CN114324154A

CN114324154A - Method for analyzing particles deposited on filter disc and sample preparation and analysis equipment thereof

Info

Publication number: CN114324154A
Application number: CN202011063591.9A
Authority: CN
Inventors: 马俊安
Original assignee: Jomesa Measurement System Shanghai Co ltd
Current assignee: Yuemei Measurement System China Co ltd
Priority date: 2020-09-30
Filing date: 2020-09-30
Publication date: 2022-04-12

Abstract

The invention discloses a method for analyzing particles deposited on a filter disc and sample preparation and analysis equipment thereof, which comprise a filter disc, particles, a background, ionic liquid, a device for automatically analyzing the particles deposited on the filter disc and an optical microscope, and are characterized in that: the filter sheet mainly comprises a filter membrane but also an adhesive carrier layer, for example for use in a sink, the particles comprising black particles, white particles, transparent particles and grey particles, the backgrounds being divided into two groups, a first light white background and a second light black background, the light black background and the light white background being each divided into two levels according to colour depth. The method for analyzing particles deposited on a filter, which is useful for optical analysis, is simple and inexpensive because a filter with increased transparency can be obtained using existing knowledge and inexpensive resources, and the use of ionic liquids makes it easier to inspect the same filter using an optical microscope and an SEM-EDX system.

Description

Method for analyzing particles deposited on filter disc and sample preparation and analysis equipment thereof

Technical Field

The invention relates to the technical field of analysis of particles deposited on a filter disc, and discloses a method for analyzing particles deposited on the filter disc and sample preparation and analysis equipment thereof.

Background

In many industrial fields, determining the technical cleanliness of a product or part and determining the cleanliness of a production environment or a manufacturing process (monitoring particles as an important part) are one of the standard tools for quality assurance. The optical microscope usually used is mainly used for automatically identifying the number of particles. The advantage of using optical microscopy techniques for cleanliness is that the particles can be counted while the particles being analyzed can be measured and property classified. The use of a differential between metallic, non-metallic and particle morphology is therefore an important factor in determining the criteria.

In the field of the automotive industry, there are some standards for the determination of technical cleanliness, such as VDA 19.1 and ISO16232: 2018. There are also standards for technical cleanliness in the medical field, such as VDI 2083. These standards all describe methods for detecting dark particles on a light background based on the setting of a threshold.

Technical cleanliness can be determined directly only in a few cases, for example, when checking for particles on the surface of a product or a part. Therefore, in most cases, the technical cleanliness is indirectly determined.

For products or parts, indirect particle analysis is typically performed by removing particulate contaminants from the surface of the product or part using a cleaning solution, filtering the particulate contaminants onto a filter, and placing the filter under a microscope for examination. A cellulose filter or a polyamide filter is generally used. Under a microscope, the filter usually shows a light, off-white background, which is suitable for detecting dark particles. The process of cleaning the surface of a product or part with a cleaning fluid is commonly referred to as extraction.

Particulate contaminants in air are free to drift and adhere to the particulate trap, and this method is often used to indirectly determine the technical cleanliness of the production environment or manufacturing process. The particle catcher starts collecting particles once it is arranged and stops collecting after a specified time. After collection is complete, the particles adhering to the particle catcher are typically analyzed using an automated particle counting optical microscope. The glue-bonded side uses a light background, which is usually white.

From the document DE 102005062439B 3, a particle analysis system and a particle analysis method are known. In which particles adhering to the surface of a part to be analyzed are separated using a cleaning agent, and then the residue after filtration of the cleaning agent is analyzed for particle size, distribution, and properties (metal/nonmetal).

In addition to dark colored particles, light colored or clear particles can also appear during the manufacturing process. Such as: the plastic and ceramic particles are light-colored particles, and the glass is transparent particles. It is difficult to detect these particles completely against a light background using an optical microscope.

There are a variety of color filters on the market. Such as: grey, black and yellow filters, which can detect light colored particles. However, these filters have the same problem as the light-colored (white) filters, and it is almost impossible to detect particles having the same color as that of the transparent particles. They always have the following disadvantages: all particles could not be detected on the same filter.

