyl groups also did not impede click functionalization onto the dendrons.

Leaching pattern of phosphate glass fertilizers with different compositions under Soxhlet distillation conditions

Abstract Glass fertilizers in the phosphate systems were melted at 900-950 °C with a soaking period of 1 h. Leaching study of these glasses with a maximum time period of 300 h was conducted under Soxhlet distillation condition with distilled water. Weight loss and the leach rates of the glass fertilizer samples were calculated from BET surface area measurements. They were in the range of 6.3x10-3 to 2.3x10-3 g.m-2.h-1 at 90 °C. The effect of different modifier ions like Na+, Fe3+, Mg2+, Ca2+, and K+ in the basic phosphate networks on melting and time of melting has been found to be evident. The pH determination ranging from 4.80 up to 7.50 of the leachate solution at ambient temperature under varying time intervals showed interesting and regular variations. The leaching study of such glasses under Soxhlet condition showed Ca2+, Mg2+, and K+ to be good candidates as modifier towards faster leaching. The findings have been corroborated in terms of ionic size, ionic radius, and hence the ionic potential of the modifier ions incorporated into the glass structure. The application of glass fertilizers was made on kharif paddy.

Homogeneous Nucleation of Hydroxyapatite, Ca5OH(PO4)3, at 37 °C

Precipitation of the calcium phosphate hydroxyapatite, Ca5OH(PO4)3, is studied by simple mixing of reagent solutions and measurement of light scattering (turbidimetry) at six different wavelengths from 300 to 800 nm. Measured turbidities are analyzed using Mie’s theory of light scattering from small particles. Results are interpreted in terms of classical theory of homogeneous nucleation, and from this the surface free energy of crystals is determined. The low value thus found is explained as the effect of protonation of the strongly basic anions hydroxide and phosphate at the crystal surface. Relatively large particles registered by turbidimetry are shown to be not monocrystals, but aggregates of nanocrystals.

Polymeric monolithic microcartridges with gold nanoparticles for the analysis of protein biomarkers by on-line solid-phase extraction capillary electrophoresis-mass spectrometry

In this study, polymeric monoliths with gold nanoparticles (AuNP@monolith) were investigated as microcartridges for the analysis of protein biomarkers by on-line solid-phase extraction capillary electrophoresis-mass spectrometry (SPE-CE-MS). “Plug-and-play” microcartridges (7 mm) were prepared from a glycidyl methacrylate (GMA)-based monolithic capillary column (5 cm x 250 µm i.d.), which was modified with ammonia and subsequently functionalized with gold nanoparticles (AuNPs). The performance of these novel microcartridges was evaluated with human transthyretin (TTR), which is a protein related to different types of familial amyloidotic polyneuropathies (FAP). Protein retention depended on the isoelectric point of the protein (TTR pI~5.4) and elution was achieved with a basic phosphate solution. Under the optimized conditions, limits of detection (LODs) for TTR by AuNP@monolith-SPE-CE-MS were 50 times lower than by CE-MS (5 vs 250 mg•L−1, with an ion trap (IT) mass spectrometer). The sensitivity enhancement was similar compared to SPE-CE-MS using immunoaffinity (IA) microcartridges with intact antibodies against TTR. Linearity, repeatability in migration times and peak areas, reusability, reproducibility and application to serum samples were also evaluated.

New Insights into the Catalytic Activity of Cobalt Orthophosphate Co3 (PO4 )2 from Charge Density Analysis.

An extensive characterization of Co3(PO4)2 was performed by topological analysis according to Bader‘s Quantum Theory of Atoms in Molecules from the experimentally and theoretically determined electron density. This study sheds light on the reactivity of cobalt orthophosphate as a solid‐state heterogeneous oxidative‐dehydration and ‐dehydrogenation catalyst. Various faces of the bulk catalyst were identified as possible reactive sites given their topological properties. The charge accumulations and depletions around the two independent five‐ and sixfold‐coordinated cobalt atoms, found in the topological analysis, are correlated to the orientation and population of the d‐orbitals. It is shown that the (011) face has the best structural features for catalysis. Fivefold‐coordinated ions in close proximity to advantageously oriented vacant coordination sites and electron depletions suit the oxygen lone pairs of the reactant, mainly for chemisorption. This is confirmed both from the multipole refinement as well as from density functional theory calculations. Nearby basic phosphate ions are readily available for C−H activation.

