Method for determining chloride ion concentration in gelatin and / or collagen

Abstract

The invention relates to the technical field of analysis and detection, and discloses a method for determining the concentration of chloride ions in gelatin and / or collagen. The method comprises the following steps: mixing a PVP alcoholic solution, a to-be-detected sample and an HNO3 aqueous solution with the pH value of 2-3 to obtain a to-be-detected solution, mixing the to-be-detected solution with a chloride ion releasing agent, a silver ion-containing substance and a solvent to obtain a mixed solution, and determining the chloride ion concentration in the mixed solution by using an ultraviolet-visible spectrophotometer, determining the chloride ion concentration in the to-be-detected sample according to the chloride ion concentration in the mixed solution; the sample to be detected is gelatin and / or collagen. The method can realize rapid, accurate and high-reproducibility analysis of the chloride ion concentration in the gelatin and / or the collagen, so that the method is applied to effective and accurate monitoring of the chloride ion concentration in the gelatin and / or the collagen in an electrolysis process.

Description

Methods for determining chloride ion concentration in gelatin and / or collagen Technical Field

[0001] This invention relates to the field of analytical testing technology, and specifically to a method for determining the chloride ion concentration in gelatin and / or collagen. Background Technology

[0002] In electrolytic processes, gelatin and / or collagen are frequently used as additives in the electrodeposition solution. For the production of gelatin and collagen, regardless of the source of their natural raw materials or the production process, failure to strictly control the production process can easily lead to excessively high chloride ion content in the gelatin and collagen products. However, in some electrolytic processes, it is crucial to effectively control the chloride ion concentration in the electrodeposition solution, such as acidic copper plating solutions, electrolytic copper foil solutions, and solutions for electrolytic refining of copper. For example, the chloride ion concentration in electrolytic copper foil typically needs to be controlled below 50 μg / mL. Under such low-concentration process conditions, effectively controlling and analyzing the chloride ion concentration in gelatin and / or collagen is particularly important.

[0003] Although there are many methods for chloride ion analysis, such as ion chromatography, voltammetry, fluorescence analysis, and atomic absorption spectrometry, all of these methods require sample pretreatment, which undoubtedly increases the analysis time and reduces the sensitivity and accuracy of the analysis. Li Jiawei reported a method for directly dissolving lithium carbonate with HNO3 and hydrogen peroxide and directly determining chloride ions in lithium carbonate using AgCl turbidimetry (Hydrometallurgy, 2022, 41(02):176-180). Although this UV-Vis spectrophotometric method has a relatively fast analysis speed, it is obviously not suitable for gelatin and / or collagen that form strong complexes with silver ions. Summary of the Invention

[0004] The purpose of this invention is to overcome the problem in existing electrolysis processes of lacking a rapid and effective method for monitoring the chloride ion concentration in gelatin and / or collagen, which are used as additives in electrodeposition solutions. This invention provides a method for determining the chloride ion concentration in gelatin and / or collagen. This method shortens the analysis time, overcomes the influence of the complexation between the protein structure in gelatin and / or collagen and silver ions, eliminates the binding effect of the positive charge effect of gelatin and / or collagen on chloride ions, and improves the dispersibility and stability of AgCl in turbidity analysis. Therefore, this method can achieve rapid, accurate, and highly reproducible analysis of the chloride ion concentration in gelatin and / or collagen, and can be applied to the effective and precise monitoring of the chloride ion concentration in gelatin and / or collagen in electrolysis processes.

[0005] To achieve the above objectives, the present invention provides a method for determining the chloride ion concentration in gelatin and / or collagen, the method comprising: mixing an alcoholic solution of PVP, a sample to be tested, and an aqueous solution of HNO3 with a pH of 2-3 to obtain a test solution; mixing the test solution with a chloride ion releasing agent, a silver ion-containing substance, and a solvent to obtain a mixed solution; measuring the chloride ion concentration in the mixed solution using a UV-Vis spectrophotometer; and determining the chloride ion concentration in the sample to be tested based on the chloride ion concentration in the mixed solution; wherein the sample to be tested is gelatin and / or collagen.

[0006] Preferably, the chloride ion releasing agent and the silver ion-containing substance are AgNO3.

[0007] Preferably, the concentration of AgNO3 in the mixture is greater than 0.03 mol / L.

