Particle size distribution analyzer, particle size distribution analyzer method, and program for particle size distribution analyzer

Abstract

A centrifugal sedimentation-type particle size distribution measurement device that measures the particle size distribution in a measurement sample by rotating a measurement cell that contains the measurement sample and causing particles in the measurement sample to sediment, said particle size distribution measurement device comprising: a light source that irradiates the measurement cell with light; a scattered light detector that detects the intensity of scattered light caused by the particles in the measurement cell; and a particle size distribution calculation unit that measures the particle size distribution in the measurement sample on the basis of the change over time in the scattered light intensity, said change being caused by the particle sedimentation.

Description

Technical Field

[0001] The present invention relates to a particle size distribution measuring device, a particle size distribution measuring method, and a program for a particle size distribution measuring device.

Background Art

[0002] Conventionally, as a particle size distribution measuring device, a centrifugal sedimentation method is used in which a measurement cell containing a particle group dispersed in a dispersion medium is rotated to sediment the particles, and the particle size distribution is measured based on the time change of the transmitted light intensity (or absorbance) obtained by irradiating the measurement cell with light (Patent Document 1). In the measurement by this centrifugal sedimentation method, although there is an advantage that the particle size distribution can be measured in a relatively wide particle size range, there is a drawback that the particle size distribution cannot be measured for particles having no absorption band with respect to the light of the light source mounted on the device, or for particles having a small particle size and little light absorption.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present invention has been made in view of the above problems, and the main problem is to provide a centrifugal sedimentation type particle size distribution measuring device capable of measuring the particle size distribution of particles with low absorbance.

Means for Solving the Problems

[0005] In solving the above problems, the inventors of the present invention focused on the fact that particles with small particle size and low absorbance tend to scatter light easily. After diligent research, the inventors discovered that by detecting the intensity of scattered light obtained by irradiating particles that are settling by centrifugation and measuring its change over time, the settling time of the particles can be determined, and thereby the particle size distribution can be measured, leading to the present invention.

[0006] In other words, the particle size distribution measuring device according to the present invention is a centrifugal sedimentation type that rotates a measuring cell containing a measurement sample to settle the particles in the measurement sample and measure the particle size distribution of the measurement sample, and is characterized by comprising a light source that irradiates the measuring cell with light, a scattered light detector that detects the intensity of scattered light from the particles in the measuring cell, and a particle size distribution calculation unit that measures the particle size distribution of the measurement sample based on the time change of the scattered light intensity caused by the sedimentation of the particles.

[0007] With this type of device, the particle size distribution is measured using scattered light information, making it possible to measure the particle size distribution of particles that do not have an absorption band for the light source mounted on the device, or particles with a small particle size that absorb little light.

[0008] Specific embodiments of the scattered light detector include one comprising at least one of a forward photodetector that detects forward scattered light from the particle and a back photodetector that detects back scattered light. With this type of device, scattered light from particles can be detected efficiently.

[0009] Preferably, the particle size distribution measuring device further includes a transmitted light detector that detects the intensity of transmitted light that has passed through the measuring cell, and the particle size distribution calculation unit further measures the particle size distribution of the measurement sample based on the time change of the transmitted light intensity. With this type of device, it is possible to measure the particle size distribution by the time change of scattered light intensity and by the time change of transmitted light intensity. By using these methods appropriately depending on the absorbance of the settling particles, the particle size distribution can be measured with greater accuracy.

[0010] Furthermore, it is preferable that the particle size distribution calculation unit measures the particle size distribution of particles with a diameter greater than a predetermined threshold based on the time change of the transmitted light intensity, and measures the particle size distribution of particles with a diameter less than or equal to the predetermined threshold based on the time change of the scattered light intensity. In this way, the particle size distribution of large particles with high absorbance can be calculated using transmitted light intensity, and the particle size distribution of small particles with low absorbance can be calculated using scattered light intensity, allowing for accurate measurement of particle size distribution over a wide range.