Fabrication of pure octacalcium phosphate blocks from dicalcium hydrogen phosphate dihydrate blocks via a dissolution–precipitation reaction in a basic solution

Octacalcium phosphate (OCP) blocks are attractive as bone substitutes because of their excellent biocompatibility. They can be fabricated from precursor ceramic blocks via a compositional conversion process. Herein, high-purity OCP blocks were fabricated through a dissolution–precipitation reaction from precursor blocks of dicalcium hydrogen phosphate dihydrate (DCPD) immersed in a 1.00-mol/L basic phosphate solution of disodium hydrogen phosphate (NaAP; pH ∼ 9) at 70 °C for 2 days. The results showed that they were completely converted to OCP blocks comprising interlocking ribbon-like crystals while maintaining their shape. The diametral tensile strength of the obtained OCP blocks was ∼6 MPa, which was significantly higher than that of OCP blocks fabricated from calcium sulfate as the precursor.

Preparation of hydroxyapatite porous scaffold from a ‘coral-like’ synthetic inorganic precursor for use as a bone substitute and a drug delivery vehicle

A novel surfactant free hydrothermal method was developed for the preparation of large hydroxyapatite scaffolds. Synthetic calcium carbonate (calcite) was used as the starting material which when mixed with an inorganic setting solution containing phosphoric acid and sodium hydroxide forms the porous precursor body with pore size 20–700 μm. The porous precursor body was then hydrothermally converted to hydroxyapatite scaffolds when treated in basic phosphate solution of pH 10.5 at 150 °C and 15 bar pressure maintaining the structural stability and integrity. X-ray diffraction and the Fourier transform infrared spectroscopy confirmed that the developed material consist of single phase crystalline hydroxyapatite. Surface morphology and microstructures were studied using scanning electron microscopy and porosity was evaluated by micro CT analysis. The cell material interactions evaluated by cell viability assays and live cell staining methods confirmed the cell compatibility. The drug release study at physiological pH implied that the developed materials could be promising in sustained long-term release. The results emerged have shown that the hydrothermal conversion of inorganic coral-like precursor is effective to produce porous bioactive hydroxyapatite scaffolds for bone regeneration as well as drug delivery vehicles for the treatment of infectious bone diseases such as osteomyelitis.

Phosphorus of Genetic Horizons of the Forest Sod-Podzolic Soil of the Pre-Urals

Characteristics of the phosphate regime of forest sod-podzolic soil is presented. It is shown that the organic phosphorus content sharply decreases down the profile starting from the podzolic horizon. The maximum content of mineral phosphates determined by the method of Sanders and Williams was found in forest litter and in the transitional eluvial horizon (A2B) and amounted to 860 and 720 mg/kg. Iron phosphates prevail in the composition of mineral phosphates and, depending on the depth of the horizon, they are 48.8–63.2% of the sum of fractions. The shares of mobile and available to plants alkali metal phosphates and various basic phosphates are 2.9–10.1 and 10.0–14.9%, respectively.

Homogeneous electrocatalytic water oxidation catalyzed by a mononuclear nickel complex

Three nickel (II) complexes of o-phenylenebis(N′-methyloxamidate) (L1), o-phenylene(N′-methyloxamidate)oxamate (L2) and o-phenylenebis(oxamate) (L3) with tetradentate ligands are synthesized and characterized. These four-coordinate complexes, (Me4N)2[NiLi] (i = 1–3 for complex 1–3), are investigated for electrocatalytic water oxidation in basic phosphate buffer solution. Experimental results show that (Me4N)2[NiL1] (1) is a homogeneous catalyst for electrochemical water oxidation. However, under the same condition, 2 and 3 decompose into NiOx nanoparticles, which acts as precatalyst for the electrocatalytic water oxidation. The catalytic mechanism for electrocatalytic water oxidation by 1 is proposed using cyclic voltammetry experiments, kinetic isotope effect and Pourbaix diagram. By constructing the relationship between the molecular structure and stability of these catalysts, nitrogen atom is found to be more beneficial than carboxyl group for the stability of nickel based homogeneous electrochemical water oxidation catalysts.