[0008] More preferably, the mixing II step includes: mixing a chloride ion releasing agent and a portion of the solvent to obtain a solution containing a chloride ion releasing agent; mixing a silver ion-containing substance and the remaining solvent to obtain a solution containing silver ions; and mixing the solution containing the chloride ion releasing agent, the solution containing silver ions, and the test solution.

[0009] Preferably, the solvent is an aqueous solution of HNO3.

[0010] Preferably, in the mixture, the content of PVP is 0.01-0.05 vt; and the content of alcohol is 10-50 vt.

[0011] Preferably, the alcohol in the alcohol solution of the PVP is selected from ethanol, ethylene glycol and propanol; more preferably, it is ethanol.

[0012] Preferably, the method further includes adding citric acid before mixing I.

[0013] More preferably, the concentration of citric acid in the test solution is 0.1-0.5 mg / mL.

[0014] Preferably, the step of determining the chloride ion concentration in the mixture using a UV-Vis spectrophotometer includes: obtaining a standard curve of chloride ion concentration and absorbance, measuring the absorbance in the mixture using a UV-Vis spectrophotometer, and determining the chloride ion solubility in the mixture based on the measured absorbance and the standard curve.

[0015] Preferably, the mixing time II is 3-5 minutes.

[0016] Preferably, when measured by a UV-Vis spectrophotometer, the linear range of chloride ion concentration in the sample to be tested is 1-10 μg / mL, and the limit of detection is 0.28 μg / mL.

[0017] The present invention provides a method for determining chloride ion concentration in gelatin and / or collagen using the above technical solution. This method employs a UV-Vis spectrophotometer in the presence of an alcoholic solution of PVP, an HNO3 aqueous solution at pH 2-3, a chloride ion releasing agent, and a silver-containing substance. This method shortens the analysis time, overcomes the influence of the complexation between the protein structure and silver ions in gelatin and / or collagen, eliminates the binding effect of the positive charge effect on chloride ions in gelatin and / or collagen, and improves the dispersibility and stability of AgCl in turbidity analysis. Under UV-Vis spectrophotometry, the linear range of chloride ion concentration in the gelatin and / or collagen is 1-10 μg / mL, and the limit of detection is 0.28 μg / mL. Furthermore, in this invention, the relative standard deviation (RSD) of parallel sample measurements is <3%. In long-term experiments, the rate of change (ΔA) of absorbance values ​​within 60 minutes is <1%. Therefore, this method can achieve rapid, accurate and highly reproducible analysis of chloride ion concentration in gelatin and / or collagen, and can be applied to the effective and precise monitoring of chloride ion concentration in gelatin and / or collagen in electrolytic processes. Attached Figure Description

[0018] Figure 1 shows the wavelength scan spectrum of the mixed solution of Example 1 under a UV-Vis spectrophotometer. The horizontal axis represents wavelength, and the vertical axis represents the absorbance (A) of the gelatin sample mixed solution containing different chloride ion standard solutions, where the chloride ion standard solutions have concentrations of 0 μg / mL, 5 μg / mL, 8 μg / mL, and 10 μg / mL. Figure 2 shows the standard working curve of Example 1 at a wavelength of 300 nm, where the chloride ion concentration C... Cl With - on the x-axis and absorbance value A on the y-axis, a linear regression equation of absorbance value on chloride ion concentration is obtained. The standard curve solution contained 0.0109 g of gelatin. Detailed Implementation

[0019] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0020] As previously stated, the present invention provides a method for determining the chloride ion concentration in gelatin and / or collagen, the method comprising: mixing an alcoholic solution of PVP, a sample to be tested, and an aqueous solution of HNO3 with a pH of 2-3 to obtain a test solution; mixing the test solution with a chloride ion releasing agent, a silver ion-containing substance, and a solvent to obtain a mixed solution; measuring the chloride ion concentration in the mixed solution using a UV-Vis spectrophotometer; and determining the chloride ion concentration in the sample to be tested based on the chloride ion concentration in the mixed solution; wherein the sample to be tested is gelatin and / or collagen.

