Quantitative method of polysaccharides containing anionic groups
A method for quantifying anionic polysaccharides by reacting them with cations in a cationic solution and measuring cation concentration electrochemically addresses the complexity of conventional methods, facilitating efficient and sensitive polysaccharide quantification.
Patent Information
- Application Number
- CN202411528742.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-10-31
- Filing Date
- 2024-10-30
- Publication Date
- 2024-12-27
AI Technical Summary
Conventional methods for quantifying polysaccharides with anionic groups require complicated pretreatments such as fluorescent labeling and gelation, making them cumbersome and inefficient.
A method involving the addition of a sample containing anionic polysaccharides to a cationic solution of known concentration, allowing the polysaccharides to react and gel or thicken, followed by electrochemical measurement to determine cation concentration, which is then used to calculate the polysaccharide concentration.
Enables easy and accurate quantification of anionic polysaccharides without direct measurement, allowing for quick and sensitive determination even with small sample amounts.
Smart Images
Figure CN119198880A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a quantitative method for polysaccharides containing anionic groups. Background Art
[0002] In the past, polysaccharides such as pectin were used as gelling agents and thickeners in foods such as jams and jellies, and in pharmaceuticals. The concentration of polysaccharides has a great influence on the degree of gelation and thickening, so for quality control, especially to control gelation and thickening, it is necessary to quantify the polysaccharides.
[0003] As a method for quantifying polysaccharides, a method for detecting and quantifying fluorescently labeled uronic acid-containing polysaccharides using HPLC (high performance liquid chromatography) is known (see, for example, Patent Document 1). In addition, a method for adding an aqueous solution of a metal salt to an aqueous solution containing an acidic polysaccharide, gelling it, and recovering it, and quantifying it using HPLC, precipitation method, spectroscopy, titration method, enzyme reaction method, etc. is known (see, for example, Patent Document 2).
[0004] However, conventional quantitative methods have the problem that complicated pretreatments such as fluorescent labeling of polysaccharides and gelation and recovery are required.
[0005] Prior art literature
[0006] Patent Literature
[0007] Patent Document 1: Japanese Patent Application Publication No. 2002-131233
[0008] Patent Document 2: Japanese Patent Application Publication No. 2005-179495 Summary of the invention
[0009] The present invention has been made to improve the above-mentioned situation, and an object of the present invention is to provide a method for easily quantifying anionic group-containing polysaccharides.
[0010] The quantitative method of polysaccharides containing anionic groups of the present invention comprises: a preparation step, adding a sample containing polysaccharides containing anionic groups to a cationic solution containing cations of known concentration to obtain a mixed solution, wherein the polysaccharides containing anionic groups react with the cations to gel or thicken; a measurement step, measuring the cation concentration in the mixed solution; and a calculation step, calculating the concentration of polysaccharides containing anionic groups in the sample based on the measurement value obtained in the measurement step.
[0011] In the quantitative determination method of the present invention, for example, in the measurement step, the mixed solution may be subjected to electrochemical measurement to obtain the measurement value.
[0012] Furthermore, it is also possible to prepare the mixed solution by adding the sample to a container containing the cationic solution in the preparation step, and inserting the electrode into the container and immersing it in the mixed solution when the electrochemical measurement is performed in the measurement step. Here, the "electrode" refers to a working electrode and a reference electrode when the electrochemical measurement is a two-electrode type, and a working electrode, a reference electrode, and a counter electrode when the electrochemical measurement is a three-electrode type.
[0013] In addition, the electrochemical measurement may be performed by anodic stripping voltammetry, for example.
[0014] In the quantitative method of the present invention, for example, the following examples can be cited: the polysaccharide containing anionic groups is a polysaccharide having a carboxyl group, and the cation is a metal ion. For example, the solvent of the cationic solution and the solvent of the sample are water, the polysaccharide containing anionic groups is water-soluble pectin, and the cation is a lead ion.
[0015] Effects of the Invention
[0016] The quantitative method for anionic group-containing polysaccharides of the present invention can easily quantify the anionic group-containing polysaccharides in a sample. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Figure 1 This is a schematic diagram showing an example of an electrochemical measuring device.