[0011] In this case, it is preferable that the particle size distribution calculation unit first measures the particle size distribution of the sample based on the time change of the transmitted light intensity, and then measures the particle size distribution of the sample based on the time change of the scattered light intensity. In this way, for example, while large particles with high absorbance are settling, the particle size distribution can be measured by the time change in transmitted light intensity, and then, while only small particles with low absorbance are settling, the particle size distribution can be measured by the time change in scattered light intensity, thereby efficiently measuring the particle size distribution.

[0012] In particular, a suitable embodiment of the particle size distribution measuring device is one in which the light source comprises a semiconductor laser device and an LED device, the scattered light detector detects the scattered light from the laser light irradiated from the semiconductor laser device by the particles, and the transmitted light detector detects the transmitted light irradiated from the LED device and transmitted through the measuring cell. In this way, by using a light source suitable for each detector, the temporal changes in scattered light intensity and transmitted light intensity can be measured with greater accuracy, and the particle size distribution can be measured with greater accuracy.

[0013] In another specific embodiment of the particle size distribution measuring device, it is preferable that the scattered light detector and the transmitted light detector are configured to detect light irradiated onto the measuring cell from a common light source. In this way, the time evolution of scattered light intensity and the time evolution of transmitted light intensity are measured using a common light source, thus reducing manufacturing costs.

[0014] Furthermore, the particle size distribution measurement method of the present invention is a centrifugal sedimentation method that measures the particle size distribution of a measurement sample by rotating a measurement cell containing a measurement sample and allowing the particles in the measurement sample to settle, and is characterized by comprising the steps of: irradiating the particles with light; detecting the intensity of scattered light from the particles; and calculating the particle size distribution of the measurement sample based on the time change in the intensity of the scattered light caused by the sedimentation of the particles.

[0015] Furthermore, the present invention relates to a particle size distribution measuring device program that uses a centrifugal sedimentation method to measure the particle size distribution of a sample by rotating a measuring cell containing a sample and causing the particles in the sample to settle. The program comprises a light source that irradiates the measuring cell with light and a scattered light detector that detects the intensity of scattered light generated by irradiating the particles with light. The program is characterized in that it causes a computer to perform the function of a particle size distribution calculation unit that measures the particle size distribution of the sample based on the time change in the scattered light intensity caused by the settling of the particles.

[0016] Such a particle size distribution measurement method and program for a particle size distribution measurement device can achieve the same effects as the particle size distribution measurement device of the present invention described above. [Effects of the Invention]

[0017] According to the present invention configured in this manner, a centrifugal sedimentation type particle size distribution analyzer can be provided that can measure the particle size distribution of particles with low absorbance. [Brief explanation of the drawing]

[0018] [Figure 1] Schematic diagram showing the configuration of a particle size distribution measuring apparatus according to an embodiment of the present invention. [Figure 2] Diagram for explaining the measurement principle of the particle size distribution based on the temporal change of the transmitted light intensity of the particle size distribution measuring apparatus of the same embodiment. [Figure 3] Diagram for explaining the light source, transmitted light detector, and scattered light detector of the same embodiment. [Figure 4] Functional block diagram showing the functions of the particle size distribution measuring apparatus in the same embodiment. [Figure 5] Plan view schematically showing the arrangement pattern of each cell and each optical system in the same embodiment. [Figure 6] Diagram for explaining the measurement principle of the particle size distribution based on the temporal change of the scattered light intensity of the particle size distribution measuring apparatus of the same embodiment. [Figure 7] Flowchart showing the operation of the particle size distribution measuring apparatus of the same embodiment. [Figure 8] Diagram for explaining the light source, transmitted light detector, and scattered light detector in another embodiment. [Figure 9] Plan view schematically showing the arrangement pattern of each cell and each optical system in another embodiment. [Figure 10] Plan view schematically showing the arrangement pattern of each cell and each optical system in another embodiment. [Figure 11] Plan view schematically showing the arrangement pattern of each cell and each optical system in another embodiment.

