JP5790511B2 - Quantitative determination of fluorine with fluorapatite - Google Patents

Description

  The present invention relates to a method for quantifying fluorine containing fluorapatite as an existing form.

In the steel industry, fluorite composed of calcium fluoride (CaF ₂ ) is used as a hatching accelerator in the refining process of steel production. The slag generated during the refining process contains fluorine. There is a concern that fluorine exceeding the environmental standard value may be eluted when the fluorine-containing slag comes into contact with surface water (rainwater, groundwater). The fluorine dissolution test method from slag is defined in Ministry of the Environment (Environment Agency) Notification No. 46. The environmental standard value in the Ministry of the Environment (Environment Agency) Notification No. 46 is 0.8 ppm or less. Slag whose fluorine elution amount exceeds the environmental standard value cannot be reused for cement or roadbed materials. As a result, the slag resourceization as a whole is delayed.

Therefore, as a method for fixing fluorine, a method of adding a compound that becomes a slag modifier to slag has been proposed.
For example, Patent Document 1 discloses a method in which fluorine is fixed by adding an aluminum compound to a slag melt and adding a stable CaO—Al ₂ O ₃ —F compound as a slag modifier in the cooling process. Proposed. Patent Document 2 discloses that fluorine elution is performed by introducing fluorine-containing slag and at least one of SiO ₂ and iron oxide into hot metal during oxidative refining to prepare a slag component. Techniques for suppression are disclosed.

However, the methods described in Patent Document 1 and Patent Document 2 have a problem that the amount of slag generated increases. On the other hand, in Patent Document 3, by cooling the slag prepared at a CaO / SiO ₂ ratio of 1.5 or more and 2.5 or less from the tap temperature to 500 ° C. at a cooling rate of 3 ° C./min or less, There has been proposed a method of generating a mineral phase having a low hydration property and suppressing the elution amount of fluorine. The method described in Patent Document 3 does not require complicated component adjustment, but makes it difficult to manage the cooling rate of the entire slag.

In recent years, instead of these methods, there has been reported a technique for immobilizing fluorine by converting it into sparingly soluble fluoroapatite (Ca ₅ (PO ₄ ) ₃ F).
For example, in Patent Document 4, in order to suppress elution of fluorine from steelmaking slag, after the steelmaking slag is cooled to room temperature, an aqueous solution of phosphoric acid or phosphate is added to fix the fluorine to the apatite compound. Is disclosed.
Similarly, in Patent Document 5, an aqueous solution containing a phosphoric acid component is sprayed on slag, and fluorine apatite is generated by a chemical reaction between phosphoric acid and fluorine and calcium in the slag, and elution of fluorine is suppressed, and A technique capable of effectively suppressing an increase in pH is disclosed.

Furthermore, in Patent Document 6, as a method for immobilizing fluorine in wastewater instead of slag, ammonium hydrogenphosphate dihydrate and calcium chloride are added and mixed into fluorine-containing wastewater under the conditions of pH 4-8. Thus, a technique for insolubilizing fluorine in wastewater as fluoroapatite is disclosed.
However, in the said patent documents 4-6, the means to prove presence of a fluoroapatite is not specified, and also the ratio of the fluorine which makes a fluoroapatite into an existing form is not shown.

As a method for identifying and quantifying compounds contained in a powder sample, powder X-ray diffraction method, X-ray absorption spectroscopy using synchrotron radiation (hereinafter referred to as XAFS method), electron spin resonance method (hereinafter referred to as ESR method) And a method using a solid nuclear magnetic resonance method (hereinafter referred to as NMR method) and a solvent extraction method.
The powder X-ray diffraction method is a simple and rapid method and can be quantitatively analyzed by Rietveld analysis.
The XAFS method is element-selective and can be applied to structural analysis of a mixture regardless of whether it is crystalline or amorphous.
The NMR method is also element-selective and is a method that does not matter the crystallinity of the material. The NMR method is good at quantifying light elements such as hydrogen and fluorine as compared with the XAFS method.