Study of thermal dehydration of sodium orthophosphate monosubstituted

Depending on the conditions of conducting the synthesis, it is possible to obtain polymeric phosphates of different composition and structure. The mixtures of polyphosphates, employed in the production of technological lubricants, are expedient to synthesize by the high-temperature dehydration of sodium orthophosphate monosubstituted. The temperature ranges, over which the thermochemical transformations of sodium orthophosphate monosubstituted with the formation of polyphosphates proceed, are established by the thermogravimetric method. The composition of polyphosphates is determined using the X-ray phase analysis. Quantitative composition of the mixtures of polyphosphates is determined by applying the original method of eluent ion-exchange chromatography. It is established that the basic products of thermal dehydration of sodium orthophosphate monosubstituted in the range of temperatures 200–650 °C are Na 3 Р 3 О 9 , Na 2 H 2 P 2 O 7 and Na 6 P 6 O 18 . Thermochemical transformations of NaH 2 PO 4 into Na 6 P 6 O 18 at temperature 650 °C are accompanied by the side reactions of formation of Na 3 H 2 P 3 O 10 . We proposed the chemical scheme of the high-temperature dehydration of sodium orthophosphate monosubstituted. Kinetics of the isothermal process of obtaining the polymeric phosphates from sodium orthophosphate monosubstituted at different temperatures is examined. We established quantitative composition of the mixtures of inorganic polymeric phosphates depending on the duration of isothermal process of dehydration. The possibility of obtaining a salt mixture of polymeric phosphates of the assigned qualitative and quantitative composition is demonstrated. We proposed to use the mixture: 76 % Na 6 P 6 O 18 , 8 % Na 2 H 2 P 2 O 7 , 8 % Na 3 H 2 P 3 O 10, 8 % NaH 2 PO 4 , obtained at 650 °C, as the basic phosphate component of technological lubricants for the hot rolling of pipes.

Bis-Heteroleptic Ruthenium(II) Complex of Pendant Urea Functionalized Pyridyl Triazole and Phenathroline for Recognition, Sensing, and Extraction of Oxyanions.

A new bis-heteroleptic RuII complex based ditopic receptor, 1[PF6]2, having an anion binding triazole -CH unit and appended 4-fluorophenyl urea arm has been developed. 1H NMR and isothermal titration calorimetry (ITC) experiments showed binding of 1[PF6]2 toward oxyanions such as phosphates (e.g., H2PO4- and HP2O73-) and carboxylates (e.g., CH3CO2- and C6H5CO2-) anions selectively. 1H NMR studies showed that highly basic phosphate anions such as HP2O73-/H2PO4- are bound by both -CH and -NH units of complex 1[PF6]2. However, comparatively less basic CH3CO2-, C6H5CO2- anions interacted with the urea -NH protons only. Thermodynamic parameters obtained from ITC experiments suggested that binding of all the interacting anions with complex 1[PF6]2 are highly enthalpy and entropy driven processes. Importantly, complex 1[PF6]2 showed extraction of H2PO4-, CH3CO2-, and C6H5CO2- anions from aqueous solution via liquid-liquid extraction with efficiencies of 28%, 74%, and 80%, respectively. The influential role of the urea moiety in the course of extraction is demonstrated by comparison with a model complex, 2[PF6]2. Additionally, complex 1[PF6]2 is capable of selective sensing of phosphate anions among all investigated anions.

A novel sensor for a food dye erythrosine at glucose modified electrode

A simple and highly sensitive method for the determination of erythrosine using glucose modified carbon paste sensor was presented. The electrochemical measurements were studied using cyclic voltammetry, differential pulse voltammetry and square wave voltammetry. The modified sensor exhibited excellent catalytic activity towards electrochemical oxidation of erythrosine in highly basic phosphate buffer, i.e. pH 11.2. The modified sensor facilitated the determination of erythrosine in the linearity range 1.0×10−4M to 1.0×10−7M with a detection limit of 21.6nM. Good recovery from biological sample such as spiked urine indicates the applicability of the proposed method for clinical trials. The proposed method was successfully employed to detect erythrosine in pharmaceutical as well as food samples. The method exhibits tremendous reproducibility and has proved to be highly reliable for the analysis of erythrosine in biological samples.

