Particle size measurement method, calibration curve creation method, and particle size measurement apparatus

Abstract

To provide a particle size measurement method, a calibration curve creation method, and a particle size measurement device, which are simple in operation and do not require a power supply.SOLUTION: A method for measuring a particle diameter of a measurement target particle, comprising: a voltage change measuring step of adding a plurality of times the measurement target particle to a lower concentration electrolytic solution of a concentration cell including two electrolytic solutions having different concentrations and two electrodes respectively immersed in the electrolytic solutions and connected to each other; a reference particle concentration determining step of determining a reference particle concentration at a predetermined reference voltage change value based on a voltage change obtained in the voltage change measuring step; and a particle diameter determining step of determining a particle diameter of the measurement target particle based on the reference particle concentration and a calibration curve indicating a relationship between particle diameters and reference particle concentrations prepared in advance for the concentration cell.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a particle size measuring method and a particle size measuring device that utilize a concentration cell. [Background technology]

[0002] Known particle size measurement techniques include image analysis, dynamic light scattering, and Coulter counters. For example, a Coulter counter is a device that measures the number and size of particles suspended in an electrolyte solution. It uses the so-called Coulter principle, in which a particle passing through a pore changes electrical resistance, the magnitude of which is proportional to the particle volume. It is used to measure particles such as cells, bacteria, prokaryotic cells, and viruses. A typical Coulter counter is divided into two compartments containing an electrolyte solution, separated by a partition with one or more pores. When a fluid containing particles or cells passes through the pores, it causes a brief change in the electrolyte solution's electrical resistance.

[0003] In the technology described in Patent Documents 1 and 2, a Coulter counter device is installed in an electrolyte solution containing dispersed particles, with a wall surface having a single small through-hole. Electrodes are placed inside and outside the hole, and a constant current is passed through the hole. Then, by physically drawing the electrolyte from the inside of the hole, the particles pass through the hole along with the electrolyte. The electrolyte in the hole decreases by an amount equivalent to the volume of the particles, and the electrical resistance of the hole increases in proportion to the amount of electrolyte removed. Because the current flowing through the hole remains constant regardless of the presence of particles, the amount of voltage change is proportional to the amount of change in the electrical resistance of the hole. This voltage change is used to measure the particle volume, which is then used to calculate the equivalent sphere diameter and display the particle size distribution. This is the existing Coulter principle measurement method. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Application No. 2001-500842 [Patent Document 2] Patent Application No. 2011-85559 Summary of the Invention [Problem to be solved by the invention]

[0005] Conventional particle size measurement methods include image analysis, dynamic light scattering, and Coulter counter methods, but all of these methods have problems such as being expensive, requiring complicated operation, and requiring a power source.

[0006] In particular, conventional methods have had problems such as: 1) the need for a device that requires a power source or the like to control a constant current; 2) the need to use physical means to pass particles through one or more pores; and 3) the associated limitations on where they can be used.

[0007] SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a particle size measuring method, a method for creating a calibration curve, and a particle size measuring device that are easy to operate and do not require a power source. [Means for solving the problem]

[0008] The above problems are solved by the present invention described below. That is, the present invention (1) comprises two electrolytes with different concentrations, two electrodes each immersed in the electrolyte and connected to each other; a filter having a known pore size, the filter being provided between the electrolytes so as to allow the electrolytes to communicate with each other; a voltage change measuring step of adding the particles to be measured multiple times to the electrolyte having a lower concentration in a concentration cell, and measuring the voltage change of the concentration cell; a reference particle concentration determining step of determining a reference particle concentration at a predetermined reference voltage change value based on the voltage change obtained in the voltage change measuring step; a particle size determination step of determining the particle size of the particles to be measured based on the reference particle concentration and a calibration curve showing the relationship between particle size and reference particle concentration, which is prepared in advance for the filter of the concentration cell; The present invention provides a method for measuring the particle size of a particle to be measured, which comprises the steps of:

[0009] The present invention (2) also provides the particle size measuring method according to claim 1, wherein the reference particle concentration is a particle concentration per pore of the filter.

[0010] The present invention (3) also provides the particle size measuring method according to (1) or (2), characterized in that the particles are silica particles, carbon particles, metal particles or biological particles.

[0011] The present invention (4) also provides a particle size measurement method according to any one of (1) to (3), characterized in that it includes a charge determination step of determining the surface charge of the particle to be measured based on the voltage change obtained in the voltage change measurement step.

[0012] The present invention (5) is a method for creating a calibration curve used in any one of the particle size measurement methods (1) to (4), comprising: Two electrolyte solutions having different concentrations, two electrodes immersed in the electrolyte solutions and connected to each other, and a filter having a known pore size provided between the electrolyte solutions so as to allow the electrolyte solutions to communicate with each other; a voltage change measuring step of adding particles having a known particle size multiple times to the lower concentration electrolyte of a concentration cell comprising the above-mentioned, and measuring the voltage change of the concentration cell; a reference particle concentration determining step of determining a reference particle concentration at a predetermined reference voltage change value based on the voltage change obtained in the voltage change measuring step; is performed on a plurality of particles having different particle sizes, The present invention provides a method for creating a calibration curve, which is characterized by creating a calibration curve showing the relationship between the particle size and the reference particle concentration for the filter.

