PARTICLE TRACKING ANALYSIS METHOD USING SCATTERED LIGHT (PTA) AND DEVICE FOR DETECTING AND IDENTIFYING PARTICLES OF A NANOMETRIC ORDER OF MAGNITUDE IN LIQUIDS OF ALL TYPES

Abstract

A method and device for optically detecting particles (23) have the following features: (a) a cell wall (9) of rectangular cross-section, made of black glass, is fitted on a longitudinal surface and adjoining transverse surface with an L-shaped heating and cooling element (1); (b) the centre of the transverse surface of the cell wall (9) opposite the transverse surface which forms the support of the cell wall (9) is irradiated by an irradiation device and is observed at right angles to the optical axis of the irradiation device by means of an observation device; (c) the focus of the irradiation device and the focus of the observation device can be moved by a motor to any point in the three-dimensional inner region defined by the cell wall (9) by means of a control device; (d) the surface of the cell wall (9) opposite the optical glass window (11) through which the radiation from the irradiation device enters comprises another optical glass window (11) in the centre thereof; (e) the temperature of the surface of the cell wall (9) is monitored by means of two thermistors (8).

Claims

1: An apparatus for detecting and characterizing particles (23) in liquids of all types of the order of magnitude of nanometers of a suspension in a cell wall (9), having the following features: f) a cell wall (9) of rectangular cross section made of black glass with optical windows (11) sintered in has an L-shaped heating and cooling element (1) applied to a longitudinal face and an adjoining transverse face, the cell wall (9) bearing on the transverse face on a stand base (2) which is mounted in a defined way by means of vibration dampers (4), g) the cell wall (9) is irradiated on the transverse face which lies opposite the transverse face which forms the support of the cell wall (9) in the middle by an irradiation device through an optical glass window (11) and is observed at a right angle to the optical axis of the irradiation device through a further optical glass window (11) by an observation device (6, 6a), h) the common focus of the irradiation device and the focus of the observation device can be displaced in a motorized fashion over the spatial inner region of the cell wall (9) to an arbitrary point by a control apparatus, i) the face of the cell wall (9) which lies opposite the optical glass window (11) through which the irradiation device radiates has a further optical glass window (11) in the middle, this face of the cell housing (9) having a congruent nanocarbon layer (5) externally covering it, j) the face of the cell wall (9) in which the optical glass window (11), through which the optical axis of the observation device extends, is situated is monitored in respect of its temperature by two thermistors (8).

2: The apparatus as claimed in claim 1, characterized in that an electrode (19) of an electrical voltage source is respectively applied to the two end sides of the cuboid cell wall (9), each of these electrodes (19) consisting of an outer and an associated inner electrode.

3: The apparatus as claimed in claim 2, characterized in that an arrangement (7) with which various filters can be switched into the beam path is provided in the optical axis of the observation device.

4: The apparatus as claimed in claim 2, characterized in that the irradiation device is a laser (10), and the observation device is a digital video camera (6) having a microscope objective (6a).

5: The apparatus as claimed in claim 2, characterized in that a storage container (12) of washing solutions or diluting solutions with a connected dosing pump (13) is provided on one end side of the cuboid cell wall (9), and a compensation container (14) for sample liquid is provided on the other end side, an additional sample container (15) with an associated dosing pump (16) being provided, and liquids being deliverable in a dosed fashion from the storage container (12) and the sample container (15) to a mixing chamber (17), and a miniature pH measuring probe being fitted in the region of the mixing chamber (17).