DE 102018207535 a1 discloses a method for indirectly analyzing the technical cleanliness of automobile parts using a particle counting microscope. In this method, the particles deposited on the filter are fixed with an adhesive before microscopic analysis of the particles deposited on the filter. The use of two light sources for the analysis, one producing visible light and the other ultraviolet light, can improve the reliability of the analysis, but still does not ensure the detection of all particles, such as transparent particles and particles of the same color as the filter.

Disclosure of Invention

Technical problem to be solved

In view of the shortcomings of the prior art, the present invention provides a method for analyzing particles deposited on a filter and a sample preparation and analysis apparatus thereof, which can measure all particles on the same filter as much as possible, and which is simple and inexpensive to implement, thereby solving the above-mentioned problems.

(II) technical scheme

The invention provides the following technical scheme: a method of analysing particles deposited on a filter using an optical microscope, comprising a filter which comprises primarily a filter membrane but also an adhesive carrier layer, for example for use as a sink point, to increase the light transmission of the filter prior to analysis for detection of particles of different contrast.

Preferably, the increase in optical transparency of the filter involves applying an ionic liquid to the filter.

Preferably, the ionic liquid comprises ethylamine nitrate and/or ethyl-methylimidazole acetate and is diluted with water in a volume ratio (ionic liquid: water) ranging from 1:2 to 10:1, the application of the ionic liquid fixing the particles on the filter sheet.

Preferably, after the ionic liquid is applied and before the analysis is performed, the filter sheet with the deposited particles is placed in a temperature range of 30 ℃ to 100 ℃ for baking for 0.5 to 5 hours and then analyzed.

Preferably, the deposited particles are analysed under first and second illumination conditions and the first illumination condition is generated by introducing a first background into the beam path.

Preferably, the second illumination condition is generated by introducing a second background, different from the first background, into the beam path.

A sample preparation analysis device, comprising: the device comprises an automatic analysis filter disc deposited particle device, a sample preparation unit and a control unit, wherein the sample preparation unit is used for automatically preparing the filter disc with deposited particles; an optical unit with an optical microscope for automatic analysis of the deposited particles.

Preferably, the optical microscope is provided with a dedicated holder, the background of which is automatically introduced into the light path.

Preferably, the sample preparation unit may improve light transmittance of the filter.

Preferably, the sample preparation unit is designed for automated application of ionic liquid to the filter.

(III) advantageous effects

Compared with the prior art, the invention provides a method for analyzing particles deposited on a filter disc and a sample preparation and analysis unit thereof, which have the following beneficial effects:

the method of analyzing particles deposited on a filter is based on the idea of changing the color of the filter itself by increasing the light transmission before analyzing the particles on the filter. Preparatory steps for depositing particles on the filter have been completed before the filter itself is reduced in color, for example, filtering particles in a cleaning solution on the filter, transferring the filter to a glass support or fixing the particles on the filter. The invention reduces the color of the filter sheet by increasing the light transmittance of the filter sheet. The increase in light transmission can be achieved by chemical and/or physical treatment of the filter. Physical treatments such as filling the pores of the filter with a liquid reduce the refraction of light on the filter. Or by chemically treating to partially dissolve or dissolve the filter, the filter with increased light transmission is partially or completely transparent. As opposed to conventional non-transparent filter sheets. This light transmission also allows the particles on the filter to be analyzed using a transmission light microscope, which has significant advantages in analyzing transparent particles.

The method for analyzing particles deposited on a filter, which is useful for optical analysis, is simple and inexpensive because a filter with increased transparency can be obtained using existing knowledge and inexpensive resources, and the use of ionic liquids makes it easier to inspect the same filter using an optical microscope and an SEM-EDX system.

The method for analysing particles deposited on a filter disc allows to measure as many as possible all particles on the same filter disc and is simple and inexpensive to implement.

Furthermore, the object of the present invention is to propose an apparatus for the automatic analysis of particles deposited on a filter disc which is able to measure as much as possible all the particles on the same filter disc.