[0018] Figure 2 This is a plan view of an electrode tip including an example of an electrode used in electrochemical measurement.
[0019] Figure 3 It is a diagram schematically showing a tube container for accommodating a mixed solution and an electrode tip.
[0020] Figure 4 This is a graph showing the measurement results of a mixed solution of water-soluble pectin and an aqueous lead ion solution.
[0021] Figure 5 This is a graph showing the measurement results of a plurality of samples having different water-soluble pectin concentrations.
[0022] Description of Reference Numerals
[0023] 10: mixed solution; 11: cationic solution; 12: sample; 13: tube container; 14: gel-like substance. DETAILED DESCRIPTION
[0024] In order to solve the above technical problems, the present inventors have found the following: adding a sample containing polysaccharides containing anionic groups to a cationic solution with known cation concentration can quantify the polysaccharides containing anionic groups according to the amount of cations adsorbed on the polysaccharides containing anionic groups (relative to the amount of cation reduction in the cationic solution). That is, the quantitative method of polysaccharides containing anionic groups of the present invention can simply quantify the polysaccharides containing anionic groups even if the polysaccharides containing anionic groups and their derivatives are not directly quantified. Below, the present invention is described based on its preferred embodiment.
[0025] [First embodiment]
[0026] The quantitative method of polysaccharides containing anionic groups of the first embodiment includes: a preparation step, adding a sample containing polysaccharides containing anionic groups to a cationic solution containing cations of known concentration to obtain a mixed solution, wherein the polysaccharides containing anionic groups react with the cations to gel or thicken; a measurement step, measuring the cation concentration in the mixed solution; and a calculation step, calculating the concentration of polysaccharides containing anionic groups in the sample based on the measurement value obtained in the measurement step.
[0027] [Measurement object]
[0028] The quantitative method for determining the polysaccharide containing anionic groups of the present invention is directed to a sample containing polysaccharide containing anionic groups, which reacts with cations to form a gel or thicken. Polysaccharides containing anionic groups include various polysaccharides containing anionic groups such as carboxyl groups, sulfonic acid groups, and phosphoric acid groups. Examples of such polysaccharides include polysaccharide substances such as pectin, pectic acid, pectinic acid, alginic acid, gellan gum, xanthan gum, tragacanth gum, carrageenan, gum arabic, anionic starch, propylene glycol alginate, carboxymethyl cellulose, starch glycolate, cellulose glycolate, and starch phosphate, as well as their alkali metal salts.
[0029] [Cationic solution]
[0030] The cations contained in the cationic solution include, for example, monovalent metal ions such as sodium ions and potassium ions; divalent metal ions such as calcium ions, copper ions, strontium ions, nickel ions, zinc ions, cadmium ions, lead ions, magnesium ions, and ruthenium ions; trivalent metal ions such as aluminum ions, lanthanum ions, and iron (III) ions, etc. In addition, the solvent of the cationic solution, in addition to water, can also include alcohol solutions such as ethanol and methanol; acetone, acetonitrile, glutaraldehyde, toluene, tetrahydrofuran, dichloromethane, etc.
[0031] [Preparation process]
[0032] In the preparation process, a sample containing anionic group-containing polysaccharides is added to a cationic solution containing cations of known concentration to obtain a mixed solution, wherein the polysaccharides containing anionic groups react with the cations to gel or thicken. In the mixed solution, the cations are adsorbed on the polysaccharides containing anionic groups, and the amount of cations is reduced. Here, the sample can be any form of a liquid or solid containing polysaccharides containing anionic groups, and is preferably a liquid obtained by dissolving or extracting the polysaccharides containing anionic groups in the same solvent as the solvent of the cationic solution.
[0033] [Measurement process]
[0034] In the determination step, the cation concentration in the mixed solution is determined. In this step, the method for determining the cation concentration is not particularly limited, and for example, electrochemical determination, plasma emission spectrometry, atomic absorption spectrometry, fluorescent X-ray analysis, mass spectrometry, chelate titration, HPLC, etc. can be used.
