Method for measuring zinc content in calcium zinc gluconate preparation

Abstract

The invention relates to the technical field of pharmaceutical analysis, and discloses a method for determining the zinc content in a calcium zinc gluconate preparation. The determination method comprises the following steps: reacting a calcium zinc gluconate preparation with a complexing agent to obtain a zinc ion-complex; determining the absorbance of the zinc ion-complex by using an ultraviolet-visible spectrophotometric method; and calculating the zinc content based on the standard curve. According to the determination method provided by the invention, the complexation reaction and the ultraviolet spectrophotometry are combined, the zinc content in the calcium zinc gluconate preparation is calculated by the standard curve, the result accuracy is high, and the defect that the determination result is inaccurate due to the reason that an end point is subjectively judged by virtue of color and the like in an EDTA titration method is overcome; the complexing agent [o-[2-(2-hydroxy-5-sulfo-phenylazo) benzal] hydrazinobenzoic acid and xylenol orange are only complexed with zinc ions under a specific pH condition, so that the specificity is high, and the interference of other raw and auxiliary materials in the calcium zinc gluconate preparation can be avoided.

Description

Technical Field

[0001] This invention relates to the field of pharmaceutical analysis technology, and in particular to a method for determining the zinc content in calcium gluconate zinc preparations. Background Technology

[0002] Calcium gluconate and zinc gluconate preparations are compound preparations composed of calcium gluconate, zinc gluconate, and other potentially active ingredients. Currently, they are mainly available in oral solutions, granules, and effervescent tablets. Calcium gluconate participates in bone formation and bone tissue reconstruction after fractures, as well as in processes such as muscle contraction, nerve transmission, and coagulation inhibition, and can reduce capillary permeability. Zinc gluconate, as an important component of many enzymes in the body, promotes growth and development and improves taste.

[0003] Regarding the determination methods for the content of calcium gluconate and zinc gluconate in calcium gluconate and zinc gluconate preparations, the current pharmacopoeia reference standards and the standards declared by marketed manufacturers all adopt the EDTA titration method. That is, the content of calcium gluconate is determined by titrating with a specific concentration of disodium ethylenediaminetetraacetate titrant (EDTA-2Na) and calciferol indicator, and the content of zinc gluconate is determined by titrating with a specific concentration of disodium ethylenediaminetetraacetate titrant and xylenol orange indicator.

[0004] In principle, the determination of calcium gluconate content is carried out in an alkaline solution, using calcein as an indicator, and titrating the Ca in the test solution with 0.05 mol / L EDTA-2Na titrant. 2+ The endpoint is when the solution changes from purplish-red to pure blue, but under these conditions, Zn... 2+ It also reacts with EDTA-2Na, so the actual Ca 2+ and Zn 2+ Both methods consume EDTA-2Na (volume V1); the determination of zinc gluconate content is carried out under pH=6 conditions, using xylenol orange as an indicator, and titrating the Zn in the test solution with 0.05mol / L EDTA-2Na titrant. 2+ The endpoint was determined by the change in solution color from red to yellow, and Zn was calculated based on the amount of EDTA-2Na consumed. 2+ The content of calcium gluconate and zinc gluconate can be determined by titration. The content of zinc gluconate is calculated from V2, and the content of calcium gluconate is calculated from V1-V2.

[0005] However, in actual experiments, it was found that during the titration of zinc gluconate, the change of xylenol orange indicator from red to yellow was not obvious, but rather a gradual change rather than an abrupt one. This made it impossible to clearly determine the titration endpoint, leading to inaccurate zinc content determination. Furthermore, inaccurate zinc content determination further resulted in inaccurate calcium content calculation. Therefore, how to accurately determine the calcium content in calcium gluconate preparations is crucial. 2+ and Zn 2+ In the case of coexistence, determining the content of zinc gluconate accurately and conveniently without interference becomes a challenge.

