Method and device for determining particle characteristics by multi-parametric detection of scattered light and extinction signals

Abstract

This invention relates to a method and apparatus for determining characteristic parameters, quantity distribution, and concentration of particles in the nanometer and micrometer size range dispersed in gases and liquids using particle photometry. According to the invention, this is achieved by measuring scattered light in a photometer for different numbers of angular or receptive angles and evaluating particle characteristics using an analytical algorithm based on the determined scattered light intensity. The determination of particle characteristics in the tens of size range can be achieved without changing or adjusting the geometry of the sample measurement chamber. The apparatus according to the invention includes at least one laser (1) for generating at least one laser beam (3), at least one optical input module (2) for shaping the laser beam (3) and constructing a focal geometry (6), a continuous flow measurement unit (5) advantageously having hydrodynamic focusing, in which a forward-scattered beam (6) and a side-scattered beam (7) are generated by the laser beam (3), an optical output module (8) in the forward-scattered beam (6) and an optical output module (9) in the side-scattered beam (7), a semi-transparent mirror (10), a camera (12), and photomultipliers (11a, 11b), wherein the photomultipliers (11a, 11b) are used to perform scattered light measurements for different numbers of divergence or reception angles and the particle characteristics are determined by an analysis algorithm based on the intensity of the scattered light determined by the forward-scattered beam (6) and the side-scattered beam (7).

Description

[0001] The present invention relates to a method and apparatus for determining, by means of particle photometry, the characteristic parameters, quantity distribution and concentration of particles in the nanometer and micrometer size range dispersed in a gas or liquid.

[0002] According to the present invention, this is achieved by measuring the scattered light of particles at different numbers of divergent or receptive angles in a photometer, and using an analysis algorithm to determine characteristic features (e.g., size, refractive index) for each particle based on the determined scattered light intensity, thereby classifying the particles contained in the measurement sample accordingly. The determination of particle characteristics in the size range greater than twenty can be achieved without changing or adjusting the geometry of the sample measurement chamber or optics. Existing technology

[0003] There are numerous methods available for determining the size of colloidal particles (e.g., nanoparticles, emulsion droplets) or coarsely dispersed particles.

[0004] Known optical methods include static and dynamic scattered light measurements (ISO 13320, ISO 22412) and sedimentation methods based on gravity and centrifugal force (ISO 13317-1, ISO 13318-2). For the study of suspensions and emulsions using volumetric scattered light methods or sedimentation methods, it is common for the determined particle parameters to be a superposition of the scattering behavior of all particles (the particle as a whole) within the geometrically measured volume. Here, the resulting scattered light intensity or extinction depends on the particle concentration and the optical particle characteristics (size, geometry, and refractive index contrast). Particle size distribution is obtained mathematically from the superimposed measurement signals. Regardless of the algorithm used, the particle size distribution is always based on intensity or extinction and can only be transformed, for example by Mie theory, into a distribution assessing volume or number, given the optical characteristics of the particles (assuming the same refractive index and spherical shape), which allows for comparison with imaging methods. Disadvantageously, the physics of these methods cannot, in principle, provide information about the characteristics of individual particles. The interaction of sound waves and X-ray waves with particles has also been used to determine particle size. These methods, however, only provide average overall values, not the distribution of the assessed quantity or the characteristics of individual particles. It can also be determined that the scattering methods described to date cannot obtain the concentration of particles at each individual size level for polydisperse suspensions and emulsions.

[0005] Different measurement methods for assessing the quantity of particle size distribution are also described in the literature. First and foremost, optical methods are mentioned, which use imaging to statically or dynamically detect particles and determine the size of each imaged particle manually or with the aid of computer-aided image analysis. For submicron and nanometer-scale particles, classical static transmission or electron microscopy methods are used, as well as the more recent atomic force microscopy method.

[0006] In any case, 2D-based recording (or imaging) can only calculate volume-based particle size distributions by assuming a 3D shape. For wide distributions, recording is required in different magnified images, which significantly increases the difficulty of calibration and calculating cumulative distributions and practically makes concentration determination impossible. These methods are also very time-consuming. Furthermore, the described methods can only be used for dry particles (powders). Dynamic imaging techniques (e.g., Flow Cam, Bettersizer, Camsizer, QICPIC) are distinguished by better statistical properties. However, dynamic methods are limited to particles larger than 800 nm [ISO 13322].

[0007] The principle of flow cytometry is single-particle scattered light photometry. Current technology does not disclose any capability to simultaneously determine the particle size and refractive index of nanoparticles and microparticles experimentally. Analysis of particle size at the micrometer scale is not always achievable due to the ambiguity of the scattered light intensity distribution curve relative to the particle diameter (see, for example, [link to relevant documentation]). Figure 7 Furthermore, no solution to this problem has been publicly disclosed to date. Experimental experience also shows that in the described arrangement, especially for particles with larger mass, the number of particles (separation) is significantly underestimated, particularly at larger levels, due to geometry or density. However, it should also be noted that the superposition of scattered light with very different intensities due to significantly different particle sizes leads to an underestimation of smaller particles. For particle fractions with very different refractive indices or very small refractive index contrasts, this may also be independent of size.

[0008] Also known is patent document EP 2908119 B1, which addresses a "method for detecting nanoparticles" based on flow cytometry principles. The measurement range for smaller particles (preferably <100 nm) should be expanded by reducing the detection area. Measurements are performed only at angles in lateral scattering. The patent document describes a method that extends the typical measurement range of flow cytometers to the nanometer range and is, in principle, unsuitable for micrometer-scale particles.

[0009] Patent document EP 2388569 A1 discloses a method and apparatus with two sensors operating according to different physical measurement methods for determining the size and number of particles dispersed in a liquid, termed Single Particle Optical Sensing (SPOS). The significant difference in measurement technique from the principle of flow cytometry lies in the operation of different physical measurement principles to analyze a wide distribution of particle sizes (scattering and extinction sensors), and the method results in a strong minimization of the measurement chamber depth and a laser beam with a small focal diameter, distributed with Gaussian intensity across the cross-section. Simultaneous enhancement of extinction and scattering for the same particle is not disclosed in this patent document and cannot be achieved from a technical perspective using the proposed implementation principle. The simultaneous determination of multiple particle characteristics (e.g., size, refractive index, geometry) for all single particles in a measurement sample is not disclosed.

[0010] Particle tracking analysis (ISO 19430:2016), established in the market in recent years, measures the displacement of nanoparticles and sub-mass particles over time using scattered light generated by laser sensing, and calculates the particle size from the square of the average path distance per unit time according to Einstein and Smolukhovsky theory. A drawback of this method is the dependence of detection sensitivity on physical parameters, which leads to losses in determining the number of particles and distortions in particle distribution, especially in the case of fine particles. Furthermore, determining the effective measurement volume is not feasible, as it depends on the size and / or refractive index of the dispersed particles. Therefore, the determination of particle concentration in polydisperse samples is always erroneous. This technique is also only applicable to particles dispersed in liquids.

[0011] All the principles and measuring devices mentioned above cannot simultaneously determine multiple characteristics (such as size, refractive index, geometry, quantity, concentration) of particles dispersed in air or liquid, i.e., suspensions, emulsions, or aerosols.

[0012] For the sake of completeness, it should be mentioned that some published documents describe the simultaneous determination of particle size and refractive index in dispersions for specific cases. These differ from the claimed invention in methodological technique and also have a number of limitations. Patent document WO 2017 / 072360 A1 should preferably be applicable to particles with wavelengths smaller than the incident light (preferably 405 nm or 488 nm). However, this measurement range should be broadened to three times the wavelength. The optical scattering ratio (forward scattering / side scattering) should be independent of the refractive index within this range. The size can thus be determined, and theoretically, the refractive index can be determined by one of the two scattered light measurements.

[0013] The publicly available tables with experimental results only record results for particles smaller than the incident wavelength (405 nm). Measurements using both PS and SiO2 particles are described, and the error data for these measurements are all greater than the error data in the manufacturer's data.

[0014] Theoretical calculations confirmed a larger error range, specifically, the method fails if the previously mentioned intensity oscillations enter the receiving angle range. Therefore, this method generally cannot be extended to cases where the particle size is greater than the incident light wavelength.

[0015] A highly complex measurement method, according to US Patent Document 9,068,915 B2, determines the refractive index of a particle type by comparing the forward and lateral scattering of two samples. This method presupposes that the two samples have different particle sizes, and that the particle size and refractive index of one sample (batch) are known. Alternatively, if the particle size is known, the particle's refractive index can be determined using this method; that is, in any case, both size and refractive index are not simultaneously determined. How this method is performed in the case of polydisperse distributions is not disclosed.

