Method for detecting hydroxyapatite active ingredient in toothpaste

Abstract

The present invention relates to the technical field of oral care product detection, and particularly relates to a method for detecting the active ingredient of hydroxyapatite in toothpaste, comprising the following steps carried out in sequence: subjecting a sample to be tested to a calcination treatment, and then obtaining a sample powder after pulverization treatment; dispersing the sample powder into a buffer solution, and then obtaining a dried sample after stirring treatment, washing and drying; obtaining the Raman spectrum of the dried sample. This technical solution can solve the technical problem that when detecting the hydroxyapatite component in oral care products, the interference of impurities on the detection result is too large. Selecting the characteristic peak of hydroxyapatite near 960 cm ‑1 -1 for detection can effectively distinguish hydroxyapatite from other friction matrix components; improving the stability and signal intensity of hydroxyapatite through calcination treatment; further removing impurities such as calcium carbonate by selecting an acetic acid-sodium acetate buffer solution to dissolve the calcined sample, improving the detection accuracy, and having an ideal application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of oral care product detection, and particularly relates to a method for detecting the active ingredient of hydroxyapatite in toothpaste. Background Art

[0002] The physical structure and physicochemical properties of hydroxyapatite (HAP) make it a widely used inorganic material. Especially, due to its similar inorganic components to human bones and teeth, it has good biocompatibility, so it has become a hot topic in the research of oral medical materials, especially hard tissue repair materials. In recent years, the application of HAP in oral care products has attracted more and more attention. It has been reported that it is applied to toothpaste and mouthwash products, with the effects of inhibiting the growth of dental plaque, promoting the remineralization of tooth enamel, whitening teeth and relieving dentin hypersensitivity. Therefore, the quantitative and qualitative evaluation of HAP as an active ingredient in oral cleaning and care products has also become the focus of current research.

[0003] The detection of HAP usually adopts methods such as freeze-drying and high-temperature drying. After grinding the dried finished product, X-ray diffraction (XRD) is used to qualitatively characterize the composition and crystal phase structure of the HAP active ingredient. The XRD diffraction characteristic peaks (2θ) of HAP are located at 21-29°, 32-34°, 39-41°, and 46-54°. When identifying the stability of the crystal structure, it is necessary to compare the above important characteristic peak patterns and intensities at the same time to prove the existence of the HAP structure. Due to the great similarity between the structural characteristics of HAP and the structures of commonly used components in toothpaste such as calcium hydrogen phosphate and calcium carbonate, a large number of diffraction peaks of calcium hydrogen phosphate or calcium carbonate will completely cover the characteristic peaks of HAP, making it difficult to identify the phase structure of the HAP active ingredient in toothpaste. There is an urgent need to develop a method that can exclude the interference of other components in oral care products and accurately detect the HAP therein. Summary of the Invention

[0004] The present invention aims to provide a method for detecting the active ingredient of hydroxyapatite in toothpaste to solve the technical problem that other components interfere too much with the detection result when detecting the hydroxyapatite component in oral care products in the prior art.

[0005] To achieve the above object, the present invention adopts the following technical solution:

[0006] A method for detecting the active ingredient of hydroxyapatite in toothpaste, comprising the following steps carried out in sequence:

[0007] S1: Calcining the sample to be tested, and then obtaining sample powder after crushing treatment;

[0008] S2: Disperse the sample powder into the buffer solution, followed by stirring, washing, and drying to obtain a dried sample.

[0009] S3: Obtain the Raman spectrum of the dried sample.

[0010] The principle and beneficial effects of this technical solution are as follows:

[0011] This technical solution uses high-temperature sintering to solidify the crystal state of HAP, and uses weak acid buffer to dissolve impurities such as calcium hydrogen phosphate and calcium carbonate. Finally, combined with the advantages of Raman spectroscopy, a method for detecting the active ingredient of HAP in toothpaste is established.