[0006] Existing techniques have attempted to optimize the EDTA titration method, but adjusting buffer pH, calcium-zinc concentration ratio, indicator dosage, and titrant concentration has not yielded significant improvements in the measurement results. Replacing the indicator with Eriochrome Black T has limitations; since Eriochrome Black T is used in measurements at pH 10, while calcein requires pH values ​​above 12, the results are similar. Therefore, when using Eriochrome Black T to measure zinc ions, the effect of calcium ions can be felt. Adding acetylacetone or ascorbic acid + tartaric acid masking agents to mask calcium ions and other potential interfering ions has revealed that these masking agents also have a masking effect on zinc ions, significantly reducing the measured zinc ion content. Therefore, the EDTA titration method has many drawbacks and is difficult to optimize.

[0007] Existing methods for determining cation content mainly include atomic absorption spectrometry, cation chromatography, and ICP-MS. However, these methods all involve the use of expensive and sophisticated instruments. Furthermore, cation chromatography involves the development of complex separation and analysis methods, while ICP-MS is more suitable for the determination of trace elements and is often used in the compatibility studies of oral solution packaging materials to determine multiple trace impurity elements. When used to determine the content of main components, it is costly and requires a highly accurate dilution pretreatment process. Summary of the Invention

[0008] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. Therefore, the object of the present invention is to provide a method for determining the zinc content in calcium gluconate zinc preparations.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] This invention provides a method for determining the zinc content in calcium gluconate zinc preparations, comprising the following steps:

[0011] The calcium gluconate zinc preparation is reacted with a complexing agent to obtain a zinc ion-complex;

[0012] The absorbance of the zinc ion-complex was determined using ultraviolet-visible spectrophotometry.

[0013] Zinc content was calculated based on the standard curve.

[0014] In some embodiments of the present invention, the calcium gluconate zinc preparation is selected from oral solutions, granules or effervescent tablets.

[0015] In some embodiments of the present invention, the complexing agent is selected from [o-[2-(2-hydroxy-5-sulfophenylazo)benzylene]hydrazinobenzoic acid or xylenol orange.

[0016] In some embodiments of the present invention, when the complexing agent is [o-[2-(2-hydroxy-5-sulfophenylazo)benzyl]hydrazidobenzoic acid, the pH of the reaction is 8.5-9.25.

[0017] In some preferred embodiments of the present invention, when the complexing agent is [o-[2-(2-hydroxy-5-sulfophenylazo)benzyl]hydrazidobenzoic acid, the pH of the reaction is 8.75-9.25.

[0018] In some embodiments of the present invention, when the complexing agent is [o-[2-(2-hydroxy-5-sulfophenylazo)benzyl]hydrazidobenzoic acid, the ionic strength of the zinc ions is 0.02-1 mol / L.

[0019] In some embodiments of the present invention, when the complexing agent is xylenol orange, the pH of the reaction is 5.5-6.5.

[0020] In some preferred embodiments of the present invention, when the complexing agent is xylenol orange, the pH of the reaction is 5.7-6.2.

[0021] In some embodiments of the present invention, when the complexing agent is xylenol orange, the ionic strength of the zinc ions is ≤0.02 mol / L.

[0022] In some embodiments of the present invention, when the complexing agent is [o-[2-(2-hydroxy-5-sulfophenylazo)benzyl]hydrazinobenzoic acid, the wavelength of the measurement is 610-630 nm.

[0023] In some preferred embodiments of the present invention, when the complexing agent is [o-[2-(2-hydroxy-5-sulfophenylazo)benzyl]hydrazidobenzoic acid, the wavelength of the measurement is 615-625 nm.

[0024] In some embodiments of the present invention, when the complexing agent is xylenol orange, the wavelength of the measurement is 555-575 nm.

[0025] In some preferred embodiments of the present invention, when the complexing agent is xylenol orange, the wavelength of the measurement is 560-570 nm.

[0026] In some embodiments of the present invention, the determination method specifically includes the following steps:

[0027] Take the buffer solution, add the complexing agent, and obtain a blank solution;

[0028] Zinc gluconate was dissolved in water, and different volumes were added to an equal amount of blank solution to obtain a series of gradient concentration standard curve solutions.