Drawings

FIG. 1: different particles deposited on the filter disc;

fig. 2 to 5: the steps of the first method according to the invention for analysing the particles deposited on the filter disc; fig. 6 to 8: the steps of the second method according to the invention for analysing the particles deposited on the filter disc;

FIG. 9: according to an embodiment of the apparatus for automatically analyzing particles deposited on a filter according to the present invention, the apparatus comprises the sample preparation unit of the present invention.

In the figure: 1. a filter disc; 2. the top of the filter disc; 3. black particles; 4. the bottom of the filter disc; 5. white particles; 6. transparent particles; 7. a gray particle; 8. a double-sided slide; 9. a droplet; 10. a glass upper cover; 11. a cover glass; 12. gelling; 15. a solution of ethylamine nitrate; 100. an incident optical microscope; 101. a first optical imaging device; 102. an illumination device; 103. an optical polarization device; 104. an optical analyzer; 105. a first sample; 106. a background; 106a, light background; 106b, deep background; 200. a transmission optical microscope; 201. a second optical imaging device; 202. an LED lamp; 203. a diffuser; 205. water-diluted ethylamine nitrate solution; 215. a second sample; 300. equipment; 301. a sample preparation unit; 302. an autosampler for microscope samples; 303. an optical unit of an incident optical microscope; 303a, an incident light microscope body; 304. a sample dispenser; 304a, light background; 304b, dark background; 305. a conveying device; 306. a sample preparation mechanism; 307. a water-diluted ethylamine nitrate solution (mixing ratio 2: 1); 308. a memory; 310. a glass substrate; 311. and (5) an oven.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1-9, a method for analyzing particles deposited on a filter using an optical microscope includes a filter 1, where filter 1 includes primarily a filter membrane but also an adhesive carrier layer, such as a sink point, to increase the light transmission of filter 1 prior to analysis for detecting particles of different contrast.

Preferably, the increase in the light transmittance of filter 1 involves applying an ionic liquid to filter 1.

Preferably, the ionic liquid comprises ethylamine nitrate and/or ethyl-methylimidazole acetate and is diluted with water in a volume ratio ranging from 1:2 to 10:1, the application of the ionic liquid fixing the particles on the filter 1.

Preferably, after the ionic liquid is applied and before the analysis, filter sheet 1 with deposited particles is left to bake at a temperature ranging from 30 ℃ to 100 ℃ for 0.5 to 5 hours and then analyzed.

A sample preparation analysis device, comprising: an automatic analysis filter deposition particle apparatus 300, a sample preparation unit 301 for automatically preparing the filter 1 having the deposition particles; an optical unit 303 with an optical microscope for automatic analysis of the deposited particles.

Preferably, the sample preparation unit 301 may improve light transmittance of the filter sheet 1.

Preferably, the sample preparation unit 301 is designed for automatic application of ionic liquid to the filter 1.

In summary, the method for analyzing particles deposited on a filter sheet is schematically illustrated in fig. 4, which shows a filter sheet 1 having a top portion 2 and a bottom portion 4. For illustrative reasons, the schematic drawings are not drawn to scale. After the washing liquid containing particles is filtered through the filter disc 1, there are several particles deposited on the top 2 of the filter disc, shown in the schematic diagram with

particles

3, 5, 6, 7, the color and light transmission of the

particles

3, 5, 6, 7 are different from each other; the black particles 3 represent dark particles, the white particles 5 light particles, the particles 6 transparent particles, the particles 7 grey particles, the

particles

3, 5, 6, 7 dispersed on the filter disc top 2.

Example 1: this is described based on an analysis of filter 1 in schematic fig. 1. The first method, illustrated schematically in FIGS. 1, 2, 3 and 5, uses incident light microscopy to analyze the deposited particles.

In order to place filter 1 containing

particles

3, 5, 6, 7 in an optical microscope for analysis,

particles

3, 5, 6, 7 are first fixed to filter 1 and the light transmittance of filter 1 is increased.