In the case of the powder X-ray diffraction method, when the fluoroapatite is not the main mineral phase, there is a problem that the fluoroapatite cannot be detected or the quantitative accuracy of the fluoroapatite is remarkably deteriorated.
In the XAFS method, the absorption spectrum for each element can be basically observed. However, fluorine is a light element with low X-ray absorption energy. Therefore, the XAFS method has a problem that it is extremely difficult to detect fluorine derived from fluoroapatite due to attenuation of incident X-rays and interference by heavier elements.

On the other hand, the NMR method is rather good at measuring light elements. As an NMR measurement method for a solid sample, as shown in Non-Patent Document 1, the magic angle spinning (MAS) method and the cross polarization magic angle spinning (CPMAS) method are known. Yes. For example, the ¹⁹ F-MAS method can be applied to directly observe fluorine in a solid sample. However, in this method, the peak of the NMR spectrum due to fluoroapatite and the peak of the NMR spectrum due to caspidine (Ca ₅ Si ₂ O ₄ F) having a Ca—F bond are completely overlapped. It cannot be strictly divided. For this reason, there has been a problem that fluorine in fluoroapatite is evaluated excessively or conversely underestimated.

Also in ³¹ P nuclei of magic angle spinning ⁽³¹ P-MAS) method, the position of the peaks of the NMR spectrum due to the phosphate PO ₄ belonging to fluorapatite, phosphate PO ₄ belonging to other compounds The peak position of the resulting NMR spectrum matches and cannot be separated. For this reason, there has been a problem that the amount of fluoroapatite is excessively estimated, and as a result, the amount of fluorine containing fluoroapatite is excessively evaluated.

Similarly, in the ESR method, in order to distinguish fluoroapatite from other fluorine-containing minerals, it was necessary to rely on arbitrary separation of the ESR spectrum.
In addition, the solvent extraction method aims to selectively dissolve CaF ₂ with an alkaline solution and separate it from fluoroapatite, but it has a problem that it is extremely difficult to completely remove CaF ₂ in the first place.

JP 2000-247694 A JP 2005-8935 A JP 2011-37644 A JP 2008-49327 A JP 2008-127271 A JP 2011-534 A

The Chemical Society of Japan, "Experimental Chemistry Course 8 NMR / ESR", 5th Edition, Maruzen Co., Ltd. (September 15, 2006), 128-143

  The present invention has been made in view of the above-described problems, and an object of the present invention is to accurately determine the amount of fluorine containing fluoroapatite as an existing form by eliminating the influence of coexisting fluorine-containing minerals.

In order to solve the above-mentioned problems, the present inventor selectively measures only fluoroapatite from a plurality of fluorine-containing mineral phases by NMR, and quantifies the fluorine present in the mineral phase. The method was intensively studied. As a result, we focused on the coexistence of phosphorus and fluorine atoms in the crystals of fluorapatite. ³¹ P [ ¹⁹ F] cross polarization magic angle spinning method ( ³¹ P [ ¹⁹ F] cross polarization magic angle spinning method: , ³¹ P [ ¹⁹ F] CPMAS method), and quantifying the amount of fluoroapatite using a calibration curve prepared in advance. The inventors have found that the ratio of can be quantified, and have completed the present invention.