[0016] The measurement principles underlying all solutions known from the prior art are substantially different from the technical solutions of the disclosed invention, and / or have substantial limitations and disadvantages compared to the claimed inventive solutions, especially for particle samples with a wide distribution in the size range of nanometer or submicron and micrometer.

[0017] Technical issues

[0018] Suspensions (such as polymer particles, oxide particles, and biomaterials dispersed in aqueous media) or emulsions (such as nutrient solutions) are present in many fields, including nature, medicine, industry, research, and private households, and play an extremely important role in these fields. Undesirable particles generated during manufacturing operations, fouling particles in wastewater, or particulate loads (such as microplastics) in natural waters also require appropriate cleaning measures (such as drinking water treatment and air purification).

[0019] From a scientific, product-related, or risk-related perspective (e.g., in the classification of nanomaterials), it is crucial to quantitatively determine particle characteristics such as size, quantity, concentration, or optical properties. These requirements are particularly prevalent in the field of modern particle technology, which deals with nanoscale and microscale particles dispersed in gases or liquids. To better understand and influence dispersion properties or the formulation of related products, in addition to the chemical composition of the dispersed phase, it is essential to know the particle size (particle size distribution (TGV in German, PSD in English), quantity (concentration), or optical properties such as shape and refractive index.

[0020] Known measurement methods within the claimed TGV range, as exemplarily illustrated in the "Prior Art" section, have a number of drawbacks. Established reference methods (microscopy or electron microscopy) are very time-consuming and create experimental and measurement difficulties for dispersed, highly polydisperse particle systems, thus prohibiting their widespread use, especially in industry. On the other hand, widely used static and dynamic light scattering methods (ISO 13320, ISO 22412) are holistic methods. The physical measurement principles do not allow any information about individual particles; the measured scattering intensity depends on the particle size, geometry, and refractive index contrast, as well as the optical characteristics of the measuring device, and is no longer a one-to-one function of particle size from a specific particle size onwards.

[0021] Therefore, the technical problem to be solved by this invention is to determine multiple particle characteristic parameters, such as particle concentration, size distribution, and the number of particles at each size class, for each individual single particle carried by a liquid or gas in a suspension, emulsion, or aerosol, using spatial angle-dependent scattered light measurements, both for particles with narrow distributions and for particles distributed across multiple orders of magnitude, and to quantify additional particle characteristics, such as refractive index or asphericity, from the measurement signal of a single particle using analytical algorithms. This invention also focuses on high size grading accuracy down to the nanometer level. Another technical problem to be solved by this invention is, in the case of a single-particle scattered light photometer, to achieve a detection rate of, for example, at least 10,000 events per second (events / second, often also referred to as frequency), and to automatically control this detection rate using only hydrodynamic or aerodynamic devices, so as to cover a very large and high concentration range of the primary measurement sample relative to existing technologies (e.g., EP 2388569 A1), for example from 10... 2 Up to 10 9 Detecting particle characteristics per particle per ml without overlap distortion and dilution of the primary sample, preferably real-time analysis, and performing appropriate classification, all without changing the measurement chamber or making geometric changes to the measurement unit.

[0022] The technical problem of the present invention is solved by the features in claims 1, 16 and 17.

[0023] Suitable design solutions of the present invention are included in the dependent claims.

[0024] A particular advantage of the method according to the invention is the efficient determination of particle characteristics by means of multi-parameter detection of extinction and / or scattered light signals in a measurement sample, wherein the scattered light and extinction signals of the particles are counted and measured simultaneously at a high detection rate, i.e., events / second, in at least two spatial angular ranges, and compared analogously or digitally with simulated calculations of the scattered light distribution achieved by analytical or numerical methods for different spatial angular ranges, so that particle characteristic parameters can be determined over a wide dynamic particle size range even for high particle concentrations in the measurement sample.

[0025] The detection rate according to the invention represents a counting event with a pulse height higher than the noise signal, ranging from less than 10 particles per second to one million particles per second, particularly from 100 to 10,000 particles per second. For a preferred rate of 10 per milliliter... 10 The particle concentration of each particle is measured with minimal overlap in the number of particles. For a detection rate of, for example, 10 kHz, a count loss of less than 0.0035 (0.35%) occurs. In other words, the solution of this invention effectively measures all particles in the sample stream and is characterized by extremely high sensor sensitivity compared to existing technologies. Therefore, for example, in EP 2338569A1 (e.g.) Figure 9 The document states that the effectiveness factor is only a few percent to ten percent, and it also depends on the granularity.

[0026] Other advantages of the invention thus arise from the fact that different angles can be used for forward scattering or multiple detection directions and any combination thereof can be used for scattered light measurement.

[0027] When the particles have a size parameter k greater than or approximately equal to 20, different opening angles can be used, for example, for forward scattering.

[0028] An additional advantage of the invention is that, in cases where particles have forward-scattered light profiles that are almost indistinguishable at different receiving angles (especially where the size parameter k is less than or approximately equal to 20), multiple detection directions with different sensitivities along the lateral direction are used.

[0029] According to the present invention, simulation calculations using Mie theory or numerical calculations are performed in coordination with the corresponding optical structure, and uncertainties regarding particle size are eliminated by comparing theoretical and experimental scattering intensities. Therefore, it is also possible to analyze particles typically down to the micrometer scale of 100 μm.

[0030] According to the present invention, particle characteristics, such as size or optical particle parameters, are determined by testing the modeling of particle pulses for different ranges of opening angle and / or spatial angle and by experimentally determined consistency of intensity.

[0031] When the intensity of scattered light measured in the angular range does not match the possible theoretical intensity, asphericity is inferred and the asphericity index is calculated, given, for example, the known size and refractive index of the particle.

[0032] Another advantage of the present invention is that, in the case of single-particle scattering, the shape of the particle is classified as spherical or aspherical by comparing the experimental digital pulse shape of the particle with that of the corresponding simulation calculation for the same spatial angle range for the spherical particle.

[0033] Quantitative results were obtained by using the theory of the relationship between particle geometry (asphericity) and scattering behavior.

[0034] Besides particle wall adhesion or separation, this invention can analyze all particles in a sample, classifying the cumulative distribution or sub-fractions of particles based on factors such as size, shape, and refractive index. Here, the number of particles (concentration) for each characteristic unit is determined, displayed, and output in absolute value.

[0035] A laser with variable beam intensity and an aspherical beam cross-section (focal point) is used, the beam cross-section having a constant light intensity at least across the cross-section of the sample stream (see 16). Figure 1b Therefore, contrary to the prior art (SPOS), the scattered pulse is independent of the trajectory of the measured particle in the measurement volume and does not require deconvolution. In cases of insufficient intensity uniformity, the intensity is corrected using a normalization method (e.g., by experimentally determining the deviation from a constant intensity or by measuring a size-certified monodisperse reference particle). To extend the measurement range, a single laser with different wavelengths or multiple lasers, including fluorescence, can also be used.

[0036] The degree of focusing of the measurement flow in fluid dynamics or aerodynamics can be adjusted manually or automatically based on the original quantity concentration of the measurement sample, knowledge-based, or in the first measurement cycle, by the ratio of the sheath flow to the sample flow.

[0037] Another advantage of this invention is that it does not require changing the measurement chamber or altering the geometry of, for example, the sheath flow cell or optical structure, to determine the size of a very wide range of polydisperse samples. For extremely wide distributions reaching multi-digit micrometer dimensions, different scattering angles can be measured or the extinction of individual particles can be recorded simultaneously.

[0038] Additionally, it is advantageous to be able to insert or move beam stops sequentially, or to use rotatable annular detectors that each cover a angular range, or to introduce different beam stops into a circular sector. Optical elements with special coatings whose transparency can be changed, for example, by an electric field without mechanical displacement, for the corresponding laser wavelength used.

[0039] By using a ring detector or different apertures in a circular sector, the repeated measurements in other angular ranges described in the example are eliminated. This advantageously reduces experimental costs and improves measurement accuracy by simultaneously measuring different angular ranges for the same particle.

[0040] For extinction applications, the ratio of light intensity of the light source in the test tube to the extinction signal is improved by focusing in a fluid dynamic and by obscuring the area illuminated by the primary beam in the image space next to the fluidly focused particles, so as to detect smaller particles.

[0041] By inserting an aperture stop after the objective lens, having the diameter of the primary beam of the laser behind the objective lens, most of the forward scattering that would also reach the receiver is eliminated, thereby widening the measurement range to smaller particles and enabling more accurate particle size calculation. Referring to patent document EP 2 388 59 A1, it is advantageous that, through particle individualization, the transmission in the region between particles does not have turbidity dependent on the particle concentration.