[0029] Dissolve the calcium gluconate zinc preparation in water, add blank solution, and obtain the test solution;

[0030] Take blank solution, standard curve solution and test solution, and determine the absorbance using ultraviolet-visible spectrophotometry. Calculate the zinc content in the test solution using the standard curve.

[0031] In some embodiments of the present invention, when the complexing agent is [o-[2-(2-hydroxy-5-sulfophenylazo)benzyl]hydrazidobenzoic acid, the concentration of the complexing agent is 0.2-2.6 μg / mL.

[0032] In some embodiments of the present invention, when the complexing agent is [o-[2-(2-hydroxy-5-sulfophenylazo)benzylene]hydrazinobenzoic acid, the buffer solution comprises borate-potassium chloride buffer (pH = 9.0).

[0033] In some embodiments of the present invention, when the complexing agent is xylenol orange, the concentration of the complexing agent is 0.2-4.0 μg / mL.

[0034] In some embodiments of the present invention, when the complexing agent is xylenol orange, the buffer solution comprises an acetate-sodium acetate buffer solution (pH = 6.0).

[0035] The basic principles of this invention are explained as follows:

[0036] Zinc ions (Zn) 2+ Under specific pH conditions, it can form stable colored complexes with [o-[2-(2-hydroxy-5-sulfophenylazo)benzyl]hydrazinobenzoic acid or xylenol orange. These complexes exhibit characteristic absorption peaks in the UV-Vis region, and their absorbance is directly proportional to the zinc ion concentration, thus allowing for quantitative analysis. Specifically:

[0037] [o-[2-(2-hydroxy-5-sulfophenylazo)benzylidene]hydrazinobenzoic acid reacts only with Zn in a borate-potassium chloride buffer solution at pH 9.0. 2+ Xylenol orange forms a complex with a characteristic absorption wavelength of 610-630 nm; in an acetate-sodium acetate buffer solution at pH 6.0, it reacts only with Zn. 2+A complex is formed, with a characteristic absorption wavelength of 555-575 nm. By preparing zinc standard solutions of different concentrations, the absorbance is measured, and a standard curve is plotted by linear regression of absorbance against solution concentration. The absorbance of the complex at the characteristic wavelength is then measured and substituted into the standard curve to calculate the zinc content in the sample. Using spectrophotometry, the absorbance of the complex can be directly measured, thus avoiding errors caused by subjective judgment of the endpoint in the color-changing reaction. Furthermore, because both complexing agents react only with Zn at a specific pH, this method is more efficient. 2+ Complexation, not affected by Ca 2+ Interference is eliminated, therefore no masking agent is needed.

[0038] Compared with the prior art, the beneficial effects of the present invention are:

[0039] 1) The method for determining the zinc content in calcium gluconate zinc preparations provided by the present invention combines complexation reaction with ultraviolet-visible spectrophotometry and calculates the zinc content in calcium gluconate zinc preparations using a standard curve. The results are highly accurate and overcome the defects of inaccurate determination results caused by subjective judgment of the endpoint by color in EDTA titration method.

[0040] 2) The complexing agents used in this invention, [o-[2-(2-hydroxy-5-sulfophenylazo)benzyl]hydrazinobenzoic acid and xylenol orange, complex only with zinc ions under specific pH conditions, exhibiting high specificity. This avoids interference from other raw materials and excipients in calcium gluconate zinc preparations. No masking agent is needed to shield calcium ions in calcium gluconate zinc preparations or other impurities that may be introduced during production, thus avoiding the problem of low zinc content that may be caused by masking agents. The method is simple, convenient, and highly accurate.

[0041] 3) The method for determining the zinc content in calcium gluconate preparations provided by this invention uses only a UV-Vis spectrophotometer, overcoming the shortcomings of traditional methods such as high instrument costs and difficulty in developing analytical methods. The linear range of the determination method covers the concentration of actual products such as calcium gluconate oral solutions, and is suitable for determining the zinc content in conventional preparations without excessive dilution or concentration. Moreover, the zinc ion-complex has good stability. In practical applications, batch sample determination can be completed over a wide time range without worrying about the results decaying over time, making it highly practical. Attached Figure Description

[0042] Figure 1 The UV-Vis absorption spectrum of the blank excipient in Example 1 is in the range of 500-800 nm.