[0021] This method uses a UV-spectrophotometer to determine the chloride ion concentration in gelatin and / or collagen under the influence of an alcoholic solution of PVP, an aqueous solution of HNO3 at pH 2-3, and a chloride ion releasing agent. This method shortens the analysis time, overcomes the influence of the protein structure in gelatin and / or collagen complexing with silver ions, eliminates the binding effect of the positive charge effect of gelatin and / or collagen on chloride ions, and improves the dispersibility and stability of AgCl in turbidity analysis. Therefore, this method enables rapid, accurate, and highly reproducible analysis of chloride ion concentration in gelatin and / or collagen, and can be applied to the effective and precise monitoring of chloride ion concentration in gelatin and / or collagen during electrolytic processes.

[0022] To achieve rapid, accurate, and highly reproducible analysis of chloride ion concentration in gelatin and / or collagen, preferably, the chloride ion releasing agent and the silver ion-containing substance are AgNO3. When the pH is adjusted to the isoelectric point of gelatin and / or collagen, because the gelatin and / or collagen molecules are positively charged as a whole, they can "bind" chloride ions through electrostatic interactions, hydrogen bonds, or coordination interactions, resulting in a lower detected concentration of "free chloride ions" than the actual total chloride ion concentration. In this case, AgNO3 not only serves as a reactant for generating silver chloride in this invention but also as a chloride ion releasing agent to break free from the binding effect of the positive charge in gelatin and / or collagen on chloride ions. When nitrate ions reach a certain ionic strength, they can effectively release the chloride ions bound by gelatin and / or collagen. Preferably, the concentration of AgNO3 in the mixture is greater than 0.03 mol / L. More preferably, the concentration of AgNO3 is greater than 0.03 mol / L and less than or equal to 0.035 mol / L.

[0023] From the perspective of achieving a faster, more accurate, and more reproducible analysis of chloride ion concentration in gelatin and / or collagen, the mixing II step further preferably includes: mixing a chloride ion releasing agent and a portion of the solvent to obtain a solution containing a chloride ion releasing agent; mixing a silver ion-containing substance and the remaining solvent to obtain a solution containing silver ions; and mixing the solution containing the chloride ion releasing agent, the solution containing silver ions, and the test solution.

[0024] In this invention, in order to avoid introducing other anions and to prevent interference from the precipitation of other anions (such as phosphate, carbonate, oxalate, etc.) that may form insoluble silver salts under acidic conditions, the solvent is preferably an aqueous solution of HNO3.

[0025] According to the present invention, preferably, the content of PVP in the mixture is 0.01-0.05 vt%, which can be 0.01 vt%, 0.02 vt%, 0.03 vt%, 0.04 vt%, 0.05 vt%, or any value within any two of these ranges. The content of alcohol in the mixture is 10-50 vt%, which can be 10 vt%, 20 vt%, 30 vt%, 40 vt%, 50 vt%, or any value within any two of these ranges. By controlling the content of PVP and alcohol within the above-mentioned specific ranges, the dispersibility and stability of AgCl in turbidity analysis can be improved, thereby enabling rapid, accurate, and highly reproducible analysis of chloride ion concentration in gelatin and / or collagen.

[0026] To enable rapid, accurate, and highly reproducible analysis of chloride ion concentration in gelatin and / or collagen, preferably, the alcohol in the PVP alcohol solution is selected from ethanol, ethylene glycol, and propanol. Further preferably, considering the ability to achieve even faster, more accurate, and more reproducible analysis of chloride ion concentration in gelatin and / or collagen, the alcohol in the PVP alcohol solution is ethanol.

[0027] According to the present invention, preferably, the method further includes adding citric acid before mixing I. Generally, during the production of gelatin and / or collagen, some calcium, magnesium, and iron ions are inevitably introduced. To eliminate the interference of these cations coexisting with gelatin and / or collagen on chloride ion determination, citric acid (CA) is added in the present invention to mask the interference of the aforementioned metal ions, thereby enabling rapid, accurate, and highly reproducible analysis of chloride ion concentration in gelatin and / or collagen. Further preferably, considering the ability to achieve even faster, more accurate, and more reproducible analysis of chloride ion concentration in gelatin and / or collagen, the concentration of citric acid in the test solution is 0.1-0.5 mg / mL.

[0028] To further achieve rapid, accurate, and highly reproducible analysis of chloride ion concentration in gelatin and / or collagen, preferably, the step of determining the chloride ion concentration in the mixture using a UV-Vis spectrophotometer includes: obtaining a standard curve of chloride ion concentration and absorbance, measuring the absorbance in the mixture using a UV-Vis spectrophotometer, and determining the chloride ion solubility in the mixture based on the measured absorbance and the standard curve.