[0042] The invention enables the use of the apparatus and the application of the method, which are used in industrial and academic fields to analyze multiple characteristics of single particles or to classify or identify particle fractions, such as W / O or O / W emulsions, aerosols, slurries for wafer polishing, ink and pigment suspensions, samples of biologically derived cells and subcellular particles (e.g., cells, viruses, bacteria), or for applications such as the design of nanoparticles, the quantification of dispersion stability, the study of the dissolution, aggregation and flocculation behavior of dispersed phases, and the quantification of dispersion progress.

[0043] The invention is described in more detail below with reference to embodiments shown in at least part of the accompanying drawings.

[0044] In the attached diagram:

[0045] Figure 1 The extinction values ​​of some organic materials are shown (n = 1.43); λ = 532 nm; x = particle size [μm]; y = scattering cross-section [arbitrary unit].

[0046] Figure 1a This illustrates the basic optical principles of the measurement method.

[0047] Figure 1b: Indicates the geometric relationships in the sample space;

[0048] Figure 2a : Indicates fluid dynamics focusing;

[0049] Figure 2b : Shows the sheath flow pool;

[0050] Figure 3a Displays electronic charts and data streams within the device and external software SepView;

[0051] Figure 3b : Shows electronic components used for operation and for data processing;

[0052] Figure 4 The simulated individual pulses of particles and exemplary quantitative features characterizing the pulse shape for possible pulse differentiation serve as the basis for classifying particle features manually or automatically.

[0053] Figure 4a The image shows the measurement results of simultaneously probing scattered light in the forward (left) and lateral (right) directions along a mixture composed of polystyrene particles of different sizes.

[0054] Figure 5 The concentration of polystyrene particles and the counting rates of polystyrene micron particles and gold nanoparticles are shown.

[0055] Figure 6 This illustrates the basic sequence of a typical analytical procedure for calculating particle size distribution;

[0056] Figure 7 The image shows the light scattering curve of polystyrene particles; n = 1.59; receiving angle range: 4°-12.33°; λ = 532 nm.

[0057] x = particle diameter [μm];

[0058] y = Mie scattered light intensity [any unit];

[0059] Figure 8 The image shows the light scattering curves of polystyrene particles (at different receiving angles); λ = 532 nm; n = 1.59; a: 4°-12.33°; b: 5°-12.33°; c: 6°-12.33°; d: 8°-12.33°.

[0060] x = particle diameter [μm];

[0061] y = Mie scattered light intensity [any unit]

[0062] Figure 9The image shows the light scattering curves of particles with an assumed refractive index n = 1.8; (different receiving angle ranges) λ = 532 nm; a: 4°-12.33°; b: 5°-12.33°; c: 6°-12.33°; d: 8°-12.33°.

[0063] x = particle diameter [μm];

[0064] y = Mie scattered light intensity [any unit];

[0065] Figure 10 The following figures show the light scattering curves of silicon dioxide with an assumed refractive index n = 1.46 (at different receiving angle ranges); λ = 532 nm; a: 4°–12.33°; b: 5°–12.33°; c: 6°–12.33°; d: 8°–12.33°.

[0066] x = particle diameter [μm];

[0067] y = Mie scattered light intensity [any unit];

[0068] Figure 11 The scattered light curves of silicon dioxide with an assumed refractive index n = 1.47 are shown (at different receiving angle ranges); λ = 532 nm; a: 4°–12.33°; b: 5°–12.33°; c: 6°–12.33°; d: 8°–12.33°.

[0069] x = particle diameter [μm];

[0070] y = Mie scattered light intensity [any unit]

[0071] Figure 12 The image shows the light scattering curves of silica with an assumed refractive index n = 1.46; the selected particle diameters (for different ranges of receiving angles).

[0072] λ=532nm; a: 4°-12.33°; b: 5°-12.33°; c: 6°-12.33°; d: 8°-12.33°;

[0073] x = particle diameter [μm];

[0074] y = Mie scattered light intensity [any unit]

[0075] Figure 13 The following diagram shows the light scattering curves of silicon dioxide with an assumed refractive index n = 1.47; selected particle diameters (different reception angle ranges); λ = 532 nm; a: 4°–12.33°; b: 5°–12.33°; c: 6°–12.33°.

[0076] d: 8°-12.33°;

[0077] x = particle diameter [μm];

[0078] y = Mie scattered light intensity [any unit];

[0079] Figure 14 The scattered light curves (side scattering) of silicon dioxide with assumed refractive indices a:n = 1.47 and b:n = 1.46 are shown; selected particle diameter range; λ = 532 nm; half-angle: 10.02°;

[0080] x = particle diameter [μm];

[0081] y = Mie scattered light intensity [any unit];

[0082] Figure 15 The image shows the scattering curves (side scattering) of silicon dioxide with assumed refractive indices a:n = 1.46 and b:n = 1.47; selected particle diameter range; λ = 532 nm; half-angle: 10.02°;

[0083] x = particle diameter [μm];

[0084] y = Mie scattered light intensity [any unit];

[0085] Figure 16 : Showing a 2D diagram: refractive index as a function of grain size;

[0086] n = refractive index;

[0087] x = particle size

[0088] Figure 17 : Showing a 2D diagram: sphericity as a function of refractive index

[0089] AI = Asphericity Index; n = Refractive Index

[0090] Figure 18 The image shows the intensity of scattered light (lateral scattering) from silica particles dispersed in air (a:n = 1.0) and water (b:n = 1.335); angular size: 10.02°.

[0091] x = particle diameter [μm];

[0092] y = Mie scattered light intensity [any unit]

[0093] Figure 19: A schematic diagram showing the principle of a measurement region with particles observed in the direction of the laser beam; the direction of particle flow is indicated by arrows a) volume scattering light device; b) single-particle scattering photometer with laser focusing and shaping, but without hydrodynamic focusing; and c) with hydrodynamic focusing;

[0094] Figure 20 : This shows the scattered light radiation blocked by the aperture stop (dark gray circle); the primary beam of the laser with an extinction signal (light gray circle) passes through the aperture stop;

[0095] Figure 21 This shows the extinction measurement of polystyrene latex at 552 nm (with background correction);

[0096] X = the number of channels on the multichannel analyzer;

[0097] Y = Extinction [any unit];

[0098] Figure 22 The matte finish of a mixture of polystyrene (PS) and melamine resin particles (MF) of different sizes is shown.

[0099] a: 0.815μm PS; b: 1.05μm PS; c: 1.3μm MF;

[0100] X = the number of channels on the multichannel analyzer;

[0101] Y = Extinction [any unit].

[0102] Invention Description

[0103] 1. Measuring apparatus for a single-particle photometer

[0104] The technical implementation of the present invention will be illustrated below by way of example.

[0105] Optical measurement structure:

[0106] Figure 1a A typical structure of a measuring device focused on an optical element is shown in a top view (z-direction). The device according to the invention includes: at least one laser 1 for generating at least one laser beam 3, and at least one [unclear - possibly for shaping the laser beam 3 and constructing a focal geometry 16 (see [unclear - possibly for...]). Figure 1b The optical input module 2 (etc.), the sheath flow cell 5, advantageously has hydrodynamic focusing, in which a forward-scattered beam 6 and a side-scattered beam 7 are generated by a laser beam 3, and an optical output module 8 is located in the forward-scattered beam 6 and an optical output module 9 is located in the side-scattered beam 7.

[0107] 10. Semi-transparent mirror.

[0108] Camera 12, photomultipliers 11a and 11b, wherein the photomultipliers 11a and 11b are used to perform scattered light measurements for different numbers of divergence angles or reception angles, and the particle characteristics are determined by an analysis algorithm based on the intensity of the scattered light determined by the forward-scattered beam 6 and the side-scattered beam 7.

[0109] Ideally, light source 1 is a stable, monochromatic, intensity-controlled, and short-wavelength laser with a power of, for example, 100 mW. Other light sources and designs can also be used. According to the invention, all wavelengths in the visible, near-ultraviolet, and near-infrared ranges can be used. The smaller the wavelength, the smaller the particles that can be measured. Coupling of different or multiple lasers can also be achieved via optical module 2 or by means of corresponding optical components through beam 3. Optical module 2 is used to construct, for example, an elliptical focal geometry (…). Figure 1b (16) The focal geometry can tolerate both the same light intensity in the measurement volume and small overlap of particles. These two methods can also be integrated into a single module. The incident or scattered beam can also be "guided" by a light conductor, which is useful, for example, for miniaturization of the structure. The use of micro-optical components is particularly advantageous. The incident beam 3 is focused onto the single-particle flow 4 in the sheath flow cell 5. It should be noted that the edges of the measurement unit are not touched by the relevant portions of the primary radiation in order to minimize background radiation.