The gist of the present invention is as follows.
(1) Fluorine apatite (Ca ₅ (PO ₄ ) ₃ F) is a method for quantitative determination of fluorine, comprising measuring a total fluorine concentration in an unknown sample, a known amount of fluoroapatite, and fluorine. A standard sample is prepared by mixing with a matrix material that does not contain the solid material, and a solid nuclear magnetic resonance spectrum of the standard sample is measured by a solid nuclear magnetic resonance method using a dipole interaction between ³¹ P and ¹⁹ F. Based on the results, a calibration curve of the content of fluoroapatite with respect to the peak integrated intensity of the solid nuclear magnetic resonance spectrum attributed to fluoroapatite, and a dipole between ³¹ P nucleus and ¹⁹ F nucleus The solid nuclear magnetic resonance spectrum of the unknown sample was measured by a solid nuclear magnetic resonance method using interaction, and the peak integrated intensity of the solid nuclear magnetic resonance spectrum attributed to fluoroapatite Determining the content of fluoroapatite in the unknown sample based on the calibration curve, and determining the content of total fluorine in the unknown sample based on the total fluorine concentration and the content of fluoroapatite. And a step of determining a proportion of fluorine that is an elemental composition of fluoroapatite, and a method for determining fluorine with fluoroapatite as an existing form.
(2) The solid nuclear magnetic resonance method according to (1), characterized in that it is a ³¹ P and ¹⁹ F cross polarization magic angle spinning solid nuclear magnetic resonance method Quantitative determination method of fluorine in the form of fluorapatite.
(3) The above (2) is characterized in that, in the solid nuclear magnetic resonance method, the contact time, which is the time for irradiating the ³¹ P nucleus with a radio wave pulse, is a time in the range of more than 0 ms and not more than 40 ms. A method for quantifying fluorine using the described fluoroapatite as an existing form.
(4) The rotation angle of magic angle spinning in the solid nuclear magnetic resonance method is 10 kHz or more, and the fluorine of the fluoroapatite according to (2) or (3) is present. Quantitation method.
(5) The change in the intensity M ₀ (t) of the solid nuclear magnetic resonance spectrum with respect to the contact time t represents the time constant T ₁ ρ ^F relating to the decay of the peak integrated intensity of the solid nuclear magnetic resonance spectrum and the efficiency of cross polarization. The regression analysis was performed by the following equation (A) using the magnetization transfer constant T _PF and the true solid nuclear magnetic resonance spectrum intensity M _cp independent of the contact time as fitting parameters, which were determined from the results of the regression analysis. The calibration curve is created using the true solid nuclear magnetic resonance spectral intensity _Mcp independent of the contact time, and the fluorine having the fluoroapatite as described above in (3) or (4) Quantification method.
M ₀ (t) = M _cp {exp (−t / T ₁ ρ ^F ) −exp (−t / T _PF )} / (1-T _{PF /} T ₁ ρ ^F ) (A)
(6) The fluoroapatite according to any one of (1) to (5) above, wherein the total fluorine concentration in the unknown sample is quantified by a lanthanum-alizarin complexone method or an ion electrode method. Quantitative determination method of fluorine to be present.

According to the present invention, a solid nuclear magnetic resonance spectrum is obtained by using a solid nuclear magnetic resonance measurement method utilizing a dipole interaction between ³¹ P and ¹⁹ F. Therefore, only the fluoroapatite having a short interatomic distance between the phosphorus atom P and the fluorine atom F is selectively observed in the solid nuclear magnetic resonance spectrum, and the structural information appearing on the solid nuclear magnetic resonance spectrum is narrowed down. For this reason, the MAS method that observes only ¹⁹ F nuclei or only ³¹ P nuclei often suffers from separation of the solid nuclear magnetic resonance spectrum peaks and separation of each waveform of the solid nuclear magnetic resonance spectrum. And the amount of fluorine can be accurately determined.

It is a conceptual diagram explaining the principle of ³¹ P [ ¹⁹ F] CPMAS method. It is a figure which shows an example of a ¹⁹ F-MAS spectrum. Of ³¹ P ^[19 F] contact time dependency of the peak integral intensity of the CPMAS spectrum shows an example. It is a figure which shows an example of a calibration curve. Is a diagram showing the ³¹ P ^[19 F] CPMAS spectrum of Example. It is a figure which shows the ¹⁹ F-MAS spectrum in a comparative example.

One mode for carrying out the present invention will be described below.
First, the total fluorine concentration in the sample (hereinafter referred to as total fluorine concentration) is measured. As a method for measuring fluorine, it is preferable to carry out either the lanthanum-alizarin complexone method or the ion electrode method. This is because other analysis methods such as fluorescent X-ray analysis have large errors and lack accuracy.