[0029] According to the present invention, preferably, the mixing II time is 3-5 min, which can be 3 min, 4 min, 5 min, or any value within any two of these ranges. By controlling the mixing II time within the above-mentioned specific range, it is possible to further achieve rapid, accurate, and highly reproducible analysis of chloride ion concentration in gelatin and / or collagen.

[0030] According to the present invention, preferably, the linear range of chloride ion concentration in the gelatin and / or collagen, measured by a UV-Vis spectrophotometer, is 1-10 μg / mL, which can be 1 μg / mL, 2 μg / mL, 4 μg / mL, 6 μg / mL, 8 μg / mL, 10 μg / mL, or any value within any two of these ranges. The limit of detection is 0.28 μg / mL. By determining the linear range and limit of detection of chloride ion concentration in the gelatin and / or collagen, the requirements for effective and accurate monitoring of chloride ion concentration in gelatin and / or collagen during the electrolysis process can be met.

[0031] A relatively preferred embodiment of the present invention provides a method for determining the chloride ion concentration in gelatin and / or collagen, comprising the following steps: S1, solution preparation (1) preparing an aqueous solution of HNO3 with a pH value of 2-3.

[0032] (2) Using the HNO3 aqueous solution from (1) above, prepare an HNO3 aqueous solution of citric acid (CA) with a concentration of 0.1-0.5 mg / mL.

[0033] (3) Accurately weigh 0.1g of PVP into a 100mL volumetric flask and dilute to volume with ethanol.

[0034] (4) Chloride ion standard solution: Dry the analytical grade KCl to constant weight, accurately weigh the KCl and prepare an HNO3 aqueous solution with a chloride ion concentration of 100 μg / mL using the HNO3 aqueous solution from (1) above.

[0035] (5) Accurately weigh the gelatin or collagen, and use the HNO3 aqueous solution from (1) above to prepare a gelatin and / or collagen solution with a concentration of 0.01±0.004 g / mL.

[0036] (6) Using the HNO3 aqueous solution from (1) above, prepare an AgNO3 aqueous solution with a concentration greater than 0.03 mol / L and less than or equal to 0.035 mol / L.

[0037] S2. Construction of the standard curve: Take six 10mL volumetric flasks and add 0, 0.1, 0.2, 0.5, 0.8, and 1.0mL of (4) from S1 to each flask. Then add 1mL of (5), 1mL of (2), 1-5mL of (3), and 0.5mL of (6) from S1 to each flask. Finally, dilute to volume with (1) from S1 and shake well. After the mixture has reacted for 3-5 minutes, measure the absorbance at 300nm wavelength using a UV-Vis spectrophotometer and record the relationship curve between the absorbance and chloride ion concentration. The chloride ion concentration C is used as the standard curve. Cl With - as the x-axis and absorbance value A as the y-axis, the linear regression equation of absorbance value on chloride ion concentration can be obtained.

[0038] S3. The actual sample detection is based on the linear regression equation obtained from the standard curve in S2. By extrapolating the intersection of the chloride ion concentration coordinate axis, the concentration of chloride ions in gelatin or collagen can be obtained.

[0039] The above-described particularly preferred embodiments of the present invention provide a method for determining the chloride ion concentration in gelatin and / or collagen. Under UV-Vis spectrophotometry, the linear range of chloride ion concentration in gelatin and / or collagen is 1-10 μg / mL, and the limit of detection is 0.28 μg / mL. Furthermore, in this invention, the relative standard deviation (RSD) of parallel sample measurements is <3%. In long-term experiments, the rate of change (ΔA) of absorbance values ​​within 60 minutes is <1%. Therefore, this method enables rapid, accurate, and highly reproducible analysis of chloride ion concentration in gelatin and / or collagen, and can be applied to the effective and precise monitoring of chloride ion concentration in gelatin and / or collagen during electrolytic processes.

[0040] The present invention will be described in detail below through embodiments.

[0041] Example 1S1, Solution preparation (1) Prepare an aqueous solution of HNO3 with a pH value of 2.5.

[0042] (2) Using the HNO3 aqueous solution from (1) above, prepare an HNO3 aqueous solution of citric acid (CA) with a concentration of 0.1 mg / mL.