[0013] The present invention (6) also provides a concentration battery comprising two electrolyte solutions having different concentrations, two electrodes immersed in the electrolyte solutions and connected to each other, and a filter having a known pore size, which is provided between the electrolyte solutions so as to allow the electrolyte solutions to communicate with each other; a calculation unit that determines a reference particle concentration at a predetermined reference voltage change value based on a voltage change of the concentration cell when a particle to be measured is added to the electrolyte having the lower concentration in the concentration cell, and determines the particle size of the particle to be measured based on the reference particle concentration and a calibration curve that shows the relationship between particle size and reference particle concentration and is prepared in advance for the filter of the concentration cell; The present invention provides an apparatus for measuring the particle size of particles to be measured, which comprises: [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a particle size measuring method, a calibration curve creating method, and a particle size measuring device that are easy to operate and do not require a power source. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 2 is a diagram schematically illustrating an example of a concentration cell of the particle size measuring device of the present invention. [Figure 2] FIG. 1 is a schematic graph showing the relationship between the voltage change value and the added particle concentration, obtained by plotting the measured voltage change amount ΔV (mV) value (voltage change value) against the added particle concentration (particles-particles / L) in the method for creating a calibration curve. [Figure 3] This is a schematic calibration curve showing the relationship between particle size and reference particle concentration (particles / L), obtained by plotting the value of reference particle concentration (particles / L) against particle size (nm) for each particle size in a calibration curve creation method. [Figure 4] FIG. 4 is a schematic graph obtained by converting the calibration curve shown in FIG. 3, which shows the relationship between particle size and reference particle concentration (number-particles / L), into a calibration curve showing the relationship between particle size and reference particle concentration (g-particles / L) in a method for creating a calibration curve. [Figure 5]1 is a schematic graph showing the relationship between voltage change value and added particle concentration (g-particles / L) obtained by plotting the measured voltage change amount ΔV (mV) value (voltage change value) against the added particle concentration (g-particles / L) in a method for measuring the particle size of particles to be measured. [Figure 6] FIG. 10 is a diagram showing an example of a measurement graph of voltage change in a voltage change measurement step. [Figure 7] 1 is a graph plotting the measured voltage change ΔV (mV) (voltage change value) against the added particle concentration (particles / L) for particles with a particle size of 20 nm in an example. [Figure 8] 1 is a graph plotting the measured voltage change ΔV (mV) values ​​(voltage change values) against the added particle concentration (particles / L) for particles with a particle size of 51 nm in an example. [Figure 9] 1 is a graph plotting the measured voltage change ΔV (mV) (voltage change value) against the added particle concentration (particles / L) for particles with a particle size of 115 nm in an example. [Figure 10] 1 is a graph showing the relationship between particle size and reference particle concentration (particles / L) obtained by plotting the value of reference particle concentration (particles / L) against particle size (nm) for each particle size in the examples. [Figure 11] 1 is a graph showing the relationship between particle size and reference particle concentration (g-particles / L) obtained by plotting the values ​​of reference particle concentration (g-particles / L) against particle size (nm) for each particle size in the examples. [Figure 12] 1 is a graph plotting the measured voltage change ΔV (mV) (voltage change value) against the particle concentration per pore ((particles / L) / pore) for particles with a particle diameter of 20 nm in an example. [Figure 13] 1 is a graph plotting the measured voltage change ΔV (mV) (voltage change value) against the particle concentration per pore ((particles / L) / pore) for particles with a particle diameter of 51 nm in an example. [Figure 14]1 is a graph plotting the measured voltage change ΔV (mV) (voltage change value) against the particle concentration per pore ((particles / L) / pore) for particles with a particle diameter of 115 nm in an example. [Figure 15] FIG. 1 is a graph showing the relationship between particle size and the reference particle concentration per pore ((particles-particles / L) / pore) obtained by plotting the value of the reference particle concentration per pore ((particles-particles / L) / pore) against the particle size (nm) for each particle size in the Examples. [Figure 16] FIG. 1 is a graph showing the relationship between particle size and the reference particle concentration per pore ((particles-particles / L) / pore) obtained by plotting the value of the reference particle concentration per pore ((particles-particles / L) / pore) against the particle size (nm) for each particle size in the Examples. [Figure 17] In the example, the graph shows the behavior of potential change when the charge is positive. [Figure 18] In the example, the graph shows the behavior of potential change when the charge is negative. DETAILED DESCRIPTION OF THE INVENTION

[0016] The particle size measurement method of the present invention includes the steps of: Two electrolytes with different concentrations, two electrodes each immersed in the electrolyte and connected to each other; a filter having a known pore size, the filter being provided between the electrolytes so as to allow the electrolytes to communicate with each other; a voltage change measuring step of adding the particles to be measured multiple times to the electrolyte having a lower concentration in a concentration cell, and measuring the voltage change of the concentration cell; a reference particle concentration determining step of determining a reference particle concentration at a predetermined reference voltage change value based on the voltage change obtained in the voltage change measuring step; a particle determination step of determining the particle diameter of the particles to be measured based on the reference particle concentration and a calibration curve showing the relationship between particle diameter and reference particle concentration, which is previously prepared for the filter of the concentration cell; The method for measuring the particle size of a particle to be measured is characterized by comprising the steps of:

[0017] Furthermore, the particle size measuring device according to the particle size measuring method of the present invention is a concentration cell comprising two electrolyte solutions having different concentrations, two electrodes immersed in the electrolyte solutions and connected to each other, and a filter having a known pore size, which is provided between the electrolyte solutions so as to allow the electrolyte solutions to communicate with each other; a calculation unit that determines a reference particle concentration at a predetermined reference voltage change value based on a voltage change of the concentration cell when a particle to be measured is added to the electrolyte having the lower concentration in the concentration cell, and determines the particle size of the particle to be measured based on the reference particle concentration and a calibration curve that is prepared in advance for the concentration cell and shows the relationship between particle size and reference particle concentration; The particle size measuring device for measuring particles to be measured is characterized by having:

[0018] The method of the present invention for measuring the particle size of particles to be measured is a method for measuring the particle size (average particle size) of the particles to be measured using a concentration cell comprising two electrolytes of different concentrations, two electrodes immersed in the electrolytes and connected to each other, and a filter placed between the two electrolytes to allow communication between the two electrolytes.