[0035] [Calculation process]
[0036] In the calculation step, the concentration of the polysaccharide containing anionic groups in the sample is calculated based on the measured value obtained in the above-mentioned measuring step. The concentration of the polysaccharide containing anionic groups is calculated, for example, based on a calibration curve showing the relationship between the concentration of the polysaccharide containing anionic groups and the measured value, wherein the calibration curve is obtained using a standard mixed solution obtained by adding a sample of the polysaccharide containing anionic groups with a known concentration to a cationic solution with a known concentration. The calibration curve can be obtained, for example, by measuring a standard mixed solution containing polysaccharides containing anionic groups with various known concentrations and a standard mixed solution not containing polysaccharides containing anionic groups, and indicating the measured value for the concentration of the polysaccharide containing anionic groups.
[0037] According to the above-mentioned method for quantifying polysaccharides containing anionic groups, even if the polysaccharides containing anionic groups and their derivatives are not directly quantified, the polysaccharides containing anionic groups can be simply quantified based on the amount of cations adsorbed on the polysaccharides containing anionic groups (the amount of cation reduction relative to the cationic solution).
[0038] [Second embodiment]
[0039] In the measurement step of the second embodiment, the mixed solution is subjected to electrochemical measurement to obtain the measurement value. The electrochemical measurement can be performed by, for example, the following methods: Chronoamperometry (CA), Differential Pulse Voltammetry (DPV), Cyclic Voltammetry (CV), Linear Sweep Voltammetry (LSV), Square Wave Voltammetry (SWV), Anodic Stripping Voltammetry (ASV), Electrochemical Impedance Spectroscopy (EIS), etc.
[0040] Electrochemical measurement takes a short time to measure, so anionic group-containing polysaccharides can be quantified quickly and easily. In addition, electrochemical measurement can be performed using a relatively simple device, so on-site measurement can be performed by moving the device to the measurement site.
[0041] Moreover, by adopting electrochemical determination, for example, even when polysaccharides containing anionic groups that bind to cations are suspended in a mixed solution, the cation concentration in the mixed solution can be determined without separating the polysaccharides containing anionic groups from the mixed solution. For example, when the sample amount is small and the concentration of polysaccharides containing anionic groups in the sample is low, that is, when it is difficult to separate polysaccharides containing anionic groups that bind to cations from the mixed solution, the polysaccharides containing anionic groups sometimes hinder the determination in other determination methods and an accurate measurement value cannot be obtained. In contrast, with electrochemical determination, even when polysaccharides containing anionic groups that bind to cations are present in the mixed solution, the cation concentration in the mixed solution can be determined, so the polysaccharides containing anionic groups in the sample can be quantified accurately and with high sensitivity.
[0042] [Third embodiment]
[0043] In a third embodiment, in the preparation step, a sample is added to a container containing a cation solution to prepare a mixed solution, and in the measurement step, when subjected to electrochemical measurement, an electrode is inserted into the container and immersed in the mixed solution.
[0044] According to the third embodiment, the polysaccharide containing anionic groups in the sample can be quantified by a simple operation without separating the polysaccharide containing anionic groups bound to cations from the mixed solution. In addition, if a working electrode and a reference electrode are formed on a substrate; or an electrode head of a working electrode, a reference electrode and a counter electrode is used, and a tube container is used as a container, a small amount of cationic solution and a sample can be measured. For example, even a small amount of cationic solution of about 1 ml (milliliter) and a very small amount of liquid sample of less than 100 μl (microliter) can be measured.
[0045] In addition, when using the above-mentioned electrode head, the mixed solution can also be dripped across the electrodes on the substrate for measurement. In this case, the amount of mixed solution dripped onto the electrode head can be a small amount, for example, the mixed solution of about 20 to 30 μl can be dripped onto the electrode head for measurement. It should be noted that when performing electrochemical measurements, the electrodes are not limited to those formed on the substrate, for example, rod-shaped electrodes can also be used. In addition, the container in the third embodiment is not limited to small-capacity containers such as tube containers, but can also be other containers such as beakers.
[0046] [Fourth embodiment]
[0047] In a fourth embodiment, the electrochemical determination is performed using the anodic stripping voltammetry (ASV) method. In the ASV method, after the cations in the mixed solution are concentrated and precipitated on the electrode surface, the cation concentration is quantified based on the current value when the substance is electrolytically dissolved, so that high-sensitivity determination can be performed and determination can be performed using a small amount of cation solution and sample.