[0043] (3) Accurately weigh 0.1g of PVP into a 100mL volumetric flask and dilute to volume with ethanol.

[0044] (4) Chloride ion standard solution: Dry the analytical grade KCl to constant weight, accurately weigh the KCl and prepare an HNO3 aqueous solution with a chloride ion concentration of 100 μg / mL using the HNO3 aqueous solution from (1) above.

[0045] (5) Accurately weigh the gelatin and prepare a gelatin solution with a concentration of 0.0109 g / mL using the HNO3 aqueous solution from (1) above.

[0046] (6) Using the HNO3 aqueous solution from (1) above, prepare an AgNO3 aqueous solution with a concentration of 0.031 mol / L.

[0047] S2. Construction of the standard curve: Take six 10mL volumetric flasks and add 0, 0.1, 0.2, 0.5, 0.8, and 1.0mL of (4) from S1 to each flask. Then add 1mL of (5), 1mL of (2), 1mL of (3), and 0.5mL of (6) from S1 to each flask. Finally, dilute to volume with (1) from S1 and shake well. After the mixture has reacted for 5 minutes, measure the absorbance at 300 nm using a UV-Vis spectrophotometer and record the relationship curve between the absorbance and chloride ion concentration. Use the chloride ion concentration C as the standard curve. Cl With - on the x-axis and absorbance value A on the y-axis, a linear regression equation of absorbance value versus chloride ion concentration can be obtained.

[0048] S3. The actual sample test is based on the linear regression equation obtained from the standard curve in S2. By extrapolating the intersection of the chloride ion concentration coordinate axis, the chloride ion concentration in the gelatin can be obtained.

[0049] Example 2S1, Solution preparation (1) Prepare an aqueous solution of HNO3 with a pH value of 2.

[0050] (2) Using the HNO3 aqueous solution from (1) above, prepare an HNO3 aqueous solution of citric acid (CA) with a concentration of 0.5 mg / mL.

[0051] (3) Accurately weigh 0.1g of PVP into a 100mL volumetric flask and dilute to volume with ethylene glycol.

[0052] (4) Chloride ion standard solution: Dry the analytical grade KCl to constant weight, accurately weigh the KCl and prepare an HNO3 aqueous solution with a chloride ion concentration of 100 μg / mL using the HNO3 aqueous solution from (1) above.

[0053] (5) Accurately weigh the gelatin and collagen, and use the HNO3 aqueous solution from (1) above to prepare a gelatin and collagen solution with a concentration of 0.0108 g / mL.

[0054] (6) Using the HNO3 aqueous solution from (1) above, prepare an AgNO3 aqueous solution with a concentration of 0.033 mol / L.

[0055] S2. Construction of the standard curve: Take six 10mL volumetric flasks and add 0, 0.1, 0.2, 0.5, 0.8, and 1.0mL of (4) from S1 to each flask. Then add 1mL of (5), 1mL of (2), 3mL of (3), and 0.5mL of (6) from S1 to each flask. Finally, dilute to volume with (1) from S1 and shake well. After the mixture has reacted for 3 minutes, measure the absorbance at 300nm wavelength using a UV-Vis spectrophotometer and record the relationship curve between the absorbance and chloride ion concentration. Use the chloride ion concentration C as the standard curve. Cl With - on the x-axis and absorbance value A on the y-axis, a linear regression equation of absorbance value versus chloride ion concentration can be obtained.

[0056] S3. The actual sample detection is based on the linear regression equation obtained from the standard curve in S2. By extrapolating the intersection of the chloride ion concentration coordinate axis, the chloride ion concentration in gelatin and collagen can be obtained.

[0057] Example 3S1, Solution preparation (1) Prepare an aqueous solution of HNO3 with a pH value of 3.

[0058] (2) Using the HNO3 aqueous solution from (1) above, prepare an HNO3 aqueous solution of citric acid (CA) with a concentration of 0.3 mg / mL.

[0059] (3) Accurately weigh 0.1g of PVP into a 100mL volumetric flask and dilute to volume with propanol.

[0060] (4) Chloride ion standard solution: Dry the analytical grade KCl to constant weight, accurately weigh the KCl and prepare an HNO3 aqueous solution with a chloride ion concentration of 100 μg / mL using the HNO3 aqueous solution from (1) above.

