Method of determining position of impurities of nitrate compounds in hydroxyapatite

FIELD: chemistry.

SUBSTANCE: method includes irradiating a hydroxyapatite sample with X-ray, gamma-radiation or electron beams, followed by recording, using an EPR technique, the resultant paramagnetic centres on a certified EPR spectrometer; calculating spectral characteristics of the observed EPR spectrum (number of observed lines and position thereof) while monitoring the measurement error and comparing the obtained spectral characteristics with spectral characteristics of nitrogen radicals; carrying out additional comparison of previously obtained spectral characteristics with spectral characteristics of nitrogen radicals in different positions substituting OH and(or) PO4 functional groups in the hydroxyapatite structure, particularly while allowing the determination of the point(s) of incorporation(substitution) of impurities of nitrogen compounds in the hydroxyapatite structure.

EFFECT: enabling determination of positions of impurities of nitrogen compounds in hydroxyapatites.

1 dwg

 

The invention relates to physico-chemical methods of analysis, namely to methods of determining the positions of the impurities of nitrogen compounds in hydroxiapatite (more gap).

Substances with the structure of hydroxyapatite Ca10(PO4)6(OH)2are the components of biological tissues. The synthesized HAP is widely used as a preventive component of toothpastes and medical material for filling bone defects, which must be fully biocompatible with the tissues of the human body and the chemical and structural compositions should be close to the composition of dental enamel and bone tissue [1, 2]. In some known to the applicant of techniques for synthesis of HAP using solutions of salts of nitric acid, sodium and/or calcium [3-5]. It has been shown [5] that in the process of synthesis gap in the colloidal solution nitrogen compounds can be introduced into the crystalline structure of hydroxyapatite. Synthetic gap can also be used as adsorbents to remove nitrates from drinking water, for example [6].

On the one hand, numerous studies (see, e.g., [7]) indicate the toxicity of nitrates and nitrites: nitrates in the digestive tract partially restored to nitrite (more toxic compounds), and the last admission in the blood can cause methemoglobinemia�Yu. In addition, from nitrite in the presence of amines can form N-nitrosamines with carcinogenic activity, which places high demands on the chemical composition of hydroxiapatite as materials, widely used in medical purposes. On the other hand, it has been shown [8] that the content of nitrogen compounds in trace quantities in the implants on the basis of the gap improves their resorption.

The invention can be used to monitor the qualitative composition of natural and synthesized gap in the sense of determining the location (position) of the nitrogen impurities in the structure of the gap in order to increase the biocompatibility of synthesized and natural hydroxiapatite, leading to improved efficiency of hygienic and preventive measures and treatment using synthetic gap, the synthesis of new adsorbents nitrate-based gap, the development of techniques to restore adsorption capabilities gap.

The closest combination of features according to the claimed technical solution is a patent [9] (prototype). However, it presents the possibility of detecting the presence of nitrogen impurities and the determination of their concentrations in the gap and presents a way to detect their localization. For the implementation of the tasks the applicant, the known methods of determining the localization carbon�t ions in the gap of natural origin and chemically modified gap (see [10] and references therein) and the ways to determine the localization of metal ions in the structure of the gap (see [11] and references therein). Their main drawbacks is that they are not intended or used for the purposes of determining the localization of nitrogen compounds in the substances with the structure of the gap. Thus, the above methods can be used to accomplish the claimed technical solution of the task.

The claimed technical solution aimed at determining the localization of nitrogen compounds in the substances with the structure of hydroxiapatite used to conduct biomedical research and health-care activities, providing opportunities to improve the controllable indices of these materials to reduce their toxicity and increase biocompatibility, which ultimately leads to improving the efficiency of hygienic and therapeutic measures with the use of gap and materials on its basis.

Besides this, the technical solution may find application in materials science, namely to determine the localization of nitrogen compounds in the substances with the structure of hydroxiapatite used for adsorption of nitrate, providing opportunities to improve the controllable indices of these materials.

Based�Iwas on the above, the technical solution provides the implementation for the following purposes:

- determination of the content of impurities of nitrogen compounds in natural and synthesized hydroxiapatite;

- identification of position (localization) nitrogen compounds in the structure of natural and synthesized hydroxiapatite;

- definition of quantitative indicators: the ratio of concentrations of nitrogen compounds present in different positions in the structure of natural and synthesized hydroxiapatite and their total concentration;

- the ability to control the qualitative composition of the synthesized materials with the structure of hydroxyapatite in terms of the availability and distribution on the positions of the impurities of nitrogen compounds in the synthesis process and the cleaning process materials from inclusions that can be used when deciding on the acceptability of using synthetic gap in biomedical applications and will provide recommendations for improving the technology of production of materials with the structure of hydroxyapatite to minimize toxicity and increase biocompatibility with natural materials, which leads, ultimately, to enhance the effectiveness of hygienic and therapeutic measures with the use of gap or to effectively restore the adsorbent may�TEI gap, leading, ultimately, to increase the lifetime of the adsorbent materials.