Vibrational Analysis of Li1+xAlx Ti2-x(PO4)3 (0.0 < x < 0.5) Glass Ceramic Electrolytes Prepared by Acetic Acid­ Assisted Sol-Gel Method

In this study, Li1+xAlxTi2-x(PO4)3 (0.0 < x < 0.5) was prepared by acetic acid­assisted sol-gel method. The structural properties of NASICON phosphates material with chemical formula LiTi2 (PO4)3 were observed using the Fourier transform infrared spectroscopy. NASICON is a family of crystalline phosphate with a general network system consisting of PO4 tetrahedra, thus bands were assigned by vibrations contributed by basic phosphates, in the wavenumber region between 1300 cm-1 and 600 cm-1. Experimental spectra indicated that all Li1+xAlxTi2-x(PO4)3 (0.0 < x < 0.5), heat treated at 600°C and 700°C for 3 hours in air, samples showed the presence of phosphate peaks with shift in frequency as Al3+ is substituted into the structure, and with increasing temperatures. Some bands broadened and overlapped causing it hard to analyze the arising bands. It however determined the existence of NASICON structure in all of the samples under study.

Vibrational Analysis of Li1+xAlxTi2-x(PO4)3(0.0 < x < 0.5) Glass Ceramic Electrolytes Prepared by Acetic Acid­ Assisted Sol-Gel Method

In this study, Li1+xAlxTi2-x(PO4)3(0.0 < x < 0.5) was prepared by acetic acid­assisted sol-gel method. The structural properties of NASICON phosphates material with chemical formula LiTi2 (PO4)3 were observed using the Fourier transform infrared spectroscopy. NASICON is a family of crystalline phosphate with a general network system consisting of PO4 tetrahedra, thus bands were assigned by vibrations contributed by basic phosphates, in the wavenumber region between 1300 cm-1 and 600 cm-1. Experimental spectra indicated that all Li1+xAlxTi2-x(PO4)3(0.0 < x < 0.5), heat treated at 600°C and 700°C for 3 hours in air, samples showed the presence of phosphate peaks with shift in frequency as Al3+ is substituted into the structure, and with increasing temperatures. Some bands broadened and overlapped causing it hard to analyze the arising bands. It however determined the existence of NASICON structure in all of the samples under study.

Development and Validation of Reverse Phase-Ultra Performance Liquid Chromatographic Method for Estimation of Related Substances in Febuxostat Drug Substance

A novel high speed, high resolution Reverse phase-UPLC method was developed for the quantification of related substances in Febuxostat drug substance. The separation of drug from the possible impurities was achieved on a Halo C18 column. The innovative approach of using stationary phase with sub 2 μ particles provides a comprehensive combination of selectivity and speed. 10 mM mono basic potassium phosphate buffer at pH 2.7 and acetonitrile mixture was selected as mobile phase. Flow rate and detection were kept at 0.8 mL/min and 320 nm respectively. The developed UPLC method was subjected to validation parameters. System precision, accuracy, specificity, limit of detection, limit of quantification and linearity were established as per the guidelines recommended by ICH. Stability indicating nature of the method was also performed by exposing the sample under various conditions like acid, base, peroxide and photo stability exposures. Total analysis run time 7.0 minutes indicates the speed and cost saving initiation of the developed method. Using the method one can carry out the quantitative estimation of related substances in Febuxostat drug substance, further the same method can be adopted for determination of drug substance assay also.

Effect of heat treatment on optical, dielectric and mechanical properties of silver nanoparticle embedded CaO[sbnd]CaF2[sbnd]P2O5 glass

Silver nanoparticle have been embedded in CaOCaF2P2O5 glass using melt quenching technique. The quenched glasses were heat treated at 550°C for 10, 20, 30, 40 and 50h. The growth of silver nanoparticle in the glass matrix appeared to be time dependent. FTIR spectra show that silver nanoparticle formation has not affected the vibration bands of basic phosphate tetrahedral network. The increase in compactness of the glass structure is confirmed by increase in measured density of the glasses with increase in the duration of the heat treatment. Glass containing spherical silver nanoparticle shows the red shift and increase in the full width half maxima (FWHM) of the surface plasmon resonance (SPR) in the visible region with increase in the duration of the heat treatment. X-ray diffraction pattern indicated the presence of Ag crystalline peaks along with amorphous structure on heat treating at 550°C for 50h. For the glass samples, the increase in dielectric constant and low dielectric loss around 0.005 were observed with increase in duration of the heat treatment. Both Vickers hardness and fracture toughness increased while the brittleness decreased which can be attributed to the increase in size of the nanoparticles in glass matrix.

Mapping the affinity of aluminum(III) for biophosphates: interaction mode and binding affinity in 1 : 1 complexes.