Explanation of Reference Numerals

[0019] 100 ··· Particle size distribution measuring apparatus 22 ··· Second light source 32 ··· Scattered light detector 42 ··· Particle size distribution calculation unit X ··· Measurement cell

Embodiments for Carrying Out the Invention

[0020] The particle size distribution measuring apparatus 100 according to the present invention will be described below with reference to the drawings.

[0021] The particle size distribution measuring device 100 according to this embodiment measures the particle size distribution of a group of particles contained in a sample such as pharmaceuticals, food products, chemical products, or bubble particles using the centrifugal sedimentation method. More specifically, this particle size distribution measuring device 100 uses a uniform sedimentation method in which a measuring cell X containing a group of particles in a dispersion medium is rotated to cause the particles to settle by centrifugal force.

[0022] First, let's explain the general principle of measuring particle size distribution using the centrifugal sedimentation method. For example, when a group of particles is suspended in a dispersion medium such as water, the particles gradually sink. The rate of this sinking is faster the larger the particle diameter, and if the materials of the particles and the dispersion medium are known, the particle diameter can be calculated by measuring the time it takes for the particles to sink a certain distance. Specifically, light is shone onto the measurement surface of the measurement cell X, and the transmitted light is detected. The transmitted light intensity and the time change of the absorbance calculated from the transmitted light intensity are then measured. As shown in Figure 2(a), if all dispersed particles are the same size, these particles will settle at the same sedimentation velocity, and the transmitted light intensity will increase sharply after a certain amount of time has passed since the start of sedimentation. In reality, particles of various sizes are mixed together, and in this case, as shown in Figure 2(b), it appears as a composite of the changes in transmitted light intensity of particles with different sedimentation times. In this principle, smaller particles settle slowly, and measurement takes time. Therefore, in the centrifugal sedimentation method, instead of letting the particles settle by gravity, centrifugal force is used to shorten the sedimentation time.

[0023] Specifically, as shown in Figures 1 and 3, the particle size distribution measuring device 100 comprises a rotating mechanism 1 for rotating the measuring cell X, a first light source 21 for irradiating the measuring cell X with light, a transmitted light detector 31 for detecting transmitted light that has passed through the measuring cell X from the first light source 21, and a control device 4.

[0024] The rotating mechanism 1 comprises a motor 11 and a rotating disk 12 fixed to the output shaft of the motor 11. The rotating disk 12 is configured to rotate with its faceplate horizontally, using the output shaft of the motor 11 as the axis of rotation C. The rotating disk 12 is provided with a measuring cell holder in which a measuring cell X is set and a reference cell holder in which a reference cell R is set. The reference cell R contains the same dispersion medium (in this case, water) as that contained in the measuring cell X.

[0025] The first light source 21 emits light that does not contain infrared rays in order to prevent the temperature of the dispersion medium from rising, and in this case, LED devices such as blue LEDs and green LEDs are used.

[0026] The transmitted light detector 31 is located on the opposite side of the first light source 21 from the rotating disk 12. It detects the transmitted light emitted from the first light source 21 that has passed through the measurement cell X and the reference cell R, and transmits a transmitted light intensity signal indicating the intensity of the transmitted light to the control device 4. Although the transmitted light detector 31 here is a line sensor, it may also be a single light sensor (for example, a photodiode).

[0027] In this embodiment, the transmitted light from the measurement cell X and the transmitted light from the reference cell R are detected by a common transmitted light detector 31. Therefore, a synchronization signal generating LED (not shown) and a detector for detecting the light from this synchronization signal generating LED are provided so that the transmitted light intensity signal detected by the transmitted light detector 31 can distinguish which cell the transmitted light passed through.