[0110] Figure 1b The local relationship observed from lateral scattering 7 (y-direction) is shown. The focal geometry is typically chosen such that its width (x) is greater than the diameter of the particle flow. This can be achieved, for example, by a combination of appropriate lenses in module 2 and / or by using an aperture. Furthermore, the focal point can be constructed using optical module 2 such that the laser intensity is as uniform (constant) as possible across the cross-section (y-direction) of the particle flow within the optical measurement volume (optical sensing area). If this is not the case, the deviation can be measured by measuring the position-dependent laser intensity or by standardizing the measurement with highly monodisperse particles. The particle size distribution can be corrected for by a correction factor and the assumption that the particles are statistically uniformly distributed in the flow path 21, using the determined correlation between intensity and position, see [reference needed]. Figure 2b .

[0111] When a particle passes through the laser focus, the light is scattered into space. Exemplary optical modules 8 and 9 are shown for forward scattering 6 and side scattering 7 of the particle in the laser focus. These optical modules converge the light (e.g., through a beam stop) to obscure the direct beam (only for 6), containing receiving optics and focusing the light scattered in a specific area onto, for example, photomultipliers 11a, 11b. Depending on the measurement requirements, the photomultipliers can be identical or functionally adapted for different radiation angles. Photodiodes and avalanche diodes (avalanche photodiodes) can also be used. A semi-transparent mirror 10 facilitates adjustment of the optical path via a camera 12. The camera assesses the sharpness of the image of the scattered particle stream in the measurement area and its position relative to the aperture stop. Only when the edges of the aperture stop and the scattered light signal appear "sharp" can the image of the measurement volume be narrowed by the smallest possible aperture. This obscures a portion of the background radiation. Furthermore, it must be ensured that the aperture does not obscure any part of the particle scattering image to avoid resulting TGV widening and particle concentration errors.

[0112] According to the invention, beam stops of the same or different shapes (e.g., with different diameters) can be sequentially inserted into the forward-scattering beam 6 before or after the receiving optics (objective), or a beam stop of constant size can be moved within the diverging scattering cone (or focusing cone) to achieve different receiving angle ranges. Ring detectors covering different angle ranges can also be combined. Ring detectors with different radii and beam stops can also be arranged, for example, in a single component in the four quadrants of a radiation receiver. Thus, it is not necessary to mechanically place beam stops to achieve different receiving angles.

[0113] For high counting accuracy, it is important that only one particle passes through the measured volume detected by a focused laser beam. This can be achieved, in practice, by measuring the hydrodynamic focusing of the sample for particles carried by liquids and by measuring the aerodynamic focusing of the sample for particles carried by air. The maximum sample volume flow rate associated with particle concentration can be estimated using the method described in the literature (Analytical Chemistry, 1987, 59(6), 846-850, DOI:10.1021 / ac00133a013).

[0114] Figure 2aA typical flow arrangement (fluid) is shown, featuring a vertically oriented sheath flow pool 5 with hydrodynamic focusing. The sheath flow pool 5 is typically designed as a right parallelepiped (external dimensions, for example, 10 mm x 10 mm, height, for example, 30 mm; other dimensions are also possible) and is composed of a highly transparent material (e.g., quartz glass). The internal cross-section is, for example, 1500 μm x 1500 μm or 200 μm x 200 μm. Other geometries and cross-sections can also be used. The sheath flow pool 5 also has an inlet 13 and a sample inlet 14 for the sheath flow (envelope flow), and an outlet 15. The sheath flow 13 is conveyed from the storage container 17 in a controlled and pulsation-free manner via a pressure generating device 18. This is achieved, for example, by generating an adjustable gravitational pressure differential. Specific geometries in the inlet regions 13 and 5 can be used to stabilize laminar flow. Sample flow 19 is provided via a volume-controlled, calibrable syringe pump 20, which has a nominal volume of, for example, 0.5 ml to 2 ml. Larger and smaller delivery volumes can also be used. It should be emphasized that this ensures that all dispersed particles flowing through the measurement unit are analyzed, rather than only a small fraction being analyzed as described in EP2 388 569 A1. To minimize the sample volume, for example to 80 μL or 400 μL, preferably 250 μL, additional ports can be integrated into the input tubing 14, such as Hamilton syringes for different volumes and sample loops of correspondingly designed sizes. Sheath flow cell 5 (see...) Figure 2b The cross-section of flow path 21 in the experiment can be adjusted manually or automatically within a wide range of constraints based on the known sample count value or the sample count value recorded at the beginning of the experiment, through the ratio of sheath flow to sample flow. For example, the diameter of the sample flow (4, Figure 1b The diameter can be variably adjusted from 5μm to 30μm.

[0115] According to the method in the literature (Analytical Chemistry 1987 59(6), 846-850, DOI:10.1021 / ac00133a013), the sample flow diameter can be calculated based on two flow velocities used for the sheath flow and the sample flow. Thus, for example, with a laser beam height of 15 μm (exemplarily assumed to be the smaller radius of the elliptical beam cross-section (16)) and a sample flow rate in the measurement unit of, for example, 0.3 μL or 1.2 μL, the geometric optical measurement volumes are 10 pL or 295 pL, respectively. These values, according to the present invention, can be adjusted to smaller volumes, for example, to change the measurement sensitivity for smaller nanoparticles, or to larger volumes, for example, to reduce measurement time, through variable applied fluid dynamics. Thus, for example, the original concentration of the sample in the concentration range of 10,000 times can be measured mission-wise only by the appropriate flow velocity of the sample and / or sheath flow, without dilution and changes to the mechanical arrangement or sheath flow cell geometry. For example, the sample flow rate is (300-1200) nL / min and the concentration is 10 per milliliter. 9 In the case of single particles, it is generally possible to measure without overlap in practice and record the particle number very accurately with a relative error of less than 1%. Thus, it is typically possible, for example, to analyze particle concentrations of at least 10 per milliliter using single-particle detection. 9 Samples of individual particles. To achieve the necessary wide size measurement range of thirty to forty particles, the sheath flow cell 5 and applied fluid dynamics are structurally designed and implemented such that the input of the sheath flow 13 and the sample input 14 can be achieved from above or below. This prevents counting losses due to the settling of larger particles or the emulsification of larger droplets. Additionally or alternatively, devices such as one or more mixers may be used in the sample input piping system to input the sample into the sheath flow cell 5 without particle loss.

[0116] Instead of fluid dynamic focusing, acoustic focusing in the particle measurement volume 4 at the center of the sheath flow pool 5 is also feasible.

[0117] Special devices for sequentially sampling from reactors or pipelines and via 14 input samples can also be used to measure, to some extent, continuously over time, for example, the manufacturing process (online). Advantageously, the initial raw particle concentration is examined by optical sensors or other suitable measuring sensors, and if the initial concentration of the primary sample extracted from the process is too high, one or more dilution steps are performed by a calibrable mixer, and these are technically and in accordance with standard operating procedures (SOPs), for example with software assistance, through appropriate software (e.g., SEPView) and included in the concentration calculation.

[0118] The incident laser beam 3 penetrates the sheath flow cell 5 and interacts with the hydrodynamically or aerodynamically separated particles in the sample flow 21. Scattered radiation (e.g., forward beam 6 and side beam 7) exits the sheath flow cell 5. In principle, for example, two different lasers with parallel or, for example, 90° offset incident beams 3 could also be used to improve the measurement resolution for each individual application. In practice, with parallel incident beams 3, the height difference with respect to the sheath flow cell 5 is very small, but no interaction between the two beams occurs. The intensity-time curves of the scattering events recorded by the two lasers must be synchronized accordingly.

[0119] The structure of aerodynamic focusing is similar to that of hydrodynamic focusing. The aerosol beam is surrounded by a clean air hood and is limited by the ratio of the sample volume flow rate to the envelope flow volume of the air hood and the shape of the nozzle in the sheath flow cell 5.

[0120] Due to the non-spherical shape of the laser beam (see 16, Figure 1b The present invention is characterized by a very low intensity correlation across the beam cross-section compared to the typically occurring Gaussian distribution of a spherically focused laser beam (see EP 2388569 A1). Figure 16 In the elliptical beam cross-section exemplarily shown, sufficiently uniform laser intensity can be achieved within the optical measurement range through a large axial ratio. Alternatively, given that the intensity distribution of the primary beam of laser 1 is known, the technically achieved intensity curve can be corrected by simulation calculations of the optical ratio or experimental determination based on the intensity distribution in the detected measurement stream, for example, by integrating over the measurement range and determining a deviation factor from a constant intensity distribution, thus obtaining an accurate granular distribution.