[0012] Through high-temperature calcination, water, flavors, colloids, and other volatile carbon oxides, nitrogen oxides, and other impurities in the sample can be fully removed. HAP has a hexagonal atomic framework, with a dominant element (Ca) at two cation sites, P at the third cation site, and OH at another structural site. During the high-temperature calcination process in the range of 700 - 800 °C, HAP can further enhance its mechanical strength to avoid being dissolved during subsequent acid dissolution. However, when the temperature exceeds 800 °C, the OH ions in the HAP structure may displace along the channel axis, and the hydroxyl peak at ~3572 cm -1 shows the degree of crystal dehydrogenation, resulting in structural defects. Therefore, by monitoring the -OH peak at around ~3572 cm -1 and setting the calcination temperature to 700 °C - 800 °C, the purpose of fully removing organic impurities while making the structure of useful components more stable and enriched can be achieved. The solid after high-temperature calcination is fully ground to obtain a highly dispersed powder, and a weak acid acetic acid - sodium acetate buffer solution with a pH of 4.8 - 5.8 is used to ensure that impurities such as calcium carbonate and calcium hydrogen phosphate commonly used in oral care products can be fully dissolved by the acid, overcoming the interference of calcium carbonate and calcium hydrogen phosphate and other impurities on the determination of HAP, and realizing the qualitative detection of HAP in oral care products.

[0013] Furthermore, in S1, the conditions for the calcination treatment are: heating to 700 - 800 °C at a heating rate of 2 - 10 °C / min, and then holding for 1 - 2 h. Calcination at 700 - 800 °C can ensure the stability of the crystal size and the d-spacing value of the main peak (211), and the stability of -OH ions is good, improving the stability of HAP in a weak acid environment. Moreover, 700 - 800 °C can remove organic substances, eliminate interference factors during the detection process, and make the dissolution capabilities of HAP, calcium carbonate, and calcium hydrogen phosphate different in a weak acid environment, so that calcium carbonate and calcium hydrogen phosphate can be removed through subsequent weak acid treatment.

[0014] Furthermore, in S1, the sample powder passes through a 200-mesh sieve.

[0015] Further, in S2, the mass ratio of the sample powder to the buffer solution is 1:(5 - 20).

[0016] Further, in S2, the buffer solution is an acetic acid - sodium acetate buffer solution. Using the acetic acid - sodium acetate buffer solution to treat the calcined sample can remove calcium carbonate and calcium hydrogen phosphate, and does not affect the structure of HAP nor dissolve HAP.

[0017] Further, in S2, the concentration of the acetic acid - sodium acetate buffer solution is 0.2 - 0.5 M and the pH is 4.8 - 5.8. Under the above pH conditions, HAP has good stability in the buffer solution and can fully dissolve calcium carbonate and calcium hydrogen phosphate. If the pH used is too high or too low, it will cause all of the calcined HAP, calcium carbonate, and calcium hydrogen phosphate to be unable to dissolve, or all of the calcined HAP, calcium carbonate, and calcium hydrogen phosphate to be completely dissolved, ultimately resulting in the inability to separate HAP from calcium carbonate and calcium hydrogen phosphate and the inability to accurately detect HAP in toothpaste.

[0018] Further, in S2, the stirring treatment method is: stirring at a speed of 200 - 400 rpm for 24 - 60 h under the condition of 25 - 37°C.

[0019] Further, in S1, the sample to be tested is toothpaste.

[0020] Further, the friction matrix of the toothpaste includes at least one of calcium carbonate, calcium hydrogen phosphate, hydrated silica, and aluminum hydroxide.

[0021] Further, in S3, observe whether a characteristic peak corresponding to the standard hydroxyapatite sample appears in the Raman spectrum of the dried sample at 950 - 970 cm -1 -1

[0022] Using Raman spectroscopy detection, HAP has characteristic peaks that are significantly different from matrices such as calcium hydrogen phosphate and calcium carbonate in its structure. The ν1PO4 3- stretching peak is located at 950 - 970 cm -1 -1, showing the orderliness of the crystal structure. By focusing on monitoring this characteristic peak, the structural stability of HAP can be accurately determined (see Appendix Figure 1 ).

