Hydrogen Phosphate Dihydrate Research Articles

Contribution of Microwave to the Formation of Octacalcium Phosphate Intercalating Succinate Ions

We applied microwave light with frequencies 10, 212, and 419 GHz to form octacalcium phosphate (OCP) intercalated with succinate ions (SCI). The composition of starting reagents (i.e., α-type tricalcium phosphate (TCP), calcium hydrogenphosphate dihydrate (DCPD), and SCI in pure water) did not enable us to form OCP intercalated with SCI in a thermostatic water bath. Although microwave irradiation typically acts as a heat source in water, it has brought a valuable contribution to OPC formation. This paper reports the following interesting result; microwave irradiation of power less than 0.1 W enabled us to synthesize OCP intercalated with SCI which was not possible to form with power values exceeding 0.1 W.

The Influence of Different Classes of Amino Acids on Calcium Phosphates Seeded Growth

Amino acids (AAs) attract attention for elucidating the role of proteins in biomineralization and the preparation of functionalized biomaterials. The influence that AAs exert on calcium phosphate (CaP) mineralization is still not completely understood, as contradictory results have been reported. In this paper, the influence of the addition of different classes of AAs, charged (L-aspartic acid, Asp; L-lysine, Lys), polar (L-asparagine, Asn; L-serine, Ser; L-tyrosine, Tyr), and non-polar (L-phenylalanine, Phe), on CaP growth in the presence of octacalcium phosphate (OCP) and calcium hydrogenphosphate dihydrate (DCPD) seeds was investigated. In control systems (without AAs), a calcium-deficient apatite (CaDHA) layer was formed on the surface of OCP, while a mixture of CaDHA and OCP in the form of spherical aggregates was formed on the surface of DCPD crystals. Charged and non-polar promoted, while polar AAs inhibited CaDHA formation on the OCP seeds. In the case of DCPD, Lys, Asp, and Phe promoted CaP formation, while the influence of other AAs was negligible. The most efficient promotor of precipitation in both cases was non-polar Phe. No significant influence of AAs on the composition and morphology of precipitates was observed. The obtained results are of interest for understanding biomineralization processes and additive controlled material synthesis.

Codissolution of calcium hydrogenphosphate and sodium hydrogencitrate in water. Spontaneous supersaturation of calcium citrate increasing calcium bioavailability

The sparingly soluble calcium hydrogenphosphate dihydrate, co-dissolving in water during dissolution of freely soluble sodium hydrogencitrate sesquihydrate as caused by proton transfer from hydrogencitrate to hydrogenphosphate, was found to form homogenous solutions supersaturated by a factor up to 8 in calcium citrate tetrahydrate. A critical hydrogencitrate concentration for formation of homogeneous solutions was found to depend linearly on dissolved calcium hydrogenphosphate: [HCitr2−] = 14[CaHPO4] - 0.05 at 25 °C. The lag phase for precipitation of calcium citrate tetrahydrate, as identified from FT-IR spectra, from these spontaneously formed supersaturated solutions was several hours, and the time to reach solubility equilibrium was several days. Initial calcium ion activity was found to be almost independent of the degree of supersaturation as determined electrochemically. The supersaturated solutions had a pH around 4.7, and calcium binding to hydrogencitrate as the dominant citrate species during precipitation was found to be exothermic with a determined association constant of 357 L mol−1 at 25 °C for unit ionic strength, and ΔH° = −22 ± 2 kJ mol−1, ΔS° = −26 ± 8 J K−1 mol−1. Calcium binding to hydrogencitrate and, more importantly, to citrate is suggested to decrease the rate of precipitation by lowering the driving force of precipitation, and becoming important for the robust spontaneous supersaturation with perspectives for design of functional foods with increased calcium bioavailability.

Effects of heating and calcium and phosphate mineral supplementation on the physical properties of rennet-induced coagulation of camel and cow milk gels.