[0043] Figure 2 The linear regression curve for zinc gluconate in Example 2;

[0044] Figure 3The UV-Vis absorption spectra of the blank solution, blank excipient, and reference solution in Example 5 are in the range of 400-800 nm.

[0045] Figure 4 The linear regression curve for zinc gluconate in Example 6 is shown. Detailed Implementation

[0046] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments can be obtained from conventional commercial sources or by existing technical methods. Unless otherwise specified, the experimental or testing methods are conventional methods in the art.

[0047] Example 1

[0048] This embodiment verifies the specificity of the method for determining the zinc content in calcium gluconate zinc preparations using [o-[2-(2-hydroxy-5-sulfophenylazo)benzyl]hydrazinobenzoic acid as a complexing agent. The steps are as follows:

[0049] Take 3.09 g of boric acid, add 500 mL of 0.1 mol / L potassium chloride solution to dissolve it, then add 210 mL of 0.1 mol / L sodium hydroxide solution to obtain a boric acid-potassium chloride buffer solution with pH = 9.0; take 0.13 g of [o-[2-(2-hydroxy-5-sulfonylphenylazo)benzylidene]hydrazinobenzoic acid, add 2 mL of 1 mol / L sodium hydroxide solution, and add water to make up to 100 mL to obtain an [o-[2-(2-hydroxy-5-sulfonylphenylazo)benzylidene]hydrazinobenzoic acid solution;

[0050] Take 10 mL of borate-potassium chloride buffer solution with pH = 9.0 and place it in a 100 mL volumetric flask. Add 3 mL of [o-[2-(2-hydroxy-5-sulfophenylazo)benzylene]hydrazinobenzoic acid solution, mix well, dilute with water to 100 mL, and shake well to obtain a blank solution.

[0051] Take 3 mL of blank excipient (without zinc gluconate, but containing calcium gluconate and other excipients) and place it in a 100 mL volumetric flask. Dilute with water to 100 mL and shake well. Take 5 mL of the blank excipient and place it in a 50 mL volumetric flask. Add 10 mL of borate-potassium chloride buffer solution with pH 9.0, and then add 3 mL of [o-[2-(2-hydroxy-5-sulfophenylazo)benzylidene]hydrazinobenzoic acid solution. Mix well, dilute with water to 50 mL, and shake well to obtain the blank excipient solution.

[0052] The absorption spectra of the blank solution and the blank excipient solution were scanned in the range of 500-800 nm, and the background of the blank solution was subtracted.

[0053] Figure 1The UV-Vis absorption spectrum of the blank excipient in Example 1 in the 500-800 nm range is given by [the relevant data]. Figure 1 It can be seen that the blank excipient without zinc gluconate has no significant absorption peak at 620 nm, indicating that the calcium ions (Ca) in the excipient are present. 2+ Other components do not interfere with the determination of zinc, which also indicates that the method provided by this invention for determining the zinc content in calcium gluconate zinc preparations using [o-[2-(2-hydroxy-5-sulfophenylazo)benzyl]hydrazinobenzoic acid as a complexing agent is highly specific, and the signal comes only from Zn. 2+ A complex with [o-[2-(2-hydroxy-5-sulfophenylazo)benzylidene]hydrazinobenzoic acid].

[0054] Example 2

[0055] This embodiment verifies the linear range of the method for determining the zinc content in calcium gluconate zinc preparations using [o-[2-(2-hydroxy-5-sulfophenylazo)benzylene]hydrazinobenzoic acid as a complexing agent. The steps are as follows:

[0056] Take 11 mg of zinc gluconate raw material dried to constant weight at 105℃, place it in a 50 mL volumetric flask, add water to dissolve it, and make up to 50 mL. Shake well to obtain zinc gluconate stock solution.