A glass carrier, which is provided in the form of a double-sided slide 8 in the schematic drawing 2, is applied with 0.3ml of an ethylamine nitrate solution 15 to form droplets 9. By mixing ethylamine nitrate salt and water at a ratio of 2: 1 to obtain a water diluted ethylamine nitrate solution 15, or the ethylamine nitrate may be applied undiluted to a glass support. The water diluted ethylamine nitrate solution 15 has the following advantages over the undiluted ethylamine nitrate solution: its specific lower viscosity, which allows better distribution of the ENA solution 15 diluted with water on the hydrophilic filter.

The bottom 4 of filter 1 containing

particles

3, 5, 6, 7 is then placed on droplet 9. Due to capillary action, the water-diluted ethylamine nitrate solution 15 of droplets 9 permeates from the bottom 4 of filter 1 through the pores to the top 2 and contacts the surface of

particles

3, 5, 6, 7 on filter 1. The water diluted ethylamine nitrate solution 15 is slightly above the surface of the particles due to capillary action and surface tension. The water-diluted ethylamine nitrate solution 15 accomplishes two purposes, on one hand, filling the pores of the filter 1 and partially dissolving the filter 1 to increase the light transmittance of the filter 1, thereby reducing the light refraction of the cellulose filter 1 and increasing the light transmittance of the filter; on the other hand, a gel 12 of water diluted ethylamine nitrate solution 15 and dissolved cellulose immobilizes the

particles

3, 5, 6, 7 on the filter 1, as shown schematically in fig. 3. The double-sided slide 8 is covered by a removable framed glass cover 10. The glass cover 10 covers over to ensure that filter 1 is protected from further contamination. The glass of the glass cover 10 should ensure that it does not change the polarization state of the light and does not affect the optical analysis in the case of dark field illumination. However, it takes several hours to increase the light transmittance of filter sheet 1 under standard conditions, the increase in light transmittance can be accelerated by increasing heat, and at a temperature of 60 ℃, it takes about 240 minutes to increase the light transmittance of filter sheet 1. Since the diluted ethylamine nitrate solution with water remains in the filter disc in liquid state, the transparency of the obtained filter disc is permanent. The filter transmittance achievable by this processing step is 5 times or more the original state and exhibits higher transparency, not just "frosty glass", without interfering with particle imaging in optical microscopy, even at high magnification and transmitted light.

The filter sheet prepared as described above is hereinafter referred to as a first sample 105; the analysis can be carried out either with an incident light microscope or with a transmission light microscope.

Schematic fig. 1 and 5 illustrate analysis of a first sample 105 by an incident light microscope 100. The incident light microscope 100 includes a first optical imaging device 101 that images particles deposited on the filter 1, an illumination device 102 arranged around the first optical imaging device 101, an optical polarization device 103, an optical analyzer 104, and a carriage that can move in all spatial directions for microscope observation. The

schematics

4 and 5 show in simplified form only the sample 105 placed on the carrier, the movable carrier itself not being shown.

A 106-insertion type background plate serving as a background is disposed below a bracket (not shown). In contrast, the schematic diagrams 4 and 5 show only the insertion background 106.

In the schematic illustration of fig. 1, the background 106 is a light (white) background 106a, and bright field or dark field can be selected as the illumination type. To distinguish between metallic and non-metallic particles, polarized light and dark field illumination are used. In this background, the gray particles 7 and the black particles 3 can be easily detected. In contrast, the white particles 5 and the transparent particles 6 are hardly detectable.

In the schematic illustration of fig. 5, the background 106 is not already a light (white) background 106a but a dark (black) background 106 b. Instead of a black background, a metallic background can also be inserted, which also appears black in the case of linearly polarized and orthogonally polarized light positions. In this background, the gray particles 7 and the white particles 5 can be easily detected. In contrast, the black particles 3 and the transparent particles 6 are hardly detectable.

In this analysis, the size distribution is determined by counting and measuring the particles. Usually, a qualitative differentiation of metallic and non-metallic particles is also performed or fibrous particles are differentiated according to particle shape.

Since the sample is examined under two lighting conditions, i.e. white and black background, the

particles

3, 5, 7 are well detectable in any case. With regard to the transparent particle 6, it is difficult to predict whether the particle is recognized in a light or dark background. Both lighting conditions increase the probability of detecting the transparent particles 6 and thus increase the detectability of the transparent particles as a whole.