[0028] The control device 4 is a general-purpose or dedicated computer equipped with a CPU, memory, input / output interface, etc. This control device 4, by coordinating the CPU and peripheral devices according to a predetermined program stored in a predetermined area of ​​memory, performs at least the functions of a motor control unit 41 and a particle size distribution calculation unit 42, as shown in Figure 4. These functions may be provided in one or more other computers.

[0029] The motor control unit 41 controls the rotational speed of the motor 11 so that the rotating disk 12 rotates at a predetermined target rotational speed. Specifically, the motor control unit 41 obtains a position detection signal from a position detector such as an encoder (not shown) that detects the position of the rotating disk 12, calculates the rotational speed of the rotating disk 12, and provides feedback control to the motor 11 so that the rotational speed becomes a preset target rotational speed. The target rotational speed may be set to a constant rotational speed, or it may be set to increase over time. In other words, the motor control unit 41 may rotate the rotating disk 12 at a constant speed, or it may accelerate its rotation.

[0030] The particle size distribution calculation unit 42 calculates the particle size distribution (hereinafter also referred to as the first particle size distribution) based on the time change of the transmitted light intensity signal detected by the transmitted light detector 31. The particle size distribution calculation unit 42 may also be configured to calculate the first particle size distribution based on the time change of absorbance calculated using the transmitted light intensity signal.

[0031] Specifically, the particle size distribution calculation unit 42 calculates the absorbance A(t) for the measurement cell X based on the reference transmitted light intensity Ia of the transmitted light that has passed through the reference cell R and the measured transmitted light intensity Ib of the transmitted light that has passed through the measurement cell X, which is obtained each time the rotating disk 12 rotates. Based on the time change of this absorbance A(t), the unit calculates the first particle size distribution. This absorbance A(t) represents an absorbance curve, which is the time change of absorbance caused by particle sedimentation, and is calculated using an equation such as A(t) = -log(Ia / Ib). When calculating the absorbance A(t), the particle size distribution calculation unit 42 may acquire the reference transmitted light intensity Ia only once at the beginning and use it, or it may acquire the reference transmitted light intensity Ia each time the rotating disk 12 rotates and use it.

[0032] However, the particle size distribution measuring device 100 of this embodiment is configured to measure the particle size distribution of particles with low absorbance, and as shown in Figures 1 and 3, further includes a second light source 22 that irradiates the measuring cell X with light, and a scattered light detector 32 that detects scattered light generated when light from the second light source 22 is scattered by particles in the measuring cell X. The particle size distribution calculation unit 42 is further configured to acquire the scattered light intensity signal detected by the scattered light detector 32 and calculate the particle size distribution (hereinafter also referred to as the second particle size distribution) based on the time change of this scattered light intensity signal.

[0033] The second light source 22 is, for example, a semiconductor laser that emits laser light, and is positioned so as to irradiate the measurement cell X along its rotational trajectory.

[0034] The scattered light detector 32 detects scattered light scattered by particles in the measurement cell X and transmits a scattered light intensity signal indicating the intensity of the scattered light to the control device 4. Specifically, it is a photomultiplier tube (PMT) or an avalanche photodiode (APD). Since detectors such as PMTs and APDs are susceptible to temperature changes, a temperature control element such as a Peltier element may be provided when using these detectors as the scattered light detector 32. The scattered light detector 32 may be a forward light detector that detects forward scattered light from the sample, or a back light detector that detects back scattered light. Here, the scattered light detector 32 is located on the opposite side of the second light source 22 from the rotating disk 12. The placement of the scattered light detector 32 may be changed as appropriate, for example, to the same side as the second light source 22 from the rotating disk 12, as long as it can detect scattered light from particles in the measurement cell X.