[0019] The particle size measuring device according to the particle size measuring method of the present invention is a device used in the particle size measuring method of the present invention for measuring the particle size of a particle to be measured, and has a concentration cell that includes two electrolytes of different concentrations, two electrodes that are immersed in the electrolytes and connected to each other, and a filter that is placed between the two electrolytes so that the two electrolytes can communicate with each other.

[0020] Fig. 1 is a schematic diagram illustrating an example of a concentration cell for the particle size measurement method and particle size measurement device of the present invention. In Fig. 1, concentration cell 1 includes low-concentration electrolyte 10, low-concentration electrolyte container 2 for containing electrolyte 10, high-concentration electrolyte 11, high-concentration electrolyte container 3 for containing electrolyte 11, low-concentration electrolyte electrode 4 immersed in electrolyte 10, high-concentration electrolyte electrode 5 immersed in electrolyte 11, connection path 12 electrically connecting low-concentration electrolyte electrode 4 and high-concentration electrolyte electrode 5, voltmeter 6 attached to connection path 12, low-concentration electrolyte communication passage 7 connected to low-concentration electrolyte container 2 and communicating with high-concentration electrolyte container 3, high-concentration electrolyte communication passage 8 connected to high-concentration electrolyte container 3 and communicating with low-concentration electrolyte container 3, and filter 9 attached between low-concentration communication passage 7 and high-concentration communication passage 8. In the concentration cell 1, the electrolyte solution 10 with a lower concentration moves through the pores of the filter 9 to the electrolyte solution 11 with a higher concentration due to osmotic pressure.

[0021] <Concentration battery> The concentration battery of the present invention is constructed by preparing, for example, a cell containing a dilute electrolyte (e.g., a low-concentration CuSO4 aqueous solution) and a cell containing a more concentrated electrolyte (e.g., a high-concentration CuSO4 aqueous solution), connecting the two cells via a filter, placing electrodes (e.g., copper plates) in both electrolytes, and connecting them via a voltmeter.

[0022] The concentration cell of the present invention utilizes the change in electrode potential depending on the concentration (activity, partial pressure) of the same substance. Its principle can be easily understood, for example, from the Nernst equation. In a concentration cell, electrons move through two interconnected electrolytes with different concentrations to eliminate the overall difference in electrolyte concentration, with the electrodes acting as anode and cathode, respectively. The higher-concentration electrolyte becomes lower in concentration and the lower-concentration electrolyte becomes higher in concentration. As a result, metals in the lower-concentration electrolyte release electrons and become ionized, while the higher-concentration electrolyte receives the electrons released by the lower-concentration electrolyte, resulting in metal precipitation. Therefore, when considered as a battery, the electrode with the higher-concentration electrolyte becomes the positive electrode. Due to osmotic pressure, the lower-concentration electrolyte moves through the pores of the filter into the higher-concentration electrolyte. Therefore, particles added during particle size measurement reach the filter and pass through the pores of the filter along with the lower-concentration electrolyte.

[0023] <About other batteries> The particle size measuring device according to the particle size measuring method of the present invention utilizes the phenomenon (in this device, an increase in the internal resistance of a concentration cell) that occurs when particles move in conjunction with the movement of the dispersion medium (water in this device) caused by an osmotic pressure difference, blocking the pores. Any device other than a concentration cell can be used as long as it can utilize this phenomenon. Even without an osmotic pressure difference, applying external pressure causes particles to block the pores in the diaphragm, lowering the measurement voltage and making measurement possible.

[0024] <Electrode> The shape of the electrodes of the concentration battery according to the present invention is not particularly limited as long as they can be immersed in the electrolyte in a cell containing the electrolyte. The material of the electrodes is not particularly limited as long as they function as a battery, and copper, zinc, or silver are preferably used for ease of handling and reactivity. The concentration battery also has two electrodes immersed in a low-concentration electrolyte and a high-concentration electrolyte, respectively. The two electrodes are electrically connected, and a voltmeter is installed along the path connecting the two electrodes.

[0025] <Electrolyte> The concentration battery according to the present invention contains two electrolytes with different concentrations. It is preferable to select an electrolyte that basically promotes the reactions accompanying the ionization and precipitation of the electrode material. The electrolyte is preferably an AgNO3 aqueous solution, a CuSO4 aqueous solution, a NaCl aqueous solution, a KCl aqueous solution, or the like. The concentration of each electrolyte is selected appropriately. For example, combinations of electrodes and electrolytes such as Cu electrode | dilute CuSO4 aqueous solution | concentrated CuSO4 aqueous solution | Cu electrode, or Ag electrode | dilute AgNO3 aqueous solution | concentrated AgNO3 aqueous solution | Ag electrode are preferable when considering long-term operation of the battery.

[0026] <filter> In the concentration cell of the present invention, the two types of electrolytes are separated by a filter. A filter refers to a partition with a large number of pores. The filter refers to, for example, a membrane filter, and suitable materials include polyethersulfone, polyvinylidene fluoride, cellulose mixed ester, polytetrafluoroethylene, alumina, and hydrophilic polycarbonate track etched (PCTE), but there are no particular limitations. The filter is provided between the two electrolytes to allow communication between the two electrolytes. The filter used has a known pore size (average pore size). In the particle size measurement method of the present invention, the filter used to measure the particles to be measured and the filter used to create a calibration curve for particle size determination are the same.

[0027] The pore size of the filter is appropriately selected depending on the particles to be measured, but for example, a filter with an average pore size of 10 nm to 20 μm, preferably 50 nm to 12 μm, can be used.

[0028] The particle size measuring device of the present invention includes a calculation unit that determines a reference particle concentration at a predetermined reference voltage change value based on a voltage change across the concentration cell when particles to be measured are added to the electrolyte with the lower concentration in the concentration cell, and determines the particle size of the particles to be measured based on the reference particle concentration and a calibration curve that shows the relationship between particle size and reference particle concentration and is prepared in advance for the filter of the concentration cell.