The interaction of aluminum with biomolecular building blocks is a topic of interest as a first step to understand the potential toxic effects of aluminum in biosystems. Among the different molecules that aluminum can bind in a biological environment, phosphates are the most likely ones, due to their negatively charged nature. In the present paper, we combined DFT quantum mechanical calculations with the implicit solvent effect in order to characterize the interaction of Al(III) with these molecules. An extended set composed of a total of 59 structures was investigated, which includes various types of phosphates (monoester, diester, triester-phosphates) and various phosphate units (mono-, di- and tri-phosphate), considering various charge and protonation states, and different binding modes. The goal is to unveil the preferential interaction mode of Al(III) with phosphates in 1 : 1 complexes. Our results reveal that Al(III) prefers to form dicoordinated complexes with two phosphates, in which the interaction with each of the phosphates is of monodentate character. Our results also suggest a high affinity for binding basic phosphate groups, pointing to ATP, phosphorylated peptides, and basic diphosphates (such as 2,3-DPG) as strong aluminum chelators.

Optical, dielectric and mechanical properties of silver nanoparticle embedded calcium phosphate glass

Silver nanoparticles have been embedded in 50mol% CaO–50mol% P2O5 glass using melt quenching technique. The quenched glasses were heat treated at 550°C for different durations between 10 and 50h. The growth of silver nanoparticles in glass matrix appeared to be time dependent. FTIR spectra revealed that silver nanocluster formation had not affected the position of vibration bands of basic phosphate tetrahedral network. The Ag nanoparticle embedded glass matrix showed the red shift and broadening of the surface plasmon resonance (SPR) peak in the visible region with the increase in the duration of the heat treatment. Results showed the increase in size of the nanoparticles in glass matrix with heat treatment which was further confirmed using transmission electron microscopy and XRD. X-ray diffraction studies indicated the presence of Ag crystalline peaks along with amorphous structure on heat treatment at 550°C for 50h. The dielectric constant of these glasses increased as the duration of the heat treatment increased. Increase in both Vickers hardness and fracture toughness, and decrease in brittleness were observed which can be attributed to the increase in size of the nanoparticles in glass matrix.

Electrochemical detection of hydrazine using a highly sensitive nanoporous gold electrode

A facile alloy–dealloy technique performed in aqueous media was employed to prepare a nanoporous gold (NPG) electrode that demonstrated extremely high sensitivity toward hydrazine oxidation. An Ag ∼60Au ∼40 alloy was electrodeposited at a constant potential on sequentially Cr- and Au-deposited indium tin oxide (Au/Cr/ITO) from a bath that contained sulfuric acid, thiourea, HAuCl 4·3H 2O, and AgNO 3. The dealloying step was performed in concentrated HNO 3, where Ag in the alloy was selectively oxidized to leave the NPG structure. The NPG electrode was employed to study the hydrazine oxidation in basic phosphate buffer solution (PBS), and the results were compared with those obtained using the gold nanoparticle (AuNP)-modified ITO (AuNP/ITO) electrode. The NPG electrode demonstrated an unusual surface-confined behavior, which probably resulted from the thin-layer characteristics of the nano-pores. Hydrazine was detected by hydrodynamic chronoamperometry (HCA) at +0.2 V (vs. Ag/AgCl). The steady-state oxidative current exhibited a linear dependence on the hydrazine concentration in the concentration range of 5.00 nM–2.05 mM, and the detection limit was 4.37 nM ( σ = 3). This detection limit is the lower than the detection limits reported in the current literature concerning the electrochemical detection of hydrazine. The NPG electrode indeed demonstrates greater stability after hydrazine detection than the AuNP/ITO electrode.

Structures and Catalytic Properties of Lithium Phosphates

Basic lithium phosphate and stoichiometric lithium phosphate were prepared and their catalytic properties were compared. Using basic lithium phosphate as the isomerization catalyst for propylene oxide led to higher selectivity in allyl alcohol and better propylene oxide conversion than stoichiometric lithium phosphate. The fresh and deactivated basic lithium phosphates were also characterized by X-ray diffraction. Results showed that new phases appeared in the deactivated catalyst. An isomerization mechanism for propylene oxide catalyzed by basic lithium phosphate was proposed. Results of temperature programmed desorption of CO2 showed that the surface basicity of the catalysts had a great effect on their catalytic properties and that the catalyst with pH = 12 had two basic centers and its catalytic properties were the best. Basic lithium phosphate had better catalytic properties for isomerization of propylene oxide to allyl alcohol than stoichiometric lithium phosphate. Results of CO2-TPD showed that surface basicity of the catalysts had much effect on catalytic properties. And a mechanism was proposed.