[0057] Take 1 mL, 1.5 mL, 2 mL, 2.5 mL and 3 mL of zinc gluconate stock solution respectively and place them in 50 mL volumetric flasks. Add 10 mL of borate-potassium chloride buffer solution with pH=9.0 and 3 mL of [o-[2-(2-hydroxy-5-sulfophenylazo)benzyl]hydrazinobenzoic acid solution (prepared in the same way as in Example 1, freshly prepared and used immediately), mix well, dilute each with water to 50 mL, shake well, and obtain linear solutions L1, L2, L3, L4 and L5;

[0058] The absorption spectra of blank solution (prepared in the same way as in Example 1) and linear solutions L1-L5 were scanned in the range of 500-800 nm. The background of the blank solution was subtracted, and the absorbance of each linear solution at a wavelength of 620 nm was selected. The absorbance was used to perform linear regression on the solution concentration. The results are shown in Table 1.

[0059] Table 1 shows the linear range of zinc gluconate in Example 2. As can be seen from Table 1, the method for determining the zinc content in the calcium zinc gluconate preparation provided by the present invention, when using [o-[2-(2-hydroxy-5-sulfophenylazo)benzyl]hydrazidobenzoic acid as a complexing agent, shows good linearity in the concentration of zinc gluconate within the range of 0.0046-0.0137 mg / mL, and the absorbance steadily increases with increasing concentration (0.209→0.683) without abnormal fluctuations, indicating that the complex has good stability.

[0060] Table 1. Linear range of zinc gluconate in Example 2

[0061]

[0062] Figure 2 The linear regression curve for zinc gluconate in Example 2 is obtained from... Figure 2 It can be seen that the zinc concentration and absorbance satisfy a linear regression equation: y = 51.9318x - 0.0274, R0 2 =1.0000, slope is 51.9318. The larger the slope, the more significant the change in absorbance caused by a unit change in concentration, reflecting high sensitivity of the method. The intercept is -0.0274, close to zero, indicating that the blank solution (without Zn) is suitable. 2+ Background interference is minimal, R 2 =1.0000, indicating a perfect linear relationship between concentration and absorbance, with extremely high data fit and reliable quantitative results.

[0063] Example 3

[0064] This embodiment verifies the repeatability and accuracy of the method for determining the zinc content in calcium gluconate zinc preparations using [o-[2-(2-hydroxy-5-sulfophenylazo)benzylene]hydrazinobenzoic acid as a complexing agent. The steps are as follows:

[0065] Take 3 mL of calcium gluconate zinc oral solution (commercially available Aono oral solution, batch number: 2306517-H168) and place it in a 100 mL volumetric flask. Add water to make up to 100 mL and shake well. Take 5 mL and place it in a 50 mL volumetric flask. Add 10 mL of borate-potassium chloride buffer solution with pH = 9.0 and 3 mL of [o-[2-(2-hydroxy-5-sulfophenylazo)benzylene]hydrazinobenzoic acid solution (prepared in the same way as in Example 1, freshly prepared and used immediately). Mix well and add water to make up to 50 mL. Shake well. Prepare 6 parallel aliquots. Measure the absorbance at 620 nm using a UV-Vis spectrophotometer and calculate the zinc gluconate content in the calcium gluconate zinc oral solution using the standard curve in Example 2.

[0066] Table 2. Results of zinc content determination in calcium gluconate zinc oral solution in Example 3

[0067]

[0068]

[0069] Table 2 shows the determination results of zinc content in the calcium zinc gluconate oral solution of Example 3. As shown in Table 2, the average zinc content in the six parallel samples was 100.18%, with a relative standard deviation of 0.3%, far less than the ≤2% requirement of the pharmacopoeia. This indicates that the method provided by this invention is simple to operate, yields stable results, and is suitable for routine testing. Compared with atomic absorption spectrometry, the relative deviation between the average content (100.18%) measured by the method provided by this invention and the atomic absorption spectrometry result (100.86%) is only 0.7%, proving that this method has high consistency with authoritative methods, i.e., high accuracy. Furthermore, the absorbance (0.407-0.410) matches the linear range (0.0046-0.0137 mg / mL) of the standard curve in Table 1, indicating that the linear range covers the actual sample concentration. This means that this method is suitable for the determination of zinc content in routine preparations without excessive dilution or concentration.