[0029] <Arithmetic section> The calculation unit may be part of an information processing device such as a personal computer. The information processing device may be a general device including an input unit that accepts input, a calculation unit that performs calculation processing based on the input from the input unit, a control unit that controls the calculation unit, a memory unit that stores a control program and various data, and an output unit that outputs the results of the calculation processing. The calculation unit is capable of acquiring data on voltage changes measured by a voltmeter in the concentration cell and data on particle concentrations. The calculation unit can create a graph showing the relationship between voltage changes and particle concentrations based on the acquired data on voltage changes and data on particle concentrations, and perform calculations to determine a reference particle concentration at a predetermined reference voltage change value from the graph. The calculation unit can also perform calculations to determine the particle size of particles to be measured based on the reference particle concentration and a calibration curve that has been created in advance. Furthermore, for a filter having a known pore size used in the measurement, data on voltage change and data on particle concentration can be obtained for particles of different known particle sizes, a graph showing the relationship between voltage change and particle concentration for each particle can be created, a calculation can be performed to determine a reference particle concentration at a predetermined reference voltage change value from the graph, a calculation can be performed to determine a reference particle concentration for each particle at a predetermined reference voltage change value from the graph, and a calculation can be performed to create a calibration curve showing the relationship between particle size and reference particle concentration.The created calibration curve data can be stored in a memory unit.

[0030] This invention is a novel particle size measurement method that utilizes the voltage change of a concentration cell. Compared to conventional principles and devices, it is inexpensive, simple, and requires no power source. In a concentration cell, an electromotive force is generated by the potential difference between a high-concentration electrolyte and a low-concentration electrolyte. Particles are added to a low-concentration electrolyte, and particle movement due to osmotic pressure is utilized to measure particles. Specifically, when added particles move from a low-concentration electrolyte through a filter to a high-concentration electrolyte, the voltage change occurring when larger particles pass through the filter pores is greater than the voltage change occurring when smaller particles pass through the filter pores. This allows the particle size of the added particles to be measured based on the voltage change.

[0031] In the method of measuring the particle size of a particle to be measured according to the present invention, the particle size of the particle to be measured is determined using a calibration curve prepared in advance.

[0032] An example of a method for creating a calibration curve for the particle size measurement method of the present invention will be described with reference to FIGS. 2 to 4. First, using standard particles with known average particle size and particle concentration, standard particles P (average particle size x (nm), particle concentration a (particles / L)) are added multiple times (six times in FIG. 2) to the lower concentration electrolyte of a concentration cell of filter A with a known pore size (average pore size α (nm)), and the voltage change of the concentration cell is measured after each particle addition. Next, as shown in FIG. 2, the measured voltage change ΔV (mV) (voltage change value) is plotted against the added particle concentration (particles / L) for each particle addition, creating a graph showing the relationship between the voltage change value and the added particle concentration. Next, from the graph of FIG. 2, the reference particle concentration (reference number 23) at a predetermined reference voltage change value (reference number 22) set at or above the detection limit voltage change (reference number 21) is read, and the reference particle concentration (particles / L) is determined. The reference particle concentration (particles / L) determined in this manner is the reference particle concentration (particles / L) corresponding to the average particle diameter x (nm) of particles when filter A having a pore diameter α (nm) is used. A similar procedure is performed on filter A having a pore diameter α (nm) using one or more standard particles of different diameters. For example, in the example of Figure 3, standard particle Q (average particle diameter y (nm), particle concentration b (particles / L)) and standard particle R (average particle diameter z (nm), particle concentration c (particles / L)) are used to determine the reference particle concentration (particles / L) corresponding to the average particle diameter y (nm) and the reference particle concentration (particles / L) corresponding to the average particle diameter z (nm) when filter A having a pore diameter α (nm) is used. Next, as shown in Figure 3, the values ​​of the reference particle concentration (particles / L) against the particle diameter (nm) are plotted for each particle diameter, and a calibration curve showing the relationship between particle diameter and reference particle concentration (particles / L) is created. Next, the density (g / cm) of each standard particle is calculated. 3 ) is used to convert the calibration curve in Figure 3 into a calibration curve showing the relationship between particle size and reference particle concentration (g-particles / L), as shown in Figure 4.

[0033] An example of a particle size measurement method for target particles according to the present invention will be described with reference to FIGS. 4 and 5. First, prior to measurement, the target particles are dried to determine their concentration (g-particles / L). Next, the target particles are added multiple times (six times in FIG. 5 ) to the lower-concentration electrolyte in the concentration cell, and the voltage change in the concentration cell is measured after each particle addition. Next, as shown in FIG. 5 , the measured voltage change ΔV (mV) is plotted against the added particle concentration (g-particles / L) for each particle addition, creating a graph showing the relationship between the voltage change and the added particle concentration (g-particles / L). Next, a reference particle concentration (25) at a predetermined reference voltage change value (24) identical to the calibration curve is read from the graph in FIG. 5 to determine the reference particle concentration (g-particles / L) of the target particles. Next, based on the calibration curve in FIG. 4 , the particle size (nm) corresponding to the reference particle concentration (g-particles / L) of the target particles is read, and the particle size of the target particles is determined.

[0034] The particle size measurement method of the present invention for measuring the particle size of a particle to be measured includes a voltage change measurement step of adding the particle to be measured multiple times to the electrolyte with a lower concentration in a concentration cell of the particle size measurement device of the present invention and measuring the voltage change in the concentration cell.

[0035] The particles to be measured may be inorganic particles, organic particles, or organic-inorganic hybrid particles. Examples of particles to be measured include inorganic particles such as silica particles, carbon particles, and metal particles; particulate industrial raw materials such as dyes, toners, food, abrasives, explosives, and clay; and organic particles including biological particles such as blood, cells, bacteria, viruses, and intracellular organelles. Regarding the particle size of the particles to be measured, various particle sizes can be measured by selecting an appropriate filter pore size for each particle to be measured. The particle size measurement method for particles to be measured and the particle size measurement device for particles to be measured of the present invention are particularly suitable for measuring particles with a relatively uniform particle size distribution.