[0061] (5) Accurately weigh the collagen and prepare a collagen solution with a concentration of 0.01138 g / mL using the HNO3 aqueous solution from (1) above.

[0062] (6) Using the HNO3 aqueous solution from (1) above, prepare an AgNO3 aqueous solution with a concentration of 0.035 mol / L.

[0063] S2. Construction of the standard curve: Take six 10mL volumetric flasks and add 0, 0.1, 0.2, 0.5, 0.8, and 1.0mL of (4) from S1 to each flask. Then add 1mL of (5), 1mL of (2), 5mL of (3), and 0.5mL of (6) from S1 to each flask. Finally, dilute to volume with (1) from S1 and shake well. After the mixture has reacted for 4 minutes, measure the absorbance at 300nm using a UV-Vis spectrophotometer and record the relationship curve between the absorbance and chloride ion concentration. Use the chloride ion concentration C as the standard curve. Cl With - on the x-axis and absorbance value A on the y-axis, a linear regression equation of absorbance value versus chloride ion concentration can be obtained.

[0064] S3. The actual sample detection is based on the linear regression equation obtained from the standard curve in S2. By extrapolating the intersection of the chloride ion concentration coordinate axis, the chloride ion concentration in collagen can be obtained.

[0065] Example 4: The chloride ion concentration in gelatin and / or collagen was determined according to the method of Example 1, except that "preparing a gelatin solution with a concentration of 0.0109 g / mL" in S1 was replaced with "preparing a gelatin solution with a concentration of 0.0105 g / mL"; "0.031 mol / L AgNO3 aqueous solution" was replaced with "0.03 mol / L AgNO3 aqueous solution"; and the linear regression equation was changed. Replace with linear regression equation The results are shown in Table 1.

[0066] Example 5: The chloride ion concentration in gelatin and / or collagen was determined according to the method of Example 1, except that "preparing a gelatin solution with a concentration of 0.0109 g / mL" in S1 was replaced with "preparing a gelatin solution with a concentration of 0.0134 g / mL"; "aqueous solution of citric acid (CA) with HNO3 at a concentration of 0.1 mg / mL" was removed; and the linear regression equation was changed. Replace with linear regression equation The results are shown in Table 1.

[0067] Comparative Example 1: The chloride ion concentration in gelatin and / or collagen was determined according to the method in Example 1, wherein the gelatin solution concentration was 0.0136 g / mL; the difference was that "preparing an HNO3 aqueous solution with a pH of 2" was replaced with "aqueous solution"; and the linear regression equation was... Replace with linear regression equation The results are shown in Table 1.

[0068] Comparative Example 2 determined the chloride ion concentration in gelatin and / or collagen according to the method of Example 1, wherein the gelatin solution concentration was 0.0128 g / mL; the difference was that step (3) in S1 was removed, i.e., the alcohol solution of PVP was removed; the linear regression equation was then used. Replace with linear regression equation The results are shown in Table 1.

[0069] Comparative Example 3 determined the chloride ion concentration in gelatin and / or collagen according to the method of Example 1, wherein the gelatin concentration was the same as in Example 1; the difference was that "alcoholic solution of PVP" was replaced with "aqueous solution of PVP"; and the linear regression equation was... Replace with linear regression equation The results are shown in Table 1.

[0070] Comparative Example 4 determined the chloride ion concentration in gelatin and / or collagen according to the method of Example 1, wherein the gelatin concentration was the same as in Example 1; the difference was that "an aqueous solution of HNO3 with a pH of 2.5" was replaced with "an aqueous solution of HNO3 with a pH of 4"; and the linear regression equation was... Replace with linear regression equation The results are shown in Table 1.

[0071] The test examples were used to examine the speed, accuracy, and high reproducibility of the measurement method of the present invention.

[0072] On the one hand, the absorbance values ​​of the examples and comparative samples were measured using a UV-spectrophotometer within 5 minutes of mixing to obtain the percentage (%) of chloride ions in gelatin and / or collagen; the relative standard deviation (RSD) was obtained by performing three parallel measurements on the examples and comparative samples; and the absorbance values ​​of the examples and comparative samples were measured again within 60 minutes of mixing to obtain the rate of change of absorbance values ​​within 60 minutes of mixing based on the absorbance values ​​before and after mixing; the results are recorded in Table 1.