Next, the NMR spectrum of the sample is measured, and a calibration curve relating to fluoroapatite is created from the NMR spectrum data.
As a method for measuring the NMR spectrum, ³¹ P [ ¹⁹ F] cross polarization magic angle spinning ( ³¹ P [ ¹⁹ F] CPMAS method) using dipole interaction between ³¹ P and ¹⁹ F is used.
FIG. 1 is a conceptual diagram illustrating the principle of the ³¹ P [ ¹⁹ F] CPMAS method. Specifically, FIG. 1A is a diagram illustrating an example of pulse irradiation timing on a sample. FIG. 1B is a diagram conceptually showing the spin of ¹⁹ F nucleus and the spin of ³¹ P nucleus. Details of the CPMAS method are described in Non-Patent Document 1, for example.

In the ³¹ P [ ¹⁹ F] CPMAS method used here, an NMR spectrum is measured by irradiating a sample with a radio wave (RF) pulse composed of the pulse sequence shown in FIG. The FID shown in FIG. 1A is a free induction decay signal, and an NMR spectrum can be obtained by fast Fourier transforming this free induction decay signal.
First, the ¹⁹ F nucleus is irradiated with an RF pulse P1, and as shown in FIG. 1 (b), the spin of the ¹⁹ F nucleus that has been oriented in the z-axis direction is tilted by 90 ° to be in the y-axis direction.

Next, when an RF pulse P2 that holds the spin of the ¹⁹ F nucleus that has fallen in the y-axis direction in the y-axis direction is irradiated (this pulse is referred to as a spin lock pulse), the ¹⁹ F nucleus has a magnetic field H ^{1 in the} y-axis direction. It is put in the state where _F is hung. At this time, the static magnetic field H ₀ in the z-axis direction perpendicular to the y-axis can be ignored. Zeeman splitting in this state occurs at an interval equal to the frequency ω _F expressed by γ _F H ¹ _F (γ _F : ¹⁹ F nuclear nuclear magnetic rotation ratio) (this is called Zeeman splitting in a rotating system).

In addition, when the RF pulse P2 (pulse spin lock pulse) is irradiated on the ¹⁹ F nucleus side and the ³¹ P nucleus is also irradiated with the RF pulse P3 (this is called a contact pulse) in the y-axis direction, the ³¹ P nucleus Also, a static magnetic field H ¹ _P is applied in the y-axis direction. The Zeeman splitting in the rotating system in this state occurs at an interval equal to the frequency ω _P expressed by γ _P H ¹ _P (γ _P : nuclear magnetic rotation ratio of ³¹ P nucleus). However, unlike the ¹⁹ F nucleus, the spin of the ³¹ P nucleus does not fall in the y-axis direction at this stage, so the magnetization in the y-axis direction does not actually exist. At this time, when the magnetic field H ¹ _F and the magnetic field H ¹ _P are given so that the Zeeman splitting of the ³¹ P nucleus and the ¹⁹ F nucleus is equal, the Hartmann-Hahn condition of the following equation (1) is satisfied, and the ¹⁹ F nucleus To ³¹ P nucleus occurs.
γ _F H ¹ _F = ω _F = ω _P = γ _P H ¹ _P (1)

Such a phenomenon in which magnetization transfer from ¹⁹ F nuclei to ³¹ P nuclei occurs is called cross polarization (CP). In a solution having a fast molecular motion or a system conforming thereto, the molecular motion is averaged, and therefore, measurement using cross polarization (CP) cannot be performed by the NMR method. Further, in the cross polarization (CP), ¹⁹ F and ³¹ P are contained in the same sample, and an NMR spectrum (signal) is not provided unless they are close to each other at the atomic level. Therefore, according to as long as both the phosphorus P and fluorine F as fluorapatite is not included in the crystal structure, ³¹ P ^[19 F] NMR spectrum is not detected by the CPMAS method (hereinafter, ³¹ P ^[19 F] CPMAS method NMR spectrum is referred to as ³¹ P [ ¹⁹ F] CPMAS spectrum).