[0036] The particles to be measured are either powder particles or a suspension in which the particles to be measured are dispersed in an aqueous dispersion medium. To determine the concentration of the added particles, a portion is sampled and dried, and the concentration of the particles to be measured is calculated from the dry mass and the sample amount.

[0037] Next, the particles to be measured are added to the lower-concentration electrolyte in the concentration cell at appropriate time intervals, and the voltage change is measured for each particle addition. When the particles to be measured are added to the lower-concentration electrolyte in the concentration cell, the lower-concentration electrolyte passes through the filter due to osmotic pressure and moves into the higher-concentration electrolyte, causing the particles to pass through the filter. At this time, the voltage of the concentration cell changes.

[0038] The voltage change in the voltage change measurement step is the voltage drop from the baseline voltage value. The voltage change amount in the voltage change measurement step is the total voltage change from the first particle addition. In the particle size measurement method of the present invention, the detection limit is defined as three times the noise width. Previous experiments have shown that the noise width is 0.05 to 0.08 mV, so the detection limit value is 0.15 to 0.24 mV, and the detection limit voltage can be fixed at 0.20 mV on average. Figure 6 shows an example of a voltage change measurement graph. In Figure 6, the voltage value from point 32 where the peak rises from baseline 31 to peak top 33 is the voltage change amount 34. Since the voltage change is observed with each particle addition, the voltage change for each addition is measured.

[0039] The particle size measurement method of the present invention includes a reference particle concentration determination step of determining a reference particle concentration at a predetermined reference voltage change value based on the voltage change obtained in the voltage change measurement step. The reference voltage change value is equal to or greater than the detection limit voltage value and is selected according to the object to be measured. The reference voltage change value in the reference particle concentration determination step is the same as the reference voltage change value used to create a calibration curve that is prepared in advance. The reference particle concentration is the particle concentration at the reference voltage change value. For example, the measured voltage change amount ΔV (mV) is plotted against the added particle concentration (g-particles / L) for each particle addition to create a graph showing the relationship between the voltage change value and the added particle concentration (g-particles / L). Next, the reference particle concentration at the predetermined reference voltage change value that is the same as the previously prepared calibration curve is read from the obtained graph to determine the reference particle concentration (g-particles / L) of the particles to be measured.

[0040] The method for measuring the particle size of a particle to be measured of the present invention includes a particle size determination step of determining the particle size of the particle to be measured based on a reference particle concentration and a calibration curve previously prepared for a concentration cell, the calibration curve showing the relationship between particle size and reference particle concentration. For example, the particle size corresponding to the reference particle concentration (g-particles / L) of the particle to be measured determined in the reference particle concentration determination step is read based on the previously prepared calibration curve, and the particle size of the particle to be measured is determined.

[0041] The calibration curve used in the particle size determination step in the particle size measurement method of the present invention for particles to be measured will be described with reference to the calibration curve creation method of the present invention. The method for creating a calibration curve of the present invention is a method for creating a calibration curve used in the method for measuring the particle size of particles to be measured of the present invention, which comprises the steps of: Two electrolyte solutions having different concentrations, two electrodes immersed in the electrolyte solutions and connected to each other, and a filter having a known pore size provided between the electrolyte solutions so as to allow the electrolyte solutions to communicate with each other; a voltage change measuring step of adding particles having a known particle size multiple times to the lower concentration electrolyte of a concentration cell, and measuring a voltage change of the concentration cell; a reference particle concentration determining step of determining a reference particle concentration at a predetermined reference voltage change value based on the voltage change obtained in the voltage change measuring step; is performed for particles of different sizes, The method for creating a calibration curve is characterized by creating a calibration curve showing the relationship between the particle size and the reference particle concentration for the filter.

[0042] In the method for creating a calibration curve of the present invention, the calibration curve is created using the particle size measuring device according to the particle size measuring method of the present invention.

[0043] The method for creating a calibration curve of the present invention includes a voltage change measurement step of adding particles having a known particle size multiple times to a low-concentration electrolyte of a concentration cell and measuring the voltage change of the concentration cell.

[0044] The particles having a known particle size used in the voltage change measurement step in the method for creating a calibration curve of the present invention are particles with known average particle size and particle concentration (individual particles / L or g particles / L). The particles having a known particle size are a suspension in which particles having a known particle size are dispersed in an aqueous dispersion medium. The particles having a known particle size are preferably uniform in size, and for example, particles having a coefficient of variation (CV) of 20% or less, calculated by dividing the standard deviation of the particle size by the mean value, are preferred.

[0045] Next, particles having a known particle size are added to the less concentrated electrolyte in the concentration cell at appropriate time intervals, and the change in voltage for each particle addition is measured.

[0046] The voltage change in the voltage change measurement step is the voltage drop from the baseline voltage value. The voltage change amount in the voltage change measurement step is the total voltage change from the initial particle addition. In the present invention, the detection limit is defined as three times the noise width. Previous experiments have shown that the noise width is 0.05 to 0.08 mV, so the detection limit is 0.15 to 0.24 mV, and the detection limit voltage can be fixed at 0.20 mV on average. In the voltage change measurement step of the particle size measurement method of the present invention, the particles added are particles to be measured with unknown particle sizes, whereas in the voltage change measurement step of the calibration curve creation method of the present invention, the particles added are particles with known particle sizes. However, the voltage change measurement step of the calibration curve creation method of the present invention can be performed in the same manner as the voltage change measurement step of the particle size measurement method of the present invention.