[0048] [Fifth embodiment]
[0049] In a fifth embodiment, the polysaccharide containing anionic groups is a polysaccharide having a carboxyl group, and the cation is a metal ion. For example, the solvent of the cationic solution and the solvent of the sample are water, the polysaccharide containing anionic groups is a water-soluble pectin, and the cation is a lead ion. It should be noted that the polysaccharide containing anionic groups as the object of measurement of the present invention is not limited to polysaccharides having a carboxyl group, and the polysaccharide having a carboxyl group is not limited to water-soluble pectin. In addition, the cation is not limited to lead ions.
[0050] [First embodiment]
[0051] Next, embodiments of the present invention will be described with reference to the drawings. Figure 1 This is a schematic diagram showing an example of an electrochemical measuring device. Figure 2 This is a plan view of an electrode tip including an example of an electrode used in electrochemical measurement. Figure 3 It is a diagram schematically showing a tube container for accommodating a mixed solution and an electrode tip.
[0052] like Figure 1 As shown, the electrochemical measuring device 1 comprises: an electrode tip 2; a potentiostat 3 connected to the electrode tip 2; an operation unit 4, a display unit 5, a power supply unit 6 and an external output unit 7 connected to the potentiostat 3. In this embodiment, the electrode tip 2 is a disposable electrode tip.
[0053] like Figure 2 As shown, the electrode head 2 has a flat insulating substrate 21, on which a working electrode 22, a counter electrode 23, and a reference electrode 24 are provided insulated from each other. The substrate 21 has a substantially rectangular shape when viewed from above. The working electrode 22, the counter electrode 23, and the reference electrode 24 are provided from near one end of the long dimension of the substrate 21 to near the other end. It should be noted that the configuration and shape of the working electrode 22, the counter electrode 23, and the reference electrode 24 in the electrode head 2 are not limited to Figure 2 The configuration and shape can be appropriately changed, for example, a configuration in which the end of the counter electrode 23 and the end of the reference electrode 24 sandwich a circular end of the working electrode 22 in the long direction of the substrate 21 at one end of the substrate 21.
[0054] like Figure 2 As shown, in the electrode head 2, one end side of the working electrode 22, the counter electrode 23 and the reference electrode 24 is in contact with the mixed solution 10, and the mixed solution 10 is obtained by mixing the sample 12 containing the polysaccharide containing anionic groups into the cationic solution 11. Figure 3 As shown in (2), one end of the electrode tip 2 is inserted into the tube container 13 containing the mixed solution 10, and the working electrode 22, the counter electrode 23 and the reference electrode 24 are in contact with the mixed solution 10. The other ends of the working electrode 22, the counter electrode 23 and the reference electrode 24 of the electrode tip 2 are connected via the connector 8 and the cable 9 ( Figure 1 The electrode tip 2 is electrically connected to the potentiostat 3 (not shown in the figure). The electrode tip 2 is detachably mounted on the connector 8.
[0055] At least one surface of the substrate 21 of the electrode head 2 is formed of a flat insulating material. The material of the substrate 21 is not particularly limited, and examples thereof include: polyimide (PI), polyethylene terephthalate (PET), single crystal silicon (silicon wafer), glass, methyl methacrylate (PMMA), polycarbonate (PC), polypropylene (PP), polyethylene (PE), polystyrene (PS), polyvinyl chloride (PVC), polyoxymethylene (POM), ABS resin (ABS: Acrylonitrile Butadiene Styrene, acrylonitrile-butadiene-styrene), etc. However, the material of the substrate 21 is not limited thereto, and may also be ceramic, quartz, etc. In addition, the shape, thickness, and size of the substrate 21 are not particularly limited.
[0056] As the material forming the conductive layer of the working electrode 22, the counter electrode 23 and the reference electrode 24, for example, gold, silver, titanium, nickel, aluminum, ruthenium, tantalum, copper, platinum, niobium, zirconium, or alloys of these elements, or alloys of these elements and carbon, or single carbon, etc. can be used. In addition, the conductive layer may be a single-layer film or a multilayer film formed by stacking a plurality of films.