Example 2: schematic figures 6-8 illustrate another method in which filter 1 is placed on slide 210 instead of double-sided slide 8 and ethylamine nitrate solution 205 diluted with water is applied to top 2 of filter 1. Filter 1 is then covered with a cover slip 11 and analyzed with a transmission light microscope 200.

FIG. 6 is a schematic diagram showing the step of applying a water-diluted ethylamine nitrate solution to filter 1. In order to avoid covering the

particles

3, 5, 6, 7 with ionic liquid, the application should be done at the edge of the filter or at another point. It is preferred to apply the ionic liquid at the edge of the filter top 2 or at a location not covered by

particles

3, 5, 6, 7. The ethylamine nitrate solution 205 applied until water dilution diffused to wet the entire filter.

Schematically, filter 1 is covered with cover glass 11 and baked at a temperature ranging from 30 ℃ to 100 ℃ for 0.5 to 5 hours to increase the light transmittance of filter 1. Filter 1 prepared in this manner is hereinafter referred to as second sample 215.

Subsequently, the second sample is analyzed in the transmission light microscope 200. Fig. 8 illustrates analysis of a second sample 215 using a transmission light microscope 200. The transmission optical microscope 200 includes: a second optical imaging device 201 for particle imaging, an LED lamp 202, a diffuser 203 and a carriage that can be moved in all spatial directions for microscopic observation. The schematic diagram 8 shows in simplified form only the second sample 215 placed on the carrier, the movable carrier itself not being shown

In transmitted light, all particles (except flat, transparent) create shadows because light is refracted out of the beam path. It is not possible to distinguish between metallic and non-metallic particles in this way. But is advantageous for analyzing transparent particles, such as glass beads from sandblasting material, e.g. glass spheres which, due to their refractive behavior in transmitted light, result in a clear shadow pattern and are not easily detectable in incident light.

Fig. 9 shows an apparatus 300 for automatically analyzing particles deposited on a filter. The apparatus 300 comprises: a sample preparation unit 301, a microscope sample autosampler 302, an optical unit 303 with an incident optical microscope. Apparatus 300 is designed to allow for fully automated sample preparation and analysis of particles deposited on filter 1.

The apparatus 300 may be divided into six functional sections. In I, there is a memory 308 storing a glass substrate 310. For simplicity of illustration, the apparatus is described below based on the preparation and analysis of a single sample. First, the conveyor 305 transports the glass substrate 310 from the storage to the sample preparation mechanism 306 in II. 0.3ml of water diluted ethylamine nitrate solution was dissolved and the sample stored before being analysed by microscopy. The microscope autosampler 302 automatically supplies a sample to be applied 307 (mixing ratio 2: 1) on the glass substrate 310 using the incident optical microscope body 303a, and then transports the glass substrate applied with the ionic liquid to III. The placement of the filter containing the particles to be measured on the glass substrate to which the ionic liquid is applied is automated by a sample dispenser 304 to which the sample may be dispensed automatically or manually. The sample is stored in a sample dispenser 304 under standard conditions before starting the analysis. When starting the analysis, the sample is placed on the glass substrate 310, so that the water diluted ethylamine nitrate solution on the glass substrate 310 passes through the hole to the top 2, so that the solution comes into contact with the particle surface on the filter 1, and the sample is covered with a glass cover. Subsequently, entering section IV, the sample is placed in an oven 311 heated at 60 ℃ for 240 minutes. Finally, the transport device 305 transports the sample to the microscope autosampler 302 for analysis.

The incident light microscope 303a body has a field of view of 0.1mm2 to 100mm2 and is equipped with a digital camera connected to a computer (not shown). The computer will automatically evaluate and analyze the images transmitted to the computer by the digital camera. The incident light microscope 303a can perform automatic analysis on a light background 304a and a dark background 304b (both can be automatically switched).

In summary, the above object is achieved in a method of the type mentioned at the outset in that the light transmission of the filter is increased before the particles are analyzed in order to detect particles of different contrast.