[0047] The calibration curve creation method of the present invention includes a reference particle concentration determination step of determining a reference particle concentration at a predetermined reference voltage change value based on the voltage change obtained in the voltage change measurement step. The reference voltage change value is an arbitrary voltage change value equal to or greater than the detection limit voltage, and the reference particle concentration is the particle concentration at the reference voltage change value. The reference voltage change value in the reference particle concentration determination step of the calibration curve creation method of the present invention is the same as the reference voltage change value in the reference particle concentration determination step of the particle size measurement method of the present invention. The method for determining the reference particle concentration in the reference particle concentration determination step of the calibration curve creation method of the present invention is the same as the method for determining the reference particle concentration in the reference particle concentration determination step of the particle size measurement method of the present invention. For example, when the concentration of particles having known particle sizes used in the voltage change measurement step is known in terms of (particles / L), the measured voltage change ΔV (mV) value (voltage change value) is plotted against the added particle concentration (particles / L) for each particle addition, and a graph showing the relationship between the voltage change value and the added particle concentration (particles / L) is created. Next, the reference particle concentration at a predetermined reference voltage change value is read from the obtained graph, and the reference particle concentration (g-particles / L) of particles having a known particle size is determined. Furthermore, if the concentration of particles having a known particle size used in the voltage change measurement step is known as (g-particles / L), the measured voltage change ΔV (mV) value (voltage change value) is plotted against the added particle concentration (g-particles / L) for each particle addition, and a graph showing the relationship between the voltage change value and the added particle concentration (g-particles / L) is created. Next, the reference particle concentration at a predetermined reference voltage change value is read from the obtained graph, and the reference particle concentration (g-particles / L) of particles having a known particle size is determined.

[0048] The voltage change measuring step and the reference particle concentration determining step in the calibration curve creating method of the present invention are performed on particles of different particle sizes using the same filter, and a calibration curve showing the relationship between the particle size and the reference particle concentration for the filter is created. For example, when the concentration of particles with known particle sizes used in the voltage change measuring step is known as (g-particles / L), the value of the reference particle concentration (particles-particles / L) against the particle size is plotted for each particle size, and a calibration curve showing the relationship between particle size and the reference particle concentration (particles-particles / L) is created. Next, the density (g / cm) of each of the particles with known particle sizes used in the voltage change measuring step is calculated. 3 ) is used to convert the calibration curve showing the relationship between particle size and reference particle concentration (number-particles / L) into a calibration curve showing the relationship between particle size and reference particle concentration (g-particles / L). Furthermore, when the concentrations of particles with known particle sizes used in the voltage change measurement step are known as (g-particles / L), the values ​​of the reference particle concentration (g-particles / L) are plotted against particle size for each particle size to create a calibration curve showing the relationship between particle size and reference particle concentration (g-particles / L). In the calibration curve creation method of the present invention, from the viewpoint of increasing the accuracy of the calibration curve, the more data points of the "relationship between particle size and reference particle concentration" plotted to create the calibration curve, the better. In other words, the more particles with known particle sizes are used in the voltage change measurement step and the reference particle concentration determination step, the better from the viewpoint of the accuracy of the calibration curve.

[0049] In the method for measuring the particle size of a particle to be measured of the present invention, the particle size measuring device of the present invention, and the method for creating a calibration curve of the present invention, the reference particle concentration can be the particle concentration per filter pore ((particles / L) / pore) or ((g-particles / L) / pore)). In the voltage change measuring step described above, the particle concentration in the additive solution is determined as (particles / L) or (g-particles / L), but by dividing this particle concentration by the number of filter pores and converting it to a particle concentration per filter pore, the reference particle concentration can be used as the particle concentration per filter pore ((particles / L) / pore) or ((g-particles / L) / pore)).

[0050] In the method for creating a calibration curve of the present invention, calibration curves are created for a plurality of filters with different pore sizes, and by preparing calibration curves for filters with a plurality of pore sizes, the range of pore sizes of the filters used in the method for measuring the particle size of particles to be measured of the present invention can be expanded, and an appropriate filter can be used depending on the particle size of the particles to be measured, thereby improving the accuracy of the analysis.

[0051] The particle size measurement method of the present invention can include a charge determination step of determining the surface charge of the particle based on the voltage change obtained in the voltage change measurement step. Specifically, in the charge determination step, if the voltage change is below a baseline voltage value, it can be determined that the surface charge of the particle is negative, and if the voltage change is above the baseline voltage value, it can be determined that the surface charge of the particle is positive. In the voltage change measurement step, negatively charged particles approach the filter, and the surface charge of, for example, Cu on the filter is determined. 2+ It is believed that the formation of ion pairs with ions reduces the polarity of the filter, inhibiting ion migration and resulting in the observed decrease in electromotive force. On the other hand, it is believed that the approach of positively charged particles to the filter increases the polarity of the membrane, promoting ion migration and resulting in an increase in electromotive force.

[0052] A molecularly imprinted polymer (MIP) is a polymer that serves as a template for a target, such as a drug, in blood and increases in particle size by capturing the target. Therefore, by carrying out the particle size measurement method of the present invention using a molecularly imprinted polymer (MIP) that has captured a target, such as a drug, in blood as the particle to be measured, the concentration of the drug or other substance in the blood can be rapidly measured. Therefore, the particle size measurement device of the present invention for particles to be measured can be applied to a biosensor for measuring the concentration of a drug or other substance in blood, and the particle size measurement method of the present invention for particles to be measured can be applied to a particle size measurement method for measuring the concentration of a drug or other substance in blood using a biosensor for measuring the concentration of a drug or other substance in blood.

[0053] Because the particle size measurement method of the present invention uses a concentration battery, all that is required is a concentration battery and a battery-powered personal computer, such as a laptop PC, for recording and calculating the measured voltage. Therefore, the implementation of the particle size measurement method of the present invention does not require a device that requires a power source to control a constant current, or a physical means for passing particles through one or more pores, so there are no limitations on the location of use associated with these. For this reason, the particle size measurement method of the present invention can be quickly implemented at the particle manufacturing site.