6: A method for particle tracking analysis with the aid of scattered light of particles (23) of the order of magnitude of nanometers of a suspension in a cell wall (9), having the following features: e) the cell wall (9) is positioned in a defined way by means of vibration dampers (4), the cell wall (9) consisting of black glass in which optical glass windows (11) for the detection process are formed, f) the cell wall (9) is irradiated through an optical glass window (11) by means of an optical irradiation device, and is observed at a right angle to the optical axis of the irradiation device through a further optical glass window (11) by an observation device, g) the focus of the irradiation device and the focus of the observation device are displaced in a motorized fashion in a particular region of the cell wall (9) to the same point by optimizing the imaging property in relation to one or more particles (23) in this region, the electrophoresis effect being kept apart clearly from the electroosmosis effect, h) the control parameters thereby obtained are used as a basis for the representation of particles (23), the zeta potential of the sample, its conductivity and its pH being metrologically detected simultaneously.

7: The method as claimed in claim 6, characterized in that the irradiation device consists of a laser (10) and the observation device consists of a digital video camera (6) having a microscope objective.

8: The method as claimed in claim 7, characterized in that the thermal effect of the light irradiation of the irradiation device on the suspension is minimized in that it is made possible by a further glass window (11), lying opposite the optical glass window (11) which allows entry of the light of the irradiation device into the cell wall (9), for the light beam of the irradiation device to emerge from the cell wall (9) and this light beam can give up its heat in a nanocarbon layer (5).

9: The method as claimed in claim 6, characterized in that a pattern analysis in the case of particles (23) of the size range of nanometers with the aid of scattered light can be carried out for the first time in the world.

10: The method as claimed in claim 6, characterized in that during the measurement and analysis with the apparatus as claimed in one of claims 1 to 5, distinction is to be made between the following method steps: a) after starting and putting in operation, for initialization the sensors and actuators are addressed and their reference values are read out, reference measurements with pure water and/or a defined sample initially being carried out for sample recording, b) after the sample recording, camera parameters are determined and electronic filter adjustments are carried out, c) after testing of the quality parameters of the sample filling, a video sequence is recorded and is stored according to the symbol of the acquisition, d) as the next method step, the video sequence is evaluated either in real time or with a time delay, e) according to the next method step, the individual objects are brought together to form traces over the individual images, which are linked besides the data of the offset with the data of the object properties, f) in the result representation, a size distribution is represented and a multidimensional evaluation is carried out by methods of multivariate statistics, g) as a consequence, either the sample is evaluated again with different filter parameters or a new sample is measured, h) the apparatus is switched off.

11: A computer program having a program code for carrying out the method steps as claimed in claim 6 when the program is run on a computer.

12: A machine-readable medium having the program code of a computer program for carrying out the method as claimed in claim 6 when the program is run on a computer.

Description

[0057] The apparatus according to the invention will be described in more detail below. In detail:

[0058] FIG. 1 shows a cross section of the cell wall and a three-dimensional view,

[0059] FIG. 2 shows a three-dimensional view of the cell with peripheral arrangements,

[0060] FIG. 3 shows a three-dimensional view of the cell in a special embodiment,

[0061] FIG. 4 shows a representation to illustrate the measurement principle.

[0062] FIG. 1 shows a cross section of the cell wall and a three-dimensional view. The cell wall 9, which is configured rectangularly in cross section and contains the suspension to be studied, is placed with its cross section at the midpoint of the left-hand part of this figure. Cell wall 9 is held on the left-hand side by a heating and cooling element 1, which is L-shaped in cross section and the function of which will be described in more detail below. The entire apparatus is mounted on a standard base 2, which is in turn protected against shaking from the region of the surroundings by means of vibration-damping elements 4.

[0063] In order to illuminate the suspension, a laser 10 is provided on the upper side of the cell wall 9, the main beam profile of which laser is indicated by a dashed line which extends centrally through the cell wall 9.

[0064] After it has crossed the cell wall 9 through an opening, which is represented as being transmissive, the beam of the laser 10 strikes the opposite side of the cell wall 9 and is absorbed and thermally neutralized there by a nanocarbon layer 5, which likewise lies behind an opening represented as being transmissive. The function of the layer 5 will be further described below. At a right angle to this dashed line, the optical axis 3 of a digital video camera 6 and of a microscope objective 6a is indicated, likewise by means of a dashed line. This optical axis 3 also passes through an opening represented as being transmissive. At the point of intersection of these two dashed lines, the particles to be studied can be observed. Provided in the beam path of the digital video camera 6, there is a filter changer 7 which, respectively according to requirements, can place various color filters in front of the objective of the camera 6. Furthermore, a microscope objective 6a is arranged in the beam path of the digital video camera.