[0121] To extend the sensitivity of the measurement system to the lower nanometer range, it is particularly necessary to reduce the optical measurement volume and minimize scattered radiation from the component surface within the optical range, and to use a low-noise laser. Laser modules (1, 2) with integrated micro-optics and a minimized exit window can significantly reduce unwanted scattered radiation.

[0122] The solution for improving the noise-to-signal ratio according to the invention is also used in the sheath cell 5 and the region of the scattered beam detection optics. In the sheath cell 5, for example, only the necessary incident or exit windows for radiation are designed to be transparent. This can be achieved, for example, by using different transparent glass or partially coated inner walls. Additional optical components, such as multi-level diffraction optical elements or absorbing coatings, can also be used in the region of the detection optics (e.g., 8, 9, 10, 11a, and 11b).

[0123] Electronic structure:

[0124] Figure 3a The main functional elements of the electronic structure developed according to the present invention are summarized. The electronic structure is based on an embedded board having an operating interface BO, a boot medium, at least one microcontroller supported by one or more FPGAs, and a fast mass memory (e.g., SSD). Figure 3a It also reflects the basic principles of networks and the information flow between PC or server-based software SEPView and electronic structures, which realizes bidirectional real-time high-speed communication.

[0125] exist Figure 3b The diagram illustrates, for example, the electronic components that are crucial for processing information, using two scattered light sensors whose scattering angles or subtraction angles may differ. It would also be wise to specify the use of other sensors, such as those for temperature, flow rate, storage container fill level, laser intensity, optical adjustment, cameras, etc.

[0126] The analog signal from the sensor, consisting of intensity pulses emitted by a single particle, is first amplified by a low-noise, advantageously linear two-stage amplifier with automatic switching and then digitized in real time by an analog-to-digital converter. Corresponding to the scattering intensity, which decreases sharply with particle size, amplifiers with very wide bandwidths, such as 120 dB, can be used. These amplifiers are designed so that recorded sensor scattering events can be processed at very variable frequencies (clock frequencies), for example from 20 Hz to 10 kHz, and advantageously at very high frequencies up to 50-100 kHz, so that statistically reliable counts of events (the number of particles of the corresponding size class, e.g., from 80 nm to 100 nm) can be obtained in a short measurement time. Furthermore, it also allows, particularly for concentration determination, the possibility of changes in the sample during measurement, such as due to sedimentation or particle-wall contact, to be excluded. On the other hand, this also allows for the measurement of rapid changes in the dispersed phase, such as dissolution behavior or aggregation rate. The amplifiers developed for this invention can operate in both linear mode (for high-resolution pulses or single-modal particles) and logarithmic mode (a wide distribution over multiple orders of magnitude).

[0127] To achieve high resolution for pulse analysis, an AD converter with, for example, 20 to 24 bits and a sampling rate range of 0.1 to 25 MS / s, advantageously 1 to 5 MS / s, can be used.

[0128] In the preprocessing of digital values, very short interference pulses and invalid converter results are filtered out and discarded using a special algorithm. Bias processing should also be implemented here.

[0129] A special pulse recognition electronics / firmware analyzes the digitized data stream in real time and identifies the pulses that can be analyzed. Invalid pulses are discarded. Invalid data mainly includes pulses that are too long, too short, or below the trigger threshold. After digitizing the valid pulses, the pulse characteristic values ​​of the corresponding single particle are determined in real time in the FPGA, such as the maximum value of the pulse, intensity, etc. Figure 4a The duration of the pulse and the area of ​​each particle under the pulse signal are also considered. Digital pulses with, for example, 100 support points, including adjustable timing advances, and the determined characteristic parameters are stored or transmitted in real-time to the embedded board and classified in a highly sensitive manner into up to 10... 6 One Bin. Through the BO (operation interface), it is advantageous to have, for example, 10 to 10... 6 The number of bins can be selected, allowing for arbitrary combinations of particle categories. Pulse classification is displayed on the BO in real time. Additional auxiliary electronics provide parameters for pulse identification and sensor tuning. These SOP parameters are requested by the SEPView server or created via the BO and transferred from the embedded board to the electronics. All data streams from different sensors are timestamped, allowing for synchronization in visualization and analysis.

[0130] software:

[0131] It consists of three functional software components. The first integrated component is a platform-independent application server that communicates with the aforementioned measuring device. This communication is achieved using a specially developed communication protocol, which, according to the present invention, enables parallel data input and SOP programming / modification via the embedded computer of the measuring device, both through the server and directly via the BO. The core component of the server is a document-based database, which permanently stores... Complete master data and transaction data.

[0132] The second integrated component is -Explorer, which maps to a user-facing interface, is advantageously implemented as a platform-independent web interface. Through the use of a web browser, extensive data visualization is achieved, such as scattered light pulses and the classification of different particle parameters collected using a graphics processor; these are analyzed in real time during measurement and displayed on the BO. Access to Explorer can only be granted with authorization.

[0133] The third component is Recorder. It comes from -Explorer launches, controlling the entire measurement process according to SOPs received by the user, such as from the server or SOPs specifically programmed via BO. It visually displays synchronized scattered light pulses, for example, for different aperture angles or scattered light directions, as well as real-time specified measurement parameters, and records processed SOPs, all functional statuses, and measurement data. The client-server architecture decouples the management, procedural, and analytical layers, enabling adaptation to relevant client processes and distributed collaboration.

[0134] Figure 4 Typical results are shown for the simultaneous recording of single-particle scattering in the forward (left) and lateral (right) directions for a mixture of single-modal particle types (material: polystyrene) with a nominal diameter range from 143 nm to 3000 nm (logarithmic view). According to the invention, particles of different sizes in a mixed sample with the same SOP are measured simultaneously and without any change / adjustment to the geometry of the measurement chamber. For improved analysis, the forward and lateral scattering are also displayed as two-dimensional plots (axis: forward (Y-axis) relative to lateral (X-axis) or vice versa). Each particle thus corresponds to a point in the plot, which quantifies the measurement intensity in the selected scattering or extinction channel. The point density corresponds to the corresponding number of particles with these characteristics. Therefore, it is also advantageous to detect particles of the same size from different materials, as well as coated or uncoated particles.

[0135] Figure 5 (Left) Shows the results of determining the concentration of polystyrene particles with a size of 726 nm. The average with standard deviation is shown for 5 replicates (each measured for 1 minute). The average concentration is 108,960 + / - 640 particles per microliter. The standard deviation is only 0.6%, demonstrating the high counting stability of the developed method. Figure 5 (Right) shows the pure counting rates of polystyrene (80 nm) and gold nanoparticles (50 nm). As can be seen, the solution of the present invention is able to record constant, drift-free count values ​​over a measurement time (one minute in the example shown in the figures), even at very high counting rates of approximately 9000 Hz (events / second). Therefore, after calibrating the syringe pump for delivering the measurement sample, the proposed method can very efficiently determine the concentration (number of particles per milliliter) of dispersed particles at the micrometer and, especially, nanometer scales.

[0136] Figure 6 The possibility of a sequence of analytical steps for downstream analysis of sample measurements is shown for calculating particle parameters (here, for example, particle size) using the measurement method according to the present invention. Example

[0137] The following exemplifies and elaborates in more detail various individual embodiments of the present invention's solution for determining particle characteristic parameters. All calculations below are based on a 532 nm laser wavelength. Other wavelengths, such as NIR, SL, or UV, can also be used and can improve the resolution / sensitivity or dynamic measurement range for the chosen application. Thus, decreasing the wavelength enables the detection of smaller particles, while increasing the wavelength enables the detection of larger particles without entering the ambiguous regions of Mie theory. Particles are typically dispersed in water. However, depending on the materials and optical requirements of the applied fluid dynamics, any liquid, solution, solvent, or gas can be used as the carrier medium. For specific applications, for example, the refractive index contrast can be improved by selecting the liquid, and thus the detection of nanoparticles can be moved to the single-digit nanometer range, or resolution can be achieved for particles with very small size differences (e.g., <5 nm).

[0138] The scattered light curves necessary for describing the present invention were calculated for exemplary particles based on Mie theory. The calculations were interrupted at a particle diameter of 10 μm, as this size range is sufficient to illustrate the facts according to the invention. The receiving angle for the scattered light measurement, selected based on the quantity and angular range, is arbitrarily chosen and can be adjusted arbitrarily. 10.33° is a fixed critical angle at the top of, for example, a non-commercial photometer; this angle is used for simplicity.