The claimed method of determination of impurities of nitrogen compounds in the hydroxyapatite is as follows: irradiation of a sample of hydroxyapatite x-ray, gamma or electron rays with the subsequent registration of the EPR emerged during irradiation of paramagnetic centers in a certified EPR spectrometer, calculating the spectral characteristics of the observed EPR spectrum (the number of observed lines and their position) with a control measurement error and comparing the obtained spectral characteristics, primarily the hyperfine structure constants with known spectral characteristics of nitrogen radicals in a variety of positions in the hydroxyapatite.

The inventive method is characterized by the following sequence of stages:

a) placing the sample of hydroxyapatite in a standard quartz ampoule of an EPR spectrometer;

b) irradiation of a sample of hydroxyapatite x-ray, gamma or electron beams (in compliance with sanitary and hygienic norms) at room temperature, the radiation dose is from 1 to 10 kGy (kilogray);

C) registration of the EPR spectrum in a certified EPR spectrometer, allowing measurements in continuous or pulsed modes of operation;

g) calculation of �parameters in order of the EPR spectrum (the number of lines the value component of the g-tensor and hyperfine interaction tensor A, namely in conventionally parallel (||) and perpendicular orientations (⊥));

e) monitoring the error of the measurement results;

(e) comparison of the obtained values with those known for nitrogen radicals, such asNO32to gap for different positions in irradiated crystalline matrices gap (the number of lines n=3, values of the components of g-tensor and hyperfine interaction tensor A: g||=2.003(2), g⊥=2.006(3), A||=6.6(4) MT, A⊥=3.4(4) MT for substitution at position PO4and n=3, g||=2.003(2), g⊥=2.006(3), A||=5.2(4) MT, A⊥=2.5(4) MTL to replace the position of OH). It should be noted that a change in the sequence of operations a) and b) does not change the technical result obtained.

Thus, unlike the prototype [9] lies in paragraph (e) sequence, which allows to determine the position of the nitrate ion by the difference component of the hyperfine interaction tensor A.

Achieved technical result consists in the possibility of determining the position of nitrates in the structure of the gap based on the spectra of paramagnetic centers resulting from exposure above materials x-ray, gamma or elektronische, the EPR, which, ultimately, allows to determine the structural and chemical composition of gap and materials based on them.

The applicant for the first time in synthetic gap on the basis of registration by the EPR method were detected paramagnetic centers, which, according to the applicant, due to the presence of impurities of nitrogen compounds in the positions of the substituting group PO4in the above compounds. The claimed technical solution is illustrated by the following materials.

Fig. represented by curve (1): EPR spectrum obtained using the methods of detecting the spin echo at the microwave frequency of 9.6 GHz at T=300 K in the synthesized gap nanocrystals with average sizes of nanocristalline 50 nm, subjected to x-ray irradiation with the dose of 5 kGy. Specified parallel and perpendicular components of the component values of g-tensor and hyperfine structure tensor A. By x-axis values of the magnetic field (in millitesla), the ordinate is the amplitude of the spin echo signal (in arbitrary units). Curve (2): EPR spectrum, calculated in a known manner (see source 9, as described hereinafter in formula 1) with parameters g||=2.003, g⊥=2.006, A||=6.6 MT, A⊥=3.4 MT. Curve (3): EPR spectrum, calculated in a known manner (see source 9, as described hereinafter in formula 1) with parameters g||=2.003, g⊥=2.006, A||=5.2 MT, A⊥=2.5 MT.

Examples to�specific execution

The applicant had obtained the EPR spectra in pulsed mode [12] of the spectrometer X-band Bruker Elexsys 580 with an operating frequency of 9.6 GHz synthesized nanocrystals gap with the size of nanocristalline 50(10) nm. The EPR spectrum of hydroxyapatite nanocrystals exposed to x-ray irradiation with the dose of 10(1) GSR shown in Fig. (curve 1).

The EPR spectrum is described by the spin Hamiltonian of axial symmetry [9]:

where S=1/2, I=1; the parameters of the Hamiltonian g||=2.003(2), g⊥=2.006(3), A||=6.65(40) MT, A⊥=3.4(3) MT (Fig., curve (2)), characteristic for the substitution of the nitrate ion position PO4in the structure of the gap and is not described by the above Hamiltonian with the parameters of the Hamiltonian g||=2.003(2), g⊥=2.006(3), A||=5.2(40) MT, A⊥=2.5(3) MT (Fig., curve (3)), characteristic for the substitution of the nitrate ion of the position of OH in the structure of the gap. Thus, comparing the numerical values of the parameters A⊥ and A|| numerically describing the position of the individual components in the EPR spectrum, synthesized in this sample identified the location (localization) of nitrate ion as occupying a (replacement) position ion PO4in the structure of the gap.