[0023] In summary, the beneficial effects of the present technical solution are as follows:

[0024] (1) The present technical solution conducts Raman spectroscopy detection and research on the friction matrix and HAP in toothpaste, and finds that HAP has a ν1PO4 -1 at 950 - 970 cm 3-The stretching peak shows the orderliness of the crystal structure and can be distinguished from the characteristic peaks of matrices such as calcium hydrogen phosphate and calcium carbonate. By focusing on monitoring this characteristic peak, the structural stability of HAP can be accurately determined.

[0025] (2) Through high-temperature calcination, this technical solution not only fully removes organic impurities but also makes the HAP component structure more stable and enriched, showing a more ideal peak shape and signal intensity in Raman spectroscopy detection. After testing and research by the inventor, at a calcination temperature of 700 - 800 °C, the crystal size of HAP and the d-spacing of the main peak (211) are stable, and the frequency and intensity of the -OH stretching vibration at ~3572 cm -1 are suitable, which is conducive to maintaining the stability of the hexagonal crystal structure of HAP, thereby improving the stability of HAP. Improving the stability of HAP can improve the detection accuracy for toothpastes with different friction matrices.

[0026] (3) This technical solution has a better interference exclusion effect especially for toothpastes with calcium carbonate and calcium hydrogen phosphate as friction matrices. Since HAP is calcined at 700 - 800 °C, it becomes more stable. After subsequent treatment with an acidic buffer solution, in Raman spectroscopy detection, HAP can still maintain an ideal peak shape and signal intensity. At the same time, interfering substances such as calcium carbonate and calcium hydrogen phosphate are removed by the acidic buffer solution. Calcination treatment at a certain temperature makes the solubility of calcium carbonate and calcium hydrogen phosphate in a specific buffer solution different from that of HAP, thereby achieving interference exclusion in Raman spectroscopy detection. If the toothpaste sample is directly dissolved in a buffer solution, it will cause the dissolution of substances such as calcium carbonate and calcium hydrogen phosphate while HAP also dissolves, making it impossible to effectively carry out subsequent Raman spectroscopy detection.

[0027] (4) The selection of the type of buffer solution plays a very important role in achieving accurate detection of HAP. Only by using an acetic acid - sodium acetate buffer solution can the calcined HAP be separated from substances such as calcium carbonate and calcium hydrogen phosphate, excluding interference in Raman spectroscopy detection. Using other buffer solutions will cause calcium carbonate and calcium hydrogen phosphate to not dissolve effectively or cause the characteristic peak to shift, affecting the detection accuracy.

[0028] (5) The selection of the pH value range of the acetic acid - sodium acetate buffer solution plays a crucial role in whether HAP can be separated from substances such as calcium carbonate and calcium hydrogen phosphate. If the pH is too low, HAP and substances such as calcium carbonate and calcium hydrogen phosphate will be dissolved together; if the pH value is too high, the interfering substances (calcium carbonate and calcium hydrogen phosphate) will not be removed, and the characteristic peak of HAP cannot be observed. Description of the Drawings

[0029] Figure 1 is the Raman spectrum diagram of common different matrices of toothpaste.

[0030] Figure 2 It is the Raman spectra of Examples 1-5 and standard HAP.

[0031] Figure 3 It is the Raman spectra of Comparative Examples 1-4 and standard HAP.

[0032] Figure 4 The Raman spectra of HAP calcined at different temperatures and excited by 365 nm ultraviolet light in Experimental Example 1. Detailed implementation mode

[0033] The present invention will be further described in detail below in conjunction with the examples, but the implementation modes of the present invention are not limited thereto. Unless otherwise specified, the technical means used in the following examples and experimental examples are conventional means well-known to those skilled in the art, and the materials, reagents, etc. used can all be obtained through commercial channels.

[0034] The overall situation of this technical solution is as follows:

[0035] S1: The toothpaste sample to be tested is pre-treated by high-temperature calcination. The heating rate is 2-10 °C / min, and the temperature is controlled at 700-800 °C for heat preservation for 1-2 h to obtain a calcined sample. The calcined sample is ground and passed through a 200-mesh sieve to obtain sample powder.