A filter for particle analysis is known to have the disadvantage that all particles on the same filter cannot be detected due to its own colour. However, the color of the filter itself cannot be easily changed without affecting other important properties of the filter, such as mechanical or thermal stability, porosity or surface smoothness.

The mechanical stability of the filter discs in both the dry and wet state is necessary in order to be able to withstand the pressures occurring during the filtration process and to be transportable to a designated site (e.g. a drying cabinet) in the dry and wet state. Furthermore, the filter surface must not be too smooth to prevent particles from "floating back and forth" on the surface during extraction and analysis. In addition, the porosity of the filter disc cannot be too low to ensure a faster filtration process.

If the performance of the filter changes, the performance of the analysis process or the final analysis result is affected. For example, known transparent polycarbonate filters have low porosity and very smooth surfaces. Furthermore, in practice, due to the small thickness of the filter, which is difficult to handle, when trying to adhere polycarbonate filters to glass surfaces, non-uniform adhesion often occurs, which can seriously interfere with subsequent optical analysis.

The invention is therefore based on the idea of changing the colour of the filter itself by increasing the light transmission before analysing the particles on the filter. Preparatory steps for depositing particles on the filter have been completed before the filter itself is reduced in color, for example, filtering particles in a cleaning solution on the filter, transferring the filter to a glass support or fixing the particles on the filter. The invention reduces the color of the filter sheet by increasing the light transmittance of the filter sheet. The increase in light transmission can be achieved by chemical and/or physical treatment of the filter. Physical treatments such as filling the pores of the filter with a liquid reduce the refraction of light on the filter. Or partially dissolve or dissolve the filter disc by chemical treatment.

Increasing the light transmission by reducing the color of the filter itself prior to analysis of the particles on the filter has several advantages:

for example, any filter or background may be introduced into the beam path due to the absence or reduction of the color of the filter itself. By using different filters or backgrounds, particles of different contrast, i.e. light and dark particles, on the same filter can be examined under different conditions.

The filter with increased light transmission is partially or completely transparent. As opposed to conventional non-transparent filter sheets. This light transmission also allows the particles on the filter to be analyzed using a transmission light microscope, which has significant advantages in analyzing transparent particles.

Another advantage is that filters with increased light transmission can be used for optical analysis, which is simple and inexpensive because filters with increased transparency can be obtained using prior knowledge and inexpensive resources.

In a preferred embodiment of the method of the invention, the application of the ionic liquid to the filter increases the light transmission of the filter.

With respect to increasing the light transmission of the filter, it has been confirmed that the effect of increasing the light transmission of the filter is better if the melting temperature of the ionic liquid is lower than the standard temperature, preferably lower than 15 ℃.

Ionic liquids are suitable for both filling the pores of the filter and partially dissolving or dissolving the filter, both of which reduce the refraction of the filter to light, especially cellulose filters. The ionic liquid may be applied to the filter disc as a pure substance or as a mixture.

Time and economic costs can be saved if the ionic liquid can also immobilize the particles when applied to the filter sheet.

The ionic liquid forms a gel-like substance when dissolving the filter disc so as to fix the particles on the filter disc. Thus, both fixing the particles on the filter and increasing the light transmission of the filter in the same step.

Particularly good results are obtained when the filter used is a cellulose filter, in particular a nitrocellulose filter, with the application of an ionic liquid.

The use of ionic liquids also has the following advantages: the filter with the applied ionic liquid can be detected under an optical microscope or in an SEM-EDX system.

With increasing demand, more accurate material analysis is required, typically using SEM-EDX (SEM scanning electron microscope, EDX or EDS energy dispersive X-ray spectrometer). SEM-EDX analysis provides further structural information and the proportion of chemical elements. The atoms of the particles are excited by an electron beam of a certain energy and thus emit X-characteristic rays of the corresponding chemical element.

Problems can arise if the particles to be detected are located on a non-conductive substrate, for example on a filter sheet. With the substrate and particles charged, the particles can move or fly uncontrollably and risk electromagnetic fields deflecting the electron beam. In addition, electrical discharges can occur in the substrate and particles, which can lead to transient signal disturbances in the imaging detector. In particular in SEM-EDX analysis, the bombardment with electrons must be carried out in a concentrated manner over a longer period of time in order to obtain a sufficient "count rate".