[0073] On the other hand, the chloride ion content in the same samples of the examples and comparative examples was analyzed by ion chromatography, and the results are listed in Table 1. Prior to ion chromatography analysis, the gelatin samples were nitrated. The chromatographic column was a Metrosep A Supp 4 from Metrohm, Switzerland. The analytical conditions were as follows: a mixed solution of 0.8 mM NaCO3 and 4 mM NaHCO3 as the mobile phase, and a flow rate of 1.0 mL / min.

[0074] Table 1

[0075] As can be seen from the results in Table 1, the spectrophotometric method of this invention can determine the chloride ion concentration in gelatin and / or collagen within 5 minutes of mixing. Compared with the longer pretreatment and equilibration times of ion chromatography, this method shortens the analysis time and fully demonstrates the speed of the method of this invention. The results of Examples 1-5 of this invention are basically consistent with the results of ion chromatography, demonstrating the accuracy of the method of this invention. The relative standard deviation (RSD) of the parallel sample measurements in Examples 1-5 is <3%, and the rate of change (ΔA) of the absorbance value of the sample within 60 minutes is <1%, fully demonstrating the high reproducibility of the method of this invention. Furthermore, a comparison of the results of Comparative Examples 1 and 4 (HNO3 aqueous solution without pH 2-3), Comparative Examples 2-3 (PVP-alcohol solution environment) with Examples 1-8 of the present invention shows that, under HNO3 aqueous solution without pH 2-3, the content measured in Comparative Examples 1 and 4 is significantly lower than the actual value; under the PVP-alcohol solution environment, the relative standard deviation (RSD) of the measured values ​​of the parallel samples in Comparative Examples 2-3 is >3%, and the rate of change (ΔA) of the absorbance value of the sample within 60 min of mixing is >1%. Therefore, the method for determining the chloride ion concentration in gelatin and / or collagen provided by the embodiments of the present invention is more rapid, accurate, and highly reproducible.

[0076] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for determining the chloride ion concentration in gelatin and / or collagen, characterized in that, The method includes: mixing an alcoholic solution of PVP, a sample to be tested, and an aqueous solution of HNO3 with a pH of 2-3 to obtain a test solution; mixing the test solution with a chloride ion releasing agent, a silver ion-containing substance, and a solvent to obtain a mixed solution; measuring the chloride ion concentration in the mixed solution using a UV-Vis spectrophotometer; and determining the chloride ion concentration in the sample to be tested based on the chloride ion concentration in the mixed solution; wherein the sample to be tested is gelatin and / or collagen.

2. The method according to claim 1, characterized in that, The chloride ion releasing agent and the silver ion-containing substance are AgNO3.

3. The method according to claim 2, characterized in that, In the mixture, the concentration of AgNO3 is greater than 0.03 mol / L; preferably, the mixing step II includes: mixing the chloride ion releasing agent and a portion of the solvent to obtain a solution containing the chloride ion releasing agent, mixing the silver ion-containing substance and the remaining solvent to obtain a solution containing silver ions, and mixing the solution containing the chloride ion releasing agent, the solution containing silver ions, and the test solution.

4. The method according to claim 1 or 3, characterized in that, The solvent is an aqueous solution of HNO3.

5. The method according to claim 1 or 3, characterized in that, In the mixture, the content of PVP is 0.01-0.05 vt; the content of alcohol is 10-50 vt.

6. The method according to claim 1 or 3, characterized in that, The alcohol in the PVP alcohol solution is selected from ethanol, ethylene glycol and propanol; preferably ethanol.

7. The method according to claim 1 or 3, characterized in that, The method further includes adding citric acid before mixing I; preferably, the concentration of citric acid in the test solution is 0.1-0.5 mg / mL.

8. The method according to claim 1 or 3, characterized in that, The step of determining the chloride ion concentration in the mixture using a UV-Vis spectrophotometer includes: obtaining a standard curve of chloride ion concentration and absorbance, measuring the absorbance in the mixture using a UV-Vis spectrophotometer, and determining the chloride ion solubility in the mixture based on the measured absorbance and the standard curve.

9. The method according to claim 1 or 3, characterized in that, The mixing time for the second stage is 3-5 minutes.

10. The method according to any one of claims 1 to 8, characterized in that, Under UV-Vis spectrophotometry, the linear range of chloride ion concentration in the sample to be tested is 1-10 μg / mL, and the limit of detection is 0.28 μg / mL.

Images