[0070] Example 4

[0071] This embodiment verifies the solution stability of the method for determining the zinc content in calcium gluconate zinc preparations using [o-[2-(2-hydroxy-5-sulfophenylazo)benzylene]hydrazinobenzoic acid as a complexing agent. The steps are as follows:

[0072] The test sample solution was the same as in Example 3. After the solution was placed at room temperature for 15, 30 and 60 min, the absorbance at 620 nm was measured respectively, and the content of zinc gluconate in the calcium zinc gluconate oral solution was calculated using the standard curve in Example 2.

[0073] Table 3. Results of solution stability test for calcium gluconate and zinc oral solution in Example 4.

[0074]

[0075] Table 3 shows the solution stability test results of the calcium zinc gluconate oral solution in Example 4. As can be seen from Table 3, the zinc content measurement results fluctuated very little within 0-60 min (99.87%→100.33%), with a relative standard deviation of 0.3%, indicating that the complex is stable at room temperature for at least 1 hour. After 15 min, the absorbance increased slightly (0.407→0.408), which may be due to the complete equilibrium of the colorimetric reaction, but there was no further change at subsequent time points, indicating that the system is stable. In practical applications, it is permissible for experimenters to complete the determination of batch samples within 60 min without worrying about the results decaying over time.

[0076] Example 5

[0077] This embodiment verifies the specificity of the method for determining the zinc content in calcium gluconate zinc preparations using xylenol orange as a complexing agent. The steps are as follows:

[0078] Take 54.6g of sodium acetate (crystalline sodium acetate), add 20mL of 1mol / L acetic acid solution to dissolve it, and dilute with water to 500mL to obtain an acetate-sodium acetate buffer solution with pH=6.0; take 0.3g of xylenol orange, add 100mL of water to dissolve it to obtain xylenol orange colorimetric solution;

[0079] Take 2 mL of pH 6.0 acetate-sodium acetate buffer solution and place it in a 25 mL volumetric flask. Add 1 mL of xylenol orange colorimetric solution, mix well, add water to make up to 25 mL, shake well, and let stand for 10 min to obtain a blank solution.

[0080] Take 1 mL of blank excipient (without zinc gluconate, but containing calcium gluconate and other excipients) and place it in a 50 mL volumetric flask. Dilute with water to 50 mL and shake well. Take 2 mL of the blank excipient and place it in a 25 mL volumetric flask. Add 2 mL of acetate-sodium acetate buffer solution with pH 6.0 and 1 mL of xylenol orange colorimetric solution. Mix well, dilute with water to 25 mL, shake well, and let stand for 10 min to obtain the blank excipient solution.

[0081] Take 14 mg of zinc gluconate raw material dried to constant weight at 105℃, place it in a 100 mL volumetric flask, add water to dissolve it, and make up to 100 mL. Shake well, take 1 mL and place it in a 25 mL volumetric flask, add 2 mL of acetate-sodium acetate buffer solution with pH=6.0, then add 1 mL of xylenol orange colorimetric solution, mix well, dilute with water to 25 mL, shake well, and let stand for 10 min to obtain the reference solution.

[0082] The absorption spectra of blank solution, blank excipient solution and reference solution were scanned in the range of 400-800 nm, with background subtraction using acetate-sodium acetate buffer solution at pH 6.0.

[0083] Figure 3 The UV-Vis absorption spectra of the blank solution, blank excipient, and reference solution in Example 5 are shown below, in the range of 400-800 nm. Figure 3 The absorption curves of the blank solution and the blank excipient coincide at 578.0 nm, indicating that the excipient does not interfere and the method has good specificity. The reference solution has a significant absorbance at 574.5 nm (slightly deviating from the literature reference value of 566.5 nm), but this still proves that the signal originates from Zn. 2+ -Xylenol orange complex.