[0035] As shown in Figure 5, the rotating disk 12 is configured such that, when viewed from a direction along the rotation axis C, the measurement cell X and the reference cell R are positioned 180° apart from each other along the rotation direction. The transmission optical system T, which includes the first light source 21 and the transmitted light detector 31, and the scattering optical system S, which includes the second light source 22 and the transmitted light detector 33, are also positioned 180° apart from each other along the rotation direction. In Figure 5, the positions of the transmission optical system T and the scattering optical system S represent the positions of the principal ray axes of the light emitted from each light source 21 and 22.

[0036] The particle size distribution calculation unit 42 then calculates a second particle size distribution based on the time change of the scattered light intensity signal detected by the scattered light detector 32, which occurs due to particle sedimentation.

[0037] Here, we will explain the measurement principle of the second particle size distribution using the centrifugal sedimentation method with scattered light intensity in this embodiment. The principle for measuring the second particle size distribution using scattered light intensity is basically the same as the principle for measuring the first particle size distribution using transmitted light intensity. It calculates the particle size by measuring the time it takes for particles to settle a certain distance in a dispersion medium such as water. Specifically, light is shone onto the measurement surface of measurement cell X, and scattered light from particles is detected. The time change in the intensity of this scattered light, caused by particle sedimentation, is then measured. As shown in Figure 6(a), if all dispersed particles are the same size, these particles will settle at the same sedimentation velocity, and the scattered light intensity will decrease sharply after a certain amount of time has passed since the start of sedimentation. In reality, particles of various sizes are mixed together, and in this case, as shown in Figure 6(b), it appears as a composite of the changes in scattered light intensity of particles with different sedimentation times.

[0038] Specifically, the particle size distribution calculation unit 42 calculates the scattered light intensity B(t) based on the background light intensity Id detected by the scattered light detector 32 when light from the second light source 22 is irradiated onto the reference cell R, and the measured scattered light intensity Ie scattered by particles in the measurement cell X each time the rotating disk 12 rotates. Based on the time change of this scattered light intensity B(t), the second particle size distribution is calculated. This scattered light intensity B(t) represents a scattered light intensity curve, which is the time change of scattered light intensity caused by particle sedimentation, and is calculated using an equation such as B(t) = -log(Id / Ie). When calculating the scattered light intensity B(t), the particle size distribution calculation unit 42 may acquire the background light intensity Id only once at the beginning and use it, or it may acquire the background light intensity Id each time the rotating disk 12 rotates and use it. In this embodiment, the scattered light from the measurement cell X and the scattered light from the reference cell R are detected by a common scattered light detector 32. Therefore, a synchronization signal generating LED (not shown) and a detector for detecting light from this synchronization signal generating LED are provided so that the scattered light intensity signal detected by the scattered light detector 32 can be distinguished as to which cell the scattered light originates from.

[0039] Furthermore, the control device 4 of this embodiment is configured to measure the first particle size distribution based on transmitted light intensity, and then measure the second particle size distribution based on scattered light intensity. Specifically, as shown in Figure 4, this control device 4 further functions as a measurement method switching unit 43.

[0040] The operation of the particle size distribution measuring device 100 of this embodiment will be explained below, referring to the flowchart shown in Figure 7, while also describing each part. Here, the particle size distribution measuring device 100 first performs a measurement of the first particle size distribution (hereinafter also referred to as the first measurement), and then performs a measurement of the second particle size distribution (hereinafter also referred to as the second measurement).

[0041] First, for example, when a user inputs a measurement start signal using an input means, the particle size distribution measuring device 100 starts the first measurement (S1). Specifically, the motor control unit 41 outputs a control signal to the motor 11 to rotate the rotating disk 12, and at the same time, it irradiates the measurement cell X with light from the first light source 21, causing the particle size distribution calculation unit 42 to calculate the first particle size distribution.