[0139] For the lower variable receiving angle limit, four angles were selected for the exemplary calculation. 5°, 6°, and 8°, therefore, can be used according to the needs of the analysis. The angle range is between 10.33° and 10.33°. It should be emphasized that these angles can be set very variably. In the corresponding optical arrangement, the lower critical angle can also be less than 1°.

[0140] a) Expand the application of scattered light measurements to determine the size of micrometer-scale particles when the refractive index is known.

[0141] "Typically," so-called forward scattering is used to determine the size of particles falling outside the Rayleigh scattering range and the intensity is measured within a specific angular range. Since the intensity of the scattered light increases monotonically as a function of particle size at first, but has a maximum and a minimum value for larger particles (…),… Figure 7-13 This means that a clear correspondence with particle size cannot be achieved, so for dispersions in the size range of a few micrometers, the size cannot be clearly determined based on their optical properties.

[0142] like Figure 7As shown, the particle size of commonly used reference particles (polystyrene) cannot be definitively determined, for example, at an angle of 4°–10.33°, up to a diameter of 1.17 μm. The intensity of scattered light is... Figure 7 The value is at I = 1.2. A particle diameter of 2.36 μm is also feasible according to Mie theory when the scattered light intensity is slightly higher. According to the present invention, this ambiguity is eliminated through measurements over multiple angular ranges. Figure 8 ).

[0143] When the intensity of the scattered light is, for example, I = 2, it can be determined according to... Figure 8 Particle sizes of 1.20 μm, 2.05 μm, and 2.63 μm were read within an angular range of 4°–12.33°. To address ambiguities, an angular range of 6°–12.33° can be used for additional measurements, for example. Figure 8 This allows for the determination of the actual particle size. Within this angular range, the Mie calculations of scattering intensity for an angular range of 4°–12.33° yielded possible particle sizes of 1.59 (1.20 μm), 1.04 (2.05 μm), and 1.34 (2.63 μm). The intensity differences are large enough that a clear (correct) diameter can be assigned to the particle. If, for example, an intensity of 1.04 is measured experimentally for the second angular range, the particle size is 2.05 μm. If the intensity determined for the second angular range is inconsistent with the calculations, it is reasonable to infer that the observed particle is aspherical. Accurate measurement and analysis of the pulse shape can quantify this optical particle characteristic. In addition to Rayleigh-Debye-Gans theory (which is only applicable to limited applications), other theories of asphericity (such as the discrete dipole approximation) can also be used to obtain specific quantitative parameters.

[0144] After measurements are taken within an angular range of 4°–12.33°, similar measurements can be taken within a particle size range of 4.0 μm–5.0 μm. A suitable combination here is an angular range of 6°–12.33° and 8°–12.33°. A particle size of 5.9 μm is also feasible, determined by the latter curve. Here, if the particles have this diameter, the measured intensity should be 3.

[0145] As another example, the intensity of scattered light at I=14 was studied in a dispersion of particles with a refractive index of 1.8. Figure 9 ).

[0146] Within an angular range of 4°–12.33°, possible particle diameters are 8.1 μm, 8.5 μm, and 9.0 μm. To eliminate ambiguity, measurements must be taken within a second angular range according to the invention. Within an angular range of 6°–12.33°, the corresponding intensities are 6.6, 9.5, and 10.1. If the difference between 9.5 and 10.1 appears insufficient for determination, an angular range of 8°–12.33° can be used. The intensities here are 4.8 and 7.1. These examples also demonstrate that theoretical Mie calculations can identify which angular ranges can still be used for experimental determination after the initial measurement.

[0147] Furthermore, it can be well identified that for particles with a diameter greater than 10 μm, the scattered light curves in the four corner ranges under consideration differ more from each other, thus making it easier to achieve corresponding assignments.

[0148] b. Determine both grain size and refractive index simultaneously.

[0149] This part of the specification extends the application a) to cases where the refractive index of the corresponding particle is unknown, for the purpose of simultaneously determining the refractive index and particle size experimentally.

[0150] In principle, the method described in a) remains unchanged. Within the four arbitrarily selected receiving angle ranges of embodiment a), there are no longer four matrices of scattered light intensities with the same value across the angular range for different refractive indices and particle sizes. If the measurement error of the scattered intensity present in the experiment exceeds the required accuracy, a wider angular range (e.g., less than 4°) can also be used here, or as... Figure 1a As shown, lateral scattering, for example, lateral scattering at a 90° angle, is also used to determine particle parameters.

[0151] Here, as in the examples already illustrated, in cases where intensity values ​​are inconsistent, it must be inferred that the particles are not spherical, for example, by quantifying this through pulse shape analysis.

[0152] The refractive index of a large number of particles in a material varies due to manufacturing processes, for example, in the case of SiO2 (porosity). The proposed invention allows for the determination of even small differences in refractive index between the analyzed particles (in this case, silicon dioxide). This will be exemplarily shown on the corresponding scattered light curves for n = 1.46 and n = 1.47.

[0153] For particles larger than 3μm, the corresponding distribution is not a problem. Figure 10 and Figure 11 ).For example Figure 10 and 11 The superposition proves that the intensity is sufficiently different across the angular range.

[0154] The invention now describes the explicit assignment of refractive indices to particles of unknown size for any chosen diameter, such as 2 μm and 0.5 μm, wherein, for simplicity, SiO2 is also used as an example. Figure 12 and Figure 13 or Figure 14 and Figure 15 ).

[0155] like Figure 12 As shown, a particle with a diameter of 2.00 μm and a refractive index of n = 1.46 has a scattering intensity I = 5.60 according to Mie theory in the range of receiving angles of 4°–12.33°. However, this has two implications, because a particle with a refractive index of n = 1.47 also has this intensity when the particle diameter is 1.95 μm. Figure 13 If a receiving angle range of 8°–12.33° is additionally used, particles with a diameter of 2 μm and n = 1.46 are scattered with an intensity of I = 1.84. Figure 12 The intensity ratio is 3.044. Assuming a refractive index of n = 1.47, this produces a scattering intensity of I = 1.91. Figure 13 And the intensity ratio is 2.93. Lateral scattering can also be additionally used to verify / confirm the determined refractive index. Figure 14 ).

[0156] To calculate the Mie intensity of lateral scattering, for example, assuming in Figure 1 The half-angle (10.02°) of the photometer depicted at λ = 532 nm is shown.

[0157] When the particle diameter is 2.00 μm, the scattered light intensity is calculated to be I = 0.00116. The scattered light intensity of particles with diameters of n = 1.47 and 1.95 μm is approximately 20% greater (I = 0.00133). Generally, it can be determined that side scattering can be used for particles with a size parameter k less than or equal to 20. The size parameter k is calculated as follows:

[0158] k = πnx / λ

[0159] x: Particle diameter

[0160] n: Refractive index of the continuous phase (dispersion medium)

[0161] λ: Wavelength of radiation in a vacuum

[0162] The determination of size and refractive index (1.46 or 1.47) will now be shown for an exemplary particle with a size of 0.5 μm. An intensity I = 0.00765 was measured in the angular range of 8°–12.33°. This corresponds to 0.500 μm (n = 1.46) or 0.487 μm (n = 1.47). In the other three receiving angle ranges considered here for forward scattering, the corresponding intensities differ by only about 1%. Lateral scattering at a 90° angle, according to... Figure 15 We get: I = 5.68 10 -5 (0.500 μm; n = 1.46) or I = 5.91 10 -5 (0.487 μm; n = 1.47). The intensity difference is large enough to make a decision.

[0163] When making initial measurements within the range of 4°–12.33°, it should be noted that measurement inaccuracies may occur, as is common in measurements.

[0164] Generally, the required accuracy for measuring the intensity of the scattered light curve is determined by the correlation between the change in scattered light intensity and particle size (e.g., Figure 14 For a large correlation between scattering intensity and particle size (slope, e.g., within the size range of 0.70 μm–0.75 μm), Figure 15 The error of a few percent can be ignored.

[0165] If the necessary measurement accuracy is not achieved, then consider, for example, an additional angular range.

[0166] The smaller the particle, the smaller the intensity difference within the reception angle range. Within the Rayleigh range, the intensity difference no longer exists.

[0167] When the particles have a refractive index greater than that of SiO2 (n = 1.46-1.47), it is often easier to determine the size and refractive index for small particles (about 0.5 μm).

[0168] The refractive index determined for each particle will be sorted or categorized according to size, resulting in a quantity-based distribution of this refractive index characteristic for the total group measured. If the refractive index and corresponding scattering intensity, or the particle size determined thereby, are recorded in a 2D plot for each particle (see also...), Figure 16 If this is done, subgroups can be identified within the whole, and the uniformity of particle type in the measured sample can be inferred.