[0084] Example 6

[0085] This embodiment verifies the linear range of the method for determining the zinc content in calcium gluconate zinc preparations using xylenol orange as a complexing agent. The steps are as follows:

[0086] Take 14 mg of zinc gluconate raw material dried to constant weight at 105℃, place it in a 100 mL volumetric flask, add water to dissolve it, and make up to 100 mL. Shake well to obtain zinc gluconate stock solution.

[0087] Take 1 mL, 1.5 mL, 2 mL, 2.5 mL and 3 mL of zinc gluconate stock solution respectively and place them in 25 mL volumetric flasks. Add 2 mL of acetate-sodium acetate buffer solution with pH=6.0 and 1 mL of xylenol orange colorimetric solution (prepared in the same way as in Example 5, and used immediately). Mix well, dilute each solution with water to 25 mL, and shake well to obtain linear solutions L1, L2, L3, L4 and L5.

[0088] The absorption spectra of the blank solution (prepared in the same way as in Example 5) and linear solutions L1-L5 were scanned in the range of 400-800 nm. The background of the blank solution was subtracted, and the absorbance of each linear solution at a wavelength of 566.5 nm was intercepted. The absorbance was used to perform linear regression on the solution concentration. The results are shown in Table 4.

[0089] Table 4 shows the linear range of zinc gluconate in Example 6. As can be seen from Table 4, the method for determining the zinc content in the calcium zinc gluconate preparation provided by the present invention, when xylenol orange is used as the complexing agent, shows that the absorbance of zinc gluconate in the range of 0.0052-0.0155 mg / mL steadily increases with the increase of concentration (0.240→0.762) without abnormal fluctuations, and the method has good linearity.

[0090] Table 4. Linear range of zinc gluconate in Example 6

[0091]

[0092] Figure 4 The linear regression curve for zinc gluconate in Example 6 is shown below. Figure 4 It can be seen that the zinc concentration and absorbance satisfy a linear regression equation: y = 50.2533x - 0.0156, R0 2 =0.9996, indicating excellent linearity.

[0093] Example 7

[0094] This embodiment verifies the repeatability and accuracy of the method for determining the zinc content in calcium gluconate zinc preparations using xylenol orange as a complexing agent. The steps are as follows:

[0095] Take 1 mL of calcium gluconate zinc oral solution (commercially available Aono oral solution, batch number: 2306517-H168) and place it in a 50 mL volumetric flask. Add water to make up to 50 mL and shake well. Take 2 mL and place it in a 25 mL volumetric flask. Add 2 mL of acetate-sodium acetate buffer solution (pH=6.0) and 1 mL of xylenol orange colorimetric solution (prepared in the same way as in Example 5, freshly prepared and used immediately). Mix well, add water to make up to 25 mL, shake well, and let stand for 10 min. Prepare 6 parallel aliquots. Measure the absorbance at 566.5 nm using a UV-Vis spectrophotometer and calculate the zinc gluconate content in the calcium gluconate zinc oral solution using the standard curve in Example 6.

[0096] Table 5. Results of zinc content determination in calcium gluconate zinc oral solution (Example 7)

[0097]

[0098] Table 5 shows the determination results of zinc content in calcium zinc gluconate oral solution in Example 7. As shown in Table 5, the average zinc content in the six parallel samples was 102.66%, with a relative standard deviation of 0.3%, far less than the ≤2% requirement of the pharmacopoeia. This indicates that the method provided by this invention is simple to operate, yields stable results, and is suitable for routine testing. Compared with atomic absorption spectrometry, the relative deviation between the average content (102.66%) measured by the method provided by this invention and the atomic absorption spectrometry result (100.86%) is only 1.8%, proving that this method has high consistency with authoritative methods, i.e., high accuracy. Furthermore, the absorbance (0.479-0.481) matches the linear range (0.0052-0.0155 mg / mL) of the standard curve in Table 4, indicating that the linear range covers the actual sample concentration. This means that this method is suitable for determining zinc content in routine preparations without excessive dilution or concentration.