On the other hand, in the general ¹⁹ F-MAS method and ³¹ P-MAS method, since all the compounds containing each element are observed on the same NMR spectrum, the determination of fluoroapatite is greatly hindered. That is, in the ¹⁹ F-MAS spectrum, the chemical shift value of the Ca-F compound is concentrated in the vicinity of -100 ppm. For this reason, it is attributed to the peak of the NMR spectrum due to the Ca-F compound and the fluoroapatite. The peaks of the NMR spectrum overlap.
FIG. 2 is a diagram illustrating an example of a ¹⁹ F-MAS spectrum. Specifically, FIG. 2 (a) is a diagram showing the ¹⁹ F-MAS spectrum of a oxide A, FIG. 2 (b), the ¹⁹ F-MAS spectrum of Kasupidin _{(Ca 4 Si 2 O 7 F} ) FIG. 2C is a diagram showing ¹⁹ F-MAS spectra of fluoroapatite and CaF ₂ .
As shown in FIG. 2, ¹⁹ F-MAS spectrum of ¹⁹ F-MAS spectrum and fluorapatite in Kasupidin _{(Ca 4 Si 2 O 7 F} ) is a typical case in which the peak of the spectrum overlap. As shown in FIG. 2 (b), FIG. 2 (c), the one of the peaks of the two ¹⁹ F-MAS spectrum of Kasupidin, one, indistinguishable from a peak of ¹⁹ F-MAS spectrum of fluorapatite. As a result, fluoroapatite cannot be accurately quantified by waveform separation of the ¹⁹ F-MAS spectrum.

In the ³¹ P-MAS spectrum, the peak derived from phosphoric acid PO ₄ in fluoroapatite and the other peak derived from phosphoric acid PO ₄ are observed at exactly the same position. For this reason, fluoroapatite cannot be accurately quantified even by the ³¹ P-MAS method.
Therefore, in this embodiment, the ³¹ P [ ¹⁹ F] CPMAS method is adopted.

Next, an example of a method for creating a calibration curve from ³¹ P [ ¹⁹ F] CPMAS spectrum will be described.
First, a standard sample is prepared by mixing a known amount of fluoroapatite and a fluorine-free matrix material and weighing the whole.
A standard sample for preparing a plurality of calibration curves is prepared by changing the ratio between the fluoroapatite and the matrix material. Each standard sample is packed in a separate NMR sample tube and subjected to measurement of the NMR spectrum.

^{The 31} P [ ¹⁹ F] CPMAS spectrum is measured by rotating the NMR sample tube at a rotational speed of 10 kHz or higher (that is, the ³¹ P [ ¹⁹ F] CPMAS spectrum is measured at a rotational frequency of magic angle spinning of 10 kHz or higher. As do). This is because if the rotational speed is less than 10 kHz, the ³¹ P [ ¹⁹ F] CPMAS spectrum becomes wider and sufficient resolution cannot be obtained. The intensity of the ³¹ P [ ¹⁹ F] CPMAS spectrum varies depending on the intensity of the radio wave pulse irradiated on ³¹ P and its irradiation time (hereinafter referred to as contact time).

As the contact time t for the above-mentioned magnetization transfer is increased, the peak integrated intensity of the ³¹ P [ ¹⁹ F] CPMAS spectrum increases, and the closer the distance between P and F, that is, the dipole interaction. The stronger the, the steeper the rise of ³¹ P [ ¹⁹ F] CPMAS spectrum. Magnetization transfer constant in this case a (constant representing the efficiency of cross-polarization) and T _PF. When a certain contact time is reached, the peak integrated intensity of the ³¹ P [ ¹⁹ F] CPMAS spectrum starts to decline. Let T ₁ ρ ^F be the time constant related to the decay of the peak integrated intensity of the ³¹ P [ ¹⁹ F] CPMAS spectrum (the time constant representing the mobility of fluorine (due to the movement of fluorine)). Using the above parameters (M _cp , T _PF , T ₁ ρ ^F ), the contact time dependence of the peak integrated intensity M (t) of ³¹ P [ ¹⁹ F] CPMAS spectrum is regressed by the following equation (2): Analyze and find the peak integrated intensity independent of cross-polarization efficiency.