[0042] To describe the calculation of the first particle size distribution in more detail, first, the reference transmitted light intensity Ia of the transmitted light that has passed through the reference cell R is detected (S2). Note that this reference transmitted light intensity Ia only needs to be detected at least once, but it can also be used as the average value of multiple detections, for example. Next, the measured transmitted light intensity Ib of the transmitted light that has passed through the measurement cell X is detected each time the rotating disk 12 completes one rotation (S3). Then, the absorbance A(t) for the measurement cell X is calculated based on each measured transmitted light intensity Ib and the reference transmitted light intensity Ia (S4), and the first particle size distribution is calculated based on the time change of this absorbance A(t) (S5).

[0043] After the first particle size distribution is calculated in this manner, the measurement method switching unit 43 determines whether to end the first measurement and switch to the second measurement (S6). Specifically, the measurement method switching unit 43 determines whether to switch from the first measurement to the second measurement based on the transmitted light intensity transmitted through the measurement cell X. Here, it obtains the absorbance A(t) for the measurement cell X as described above, and when this absorbance A(t) falls below a predetermined threshold, it determines to switch from the first measurement to the second measurement. If it is determined to switch from the first measurement to the second measurement, the particle size distribution calculation unit 42 stops the first measurement (S7) and starts the second measurement (S8).

[0044] Specifically, when this second measurement is initiated, light from the second light source 22 is irradiated onto the measurement cell X, and the particle size distribution calculation unit 42 calculates the second particle size distribution.

[0045] To describe the calculation of the second particle size distribution in more detail, first, light from the second light source 22 is irradiated onto the reference cell R, and the background light intensity Id detected by the scattered light detector 32 is detected (S9). Next, the measured scattered light intensity Ie scattered by the particles in the measurement cell X is detected each time the rotating disk 12 rotates (S10). Then, the scattered light intensity B(t) from the measurement cell X is calculated based on the measured scattered light intensity Ie and the background light intensity Id (S11), and the second particle size distribution is calculated based on the time change of the scattered light intensity B(t) caused by particle sedimentation (S12).

[0046] According to the particle size distribution measuring device 100 of this embodiment configured in this way, the scattering light detector 32 detects the intensity of scattered light from centrifugally settling particles, and the particle size distribution can be measured based on the time change in the scattered light intensity caused by the centrifugal settling of particles. Therefore, particle size distribution measurements can be performed on particles that do not have an absorption band for the light from the first light source 21 mounted on the device for detecting transmitted light intensity, and on particles with small particle sizes that absorb little light.

[0047] In particular, the particle size distribution measuring device 100 of this embodiment can measure the particle size distribution by the time change of scattered light intensity and by the time change of transmitted light intensity. While particles with large particle sizes and high absorbance are settling, the particle size distribution is measured by the time change of transmitted light intensity, and then, while only particles with small particle sizes and low absorbance are settling, the particle size distribution is measured by the time change of scattered light intensity. This allows for accurate measurement of a wide range of particle size distributions.

[0048] However, the present invention is not limited to the embodiments described above.

[0049] For example, the particle size distribution measuring device 100 of the above embodiment performs both particle size distribution measurement based on the time change of transmitted light intensity and particle size distribution measurement based on the time change of scattered light intensity, but is not limited to this. The particle size distribution measuring device 100 of other embodiments may perform only particle size distribution measurement based on the time change of scattered light intensity. In this case, the particle size distribution measuring device 100 does not need to be equipped with the first light source 21 and transmitted light detector 31 described above.

[0050] In another embodiment, the particle size distribution calculation unit 42 may be configured to continuously calculate both the absorbance A(t) and the scattered light intensity B(t) after the start of centrifugal sedimentation of the particles, and to store these in a memory unit provided in the control device 4. In this case, after the particles in the measurement cell X have settled, the user may refer to the absorbance A(t) and scattered light intensity B(t) stored in the memory unit and calculate the particle size distribution using another calculation device.