[0065] On this side of the part of the cell wall 9 observed by the digital video camera 6, two thermistors 8 which register the development of heat of the cell wall are provided.

[0066] A three-dimensional view of the cell wall 9, from which the arrangement of the openings shown on the left-hand side of FIG. 1 can be seen better is represented in the right-hand part of FIG. 1. The openings described above represent optical glass windows 11 which are sintered into the cell wall 9. The heating and cooling element 1 and the nanocarbon layer 5 are used in order to achieve a uniform temperature distribution in the cell. This layer 5 immediately dissipates the thermal radiation, caused by the laser 10 when the laser emerges from the cell wall 9 through the window 11, laterally and into the cooling element 1. Thermal convection in the cell is therefore substantially avoided. Thermal convection is competitive with the particle diffusion and electrophoretic movement which are to be measured in the field, and is therefore to be avoided.

[0067] FIG. 2 shows a three-dimensional view of the cell with peripheral arrangements. Besides the known cell wall 9 with its optical glass windows 11 sintered in, heating and cooling element 1 and the nanocarbon layer 5 applied on the bottom of the cell wall 9 can be seen here. A negative and a positive electrode 19 are respectively fitted on the two narrow sides of the cell wall 9. These electrodes 19 respectively consist of two electrodes, respectively an outer electrode outside the cell wall 9 and an associated inner electrode, from which the relevant electric field is tapped, lying inside the cell wall 9. In this way, it is possible to compensate for perturbing effects such as bubble formation. Electrophoretic movement of particles to be studied can thereby be induced by applying a controllable electrical voltage. Two dosing pumps 13 and 16 for supplying washing or diluting solution, or suspension, from a storage container 12 or 15, respectively, are provided on the right-hand narrow side of the cell wall 9. A compensation container 14 is fitted on the left-hand narrow side of the cell wall 9.

[0068] On the right-hand narrow side, there is likewise a miniature mixing chamber 17 for receiving the sample suspension from 12 or from a syringe. In the case of simultaneous dosing of sample and diluting solution from the containers 12 and 15, defined dilution of the samples is achieved. A miniature pH measuring probe 18 is fitted at an outlet of the mixing chamber 17.

[0069] FIG. 3 shows a spatial view of the cell in a special embodiment. Here, the way in which a particular laser from a multiplicity can selectively be chosen and rapidly used, respectively according to requirements, in order to study a particular suspension, by means of a rotatable changer disk 20 is shown in principle and by way of example. The changer disk 20 may also be a horizontally mobile displacement carriage.

[0070] FIG. 4 shows a representation to illustrate the possibilities of the measurement principle according to the invention. With reference to the example of a particle 23, represented as an irregular conglomerate, having a diameter of 100 nm, it is shown here that this particle 23, when it has moved through a distance delta x in a time delta t, is not only revealed as a size peak 21 in the study but also that a broader, smaller size peak 22, which in the past has usually remained unobserved, can likewise be indicated accurately. This is because, as already mentioned, the smaller peak 22 has in the past usually been overlooked or ascribed to the effect of a smaller particle, with the method according to the invention it is possible to discover that the smaller peak 22 is to be ascribed to the effect of the rotation of the particle 23.

[0071] This is overall automatic evaluation, for the first time, of the dynamic scattered light pattern analysis.

[0072] In this case, the number of primary particles, agglomerates and aggregates is determined. Evaluation of the scattered light shape parameters (secondary shape parameters), evaluation of the intensity of the particle scattered light, of the particle scattered light area, and all dynamic values thereof, are carried out. The fluctuation width of these parameters is obtained therefrom. Evaluation of the proportions of different particle types is furthermore possible (example, milk: milk droplets, milk exosomes, caseins (example, mixture of particles and nanobubbles)).