When measuring the contact time dependence of the peak integrated intensity M ₀ (t) of ³¹ P [ ¹⁹ F] CPMAS spectrum, set two or more contact times t in the period of over 0 ms to 40 ms, and use one standard A plurality of data is measured for the sample. This is because the accuracy of fitting is reduced if there is no plurality of data within this period.
FIG. 3 is a diagram illustrating an example of the contact time dependency of the peak integrated intensity M ₀ (t) of the ³¹ P [ ¹⁹ F] CPMAS spectrum. In FIG. 1-No. The one obtained from 3 is shown.
^{When the} dependence of the peak integrated intensity M ₀ (t) of the ³¹ P [ ¹⁹ F] CPMAS spectrum on the contact time is measured and the measured data is fitted with the equation (2), curves 301 to 303 as shown in FIG. From the result, the true peak integrated intensity M _cp (coefficient of equation (2)) can be calculated. The same is done for a plurality of standard samples with different amounts of fluoroapatite. As shown in FIG. 4, the true peak integrated intensity M _cp of ³¹ P [ ¹⁹ F] CPMAS spectrum is plotted on the horizontal axis, A calibration curve 401 is obtained by creating a graph in which the content of oroapatite is plotted on the vertical axis and performing linear regression analysis.

Incidentally, the calibration curve 401, and ³¹ P ^[19 F] CPMAS true peak integrated intensity M _cp spectrum, as long as information indicative of a relation between the content of fluoroalkyl apatite in the standard samples, necessarily equation (function) Need not be. For example, a ³¹ P ^[19 F] CPMAS true peak integrated intensity M _cp spectrum, may be employed to the data table to be stored in association with each other and the content of fluoroalkyl apatite in the standard samples. In this case, values not in the data table can be derived by performing an interpolation process.

Next, packed unknown sample which is separately weighed into NMR sample tube, ³¹ P ^[19 F] CPMAS spectrum was measured, the contact time dependence of the peak integrated intensity was analyzed by Equation (2), ³¹ P for the unknown sample Request ^[19 F] CPMAS true peak integrated intensity M _cp of the spectrum. The ³¹ P ^[19 F] CPMAS true peak integrated intensity M _cp spectrum, by substituting the calibration curve 401 shown in FIG. 4, it is possible to determine the amount of fluoroapatite in the unknown sample [g]. The mass of the powder sample in the NMR sample tube is a [g], the total fluorine concentration in the powder sample is w [mass%], the molecular weight of fluoroapatite is A, the atomic weight of fluorine is N, and the fluoroapatite content in the powder sample is Assuming y [g], first, the amount of fluorine [g] present as fluoroapatite in the powder sample packed in the NMR sample tube can be expressed as the following formula (3).
Fluorine content = y × (N / A) (3)

Further, the total fluorine amount [g] in the powder sample packed in the NMR sample tube is expressed by the following equation (4).
Total fluorine amount = a × (w / 100) (4)
Therefore, the ratio [mass%] of fluorine existing as fluoroapatite out of the total fluorine in the unknown sample can be obtained by the following formula (5).

As described above, in this embodiment, an NMR spectrum is obtained by using the NMR measurement method using the dipole interaction between ³¹ P nucleus and ¹⁹ F nucleus. Therefore, only the fluoroapatite having a close interatomic distance between the phosphorus atom P and the fluorine atom F is selectively observed in the NMR spectrum, and the structural information appearing on the NMR spectrum is narrowed down. For this reason, in the MAS method in which only ¹⁹ F nuclei or only ³¹ P nuclei are observed, there is no need to bother the overlap of NMR spectrum peaks and separation of each waveform of NMR spectra, which is often a problem. The amount of fluorine in the existing form can be accurately determined.

Of the embodiments of the present invention described above, at least processing for the NMR spectrum can be realized by a computer executing a program. Further, a computer-readable recording medium in which the program is recorded and a computer program product such as the program can also be applied as an embodiment of the present invention. As the recording medium, for example, a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.
In addition, the embodiments of the present invention described above are merely examples of implementation in carrying out the present invention, and the technical scope of the present invention should not be construed as being limited thereto. Is. That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof.