The physical properties of rennet-induced coagulation of preheated camel and cow milk gels (50 and 70 °C for 10 min) enriched with calcium chloride (CaCl2) and hydrogen phosphate dihydrate (Na2HPO42H2O) were evaluated using the dynamic low amplitude oscillatory shear analysis. The storage modulus (G') and loss modulus (G") of camel milk gels showed significant (P < 0·05) lower values than those of cow milk gels. The preheating of camel milk at 50 °C affected negatively the gelation properties, while the preheating at 70 °C prevented the formation of rennet-induced milk gels. No effect was observed on the gelation properties of cow milk gels. The CaCl2 added at 10 and 20 mM to preheated camel and cow milk reduced significantly (P < 0·05) the gelation time and increased the gel firmness. In contrast, Na2HPO42H2O added at 10 and 20 mM induced the formation of weak gels for preheated camel and cow milk at 50 °C, and even no gelation for preheated camel milk at 70 °C.

Induction of nano-surface structure on the DCPD particles (Calcium hydrogenphosphate dihydrate)

Induction of nano-surface structure on the DCPD particles (Calcium hydrogenphosphate dihydrate)

Physico-chemical properties of calcium phosphates

Calcium phosphates have important role in biological and pathological mineralization. While only one of calcium phosphates, carbonate apatite, represents the main mineral component of teeth and bones, octacalcium phosphate, calcium hydrogenphosphate dihydrate and beta-tricalcium phosphate occur in pathological deposits. From the stand-point of chemists, processes of biological and pathological mineralization could be considered as deposition of inorganic phase within organic matrix, i.e. formation of inorganic-organic composites. Although this approach is very simplified at first glance, it allows clarification of important issues related to biomineralization (e.g. what is the role of individual components of organic matrix in the emerging solid tissue), and design and preparation of new materials for hard tissue regeneration (e.g. process of transformation after implantation). The importance of investigation about calcium phosphates will be presented through the overview of basic physico-chemical reactions related to the formation and transformation of biologically relevant calcium phosphates and their interaction with various organic additives in the laboratory.

Determination of Aqueous Fluoride by Continuous Powder Introduction Microwave-Induced Plasma Optical Emission Spectrometry after Preconcentration on Various Sorbents

ABSTRACT A spectrometric determination of aqueous fluoride has been improved by coupling of continuous powder introduction microwave-induced plasma optical emission spectrometry with separation of the analyte onto powdered sorbents. A selective solid phase extraction method for preconcentrating trace fluoride from aqueous environmental samples on calcium hydrogenphosphate dihydrate in batch operation was employed while, for flow operation, the zirconium modified activated carbon method was adopted. The fluoride could be readily excited in helium plasma at 685.6 nm. Using a 1-L sample volume and a preconcentration factor of 1000, practical detection limit with respect to water sample is in the range 4.0–4.7 ng mL−1, depending on the sorbent used. External calibration was done using standards obtained by the dropping of standard fluoride solution on the powdered sorbent covering fluoride content from 50 to 5000 µg g−1. The procedure was applied to the determination of fluoride in mineral waters and certified reference material (CRM) drinking water.

Two caesium vanadium hydrogenphosphates with tunnelled structures: Cs2V2O3(PO4)(HPO4) and Cs2[(VO)3(HPO4)4(H2O)]·H2O

Dicaesium divanadium trioxide phosphate hydrogenphosphate, Cs(2)V(2)O(3)(PO(4))(HPO(4)), (I), and dicaesium tris[oxidovanadate(IV)] hydrogenphosphate dihydrate, Cs(2)[(VO)(3)(HPO(4))(4)(H(2)O)].H(2)O, (II), crystallize in the monoclinic system with all atoms in general positions. The structures of the two compounds are built up from VO(6) octahedra and PO(4) tetrahedra. In (I), infinite chains of corner-sharing VO(6) octahedra are connected to V(2)O(10) dimers by phosphate and hydrogenphosphate groups, while in (II) three vanadium octahedra share vertices leading to V(3)O(15)(H(2)O) trimers separated by hydrogenphosphate groups. Both structures show three-dimensional frameworks with tunnels in which Cs(+) cations are located.