[0054] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples shown below. [Example]

[0055] The particle size measuring method and particle size measuring device of the present invention will be described below with reference to examples, although the present invention is not limited to these embodiments.

[0056] In this example, the detection limit is defined as three times the noise width. Previous experiments have confirmed that the noise width is 0.05 to 0.08 mV, and the average detection limit is 0.2 mV, so the reference voltage change value was set to 0.2 mV.

[0057] (Particle size measurement method) A 0.01 mM CuSO4 aqueous solution and a 100 mM CuSO4 aqueous solution were prepared as electrolytes and placed in the measurement device. Nine types of polycarbonate filters with different pore sizes (10 nm, 30 nm, 50 nm, 100 nm, 200 nm, 400 nm, 1 μm, 8 μm, and 12 μm) were used. Three types of particles with different particle sizes were used. The particles used were silica particles, PL-1 (particle size 20±3 nm) manufactured by Fuso Chemical Co., Ltd. (addition concentration: 1.4 × 10 15 ~1.4×10 16 particles / L), PL-3 (particle size 51 ± 10 nm) (addition concentration: 1.2 × 10 14~1.2×10 15 particles / L), PL-7 (particle size 115±9nm) (addition concentration: 2.1×10 13 ~2.1×10 14 Three types of chlorine were added to the concentration cell every 10 minutes for a total of six times, and the voltage change of the concentration cell was measured.

[0058] As a result, it was confirmed that particle measurement was impossible due to noise when the filter pore diameters were small, 10 nm and 30 nm, and therefore these were excluded from the evaluation.

[0059] Next, based on the obtained data, data processing was carried out in the following procedure. <Method for determining particle size from reference particle concentration [particles / L]> (1) Calculation of the reference particle concentration [particles / L] at a reference voltage change value of 0.2 mV To determine the particle concentration at a reference voltage change of 0.2 mV, i.e., the reference particle concentration [particles / L], the correlation between the concentration and the voltage change value at each addition of silica particles, which was carried out six times every 10 minutes, was plotted for each particle. The results are shown in Figures 7 to 9. It was confirmed that the voltage change increased as the particle concentration increased for all particle sizes, but no correlation was observed between the pore size and the voltage change. Furthermore, no voltage change was observed when the filter pore size was 12 μm for a particle size of 20 nm, presumably because the particle size was too small for the pore size or the concentration was too low. In Figure 7, the plots with the highest added particle concentrations for each pore size are, in order from largest to smallest voltage change, 50 nm, 100 nm, 200 nm, 8 μm, 1 μm, 400 nm, and 12 μm. In Figure 8, the plots with the highest added particle concentrations for each pore size are, in order from largest to smallest voltage change, 1 μm, 200 nm, 50 nm, 100 nm, 400 nm, 8 μm, and 12 μm. In Figure 9, the plots with the highest added particle concentrations for each pore size are, in order from largest to smallest voltage change, 1 μm, 50 nm, 400 nm, 200 nm, 100 nm, 8 μm, and 12 μm.

[0060] (2) Calculation of reference particle concentration [g-particles / L] Based on the above plot, the reference particle concentration [particles / L] at a reference voltage change value of 0.2 mV was determined for each pore size and particle size.

[0061] (3) Creating a graph showing the relationship between reference particle concentration [particles / L] and particle size at a reference voltage change value of 0.2 mV The correlation between particle size and reference particle concentration [particles-particles / L] at a reference voltage change of 0.2 mV was plotted for each pore size and particle size obtained above. The results are shown in Figure 10. In FIG. 10, the largest particle diameters plotted in the graph for each pore diameter are 12 μm, 8 μm, 200 nm, 400 nm, 100 nm, 1 μm, and 50 nm, in order of highest detection limit particle concentration.

[0062] (4) Create a graph showing the relationship between reference particle concentration [g-particles / L] and particle size at a reference voltage change value of 0.2 mV. The reference particle concentration [particles / L] at a reference voltage change value of 0.2 mV for each pore size and particle size obtained above was calculated as the density of each particle [g / cm 3 The particle size was converted into the reference particle concentration [g-particles / L] at a reference voltage change of 0.2 mV using the value of [ ], and the correlation between the particle size and the reference particle concentration [g-particles / L] at a reference voltage change of 0.2 mV was plotted. The results are shown in Figure 11. In FIG. 11, the largest particle diameters plotted in the graph for each pore diameter are 12 μm, 8 μm, 200 nm, 400 nm, 100 nm, 1 μm, and 50 nm, in order of highest detection limit particle concentration.

[0063] These results show that the particle size is determined by the filter pore size and particle concentration [g-particles / L]. It is also clear that calibration curves for filters with different pore sizes can be prepared in the manner described above. Furthermore, for particles of unknown particle size, the reference particle concentration of the particles of unknown particle size can be determined as described above, and then the particle size at the reference particle concentration can be read from the calibration curve created as described above, thereby determining the particle size of the particles of unknown particle size.

[0064] <Method for determining particle size from the reference particle concentration per pore [(g-particles / L) (pores)] at a reference voltage change of 0.2 mV> (1) Calculation of the reference particle concentration per pore [(g-particles / L) (pore)] at a reference voltage change value of 0.2 mV The number of pores in each filter used above is as follows. Therefore, the particle concentration per pore ((particles / L) / pore) is calculated by dividing the particle concentration [particles-particles / L] measured when the voltage change was measured above by the number of pores in each filter (pores).