[0036] S2: The sample powder is dispersed in 0.2-0.5 M, pH 4.8-5.8 acetic acid-sodium acetate buffer solution (specifically, the total concentration of acetic acid / acetic acid root in the buffer solution is 0.2-0.5 M) according to a mass ratio of 1:(5-20). Then, it is stirred at 200-400 rpm for 24-60 h at 25-37 °C. After separating the powder, it is washed thoroughly with water and then dried, and placed at 70-80 °C for 24-48 h (since Raman uses laser, compared with infrared spectroscopy, the Raman activity of water is small and its interference is relatively small. In the test, as long as the water is appropriately dried), a dried sample is obtained.

[0037] S3: Carry out conventional Raman spectroscopy detection of the dried sample and the standard HAP sample in the prior art, and identify and analyze the HAP component in the sample.

[0038] Among them, the 0.2-0.5 M, pH 4.8-5.8 acetic acid-sodium acetate buffer solution specifically means that the total concentration of acetic acid / acetic acid root is 0.2-0.5 M. In the prior art, glacial acetic acid and sodium acetate are often used for preparation. According to the required pH value, the amounts of glacial acetic acid and sodium acetate are calculated according to the existing formula, and the preparation can be completed using water as a solvent, which will not be elaborated here. The above acetic acid-sodium acetate buffer solution can also be obtained directly by commercial means.

[0039] Toothpaste contains a large amount of organic additives, which will interfere with the detection of hydroxyapatite. These organic substances can be removed by high-temperature calcination and the stability of hydroxyapatite can be improved.

[0040] Figure 1 In the figure, pure products of various friction matrices are tested, including: silica standard, aluminum hydroxide, calcium carbonate, calcium hydrogen phosphate and HAP standard commonly used in toothpaste. From the figure, it can be seen that when various friction matrices exist independently, the characteristic peaks of various substances are different, so they can be distinguished by the position of the characteristic peaks (located at 950-970cm -1 ν1PO4 3- Stretching peak). However, the characteristic peaks of calcium carbonate, calcium hydrogen phosphate and HAP are relatively close. Therefore, when a large amount of calcium carbonate or calcium hydrogen phosphate exists in the toothpaste powder, the following situations may occur: when a large amount of calcium carbonate or calcium hydrogen phosphate exists, the characteristic peak of HAP is completely covered by the strong peak of impurities and cannot appear; when calcium carbonate or calcium hydrogen phosphate is relatively small, the combination of the two and HAP (such as calcium hydrogen phosphate and HAP) becomes a wider peak, causing the peak shape to change or shift. Therefore, calcium carbonate or calcium hydrogen phosphate needs to be removed as much as possible.

[0041] Example 1

[0042] Weigh 5g of commercially available sample 1 (a toothpaste containing HAP whose matrix is calcium carbonate) for high-temperature calcination pretreatment, with a heating rate of 2℃ / min, and the temperature is controlled at 700℃ for 2h to obtain a calcined sample. Grind it, and disperse the ground powder in a buffer solution of 0.2M pH 5.8 acetic acid-sodium acetate at a mass ratio of 1:5, stir it at 25℃ for 60h, separate the powder, wash it with water, and then dry it; carry out Raman spectroscopy detection on the dried sample and the standard HAP sample, as shown in the attached figure. Figure 2 As shown, 960cm -1 The peaks on the left and right correspond to the standard peaks, and it was found that they contained HAP components.

[0043] Example 2

[0044] Weigh 5g of commercially available sample 2 (a toothpaste containing HAP whose matrix is calcium hydrogen phosphate) for high temperature calcination pretreatment, with a heating rate of 4℃ / min, and the temperature is controlled at 750℃ for 1h to obtain a calcined sample. Grind it, and disperse the ground powder in a buffer solution of 0.3M pH 4.8 acetic acid-sodium acetate at a mass ratio of 1:10, stir at 30℃ for 48h, separate the powder, wash and dry it with water, and then dry it; carry out Raman spectroscopy detection on the dried sample and the standard HAP sample, as shown in the attached figure. Figure 2 As shown, 960cm -1The peak at the position corresponds to the standard peak, and it is measured that it contains HAP component.