Mechano-Chemical Synthesis of Biphasic Calcium Phosphates with the Various Ratio of HA and β-TCP

Biphasic calcium phosphate powders (BCP) of hydroxyapatite (HA) and tricalcium phosphate (β-TCP) with the various ratio of HA to β-TCP were prepared by utilizing mechanochemical synthesis. Calcium hydrogen-phosphate dihydrate (brushite, CaHPO4⋅2H2O) and calcium carbonate (calcite, CaCO3) powders have been chosen as the starting materials. The original Ca/P ratio of CaHPO4⋅2H2O - CaCO3 batch was set to be 1.67. A mixture of starting materials was milled using a planetary mill (ZrO2 jar and balls) with water for 3, 4, 5, 6 and 7 hrs. The XRD study of calcined powders was conducted for phase identification and for HA/β-TCP ratio as well. The phases of the calcined powders were HA and β-TCP, and the HA/β-TCP ratio varied with the milling time. The mass fraction of HA and β-TCP phases was calculated from the XRD intensities of HA and β-TCP. The ratio of the mixture milled for 4 hrs and calcined at 900°C was 85(HA):15(β-TCP) (BCP 85/15) and the content of β-TCP increased with the milling time. It is believed defective HA powder formed at relatively short period of milling time (less than 3 hrs The research revealed that nanocrystalline BCP powders could be synthesized by an employment of a medium-high energy mechanical activation at room temperatures (~25°C) without any preliminary chemical processing.

Reaction of Calcium Hydrogenphosphate Dihydrate (DCPD) with a Solution Containing a Small Amount of Fluoride

Calcium hydrogenphosphate dihydrate (DCPD) efficiently reacts with fluoride ion in a solution to form fluorapatite (FAp). In this paper, the reaction of DCPD with a solution containing a small amount of fluoride was investigated. 2.0 g of DCPD was added to 2.0 dm3 of solution containing 20 mg dm-3 of fluoride, and then reacted for various periods. We observed a “lag time” within which the concentration of fluoride ions in the solution did not change. After this lag time, the fluoride ion concentration in the solution quickly decreased. From the results of powder X-ray diffraction, fied emmision-scanning electron microscopy (FE-SEM) observation and chemical analysis of the solid phase, DCPD did not directly react with the fluoride ions, but formed a nano-scale particle on the surface of the DCPD particles, and then reacted with the fluoride to form calcium deficient FAp. From these results, the lag time could be considered to be the time needed to form nano-scale particles on the surface of the DCPD particles. It was also found that the amount of fluoride reactable with DCPD was larger at lower temperatures.

リン酸水素カルシウム二水和物（ＤＣＰＤ）の転化反応を用いた地下水中微量フッ化物の簡易定量法

Ion-selective electrodes (ISE) are widely utilized for the determination of fluoride in water. For the determination of trace amounts of fluoride in groundwater, a pre-concentration process is required because of lack of sensitivity of ISE to fluoride. Calcium hydrogenphosphate dihydrate (DCPD) efficiently reacts with fluoride ion in a solution to form fluorapatite (FAp). The aim of this study was to develop a simplified method of determination of trace amounts of fluoride in groundwater using DCPD. In this paper, a suitable pH range for measuring fluoride using ISE was assessed on the basis of chemical equilibrium. It was found that the suitable pH for fluoride determination by ISE is 5.5-7.0, and FAp can be dissolved in this pH range by the complex-forming reaction of CyDTA. From the obtained results, a simple method for determining trace amounts of fluoride in groundwater has been established. Fluoride in a 100 ml water sample is quantitatively fixed as FAp using 0.10 g of DCPD at 60°C for 1hr. The fluoride that separated as FAp is dissolved in a 10 ml solution containing NaCl, CyDTA and HEPES. The amount of fluoride ion in the solution is easiliy measured by using ISE.