[0057] like Figure 1 As shown, the potentiostat 3 is configured to control the potential of the working electrode 22 of the electrode head 2 to be constant relative to the reference electrode 24, and to measure the current flowing between the working electrode 22 and the counter electrode 23. The potentiostat 3 includes a calculation control unit 31, a voltage application unit 32, and a current detection unit 33 as a general configuration.
[0058] The calculation control unit 31 performs the following functions: performs a predetermined calculation process using the measurement value obtained in the electrochemical measurement, and sends a necessary signal to the voltage application unit 32 or displays information such as the measurement result on the display unit 5 based on the instruction from the user input through the operation unit 4. The calculation control unit 31 is realized by, for example, a microcomputer executing a predetermined program.
[0059] The voltage applying unit 32 is configured to apply a voltage of a desired waveform between the working electrode 22 and the counter electrode 23 of the electrode head 2 when receiving a measurement start signal from the operation control unit 31, and control the potential between the working electrode 22 and the reference electrode 24 to become a desired potential.
[0060] The current detection unit 33 is configured to detect the magnitude of the current flowing between the working electrode 22 and the counter electrode 23 of the electrode tip 2. A signal related to the magnitude of the current detected by the current detection unit 33 is input to the calculation control unit 31.
[0061] The calculation control unit 31 is configured to calculate the concentration of a specific component in the mixed solution 10 based on the signal taken from the current detection unit 33, for example, using a pre-prepared calibration curve, and display the measurement results on the display unit 5. In this embodiment, the calculation control unit 31 calculates the concentration of the polysaccharide containing anionic groups in the mixed solution 10.
[0062] In the electrochemical measuring device 1, the operating unit 4 is an input device for the user to perform the following operations: turning on / off the power supply, starting the measurement, and changing the information displayed on the display unit 5. The display unit 5 is implemented, for example, by a liquid crystal display. It should be noted that the display unit 5 can also be composed of a touch panel so that the display unit 5 also has the function of the operating unit 4. The power supply unit 6 can be implemented, for example, by a dry cell, a storage battery, etc. The power supply unit 6 supplies the required power to the constant potential instrument 3 and the display unit 5.
[0063] In addition, the external output unit 7 may be connected to the potentiostat 3 so that information can be output to an external device such as a personal computer via a wired communication unit such as a USB (Universal Serial Bus) terminal or a wireless communication unit. In this case, the calculation control unit 31 is configured to output measurement data, etc. to the external device via the external output unit 7.
[0064] It should be noted that the operation unit 4, the display unit 5, the power supply unit 6, and the external output unit 7 can also be implemented by a mobile computer such as a notebook computer or a tablet computer. In addition, if a small constant potential meter (such as a small constant potential meter "miniSTAT100" (manufactured by BioDevice Technology)) is used as the constant potential meter 3, the electrochemical measuring device 1 can be configured to be portable. Thus, on-site measurements using the electrochemical measuring device 1 can be performed.
[0065] like Figure 3 As shown, the electrochemical measurement using the electrochemical measurement device 1 is performed in a state where the working electrode 22, the counter electrode 23, and one end side of the reference electrode 24 of the electrode head 2 are immersed in the mixed solution 10 contained in the tube container 13. It should be noted that the measurement can also be performed in a state where the mixed solution 10 is dropped onto the substrate 21 in a manner that it contacts the working electrode 22, the counter electrode 23, and the reference electrode 24 in the electrode head 2.
[0066] Next, refer to Figure 3 The measurement operation in the first example is described. In the first example, the adsorption of lead ions by water-soluble pectin was confirmed by electrochemical measurement using a printed carbon electrode.
[0067] 890 μl of ultrapure water and 10 μl of a 100 ppm lead standard solution were injected into a 1.5 ml tube container 13 and mixed to prepare 900 μl of a lead ion aqueous solution as a cation solution 11. 100 μl of an aqueous solution containing water-soluble pectin was added to the cation solution 11 as a sample 12 (refer to Figure 3 (1)). Thus, 1 ml of mixed solution 10 was prepared. The lead concentration of mixed solution 10 was 1 ppm. In mixed solution 10, a gel-like substance 14 of water-soluble pectin adsorbing lead ions was precipitated (refer to Figure 3 (2)).