[0169] In principle, the extinction coefficient (n”) can also be determined. However, due to the introduction of another variable, more receiving angles must be used for measurement in order to make a decision amidst the increased uncertainty, as this significantly increases the number of possible combinations.

[0170] For the purposes of this invention, it is not important how the different receiving angle ranges are achieved.

[0171] In a photometer, beam stops of different diameters can be inserted sequentially before or after the receiving optics (objective). A beam stop of constant size can be moved within a diverging scattering cone (or focusing cone) to achieve different ranges of receiving angles.

[0172] Ring detectors covering different angular ranges can also be combined. Different apertures can also be introduced within the circular sector. Therefore, the intensity of scattered light for the implemented arrangement must be experimentally measured separately and individually, for example using a reflecting prism or a position-sensitive photomultiplier. Advantageously, according to the invention, the repetitive measurements in other angular ranges described in the previous examples are omitted, which advantageously reduces experimental costs and improves measurement accuracy by simultaneously measuring different angular ranges for the same particle.

[0173] In principle, multiple devices can be used. However, even with the same equipment technology, adjustments, and calibrations, a lower level of grading accuracy should be the starting point.

[0174] c) Determination of sphericity in the case of a single-particle scattering photophotometer

[0175] Besides refractive index, the optical properties of particles are also determined by their geometry (e.g., spherical, prismatic, elliptical, cylindrical, or irregular shapes). The Mie theory, most commonly used to determine particle size using light scattering, only applies to spherical particles. It is known from light scattering theory that spherical and aspherical particles of the same volume exhibit different scattering behaviors.

[0176] The methods disclosed in paragraphs a) and b) cannot describe aspherical particles. If these methods are still applied, the theoretical Mie scattering intensity will be inconsistent for different scattering angles and angular inclinations. This, on the other hand, means that the particles under study will be qualitatively classified as aspherical. This has been pointed out several times in paragraphs a) and b). For example, the percentage difference between the ratio of the theoretical Mie scattering intensity calculated for two (or more) angular inclinations and the ratio of the scattering intensity determined experimentally at the same angular inclination can be defined as a quantitative “asphericity index” (AI). Other definitions are also possible. Similarly, the “asphericity index” can be determined by the ratio of the theoretical calculation of the intensity for two scattering directions to the experimentally determined intensity for the corresponding scattering directions.

[0177] The solution of this invention also allows for the use of a second procedure to determine the "asphericity" of the particle. To determine sphericity, the intensity variation curve of the scattered light pulse over the entire time period is measured by a scattering light device during the particle's passage through the measurement volume (Fig. 1b) and analyzed or saved in real time. Saving the time-varying curve of the scattering intensity and subsequent analysis are also feasible.

[0178] If the intensity distribution in the laser focus is known, the sphericity of the particle can be derived from the intensity change curve determined by the experiment when the particle passes through the laser focus and by deconvolution.

[0179] Furthermore, according to the present invention, the theoretical pulse duration of a particle can be calculated by comparing parameters determined based on Mie's (sphere assumption) and taking into account the sample volume flow rate under experimental calibration. The pulse duration for each particle is then calculated experimentally after high-resolution digitization. Figure 4a The comparison with the theoretically calculated spherical equivalent time period, according to the present invention, can also detect small deviations and thus quantify asphericity with high resolution.

[0180] The quantitative particle geometry thus defined will be ordered according to intensity or also according to size, and will produce a quantity-based distribution of this feature in the total population being measured. If the "asphericity index - AI" is recorded for each particle along with the scattering intensity or the particle size determined therefrom, the distribution of "AI" in the sample can be quantified or possible subgroups in the overall sample can be identified. In addition to the particle size determined according to Mie, the distribution can also be recorded according to the determined refractive index. Figure 17 This indicates that the dispersed phase consists of two sub-fractions of particles with different refractive indices (different materials or non-uniform core-shell particles), and the fraction with the lower refractive index exhibits significantly stronger scattering with respect to the asphericity index.

[0181] Application examples a) through c) are described for hydrodynamic focusing because the methodological challenges are significantly greater here due to the considerably lower intensity of scattered light (lower refractive index contrast between liquid and particles compared to air). However, applications for aerodynamic focusing follow the same inventive approach in principle. In particular, the measurement limits will advantageously shift to significantly smaller particle sizes, down to the single-digit nanometer range, because the refractive index contrast increases many times over and the proportion of signal-to-noise ratio is significantly minimized due to the greater intensity of scattered light. This fact... Figure 18 The image shows silica particles in air (n = 1.000) and water (n = 1.334). A 20 nm particle has approximately 100 times the intensity of scattered light.

[0182] d) Extinction module with hydrodynamic focusing.

[0183] The inventions under a)-c) also have the inventive task of eliminating the error-laden extinction measurement (Fraunhofer approximation). However, if there are still doubts about aspherical particles through the described methods and calculations, it is appropriate to revert to extinction measurement.

[0184] Therefore, the primary beam can be deflected after the sheath pool 5 and before the beam stop, and the analysis can be performed as is known.

[0185] The solution described below demonstrates a second possibility for eliminating the need for an additional measuring arm and shifting the measurement limit to smaller particle sizes.

[0186] The expansion of the measurement range to smaller particles is contrary to the sensitivity of known receivers, which should be able to detect small temporal light losses (negative light pulses or "extinction signals") from a large amount of light even when particles pass through a relatively large measurement area.

[0187] The ratio of constant light intensity of the light source (preferably laser 1) in the test tube to the extinction signal is particularly unfavorable for measuring smaller particles.

[0188] Hydrodynamic focusing helps improve the ratio. Unlike existing techniques, hydrodynamic focusing reduces the original measurement area used for the extinction signal by imaging the entire measurement area onto an aperture (preferably an aperture stop or rectangular stop) via an optical device. Only the area with the extinction signal is not blocked by this aperture, and the extinction signal is then directed to the receiver. Therefore, light near the particles in the hydrodynamic focus is largely blocked in the image space. The measurement area is now determined only by the particle flow diameter, rather than by the entire illuminated area in the test tube.

[0189] Through this arrangement ( Figure 19 This allows for the expansion of measurable lower particle sizes to smaller diameters.

[0190] In a), the particles either fill or flow through the entire focal point. In b), it is unfavorable to operate with a drastically reduced particle concentration in order to ensure single-particle recording, as overlap occurs proportionally to the measurement volume. Due to hydrodynamic focusing, higher concentrations (e.g., up to 10⁻⁶ per milliliter) can be measured in c). 10 (Number of particles). Possible particle streams are marked with dashed lines. Areas outside the particle streams are obscured.

[0191] The task generated by this structure is to precisely position the image of the particle stream (i.e., extinction pulses) within an aperture stop or rectangular stop so that the pulses can also be recorded by the receiver (optically, the brightness fluctuations of smaller particles are too weak to be detected by a camera when passing through the laser beam). The target can be either... (The sentence is incomplete and requires more context to translate accurately.) Figure 1a In this case, the aperture stop on the objective lens is pre-adjusted and then removed, or the aperture stop is moved to the maximum extinction deflection relative to the reference latex by means of x, y adjustment (i.e., perpendicular to the laser beam propagation). Generally, a disadvantage of extinction measurements is that most of the forward scattering also hits the receiver and weakens the extinction pulse. This scattered light pulse can be eliminated by inserting an aperture stop in the optical path after the aforementioned adjustments, behind the objective lens, which only allows the primary laser beam to pass through (…). Figure 20 This arrangement is particularly effective for determining the size of small particles.

[0192] Using the experimental setup described above, polystyrene particles with a diameter of 0.726 μm can be well distinguished relative to the noise level. If the noise level is significantly suppressed mathematically using a suitable smoothing algorithm, then larger PS and SiO2 particles (0.55 and 0.50 μm) can be well recorded as shoulder peaks in the original spectrum. Figure 21 With the aid of low-noise electronics, it is expected that the achievable particle measurement range will be further expanded.

[0193] A mixture of three different latexes with a size range of 0.8 μm to 1.3 μm. Figure 22 Peaks a, b, and c in the sample can be separated with good resolution.

[0194] To calculate the particle diameter more accurately (without the Fraunhofer approximation), a spherical shape and a known refractive index are assumed. Using the aforementioned photometer, these calculations can also be performed without extended calibration curves, simply by measuring the dimensional standard, since the angular range of the scattered radiation reaching the detector is also known. By calculating the scattered light radiation incident at a known angle of incidence, the particle diameter can be calculated more precisely.