A simplified method for determination of trace amounts of fluoride in the air by using transform reaction of calcium hydrogenphosphate dihydrate (DCPD)

A simplified method for determination of trace amounts of fluoride in the air by using transform reaction of calcium hydrogenphosphate dihydrate (DCPD)

INTERACTIONS OF ORGANIC ADDITIVES WITH IONIC CRYSTAL HYDRATES: THE IMPORTANCE OF THE HYDRATED LAYER

The interactions of two groups of hydrated model crystals, calcium hydrogenphosphate dihydrate (DCPD) vs. octacalcium phosphate (OCP) and calcium oxalate monohydrate (COM) vs. calcium oxalate dihydrate (COD) with different organic additives are considered. DCPD precipitates as platelet-like crystals with the dominant faces shielded by hydrated layers and charged lateral faces. In the second system COM has charged surfaces, while all faces of COD are covered with layers containing water molecules. The organic molecules tested include negatively charged, flexible and rigid small and macromolecules (glutamic and aspartic acid, citrate, hexaammonium polyphosphate, phytate and polyaspartate) and anionic surfactants (sodium dodecyl sulphate, SDS, sodium diisooctyl sulfosuccinate, AOT, sodium cholate NaC and disodium oleoamido PEG-2 sulfosuccinate, PEG). Two types of effects have been demonstrated: (1) Effect on crystal growth morphology: Flexible organic molecules with high charge density and anionic surfactants affected the growth morphology of DCPD and COM by selectively interacting with the charged lateral faces while rigid molecules (phytate, polyaspartate) specifically recognized the dominant (010) face of DCPD due to structural and stereochemical compatibility. (2) Effect on phase composition: Anionic surfactants at concentrations above the cmc promoted growth of OCP and COD respectively by selectively adsorbing at, and inhibiting growth oif nuclei of DCPD and/or COM, which were dominant in the respective control systems. The effect was especially pronounced in the calcium oxalate precipitation system, where in some cases complete reversal of the phase composition occurred. The important role of the hydrated layer, as part of the structure of the investigated crystal hydrates, in the above crystal additive interactions is discussed.

Factors Influencing Additive Interactions with Calcium Hydrogenphosphate Dihydrate Crystals

The effect of aspartic acid, glutamic acid, hexaammonium tetrapolyphosphate, calcium phytate, and polyaspartic acid on calcium hydrogenphosphate dihydrate (CaHPO4·2H2O, DCPD) crystal growth morphology was studied. The mechanism of additive−DCPD crystal interaction depends on the size and structure of the additive molecule and the structural fit between the organic molecule and the ionic structure of particular crystal face. Small molecules with low charge (aspartic and glutamic acid) do not have a significant effect, whereas small molecules with several functional groups (citrate and hexaammonium tetrapolyphosphate) adsorb on lateral faces primarily by electrostatic interactions. Molecules with hindered structures (phytate) and macromolecules (polyaspartic acid) specifically adsorb on the dominant (010) face, for which a certain degree of structural fit is necessary.

Millennial Special Leading Papers on Ceramics in the 20&lt;sup&gt;th&lt;/sup&gt; Century: the Best of JCerSJ The Hydration of α-Tricalcium Phosphate