[0068] An aqueous solution with a known water-soluble pectin concentration was used as sample 12. Specifically, the following aqueous solution was used as sample 12: an aqueous solution with a water-soluble pectin concentration of 2.38% by weight prepared by dissolving 10.541 g of a food additive powder (manufactured by Kyoritsu Foods Co., Ltd.) containing 25% low-methoxyl pectin, 74% granulated sugar, and 1% calcium lactate in 100 ml of ultrapure water.
[0069] The mixed solution 10 prepared here can also be said to be a standard mixed solution obtained by adding an aqueous solution of a known water-soluble pectin concentration to an aqueous lead ion solution of a known lead ion concentration. In addition, a 1 ppm lead ion aqueous solution prepared by mixing 990 μl of ultrapure water and 10 μl of a 100 ppm lead standard solution was prepared as a standard mixed solution not containing water-soluble pectin.
[0070] The working electrode 22, the counter electrode 23 and the reference electrode 24 (electrodes) at one end of the electrode tip 2 are inserted into the tube container 13 and immersed in the mixed solution 10 (see Figure 3 (2)). In the first embodiment, a carbon electrode formed on a substrate 21 by screen printing is used as the working electrode 22, the counter electrode 23, and the reference electrode 24.
[0071] A small potentiostat "Interface 1010T" (GARMY) was used as the potentiostat 3. Electrochemical measurements were performed using the two-electrode system of anodic stripping differential pulse voltammetry (ASDPV). Measurements using ASDPV were performed under the conditions of a pre-concentration voltage of -1200 mV and a pre-concentration time of 200 s (seconds). The resulting current-potential curve is shown in Figure 4 .exist Figure 4 In the figure, the vertical axis represents the current and the horizontal axis represents the potential.
[0072] Depend on Figure 4 It can be seen that a clear lead oxidation peak can be seen in the waveform of the mixed solution (Pb 1ppm) not containing water-soluble pectin. In contrast, in the waveform of the mixed solution (Pb 1ppm+pectin) containing water-soluble pectin, it is confirmed that the lead oxidation peak that can be confirmed in the waveform of the mixed solution not containing water-soluble pectin is reduced and disappears. This means that if water-soluble pectin is mixed into the lead ion aqueous solution, the water-soluble pectin adsorbs lead ions and the lead ion concentration decreases.
[0073] The standard mixed solution containing various known water-soluble pectins and the standard mixed solution containing no water-soluble pectin are measured, and the oxidation peak current value of lead is marked for the water-soluble pectin concentration, so that a calibration curve representing the relationship between the water-soluble pectin concentration and the current value can be obtained. In addition, the calibration curve can be used to calculate the water-soluble pectin concentration in a sample containing water-soluble pectin with unknown concentration. It should be noted that in the first embodiment, the measured value (current value) depends on the lead ion concentration in the mixed solution 10, so the calibration curve can also represent the relationship between the lead ion concentration and the current value.
[0074] According to the first embodiment, even if the water-soluble pectin and its derivatives are not directly quantified, the water-soluble pectin can be easily quantified based on the amount of lead ions adsorbed to the water-soluble pectin (the amount of lead ions reduced relative to the cationic solution 11).
[0075] [Second embodiment]
[0076] In the second example, it was verified whether the adsorption of lead ions by water-soluble pectin can be electrochemically quantified using electrodes other than the printed carbon electrode. In addition, the dependence of the reduction in the lead oxidation peak current value on the water-soluble pectin concentration in the sample was verified.
[0077] 1 ml of a 1 ppm lead ion aqueous solution prepared by injecting 990 μl of ultrapure water and 10 μl of a 100 ppm lead standard solution into a tube container 13 was prepared as a cation solution 11. A solution obtained by adding 10 μl of a sample 12 containing water-soluble pectin to the cation solution 11 (Pb 1 ppm + pectin 10 μl), a solution obtained by adding 1 μl of the sample 12 to the cation solution 11 (Pb 1 ppm + pectin 1 μl), and a solution to which the sample 12 was not added (Pb 1 ppm) were prepared as mixed solutions 10 to be measured. The sample 12 was the same as the solution used in the first embodiment.