Thus, the claimed technical solution allows to achieve its objectives, namely to determine qualitatively and quantitatively assess the presence of nitric connected�in various positions in natural and synthesized hydroxiapatite, allowing you to monitor the qualitative composition of the synthesized materials with the structure of hydroxyapatite in the sense of the presence of impurities of nitrogen compounds in specific positions in the structure of the gap as in the synthesis process and the cleaning process materials from inclusions that can be used by consumers when deciding on the acceptability of using synthetic gap in biomedical applications and provide recommendations to producers, for example, synthetic gap to improve the technology of production of materials with the structure of hydroxyapatite to minimize toxicity and increase biocompatibility with natural materials, the increase in sorption capacity when using gap as adsorbent of nitrates, leading, ultimately, to enhance the effectiveness of hygienic and therapeutic measures with the use of gap and more efficient removal of nitrates, for example, of drinking and ground water, improve the quality thereof.

The claimed technical solution meets the criterion of "novelty" requirements for inventions, because the totality of the claimed features is not known from investigated by the applicant of the level of technology.

The claimed technical solution meets the criterion of "inventive step", presented to the invention, because I don't�is obvious to a person skilled in the art.

The claimed technical solution meets the criterion of "industrial applicability", presented to the invention, because the stated goals are implemented by the applicant in the laboratory of EPR spectroscopy, Kazan (Volga region) Federal University.

Sources of information

1. J. P. Lafon, E. Champion and D. Bemache-Assollant, Processing of AB-type carbonated hydroxyapatite Ca 10-x (PO4) 6-x (CO3) x(OH) 2-x-2y (CO3) y ceramics with controlled composition. J. Eur. Cer. Soc, 28 (1), p.139-147 (2008).

2. R. Z. LeGeros, Properties of osteoconductive biomaterials: calcium phosphates, Clin. Orthoped. rel. Res, 395 (1), p.81-98 (2002).

3. I. R. Gibson, W. to bonfield, Novel synthesis and characterization of an AB-type carbonate-substituted hydroxyapatite. J. Biomed. Mater. Res. 59(4), 697-708 (2002).

4. L. G. Ellies, D. G. A. Nelson, J. D. B. Featherstone, Crystallographic structure and surface morphology of sintered carbonated apatites. J. Biomed. Mater. Res. 22 (6), 541-553 (1988).

5. E. S. Kovaleva, M. R. Shabanov, V. I. Putlyaev, Y. D. Tretyakov, V. K. Ivanov, N. I. Silkin, Bioresorbable carbonated hydroxyapatite Ca 10-x Na x(PO4) 6-x (CO3) x(OH) 2. Cent. Eur. 1 Chem. 7(2), 168-174 (2009).

6. Islam M, Mishra PC, Patel R. Physicochemical characterization of hydroxyapatite and its application towards removal of nitrate from water. J Environ Manage 2010; 91: 1883-1891.

7. Bandman AL., Volkova N. In. and other Harmful chemicals. Inorganic compounds of elements of V-VIII groups. Reference edition. Under the editorship of V. A. Filov, etc., Leningrad: Khimiya, 1989, 592 p.

8. M. V. J Hukkanen, J. M. Polak and S. P. F. Hughes Nitric Oxide in Bone and Joint Disease, Cambridge: Cambridge University Press. 1998, p.191.

9. The patent for invention RU №2465573 Authors: Silkin N. And., Salakhov M. X., Orlinsky. V., G. V. Mamin, A. Chelyshev, L. F. Galiullina, Tokarev, G. A., E. S. Igumnov Gafurov M. R. METHOD OF DETERMINATION OF IMPURITIES OF NITROGEN COMPOUNDS IN THE HYDROXYAPATITE.

10. F. Ren, X. Lu, Y. Leng Ab initio simulation on the crystal structure and elastic properties of carbonated apatite J Mech Behav Biomed 26 (2013) 59 to 67.

11. V. V. Yavkin, G. V. Mamin, S. B. Orlinskii, M. R. Gafurov, M. Kh. Salakhov, T. B. Biktagirov, E. S. Klimashina, V. I. Putlayev, Yu.D. Tretyakov and N. I. Silkin Phys. Chem. Chem. Phys., 2012, 14, 2246-2249.

12. J. A. Weil, J. R. Bolton. Electron Paramagnetic Resonance: Elementary Theory and Practical Applications, 2 nd Edition. J. Wiley, 2007. ISBN 978-0471754961.

The method for determining the positions of the impurities of nitrogen compounds in the hydroxyapatite, which consists in the irradiation of a sample of hydroxyapatite x-ray, gamma or electron rays with the subsequent registration of the EPR emerged during irradiation of paramagnetic centers in a certified EPR spectrometer, calculating the spectral characteristics of the observed EPR spectrum (the number of observed lines and their position) with a control measurement error and comparing the obtained spectral characteristics spectral characteristics of the nitrogen radicals, characterized in that to produce an additional comparison of the previously obtained spectral characteristics spectral characteristics of the nitrogen radicals in a variety of positions, the residual functional groups of OH and(or) PO4in the structure of hydroxyapatite, in particular, with the possibility of determining(a) introduction (substitution) of impurities of nitrogen compounds in the structure of hydroxyapatite.



 

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