It can be said that this article took the lead in studying a bioceramic group called “calcium phosphate cement” or “apatite cement.” The active promotion of calcium phosphate cementing materials has been made since the Monma-Kanazawa paper appeared.Many researchers have long believed that tricalcium phosphate is stable in water. However, the authors of this paper reported that α-tricalcium phosphate (α-TCP) converts to hydroxyapatite in hot water (80-100°C) and produces hardened porous products. The main results were as follows: bulk densities of 0.9-1.2g/cm3, compressive strengths of 15-16MPa and diametral strengths of 2-3MPa. The resulting products were composed of calcium-deficient hydroxyapatites. This phenomenon was very peculiar since some other calcium phosphate did not show such a hardening property even if a similar phase change occurred.Generally, cement-type materials possess many advantages different from densely sintered ceramics. If calcium phosphate cementing materials were created, they would be a significantly new type of calcium phosphate material and also to be bioactive. Therefore, this paper concerning the hydration-hardening of α-TCP has attracted the attention of material researchers. At nearly the same time, the possibilities of various cementing calcium phosphate compositions were proposed by Brown and Chow based on thermodynamic considerations. The following two basic patents have been issued; H. Monma et al., “Production of porous apatite, ” Jpn. Pat. 1103653 (Jul. 16, 1982), Appl. 53-124025 (Oct. 7, 1978) and W. E. Brown et al., “Dental restorative cement pastes, ” U.S. Pat. 45185430 (May 21, 1985), Appl. No. 539740 (Oct. 6, 1983).Subsequently, many studies on cementing calcium phosphate materials have increasingly appeared in technical and medical journals. Details of the hydration reaction of α-TCP were clarified. The hydration-hardening of α-TCP was made even at room temperature using various additives, and its possibility as a practical cementing material was significantly improved. A mixture of α-TCP and calcium hydrogenphosphate dihydrate was found to have good hydration-hardening properties (H. Monma et al., J. Ceram. Soc. Japan, 96, 878 (1988)). This combination gave the following results; about a 10-min setting time, 50-60% porosity and 15-20MPa wet compressive strength. Presently, the compressive strength has been improved to 50-90MPa.After this author's paper, the following studies were made. The mixture of tetracalcium phosphate and calcium hydrogenphosphate dihydrate first proposed by Brown and Chow has been continuously investigated by many researchers, and its hardening properties were improved by using dilute phosphoric acid and adding synthetic hydroxyapatite powder. About 470 kinds of combinations using various calcium phosphates, calcium carbonate, calcium oxide, sodium fluoride, calcium sulfate hemihydrate, etc., were evaluated, and some available combinations for use as cementing materials were developed as follows: Lemaitre et al. in 1987, Mirtchi et al. in 1990, Bermudez et al. in 1993, and Driessens et al. in 1994. The glassy powder in the system of CaO-SiO2-P2O5 was developed as a bioactive cementing material (Kokubo et al., 1991). Hardened porous materials prepared from these calcium phosphate cements also became important also as supports for drug delivery systems. At present, α-TCP-based cementing materials are being used a a dental pulp lining (Sankin Co. Ltd., 1986), root canal filling (Sankin Co., Ltd., 1987) and osteoporosis filling (Mitsubishi Materials Co., Ltd., 2000).

Redetermination of Monoclinic VOHPO4.2H2O

Single crystals of monoclinic α-VOHPO4.2H2O, α-oxovanadium(IV) hydrogen phosphate dihydrate, were synthesized by hydrothermal reaction. The structure was refined with good accuracy (R = 0.018) and the results are compared with those of an earlier structure determination from X-ray powder data [Le Bail, Amoros & Beltran-Porter (1989). Eur. J. Solid State Inorg. Chem. 26, 419–426]. Significant differences in bond lengths were found. The structure consists of vanadyl hydrogenphosphate layers running along [100]. The layers are connected via hydrogen bonds.