[0195] To simplify particle size determination, or at least make it possible in the first place, the particles must encounter a nearly constant laser intensity. Therefore, it may be necessary to increase the laser focus by removing an active lens behind the light source.

[0196] Existing single-particle scattering photometers (based on Figure 1aThis can be extended into a combined device through the modifications described above. The aperture stop, which originally existed before or after the objective lens (or entrance lens) to block the primary beam, is adjusted and then removed from the optical path in a suitable manner (e.g., by folding). An aperture stop for reducing scattered light signals is placed in the optical path (it must be removed for adjustment).

[0197] The primary optical path with the extinction signal is either redirected to the photomultiplier after being attenuated, for example, by an optical neutral filter, or it is deflected, possibly without the need for a filter, to another receiver.

Claims

1. A method for determining particle characteristic quantities of micrometer- and sub-micrometer-sized particles by multi-parametric detection of extinction and scattering light signals in a continuous flow measuring cell with hydrodynamic focusing, the particle characteristic quantities being particle concentration, particle size, size distribution, number of particles per size class, refractive index and asphericity, wherein, The scattered light and extinction signals of each individual dispersed particle generated by means of a variable beam intensity and an aspherical beam cross section are counted and simultaneously measured at a high detection rate in at least two spatial angular ranges and compared, analogously or digitally, with a simulated calculation of the scattering light distribution for different spatial angular ranges by means of an analytical or numerical method in order to determine the individual particle characteristic parameters in a dynamic particle size range without overlap even for a high particle concentration of the measurement sample, where different opening angles are used for the forward scattering or a plurality of detection directions for the scattering light measurement and arbitrary combinations thereof, wherein the particle size and the refractive index are determined from the respective scattering intensities measured simultaneously, where the entire temporal intensity profile of the scattering light pulse is measured and analyzed in real time or saved during the passage of the particle through the measurement volume in order to determine the sphericity or asphericity.

2. The method of claim 1, wherein, In the case of particles having a size parameter k greater than or approximately equal to 20, which is calculated as follows: k = πnx / λ x: particle diameter n: refractive index of the continuous phase λ: wavelength of the radiation in vacuum.

3. The method of claim 1, wherein In the case of particles having forward scattering light curves which cannot be distinguished in different reception angles, a plurality of detection directions along the lateral direction with different sensitivities are used.

4. The method of claim 1, wherein The simulation calculations by means of Mie theory or numerical simulations are performed in coordination with the respective optical configuration and the ambiguity with regard to the particle size is eliminated by comparison between the theoretical and the experimental scattering intensity and thus also particles in the micrometer range up to 100 μm can be measured.

5. The method of claim 1, wherein The optical particle characteristic parameters are determined by checking the consistency of the modeled and experimentally determined intensities of the particle pulse for different opening angles and / or spatial angular ranges.

6. The method of claim 1, wherein In the case of a discrepancy between the scattering light intensity measured in an angular range and the possible theoretical intensity matrix of the respective particle, asphericity is inferred and quantified by means of an asphericity index.

7. The method of claim 1, wherein In the case of single particle scattering, the shape of the particle is classified as spheroidal or aspherical by comparison of the experimentally digitized pulse shape of a particle having a known refractive index with the respective simulation calculation for a spheroidal particle for the same spatial angular range.

8. The method of claim 1, wherein In the case of single particle scattering, a quantitative result is obtained by means of a theory with regard to the asphericity and / or in the case of single particle scattering, the particle fractions are classified and the number of particles per characteristic unit is determined, displayed and outputted in accordance with the particle characteristic parameters, and / or in the case of single particle scattering, a laser is used which has a variable beam intensity and an aspherical beam cross section which has a constant light intensity at least over the cross section of the sample flow or, in the case of insufficient homogeneity of the intensity, the intensity is corrected by a mathematical standardization method.

9. The method of claim 1, wherein The degree of hydrodynamic or aerodynamic measurement flow focusing can be adjusted artificially or automatically by means of a sheath flow with respect to the sample flow on the basis of a known raw number concentration of the measurement sample or based on a first measurement cycle.

10. The method of claim 1, wherein For determining the size of very broad polydisperse samples, no exchange of the measurement chamber or change of the sheath flow cell is necessary.

11. The method of claim 1, wherein Sequentially inserted or moved beam diaphragms or the use of annular detectors covering one angular range each or different diaphragms introduced into circular sectors in which different scattered light signals are measured and analyzed separately.

12. The method of claim 1, wherein By using annular detectors or different diaphragms in circular sectors, the repeated measurement in other angular ranges is cancelled, which advantageously reduces the experimental effort and increases the measurement accuracy by measuring different angular ranges simultaneously for the same particles.

13. The method of claim 1, wherein For extinction applications, the ratio of the light intensity of the light source in the cuvette relative to the extinction signal is improved by hydrodynamic focusing and by blanking the area illuminated by the primary light beam in the image space next to the hydrodynamically focused particles in order to detect smaller particles.

14. The method of claim 1, wherein For extinction applications, by an aperture diaphragm inserted after the objective with an aperture diameter behind the laser primary beam of the objective, the majority of the forward scatter which would also reach the receiver is eliminated and thereby the measurement range is widened to smaller particles and allows a more accurate calculation of the particle size.

15. An apparatus for determining particle characteristic parameters of micron-sized and sub-micron-sized particles, the particle characteristic parameters being particle concentration, particle size, size distribution, number of particles per size class, refractive index and asphericity, by multi-parametric detection of scattered light and extinction signals in a continuous flow measurement cell with hydrodynamic focusing, the apparatus comprising at least one laser (1) for generating at least one laser beam (3) having a variable beam intensity and an aspherical beam cross-section, at least one optical input module (2) for shaping the laser beam (3) and for constructing an aspherical focal geometry (16), a continuous flow measurement cell with hydrodynamic focusing in which a forward scattering light beam (6) and a side scattering light beam (7) are generated by the laser beam (3), the continuous flow measurement cell having an inflow for a sheath flow (13) and a sample inflow (14) and an outflow (15), wherein the sheath flow (13) is controlled and pulsation-free conveyed from a storage container (17) by a pressure generating device (18), an optical output module (8) in the forward scattering light beam (6) and an optical output module (9) in the side scattering light beam (7), a semi-transparent mirror (10), a video camera (12), a photomultiplier (11a, 11b), the scattered light measurement can be performed for different numbers of opening angles or acceptance angles by means of the photomultiplier (11a, 11b) and the determined scattered light intensities of the forward scattering light beam (6) and the side scattering light beam (7) enable the determination of the particle characteristic parameters by an evaluation algorithm, wherein the particle size and the refractive index can be determined from the respective scattered intensities measured simultaneously and wherein for determining the sphericity or asphericity the entire intensity profile of the scattered light pulse over time can be measured and analyzed in real time or saved during the passage of the particle through the measurement volume.

15. An apparatus for determining particle characteristic parameters of micron-sized and sub-micron-sized particles, the particle characteristic parameters being particle concentration, particle size, size distribution, number of particles per size class, refractive index and asphericity, by multi-parametric detection of scattered light and extinction signals in a continuous flow measurement cell with hydrodynamic focusing, the apparatus comprising at least one laser (1) for generating at least one laser beam (3) having a variable beam intensity and an aspherical beam cross-section, at least one optical input module (2) for shaping the laser beam (3) and for constructing an aspherical focal geometry (16), a continuous flow measurement cell with hydrodynamic focusing in which a forward scattering light beam (6) and a side scattering light beam (7) are generated by the laser beam (3), the continuous flow measurement cell having an inflow for a sheath flow (13) and a sample inflow (14) and an outflow (15), wherein the sheath flow (13) is controlled and pulsation-free conveyed from a storage container (17) by a pressure generating device (18), an optical output module (8) in the forward scattering light beam (6) and an optical output module (9) in the side scattering light beam (7), a semi-transparent mirror (10), a video camera (12), a photomultiplier (11a, 11b), the scattered light measurement can be performed for different numbers of opening angles or acceptance angles by means of the photomultiplier (11a, 11b) and the determined scattered light intensities of the forward scattering light beam (6) and the side scattering light beam (7) enable the determination of the particle characteristic parameters by an evaluation algorithm, wherein the particle size and the refractive index can be determined from the respective scattered intensities measured simultaneously and wherein for determining the sphericity or asphericity the entire intensity profile of the scattered light pulse over time can be measured and analyzed in real time or saved during the passage of the particle through the measurement volume. ​ ​ ​ ​ ​ ​ wherein ​ 16. Use of an apparatus according to claim 15 for analyzing a plurality of characteristics of single particles or for classifying or identifying particle fractions in the industrial and academic fields.

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