[0045] Example 3

[0046] Weigh 5 g of commercially available sample 3 (toothpaste containing HAP with silica hydrate as the matrix) for high-temperature calcination pretreatment. The heating rate is 6 °C / min, and the temperature is controlled at 800 °C for 1.5 h to obtain the calcined sample. Raman spectroscopy detection is carried out on the dried and ground sample and the standard HAP sample. As shown in the appendix Figure 2 The peak at 960 cm -1 corresponds to the standard peak, and it is measured that it contains HAP component.

[0047] In the toothpaste containing HAP with silica hydrate as the matrix, since silica hydrate does not interfere with the Raman spectroscopy detection of HAP, there is no need to carry out the step of acid treatment to remove the interfering matrix. However, in order to obtain better Raman spectroscopy detection results, the impurities in the toothpaste should be fully removed to obtain uniform powder. Usually, the methods of water centrifugation and resuspension or high-temperature calcination can be used. When using the method of centrifugation and resuspension, since HAP usually belongs to the nanometer level, the colloid in the toothpaste will carry away the HAP during water centrifugation and resuspension, resulting in a certain amount of loss. Therefore, the method of centrifugation and resuspension is not recommended. When using high-temperature calcination, when the temperature reaches 400 - 500 °C, the volatile flavoring agents, colloids and other impurities in the sample can be carbonized. When the temperature reaches 700 - 800 °C, the stability of the HAP crystal structure can be further improved to ensure better detection results. The peak shape of the peak at 960 cm -1 is better, narrow, sharp and with high intensity. Therefore, after calcination at 800 °C in Example 3, the interfering impurities can be effectively removed, and the crystal structure properties of HAP are enhanced, thus obtaining better Raman spectroscopy results.

[0048] Example 4

[0049] Weigh 5 g of commercially available sample 4 (toothpaste containing HAP with silica hydrate and aluminum hydroxide as the matrix) for high-temperature calcination pretreatment. The heating rate is 8 °C / min, and the temperature is controlled at 750 °C for 2 h to obtain the calcined sample, and then grind it. Raman spectroscopy detection is carried out on the ground sample and the standard HAP sample. As shown in the appendix Figure 2 The peak at 960 cm -1 corresponds to the standard peak, and it is measured that it contains HAP component.

[0050] Example 5

[0051] Weigh 5 g of the commercially available sample 5 (toothpaste containing HAP with calcium carbonate and calcium hydrogen phosphate as the matrix), perform high-temperature calcination pretreatment with a heating rate of 10 °C / min, control the temperature at 750 °C and hold for 2 h to obtain the calcined sample, and grind it. Disperse the ground powder in a 0.5 M acetic acid-sodium acetate buffer solution with a pH of 5.5 at a mass ratio of 1:20, stir at 25 °C for 48 h, separate the powder and wash and dry it thoroughly with water; carry out Raman spectroscopy detection on the dried sample and the standard HAP sample, as shown in the appendix Figure 2 As shown in, the peak at 960 cm -1 corresponds to the standard peak, and it is measured that it contains HAP components.

[0052] Experimental Example 1

[0053] HAP (HAP), usually written as (Ca 10 (PO4)6(OH)2) to highlight its two parts containing hydroxyl and apatite. Some studies have shown that the lattice points of hydroxyl are important paths for proton and oxygen ion conduction, and the stability of the hexagonal crystal structure of HAP is closely related to the stability of -OH ions in its structure. Under high-temperature conditions, the partial pressure of water is relatively low, which is prone to dehydration and generate O-HAP. At the same time, apatite is easily decomposed into tricalcium phosphate and tetracalcium phosphate.

[0054] In the experiment, the standard pure HAP sample was calcined at different temperatures, the structural information of -OH of HAP was observed by ultraviolet Raman spectroscopy, the structure of HAP after sintering at different temperatures was measured by XRD, and at the same time, the d-spacing of the main peak was obtained and the crystal size was calculated by the Scherrer method to comprehensively reveal the structure and properties of HAP.