[0078] The potentiostat 3 uses the same potentiostat as that used in the measurement of the first embodiment. The electrochemical measurement is performed using the anodic stripping differential pulse voltammetry (ASDPV) of the two-electrode system. The measurement conditions are the same as those of the first embodiment. The electrode head 2 formed with the silver electrode is immersed in the above three mixed solutions 10 respectively, and the measurement is performed. The obtained current-potential curve is shown in Figure 5 .exist Figure 5 In the figure, the vertical axis represents the current and the horizontal axis represents the potential.
[0079] Depend on Figure 5It can be seen that the waveform of the mixed solution (Pb 1ppm) without adding sample 12 shows a clear lead oxidation peak. The waveform of the mixed solution (Pb 1ppm+pectin 1μl) with 1μl of sample 12 added shows a lead oxidation peak with a smaller peak height (current value) than the waveform of Pb 1ppm. As for the waveform of the mixed solution (Pb 1ppm+pectin 10μl) with 10μl of sample 12 added, it is confirmed that the lead oxidation peak decreases and disappears.
[0080] In the second embodiment, the lower the concentration of water-soluble pectin in the mixed solution 10, the larger the current value of the oxidation peak of lead, thus confirming the dependence of the oxidation peak current value of lead on the concentration of water-soluble pectin in the sample. In addition, it can be seen that not only carbon electrodes can be used to quantify water-soluble pectin, but also metal electrodes can be used to quantify water-soluble pectin. It should be noted that the material of the electrode used in the electrochemical measurement is not particularly limited as long as it is an electrode that can measure the cation of the measurement object (here, lead ions).
[0081] The present invention is not limited to the above-mentioned embodiments and examples, and can be embodied in various schemes. The configuration of each part is not limited to the illustrated embodiments, and various changes can be made within the scope of the main purpose of the present invention. For example, the configurations described in the above-mentioned embodiments, examples, and variations (such as the supplementary remarks) can be combined, and addition, omission, substitution, and other changes of the configuration can be made.
[0082] For example, in the above-mentioned embodiment, the anodic stripping differential pulse voltammetry of the two-electrode system is used as the electrochemical measurement, but the electrochemical measurement in the measurement process of the quantitative method of the present invention may also be other electrochemical measurement methods such as chronoamperometry. In addition, the measurement process of the quantitative method of the present invention is not limited to electrochemical measurement, and various measurement methods that can quantify cations such as plasma emission spectrometry and atomic absorption spectrometry may also be used.
Claims
1. A quantitative method for polysaccharides containing anionic groups, comprising: A preparation step of adding a sample containing a polysaccharide containing an anionic group to a cationic solution containing a cation having a known concentration to obtain a mixed solution, wherein the polysaccharide containing anionic groups reacts with the cation to gel or thicken; A measuring step of measuring the cation concentration in the mixed solution; as well as The calculation step is to calculate the concentration of the anionic group-containing polysaccharide in the sample based on the measured value obtained in the measurement step.
2. The quantitative method for polysaccharides containing anionic groups according to claim 1, wherein: In the measurement step, the mixed solution is subjected to electrochemical measurement to obtain the measurement value.
3. The quantitative method for polysaccharides containing anionic groups according to claim 2, wherein: In the preparation step, the sample is added to a container containing the cationic solution to prepare the mixed solution. When the electrochemical measurement is performed in the measurement step, the electrode is inserted into the container and immersed in the mixed solution.
4. The quantitative method for polysaccharides containing anionic groups according to claim 2, wherein: The electrochemical measurement was performed using anodic stripping voltammetry.
5. The quantitative method for polysaccharides containing anionic groups according to any one of claims 1 to 4, wherein: The polysaccharide containing anionic groups is a polysaccharide having carboxyl groups. The cation is a metal ion.
6. The quantitative method for polysaccharides containing anionic groups according to any one of claims 1 to 4, wherein: The solvent of the cationic solution and the solvent of the sample are water, The polysaccharide containing anionic groups is water-soluble pectin, The cation is a lead ion.