The filter sheet using the ionic liquid has light transmittance and the ionic liquid itself has electrical conductivity, and the step of coating particles with a conductive coating before SEM-EDX analysis can be omitted. But a glass cover cannot be used in sample analysis because the electron beam in SEM-EDX cannot penetrate the glass.

It has proven to be advantageous if the ionic liquid comprises ethylamine nitrate (EAN) and/or 1-ethyl-3-methylimidazolium acetate (EMIM OAc).

The ionic liquid can increase the light transmittance of the cellulose filter disc and has a lower melting point. In a simple case, the pure ionic liquid can be applied to the substrate. However, ionic liquids diluted with water have a better effect, and the ionic liquids diluted with water have the advantages of particularly good penetration into the pores of the hydrophilic filter disc and filling, and also promote rapid and uniform distribution of the ionic liquid in the filter disc and increase in light transmittance.

Applying a water-diluted ionic liquid to the filter plate at a dilution volume ratio (ionic liquid: water) of 1:2 to 10: 1. if the dilution ratio of the ionic liquid is more than 1:2, the permeability of the ionic liquid is impaired. If the dilution is less than 10:1, corresponding to no dilution. If the ionic liquid is needed to be used for the filter disc which is not dried, a small amount of water in the filter disc can play a role in dilution.

Increasing the light transmission of the filter requires the ionic liquid to be applied to the filter for a period of time. Under standard conditions (SATP conditions), the action takes 5 to 12 hours.

According to the method of the invention, there is an optimized scheme. After the application of the ionic liquid and before the analysis, the filter with the particle deposit is heated at a temperature of 30-100 ℃ for 0.5-5 hours before the analysis is carried out.

By heating, the action time is reduced to 0.5-5 hours, so that the whole process is faster.

According to a further refinement of the method according to the invention, the particles are analyzed under a first and a second illumination condition, and the first illumination condition is generated by introducing a first background into the beam path.

The background is metal or nonmetal, and the optimized proposal is to use the transparent self-colored background.

The above description relates primarily to incident light microscopes, but may also be used for transmissive light microscopes.

Under an incident light microscope, the background is the bottom surface of the analysis object, and the illumination beam first impinges on the top of the analysis object. Due to the increased light transmission of the filter obtained according to the invention, at least part of the illumination beam is transmitted through the object to be analyzed and impinges on the bottom surface, i.e. the background, and at least part of the illumination beam reflected by the object to be analyzed and the background is reflected back into the beam path.

Two lighting conditions may be created by introducing two different backgrounds, one background may also be used. When only one background is used, the analysis will be performed once without background.

Analysis under both lighting conditions allows as comprehensive as possible detection of all types of particles in the sample, regardless of their contrast. For analysis of light colored and/or transparent particles, a background should be inserted that has good contrast with the light colored and/or transparent particles. Preferably, a gray or black background is used for analyzing the light and/or transparent particles. A light (preferably white) background is particularly suitable for analysis of dark particles. It proves to be beneficial if the dark particles are analyzed using a non-metallic background. This allows further discrimination between metallic and non-metallic particles.

It is a more efficient way to generate the second illumination condition by introducing a second background, different from the first background, into the light path.

The second background is particularly applicable to the expected spectrum of the particles. If the contaminant sample is known, the illumination conditions, and thus the entire analysis, can be optimized.

When the measurement is performed by a transmission type light microscope, it is necessary that no background or the background is transparent. For example glass, is placed in the light path between the light source and the object to be analyzed.

With respect to an apparatus for automatically analyzing particles deposited on a filter, wherein the light transmittance of the filter can be provided by a sample preparation unit.

Known devices for automatically analyzing particles deposited on a filter disc are also referred to as automatic optical microscopes or particle counting microscopes. They can be used for automatic particle counting and measurement and classification according to metallic luster or textile fiber shape. A known disadvantage of filter discs for particle analysis is that they have their own colour, which makes it difficult to measure all particles on the same filter disc. However, any change in the color of the filter itself affects other important parameters of the filter, so the color of the filter itself cannot be easily changed.