[0099] Example 8

[0100] This embodiment verifies the solution stability of the method for determining the zinc content in calcium gluconate zinc preparations using xylenol orange as a complexing agent. The steps are as follows:

[0101] The test sample solution was the same as in Example 7. After the solution was placed at room temperature for 15, 30 and 45 min, the absorbance at 566.5 nm was measured, and the content of zinc gluconate in the calcium zinc gluconate oral solution was calculated using the standard curve in Example 6.

[0102] Table 6. Solution stability test results of calcium gluconate and zinc oral solution in Example 8.

[0103]

[0104] Table 6 shows the solution stability test results of calcium zinc gluconate oral solution in Example 8. As can be seen from Table 6, within 0-45 min, the zinc content decreased slightly from 102.94% to 102.52%, with a relative standard deviation of 0.3%, indicating that the xylenol orange-zinc complex has good stability within 45 min. After 30 min, the absorbance decreased slightly (0.481→0.478), which may be due to slight decomposition of the complex or evaporation of the solution, but the change was very small (<1%), which is still within the acceptable range. Compared with the solution using [o-[2-(2-hydroxy-5-sulfophenylazo)benzyl]hydrazidobenzoic acid, the solution stability is slightly weaker, making it more suitable for the determination of trace zinc ions.

Claims

1. A method for determining the zinc content in a calcium gluconate zinc preparation, characterized in that, Includes the following steps: The calcium gluconate zinc preparation is reacted with a complexing agent to obtain a zinc ion-complex; The absorbance of the zinc ion-complex was determined using ultraviolet-visible spectrophotometry. Zinc content was calculated based on the standard curve.

2. The determination method according to claim 1, characterized in that, The calcium gluconate zinc preparation is selected from oral solutions, granules, or effervescent tablets.

3. The determination method according to claim 1, characterized in that, The complexing agent is selected from [o-[2-(2-hydroxy-5-sulfophenylazo)benzyl]hydrazinobenzoic acid or xylenol orange.

4. The determination method according to claim 3, characterized in that, When the complexing agent is [o-[2-(2-hydroxy-5-sulfophenylazo)benzyl]hydrazinobenzoic acid, the pH of the reaction is 8.5-9.

25.

5. The determination method according to claim 3, characterized in that, When the complexing agent is xylenol orange, the pH of the reaction is 5.5-6.

5.

6. The determination method according to claim 3, characterized in that, When the complexing agent is [o-[2-(2-hydroxy-5-sulfophenylazo)benzyl]hydrazinobenzoic acid, the wavelength of the measurement is 610-630 nm.

7. The determination method according to claim 3, characterized in that, When the complexing agent is xylenol orange, the wavelength of the measurement is 555-575 nm.

8. The determination method according to any one of claims 3-7, characterized in that, The specific determination method is as follows. Includes the following steps: Take the buffer solution, add the complexing agent, and obtain a blank solution; Zinc gluconate was dissolved in water, and different volumes were added to an equal amount of blank solution to obtain a series of gradient concentration standard curve solutions. Dissolve the calcium gluconate zinc preparation in water, add blank solution, and obtain the test solution; Take blank solution, standard curve solution and test solution, and determine the absorbance using ultraviolet-visible spectrophotometry. Calculate the zinc content in the test solution using the standard curve.

9. The determination method according to claim 8, characterized in that, When the complexing agent is [o-[2-(2-hydroxy-5-sulfophenylazo)benzyl]hydrazinobenzoic acid, the concentration of the complexing agent is 0.2-2.6 μg / mL; And / or, the buffer solution includes borate-potassium chloride buffer solution.

10. The determination method according to claim 8, characterized in that, When the complexing agent is xylenol orange, the concentration of the complexing agent is 0.2-4.0 μg / mL; And / or, the buffer solution includes an acetate-sodium acetate buffer solution.

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