Precipitation of calcium oxalate and calcium phosphate in the presence of uric acid

The influence of uric acid on the precipitation of calcium oxalate and calcium phosphate from electrolyte solutions with pH i 6.5, ionic strength 0.3 mol dm −3 and temperature 370 K, mimicking urinary conditions, has been investigated. The initial concentrations of precipitation components in the system were as follows: c(CaCl 2) = 5 × 10 −3–1 × 10 −1 mol dm −3, c(H 2Ox) = 3 × 10 −4–5 × 10 −4 mol dm −3; c(H 2U) = 1.5 × 10 −4–6 × 10 −3 mol dm −3, and c(H 3PO 4) = 2.5 × 10 −2 mol dm −3. Precipitates of calcium oxalate monohydrate, calcium hydrogenphosphate dihydrate, tri calcium phosphate trihydrate and sodium hydrogenurate monohydrate were characterized by X-ray diffraction, FTIR spectroscopy, and chemical and thermogravimetric analyses.

Solubilization of inorganic phosphates by microorganisms isolated from forest soils

Two strains (a Penicillium sp. and a Pseudomonas sp.) having high abilities to solubilize inorganic phosphates (hydroxylapatite and calcium hydrogenphosphate dihydrate) were screened from 600 colonies isolated from forest soils. Some of their physiological properties (nutrition, O 2-demand, temperature) were investigated. It was possible to distinguish between solubilization through release of organic acids and still unknown mechanisms. Artificial acidification of the culture medium with HCl did not cause considerable P solubilization compared with our two isolates. In nonsterile soil both organisms caused a marked increase in the P fraction extracted with Licl solution.

ChemInform Abstract: Structure of Vanadyl Hydrogenphosphate Dihydrate α‐VO(HPO4)·2 H2O Solved from X‐Ray and Neutron Powder Diffraction.

AbstractThe title compound crystallizes in the monoclinic space group P21/c with Z=4.

Decomposition and Stabilization of the Tablet Excipient Calcium Hydrogenphosphate Dihydrate

Calcium hydrogenphosphate dihydrate is a commonly used filler in solid dosage forms. In the literature it is noticed that drug decomposition reactions can be accelerated by the decomposition of CaHPO4.2H2O. The present study has been performed to evaluate various types of this commercially available excipient and to elucidate the impact of selected factors on stability.The influence of both temperature (40, 50 and 60°C) and environmental humidity (26, 34 and 46 % rel. humidity) on the dehydration of calcium hydrogenphosphate dihydrate was studied for a period of two to three months. Five batches of CaHPO4.2H2O were used with different contents of magnesium hydrogenphosphate and sodium pyrophosphate, which are often added to stabilize CaHPO4.2H2O in preparations like aqueous dentifrices. Disks of CaHPO4.2H2O have been prepared in such a way, that the structure of the disks allowed discrimination between the batches in dehydration kinetics. A relatively low velocity of dehydration was found for the batches containing high levels of sodium pyrophosphate. The effect of environmental humidity on the dehydration velocity appeared not to be straightforward: only at 60 °C an acceleration of the dehydration rate was found for all batches due to the increase of relative humidity. The residues after dehydration were analysed by Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFT), Thermogravimetric Analysis and Differential Scanning Calorimetry.The results demonstrate that, independent of the storage condition and the type of calcium hydrogenphosphate dihydrate used, the main decomposition product is anhydrous calcium hydrogenphosphate. This contrasts with interpretations in the literature, which include the formation of decomposition products like hydroxyapatite and phosphoric acid.Although no experiments were performed in the presence of drugs, a hypothesis is proposed on the basis of this study for the mechanism of possible drug decomposition in the presence of calcium hydrogenphosphate dihydrate. The mechanism can be simplified to dissolution of drug in accumulated free water due to dehydration within the drug/excipient system with, possibly, interactions between the drug and calcium hydrogenphosphate dihydrate. Obviously, time, temperature and amount of accumulated free water are important factors in determining the amount of drug decomposed. Accumulation of free water in granulates and tablets containing calcium hydrogenphosphate dihydrate should therefore be avoided or at least limited. This will have implications for e.g. the selection of the quality of calcium hydrogenphosphate dihydrate to be used and for the manufacturing practice of solid dosage forms containing this filler excipient.