[0055] Weigh 2 g of the standard HAP powder sample and perform calcination pretreatment at different temperatures with a heating rate of 10 °C / min and hold for 1-2 h at different temperatures to obtain the calcined sample. Grind it, and carry out ultraviolet Raman and XRD detections on the dried and ground sample. Since the vibration modes of atoms in HAP strongly depend on the crystal structure and composition, and Raman scattering is sensitive to oxygen atoms, the experimental results are shown in the appendix Figure 4 , as the temperature increases, 3572 cm -1The frequency and intensity of the -OH stretching vibration at [location] gradually decrease. At high temperatures, OH moves along the channel axis. When the temperature reaches 800 °C, -OH no longer has a definite position on the channel axis. As shown in Table 1, the crystal size and the d-spacing of the main peak (211) can be relatively well stabilized at a calcination temperature of around 700 °C - 800 °C. The crystal size and the d-spacing of the main peak (211) are the main parameters of the HAP unit cell. If their values are stable, it indicates that the HAP crystal structure is stable. More specifically, when using a calcination temperature of 700 - 900 °C, the crystal size is stabilized at 22.6 nm; when using a calcination temperature of 600 - 800 °C, the d-spacing of the main peak (211) is maintained at 2.714. Therefore, at a calcination temperature of 700 - 800 °C, the two main parameters of the crystal size and the d-spacing of the main peak (211) are stable, which characterizes the stability of the crystal structure. Additionally, the position of -OH is on the channels of the unit cell (i.e., the branched structure). Although it does not affect the main structure of the crystal, -OH is an important and inseparable part of the HAP structure, and the intensity and position of its peak can also indicate that this part of the "branched structure" in the HAP crystal is stable. Therefore, when both the main structure and the branched structure are stable, the overall structure of HAP is stable.

[0056] In summary, in order to obtain a stable HAP structure, the calcination temperature is optimally controlled at 700 - 800 °C. Within this calcination temperature range, the crystal size of HAP and the d-spacing of the main peak (211) are maintained at a stable value, and the frequency and intensity of the -OH stretching vibration at 3572 cm -1 are suitable (when the temperature rises above 800 °C, it will cause the frequency and intensity of the -OH stretching vibration to be too low), and the stability of -OH ions is closely related to the stability of the HAP hexagonal crystal system structure. At a calcination temperature of 700 - 800 °C, the obtained calcined samples can remain stable in a specific buffer solution and can be distinguished from the dissolution properties of calcium-containing toothpaste friction matrices such as calcined calcium carbonate in the specific buffer solution, effectively removing impurities that affect the detection effect.

[0057] Table 1: Crystal size and lattice spacing of HAP at different calcination temperatures

[0058] Calcination temperature / °C Crystal size (nm) d-spacing of the main peak (211) 100 7.8 2.878 300 12.7 2.759 600 15.4 2.714 700 22.6 2.714 800 22.6 2.714 900 22.6 2.712 1100 22.9 2.711

[0059] Comparative Example 1

[0060] Weigh 5 g of commercially available sample 5 (toothpaste containing HAP with calcium carbonate and calcium hydrogen phosphate as the matrix) for high-temperature calcination pretreatment. The heating rate is 10 °C / min, and the temperature is controlled at 750 °C for 2 h of heat preservation to obtain the calcined sample, and then grind it. Disperse the ground powder in a 0.5 M pH 4.5 acetic acid-sodium acetate buffer solution at a mass ratio of 1:20, stir at 25 °C for 48 h, separate the powder, and wash and dry it thoroughly with water; Carry out Raman spectroscopy detection on the dried sample and the standard HAP sample at the same time. The experimental results show that after acid treatment, there are fewer residual solid powders. After Raman spectroscopy comparison, the characteristic peak of HAP at 960 cm -1 has a shift in position and a significant weakening in peak intensity (see attachment Figure 3 ). This indicates that under these conditions, HAP dissolves and its structure changes, affecting the qualitative detection of HAP. Especially when the HAP content in the toothpaste is low, it will be difficult to detect the composition of this substance.