Examples of the present invention are shown below. Note that this example does not limit the scope of the present invention.
First, a calibration curve used for quantification of fluoroapatite was prepared as follows.
Using an electronic balance, a fluorine-free matrix material and fluoroapatite were weighed and mixed, and a plurality of standard samples No. 1 and No. 1 having different mixing ratios of the two materials were mixed. 2, no. 3 was produced. Table 1 shows the ratio of the matrix material and fluoroapatite in each standard sample.

Next, as shown in FIG. 1-No. For each standard sample 3, the contact time dependency of ³¹ P ^[19 F] CPMAS peak integrated intensity M ₀ of the spectrum (t) were measured, by fitting the equation (2) with respect to the measured data, ³¹ P It was determined ^[19 F] CPMAS true peak integrated intensity M _cp of the spectrum.
As shown in FIG. 4, the content of fluoroapatite in each standard sample on the vertical axis, the ³¹ P ^[19 F] CPMAS true peak integrated intensity M _cp spectral horizontal axis, linear regression analysis correlations between them Thus, a calibration curve 401 was obtained. As a result, a calibration curve 401 of the fluoroapatite content y [g] was expressed by the following formula (6). Since the regression coefficient R is 0.99 or more and has a very excellent linearity, high accuracy can be ensured in quantification.
y = 9.7317 × 10 ⁻³ × M _cp + 6.3617 × 10 ⁻⁴ (6)
Next, the ratio of fluorine existing as fluoroapatite was investigated for the measurement sample whose total fluorine concentration had been measured in advance. Table 2 shows the chemical compositions (CaO, SiO ₂ , P ₂ O ₅ , Total F) of the measurement samples Sample A, B, and C. A measurement sample was sealed in a pre-weighed NMR sample tube and weighed again, and the mass of the measurement sample in the NMR sample tube was determined from the front and back subtraction.

FIG. 5 is a diagram showing a ³¹ P [ ¹⁹ F] CPMAS spectrum of Sample A as an example of a measurement sample. Like the ³¹ P ^[19 F] CPMAS spectrum 501 of Sample A, also ³¹ P ^[19 F] CPMAS spectra of SampleB and sample C, the peak that matches the chemical shift value of fluorapatite was observed. From the dependence of the peak integrated intensity M ₀ (t) corresponding to this fluoroapatite on the contact time, the true peak integrated intensity M _cp of the ³¹ P [ ¹⁹ F] CPMAS spectrum is obtained. And the content of the fluoroapatite in each measurement sample was calculated | required using the calibration curve 401 represented by Formula (6). Then, the ratio of fluorine having fluoroapatite as an existing form in each measurement sample was calculated using Equation (5). Table 3 shows the quantitative results in the present example and the quantitative results in the comparative example described later.

Examples 1, 2, and 3 in Table 3 show values obtained by the above-described novel quantification method for Samples A, B, and C, respectively. In Table 3, FinFAP is a ratio of fluorine having fluoroapatite as an existing form in the total fluorine concentration Total F in the measurement sample (see the above-described formula (5)).
On the other hand, Comparative Examples 1, 2, and 3 in Table 3 are values obtained by the method of waveform separation of the conventional ¹⁹ F-MAS spectrum for Samples A, B, and C, respectively. FIG. 6 is a diagram showing a ¹⁹ F-MAS spectrum of Sample A as an example of a measurement sample.
In the Sample A ¹⁹ F-MAS spectrum 601, in addition to fluoroapatite (-100 ppm), peaks corresponding to caspidine (-100 ppm, -105 ppm) are observed.
From Table 3, it can be seen that the fluorine ratio FinFAP having the fluoroapatite quantified by this example is lower than that of the comparative example. Fluoroapatite Ca ₅ (PO ₄ ) ₃ F contains 1.5 molecules of P ₂ O ₅ . Therefore, the P ₂ O ₅ / F ratio in fluoroapatite is 11.2. Multiplying the known total fluorine concentration Total F by Fluorapatite's fluorination ratio FinFAP and multiplying that value by 11.2 gives the concentration of phosphorous oxide P ₂ O ₅ necessary for fluoroapatite in terms of chemical composition Can be requested.