The invention is thus based on the idea of modifying the sample preparation unit of the device so that the colour of the filter itself is automatically reduced prior to microscopic examination.

According to the present invention, the self color of the filter is reduced by increasing the light transmittance of the filter. The increase in light transmission can be achieved by chemical and/or physical treatment of the filter. Physical treatments such as filling the pores of the filter with a liquid reduce the refraction of light on the filter. Or partially dissolve or dissolve the filter disc by chemical treatment.

The sample preparation unit is preferably a unit with a pipetting device with which the ionic liquid can be applied to the filter disc.

It has proved to be advantageous if the optical microscope is provided with a special holder, the background of which is automatically introduced into the light path

Recording one or more backgrounds are automatically inserted into the light path one after the other, and two lighting conditions can be created by introducing two different backgrounds.

Analysis under both lighting conditions allows as comprehensive as possible detection of all types of particles in the sample, regardless of their contrast.

With regard to the sample preparation unit, the object on which a sample preparation device of the type mentioned at the outset is based is achieved according to the invention in that the light transmission of the filter disc can be increased by the sample preparation device.

With reference to the above description of the apparatus and method, existing optical microscopes can be upgraded by the design of the sample preparation unit.

It has been demonstrated that the sample preparation unit of the present design can automatically apply ionic liquids to a filter.

The use of ionic liquids makes it easier to inspect the same filter using an optical microscope and SEM-EDX system.

It is to be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

The standard parts used in the present application document can be purchased from the market, and can be customized according to the description of the specification and the accompanying drawings, the specific connection mode of each part adopts the conventional means matured in the prior art, the machines, the parts and the equipment adopt the conventional types in the prior art, the circuit connection adopts the conventional connection mode in the prior art, no specific description is provided here, meanwhile, the electric elements appearing in the specification are electrically connected with the external main controller and the mains supply, the peripheral controller mentioned in the specification can play a control role for the electric elements mentioned in the specification, and the peripheral controller is the conventional known equipment.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. A method for analysing particles deposited on a filter disc, comprising a filter disc (1), said filter disc (1) mainly comprising a filter membrane, but also a carrier layer for a binder, characterized in that the light transmission of the filter disc (1) is increased before the analysis for detecting particles of different contrast.

2. A method of analysing particles deposited on a filter disc according to claim 1, wherein the increase in optical transparency of the filter disc (1) involves applying an ionic liquid to the filter disc (1).

3. A method for analysing the particles deposited on a filter disc according to claim 2, wherein the ionic liquid comprises ethylamine nitrate and/or 1-ethyl-3-methylimidazolium acetate diluted with water in a volume ratio ranging from 1:2 to 10:1, the application of the aforementioned ionic liquid immobilizing the particles on the filter disc (1).

4. A method of analysing the particles deposited on a filter disc according to claim 3, characterized in that after the application of the ionic liquid and before the analysis, the filter disc (1) with the deposited particles is left to bake for 0.5 to 5 hours at a temperature in the range of 30 ℃ to 100 ℃ before the analysis.

5. A method of analysing particles deposited on a filter according to claim 4, wherein the deposited particles are analysed under first and second illumination conditions and the first illumination condition is generated by introducing a first background into the beam path.

6. A method of analysing particles deposited on a filter according to claim 7, wherein the second illumination condition is generated by introducing a second background, different from the first background, into the beam path.

7. A sample preparation and analysis apparatus, comprising: an automatic analysis filter deposition particle apparatus (300), a sample preparation unit (301) for automatically preparing a filter (1) having deposition particles; an optical unit (303) with an optical microscope for automatic analysis of the deposited particles.

8. A sample preparation and analysis apparatus according to claim 7, wherein the optical microscope is provided with a dedicated carriage, the background of which is automatically introduced into the optical path.

9. A sample preparation and analysis device according to claim 7, characterized in that the sample preparation unit (301) is adapted to increase the light transmission of the filter (1).

10. A sample preparation and analysis device according to claim 7, characterized in that the sample preparation unit (301) is designed for automated application of ionic liquid to the filter (1).