[0061] Comparative Example 2

[0062] Weigh 5 g of commercially available sample 5 (toothpaste containing HAP with calcium carbonate and calcium hydrogen phosphate as the matrix) for high-temperature calcination pretreatment. The heating rate is 10 °C / min, and the temperature is controlled at 750 °C for 2 h of heat preservation to obtain the calcined sample; Grind it; Disperse the ground powder in a 0.5 M pH 6.2 acetic acid-sodium acetate buffer solution at a mass ratio of 1:20, stir at 25 °C for 48 h, separate the powder, and wash and dry it thoroughly with water; Carry out Raman spectroscopy detection on the dried sample and the standard HAP sample (see attachment Figure 3 ). Under higher near-neutral pH conditions, the interfering substances (calcium carbonate and calcium hydrogen phosphate) are not removed, and the characteristic peak of HAP cannot be observed.

[0063] Comparative Example 3

[0064] Weigh 5 g of commercially available sample 5 (toothpaste containing HAP with calcium carbonate and calcium hydrogen phosphate as the matrix) for high-temperature calcination pretreatment. The heating rate is 10 °C / min, and the temperature is controlled at 750 °C for 2 h of heat preservation to obtain the calcined sample, and then grind it. Disperse the ground powder in a 0.5 M pH 5.5 citric acid-sodium citrate buffer solution (citric acid / citrate ion concentration 0.5 M, prepared using citric acid solution and sodium citrate solution; or can be obtained through commercial means) at a mass ratio of 1:20, stir at 25 °C for 48 h, separate the powder, and wash and dry it thoroughly with water; Carry out Raman spectroscopy detection on the dried sample and the standard HAP sample. The experimental results are shown in attachment Figure 3 , and it is found that at 960 cm -1The characteristic peaks are shifted and no longer coincide with those of the standard HAP, indicating that the crystal structure of HAP has changed. The detection method of the comparative example is not suitable for detecting HAP in toothpaste and is prone to errors. The inventor further analyzed the reasons for the above phenomenon. It may be that in the citric acid-sodium citrate buffer solution with a pH of 5.0, due to the large polarity of citrate ions, they adsorb and bond with HAP, resulting in the 960 cm -1 The characteristic peaks are shifted.

[0065] Comparative Example 4

[0066] Weigh 5 g of commercially available sample 5 (toothpaste containing HAP with a matrix of calcium carbonate and calcium hydrogen phosphate) for high-temperature calcination pretreatment. The heating rate is 10 °C / min, and the temperature is controlled at 750 °C for 2 h to obtain a calcined sample, which is then ground. The ground powder is dispersed in a 0.5 M disodium hydrogen phosphate-citric acid buffer solution with a pH of 5.5 at a mass ratio of 1:20 (the sum of the concentrations of disodium hydrogen phosphate and citric acid is 0.5 M, prepared using disodium hydrogen phosphate solution and citric acid solution; it can also be obtained through commercial means), and stirred at 25 °C for 48 h. After separating the powder, it is washed thoroughly with water and dried; Raman spectroscopy is performed on the dried sample and the standard HAP sample, and the characteristic peaks of HAP cannot be observed (see attached Figure 3 ). The inventor analyzed that the reason may be that in the disodium hydrogen phosphate-citric acid buffer, both hydrogen phosphate and citrate ions are present in the solution, preventing the dissolution of calcium hydrogen phosphate. The peak of calcium hydrogen phosphate completely masks the peak of HAP, and the characteristic peaks of HAP cannot be observed. Moreover, slightly increasing (pH 5.8) or decreasing (pH 4.8, etc.) the pH of the disodium hydrogen phosphate-citric acid buffer solution cannot solve the problem of not being able to observe the characteristic peaks of HAP, and the interference of calcium hydrogen phosphate and calcium carbonate cannot be excluded.