[0051] In other embodiments, the particle size distribution calculation unit 42 may determine whether to perform the first measurement or the second measurement depending on the refractive index of the particles contained in the sample being measured. Specifically, the particle size distribution calculation unit 42 may determine whether to perform the first measurement or the second measurement depending on the difference between the refractive index of the particles in the sample being measured and the refractive index of the dispersion medium. For example, if the difference in refractive index between the particles and the dispersion medium is small, it is preferable to perform the second measurement because the absorption of irradiated light is small. On the other hand, if the difference in refractive index between the particles and the dispersion medium is large, it is preferable to perform particle size distribution measurement based on the time change in transmitted light intensity.

[0052] In particle size distributions calculated using the acquired scattered light intensity directly, the peak position of the particle size distribution can be obtained with high accuracy, but the quantitative accuracy is poor, and the peak height may not be obtained with high accuracy. Therefore, in the particle size distribution calculation unit 42 of other embodiments, in the second measurement, the acquired scattered light intensity may be corrected using Mie scattering theory, and the second particle size distribution may be calculated based on the corrected scattered light intensity. In this way, by correcting the acquired scattered light intensity using Mie scattering theory, which is a relationship between particle size and scattered light intensity, a particle size distribution with improved quantitative accuracy can be calculated, and the peak position and peak height can be measured with high accuracy.

[0053] Furthermore, the particle size distribution measuring device 100 of the above embodiment was configured such that the scattered light detector 32 and the transmitted light detector 31 detect light irradiated from different light sources (i.e., a first light source 21 and a second light source 22), but it is not limited to this. In other embodiments of the particle size distribution measuring device 100, as shown in Figure 8, the scattered light detector 32 and the transmitted light detector 31 may be configured to detect light irradiated onto the measurement cell X from a common light source (e.g., a semiconductor laser device). In this case, for example, as shown in Figure 8, an optical element such as a perforated mirror 51 may be placed between the transmitted light detector 31 and the rotating disk 12 to guide the transmitted light from the measurement cell X to the transmitted light detector 31 and to reflect the scattered light from the measurement cell X and guide it to the scattered light detector 32. In this case, since the light intensity would be too strong if the laser light were guided directly to the transmitted light detector 31, a diffuser plate 52 or the like may be provided between the transmitted light detector 31 and the optical element to diffuse the light.

[0054] Furthermore, while the particle size distribution calculation unit 42 in the above embodiment used background light intensity Id and measured scattered light intensity Ie to calculate the time change of scattered light intensity B(t), it is not limited to this. In other embodiments, the time change of scattered light intensity B(t) may be calculated using only the measured scattered light intensity Ie, without using background light intensity Id.

[0055] Furthermore, while the particle size distribution measuring device 100 in the above embodiment used a uniform sedimentation method, it is not limited to this. In other embodiments, the particle size distribution measuring device 100 may use a line-start method in which a sample suspension is supplied to a measuring cell X containing a density gradient solution consisting of a sucrose solution or the like, and particles in the sample suspension are centrifuged and sedimented in the density gradient solution.

[0056] In the above embodiment, the measurement method switching unit 43 determined to switch from the first measurement to the second measurement when the acquired absorbance A(t) fell below a predetermined threshold, but it is not limited to this. In other embodiments, the measurement method switching unit 43 may be configured to switch from the first measurement to the second measurement after a predetermined time has elapsed since the start of measurement.

[0057] In another embodiment of the particle size distribution measuring device 100, as shown in Figure 9, the transmission optical system T and the scattering optical system S may be positioned so that they are offset from each other by 90° (270°) along the rotational direction when viewed from a direction along the rotational axis C. However, the transmission optical system T and the scattering optical system S may be positioned so that they are offset by any angle other than 0° (360°) along the rotational direction.

[0058] In another embodiment of the particle size distribution analyzer 100, the rotating disk 12 may be configured to hold multiple measurement cells X at positions offset along its rotational direction. For example, as shown in Figure 10, the rotating disk 12 may be configured to hold three measurement cells X and a reference cell R at positions offset by 90° from each other along its rotational direction. In this way, multiple types of different samples can be measured at once. In this case, the transmission optical system T and the scattering optical system S may be positioned at positions offset by 90° from each other along the rotational direction, or at positions offset by 180° from each other as shown in Figure 11, or they may be positioned at any angle offset except 0° (360°).