The phosphorus oxide concentrations (see the column of P ₂ O ₅ ) shown in the examples and comparative examples in Table 3 are values obtained in this manner. Table than the value of the examples and comparative examples 3, concentration of phosphorus oxide P ₂ O ₅ was calculated back from fluorine ratio FinFAP determined by a novel determination method (this embodiment), the phosphorus oxide P ₂ on the chemical composition Whereas the concentration of phosphorous oxide P ₂ O ₅ calculated backward from the fluorine ratio FinFAP in the comparative example exceeds the concentration of phosphorous oxide P ₂ O _{5 in} the chemical composition, while it is less than the concentration of O ₅ It turns out that there will be a shortage. Therefore, in the comparative example, the ratio of fluorine having fluoroapatite as an existing form is excessively evaluated. On the other hand, in the new quantitative method (this example), an appropriate fluorine ratio is obtained also from the viewpoint of mass balance, and this is a more accurate analysis method.

401 Calibration curve 501 ³¹ P [ ¹⁹ F] CPMAS spectrum 601 ¹⁹ F-MAS spectrum

Claims (6)

A method for quantifying fluorine using fluorapatite (Ca ₅ (PO ₄ ) ₃ F) as an existing form,
Measuring the total fluorine concentration in the unknown sample;
A standard sample is prepared by mixing a known amount of fluoroapatite and a matrix material not containing fluorine, and the standard sample is obtained by solid nuclear magnetic resonance using a dipole interaction between ³¹ P and ¹⁹ F. Measuring a solid nuclear magnetic resonance spectrum of, and creating a calibration curve of the content of fluoroapatite with respect to the peak integrated intensity of the solid nuclear magnetic resonance spectrum attributed to fluoroapatite based on the results,
The solid nuclear magnetic resonance spectrum of the unknown sample was measured by the solid nuclear magnetic resonance method using the dipole interaction between ³¹ P nucleus and ¹⁹ F nucleus, and the solid nuclear magnetic resonance spectrum attributed to fluoroapatite. Determining the content of fluoroapatite in the unknown sample based on the peak integrated intensity of and the calibration curve;
A step of determining a proportion of fluorine that is the elemental composition of fluoroapatite out of all fluorine in the unknown sample based on the total fluorine concentration and the content of the fluoroapatite. Quantitative determination method of fluorine in the presence form. 3. The presence of fluoroapatite according to claim 1, wherein the solid nuclear magnetic resonance method is a ³¹ P and ¹⁹ F cross polarization magic angle spinning solid nuclear magnetic resonance method. A method for quantitative determination of fluorine in the form. 3. The fluoroapatite according to claim 2, wherein in the solid-state nuclear magnetic resonance method, a contact time, which is a time for irradiating a ³¹ P nucleus with a radio wave pulse, is a time in a range of more than 0 ms and not more than 40 ms. Quantitative determination method of fluorine to be present.   4. The method for quantitatively determining fluorine in the form of fluoroapatite according to claim 2, wherein the rotational frequency of magic angle spinning in the solid nuclear magnetic resonance method is 10 kHz or more. The change in the intensity M ₀ (t) of the solid nuclear magnetic resonance spectrum with respect to the contact time t, the time constant T ₁ ρ ^F relating to the decay of the peak integrated intensity of the solid nuclear magnetic resonance spectrum, and the magnetization transfer constant representing the efficiency of cross polarization. The contact time determined from the regression analysis results by regression analysis using the following equation (A) with T _PF and the true solid nuclear magnetic resonance spectrum intensity M _cp independent of the contact time as fitting parameters. The method according to claim 3 or 4, wherein the calibration curve is created using a true solid nuclear magnetic resonance spectral intensity _Mcp that does not depend on fluorapatite.

  The total fluorine concentration in the unknown sample is quantified by a lanthanum-alizarin complexone method or an ion electrode method, wherein the fluorine content of the fluoroapatite in the existing form according to any one of claims 1 to 5 is characterized. Quantitation method.

Images