[0067] Comparative Example 5

[0068] In this comparative example, 5 g of commercially available sample 5 (toothpaste containing HAP with a matrix of calcium carbonate and calcium hydrogen phosphate) is dispersed in a 0.5 M acetic acid-sodium acetate buffer solution with a pH of 5.5 at a mass ratio of 1:10, and stirred at 25 °C for 48 h. After separating the powder, it is washed thoroughly with water and dried; Raman spectroscopy is performed on the dried sample and the standard HAP sample. The powdery substance separated after the above operations is very small, and no significant and sharp 960 cm -1 Characteristic peak can be observed. This shows that without calcination, while a large amount of calcium carbonate and calcium hydrogen phosphate dissolve in the acetic acid-sodium acetate buffer solution, HAP also dissolves partially, so the separated powdery substance is less. And the crystal structure of the separated powdery substance is damaged to a certain extent due to the action of acid, and at 960 cm-1 In addition, since HAP has not been calcined, its stability is poor, resulting in its structure being destroyed during the stirring process, so the 960cm -1 The characteristic peak is difficult to be observed, or even if it is barely visible, it is 960cm -1 The characteristic peak becomes wider and shifts, which is similar to the 960cm peak of the HAP standard. -1 The characteristic peaks show great differences.

[0069] Therefore, calcination at 700-800°C has three effects: enhancing the stability of HAP in weak acid environments; making the solubility of HAP different from that of calcium carbonate and calcium hydrogen phosphate in weak acid environments, and removing calcium carbonate and calcium hydrogen phosphate; and removing organic impurities in toothpaste.

[0070] Comparative Example 6

[0071] This comparative example is basically the same as Example 5, except that the calcination temperature is 600°C or 900°C. Under these two temperature conditions, after stirring with the buffer solution, the powdery substance separated is less than that in Example 5, and under the Raman spectrum, 960cm -1 The intensity of the characteristic peak is worse than that of Example 5, the peak height is lower than that of Example 5, the peak width is wider than that of Example 5, and the characteristic peak is shifted to a certain extent. This indicates that the calcination temperature is not within the range of 700-800°C, the stability of HAP is not ideal, and it will dissolve and undergo structural changes during the acidic buffer treatment process, which is not conducive to the accurate detection of HAP in toothpaste.

[0072] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions and / or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several modifications and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for detecting the active ingredient of hydroxyapatite in toothpaste, characterized in that: It includes the following steps carried out in sequence: S1: Calcinate the sample to be tested, and then obtain sample powder after pulverization treatment; the conditions for the calcination treatment are: heat up to 700 - 800 °C at a heating rate of 2 - 10 °C / min, and then keep the temperature for 1 - 2 h; S2: Disperse the sample powder into a buffer solution, and then obtain a dried sample after stirring treatment, washing and drying; the buffer solution is an acetic acid - sodium acetate buffer solution; the concentration of the acetic acid - sodium acetate buffer solution is 0.2 - 0.5 M and the pH is 4.8 - 5.8; S3: Obtain the Raman spectrum of the dried sample: Observe whether a characteristic peak corresponding to the standard hydroxyapatite sample appears in the Raman spectrum of the dried sample at 950 - 970 cm -1 -1.

2. The method for detecting the active ingredient of hydroxyapatite in toothpaste according to claim 1, characterized in that: In S1, the sample powder passes through a 200 - mesh sieve.

3. The method for detecting the active ingredient of hydroxyapatite in toothpaste according to claim 1, characterized in that, In S2, the mass ratio of the sample powder to the buffer solution is 1:(5 - 20).

4. The method for detecting the active ingredient of hydroxyapatite in toothpaste according to claim 1, characterized in that In S2, the way of the stirring treatment is: stir at a rotation speed of 200 - 400 rpm for 24 - 60 h under the condition of 25 - 37 °C.

5. The method for detecting the active ingredient of hydroxyapatite in toothpaste according to claim 1, characterized in that, In S3, the friction matrix of the toothpaste includes at least one of calcium carbonate, dicalcium phosphate, hydrated silica and aluminum hydroxide.

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