[0059] Furthermore, it goes without saying that the present invention is not limited to the embodiments described above, and various modifications are possible without departing from its spirit. [Industrial applicability]

[0060] According to the present invention described above, a centrifugal sedimentation type particle size distribution analyzer can be provided that can measure the particle size distribution of particles with low absorbance.

Claims

1. A centrifugal sedimentation type particle size distribution analyzer that rotates a measuring cell containing a sample to be measured, causing the particles in the sample to settle and thereby measuring the particle size distribution of the sample, A light source that irradiates the aforementioned measurement cell with light, A scattering light detector for detecting the intensity of scattered light from particles in the measurement cell, A particle size distribution measuring device comprising: a particle size distribution calculation unit that measures the particle size distribution of a measurement sample based on the measurement principle of centrifugal sedimentation using the time change in the intensity of the scattered light generated by the sedimentation of the particles.

2. The particle size distribution measuring device according to claim 1, wherein the scattering light detector comprises at least one of a forward photodetector for detecting forward scattered light from the particle and a back photodetector for detecting back scattered light.

3. The measurement cell further comprises a transmitted light detector that detects the intensity of transmitted light that has passed through the measurement cell, The particle size distribution measuring device according to claim 1 or 2, wherein the particle size distribution calculation unit further measures the particle size distribution of the measurement sample based on the time change in the intensity of the transmitted light.

4. The particle size distribution measuring device according to claim 3, wherein the particle size distribution calculation unit measures the particle size distribution of particles with a diameter greater than a predetermined threshold based on the time change in the intensity of the transmitted light, and measures the particle size distribution of particles with a diameter less than or equal to the predetermined threshold based on the time change in the intensity of the scattered light.

5. The particle size distribution measuring device according to claim 4, wherein the particle size distribution calculation unit measures the particle size distribution of the measurement sample based on the time change in the intensity of the transmitted light, and then measures the particle size distribution of the measurement sample based on the time change in the intensity of the scattered light.

6. The aforementioned light source comprises a semiconductor laser device and an LED device. The scattering light detector detects the scattered light from the particles of the laser light irradiated from the semiconductor laser device, The particle size distribution measuring device according to any one of claims 3 to 5, wherein the transmitted light detector is configured to detect the transmitted light that has been irradiated from the LED device and passed through the measuring cell.

7. The particle size distribution measuring device according to any one of claims 3 to 5, wherein the scattered light detector and the transmitted light detector are configured to detect light irradiated onto the measuring cell from a common light source.

8. A method for measuring particle size distribution by centrifugal sedimentation, which involves rotating a measuring cell containing a sample to be measured, causing the particles in the sample to settle, and measuring the particle size distribution of the sample, The steps include irradiating the aforementioned particles with light, A scattered light detection step for detecting the intensity of scattered light from the aforementioned particles, A particle size distribution measurement method comprising: a particle size distribution calculation step of measuring the particle size distribution of a measurement sample based on the measurement principle of centrifugal sedimentation using the time change in the intensity of the scattered light generated by the sedimentation of the particles.

9. A centrifugal sedimentation type particle size distribution measuring device that measures the particle size distribution of a sample by rotating a measuring cell containing a sample and causing the particles in the sample to settle, comprising a light source that irradiates the measuring cell with light and a scattered light detector that detects the intensity of scattered light generated when the particles are irradiated with light, A program for a particle size distribution measuring device that causes a computer to function as a particle size distribution calculation unit, which measures the particle size distribution of a measurement sample based on the measurement principle of centrifugal sedimentation, using the time change in the intensity of the scattered light generated by the sedimentation of the particles.

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