[0065] [Table 1]

[0066] Next, to determine the particle concentration per pore at 0.2 mV, which was set as the reference voltage change value, i.e., the reference particle concentration per pore [particles-particles / L], the correlation between the particle concentration per pore calculated above ((particles-particles / L) / particles-pore) and the voltage change was plotted for each particle. The results are shown in Figures 12 to 14. When particle concentration [particles-particles / L] was plotted on the horizontal axis, no correlation was observed between pore diameter and voltage change. However, by plotting the number of particles per pore ((particles-particles) / L) / particles-pore) on the horizontal axis, a correlation was confirmed between the increase in particles per pore and voltage change, indicating that a voltage change occurs when particles pass through the pores. 12 to 14, the plots with the largest voltage change in the graphs for each pore diameter are those for pore diameters of 50 nm, 100 nm, 200 nm, 400 nm, 1 μm, 8 μm, and 12 μm, in order from lowest particle concentration per pore.

[0067] (2) Calculation of the reference particle concentration per pore [(particles / L) / pore] Based on the above plot, the reference particle concentration per pore [(particles / L) / pore] at a reference voltage change value of 0.2 mV was determined for each pore size and particle size.

[0068] (3) Creating a graph showing the relationship between the reference particle concentration per pore [(particles-particles / L) / pore] and particle size at a reference voltage change value of 0.2 mV The correlation between particle size and reference particle concentration [(particles-particles / L) / particles-pore] at a reference voltage change of 0.2 mV was plotted for each pore size and particle size obtained above. The results are shown in Figure 15.

[0069] (4) Create a graph showing the relationship between the reference particle concentration per pore [(g-particles / L) / pore] and particle size at a reference voltage change value of 0.2 mV. The reference particle concentration per pore [(particles / L) / pore] at a reference voltage change value of 0.2 mV for each pore size and particle size obtained above was calculated as the density of each particle [g / cm 3 The particle diameter was converted to the reference particle concentration per pore [(g-particles / L) / pore] at a reference voltage change of 0.2 mV using the value of [(g-particles / L) / pore], and the correlation between the particle diameter and the reference particle concentration per pore [(g-particles / L) / pore] at a reference voltage change of 0.2 mV was plotted. The results are shown in Figure 16.

[0070] From these results, it can be said that although no correlation was observed previously between pore size and particle concentration [particles / L], a correlation was observed between pore size and particle concentration in terms of particle concentration per pore ((g particles / L) / pore). This means that it is possible to measure particles at lower concentrations by making the pores smaller.

[0071] (Method for measuring particle surface charge) Silica microparticles with positive and negative zeta potentials were prepared, and four different amounts were added to the lower-concentration electrolyte in the concentration cell, as described above, and the voltage change was measured. The results are shown in Figures 17 and 18. The graph in Figure 17 shows the potential change behavior when a positive charge is applied, and the graph in Figure 18 shows the potential change behavior when a negative charge is applied. A voltage below the baseline voltage indicates a negative charge, and a voltage above the baseline voltage indicates a positive charge, demonstrating that it is possible to measure surface charge. When negatively charged particles approach the film, Cu on the film 2+ It is thought that as a result of forming an ion pair with the positively charged particles, the polarity of the membrane decreases, suppressing ion movement and resulting in the observed decrease in electromotive force. On the other hand, it is thought that as the positively charged particles approach the membrane, the polarity of the membrane increases, promoting ion movement and resulting in an increase in electromotive force.

Claims

1. Two electrolytes with different concentrations, two electrodes each immersed in the electrolyte and connected to each other; a filter having a known pore size, the filter being provided between the electrolytes so as to allow the electrolytes to communicate with each other; a voltage change measuring step of adding the particles to be measured multiple times to the electrolyte having a lower concentration in a concentration cell, and measuring the voltage change of the concentration cell; a reference particle concentration determining step of determining a reference particle concentration at a predetermined reference voltage change value based on the voltage change obtained in the voltage change measuring step; a particle size determination step of determining the particle size of the particles to be measured based on the reference particle concentration and a calibration curve showing the relationship between particle size and reference particle concentration, which is prepared in advance for the filter of the concentration cell; A method for measuring the particle size of a particle to be measured, comprising:

2. 2. The particle size measuring method according to claim 1, wherein the reference particle concentration is a particle concentration per pore of the filter.

3. 3. The particle size measuring method according to claim 1, wherein the particles are silica particles, carbon particles, metal particles, or biological particles.

4. 3. The particle size measuring method according to claim 1, further comprising a charge determining step of determining a surface charge of the particle to be measured based on the voltage change obtained in the voltage change measuring step.

5. A method for creating a calibration curve used in the particle size measurement method according to claim 1, comprising: Two electrolyte solutions having different concentrations, two electrodes immersed in the electrolyte solutions and connected to each other, and a filter having a known pore size provided between the electrolyte solutions so as to allow the electrolyte solutions to communicate with each other; a voltage change measuring step of adding particles having a known particle size multiple times to the lower concentration electrolyte of a concentration cell comprising the above-mentioned, and measuring the voltage change of the concentration cell; a reference particle concentration determining step of determining a reference particle concentration at a predetermined reference voltage change value based on the voltage change obtained in the voltage change measuring step; is performed on a plurality of particles having different particle sizes, A method for creating a calibration curve, comprising creating a calibration curve showing the relationship between the particle size and the reference particle concentration for the filter.

6. a concentration cell comprising two electrolyte solutions having different concentrations, two electrodes immersed in the electrolyte solutions and connected to each other, and a filter having a known pore size, which is provided between the electrolyte solutions so as to allow the electrolyte solutions to communicate with each other; a calculation unit that determines a reference particle concentration at a predetermined reference voltage change value based on a voltage change of the concentration cell when a particle to be measured is added to the electrolyte having the lower concentration in the concentration cell, and determines the particle size of the particle to be measured based on the reference particle concentration and a calibration curve that shows the relationship between particle size and reference particle concentration and is prepared in advance for the filter of the concentration cell; 1. A particle size measuring device for measuring particles to be measured, comprising:

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