[0073] The complex analysis of the described movement processes requires a special control program.

[0074] FIG. 5 shows a flowchart of the processing method according to the invention.

[0075] The essential method steps which can be distinguished during the measurement and analysis with the apparatus according to the invention are presented in FIG. 5.

[0076] After starting and putting in operation, the apparatus or the instrument is initialized. In this case, all sensors and actuators are addressed and their reference values are read out. If reference values, determined in this way, of individual instrument components lie in the range specified for them, the instrument is ready for a measurement.

[0077] As preparation for a sample application, reference measurements with pure water and subsequently with a known, accurately defined sample are initially carried out. For example, a defined diluted particle size standard is suitable for this purpose. The reference measurements give information about the performance of the instrument and about whether the specifications of the instrument are being complied with. This relates to the first three symbols of the flowchart.

[0078] The sample application according to the fourth symbol of the flowchart of FIG. 5 is carried out either manually or by a separate automated application system.

[0079] After the sample application, camera parameters are determined and electronic filter settings are carried out according to the fifth symbol of the flowchart.

[0080] With the aid of measured parameters, such as the conductivity and the temperature, inferences are made about the quality of the filling and the adapted concentration. Parameters from the pre-analysis of images are also used for this, changes of the objects as a function of time also being taken into account.

[0081] These so-called quality parameters such as image brightness, number of objects detected, as well as the shape and size of the objects, can provide information about the presence of bubbles or other perturbing reflections. In the event of an excessively high concentration of particles, a high image brightness is thus obtained. In this case, the sample must be diluted and transferred into the measurement cell again.

[0082] After the testing of the quality parameters of the sample filling, a video sequence is recorded and is stored according to the sixth symbol of acquisition of the flowchart.

[0083] In the seventh symbol of video analysis, the video sequence is evaluated either in real time or with a time delay. To this end, the video sequence is decomposed into its individual images, the objects of each individual image are localized and their object properties, such as the brightness, size or the shape, are determined.

[0084] According to the eighth symbol, the individual objects are combined to form so-called traces over the individual images, which are linked besides the data of the offset with the data of the object properties.

[0085] In the result representation according to the ninth symbol, a size distribution (i.e. a histogram) is represented. Furthermore a so-called multidimensional evaluation is carried out by methods of multivariate statistics with inclusion of the object properties from the image. By the multidimensionality (offset, size of the objects, brightness and time variation), a sample can be subdivided into subgroups. The presence of a plurality of different sample constituents can therefore be inferred. Furthermore, the evaluation provides information about measurement artefacts. The result is then cleaned of these artefacts. For example, this may involve the component of translational diffusion, particularly of larger particles. After the end of the evaluation and the result representation, either the sample may be evaluated again, for example with other filter parameters, or a new sample may be injected and measured. Furthermore, the program may be ended and the instrument may be shut down with a sequence (washing, cleaning, disinfection).

LIST OF REFERENCES

[0086] 1 heating and cooling element (Peltier element) [0087] 2 stand base [0088] 3 optical reference line [0089] 4 vibration-damping element [0090] 5 nanocarbon layer [0091] 6 digital video camera 6a microscope objective [0092] 7 filter changer [0093] 8 thermistor [0094] 9 cell wall [0095] 10 laser [0096] 11 optical glass window [0097] 12 storage container for diluting solution [0098] 13 dosing pump for the diluting solution [0099] 14 compensation container [0100] 15 sample container [0101] 16 dosing pump for the sample [0102] 17 mixing chamber [0103] 18 miniature pH measuring probe [0104] 19 electrodes [0105] 20 changer disk [0106] 21 size peak as indication of translation [0107] 22 size peak as indication of rotation [0108] 23 particle