Device and method for the detection of microplastics in aquatic environments

Abstract

The present disclosure relates to a device and method for the detection of microplastics in aquatic environments. An aspect of the disclosure comprises a device for the detection in situ of microplastics in aquatic environments comprising: an inlet and an outlet; a separation unit, within said inlet and outlet, with at least two arrays of micropillars separated from each other; a sample container, coupled to the inlet of the separation unit, comprising an aeration system; a detection unit aligned substantially perpendicularly to the separation unit; wherein the inlet comprises a coiled tube comprises a length from 25 cm to 125 cm; wherein the separation unit comprises a flow rate comprised from 10 µL / min to 150 µL / min, preferably from 50 µL / min to 150 µL / min, to promote particles separation according to their sizes due to an axial spreading of the particles along the direction of the laminar flow.

Description

D E S C R I P T I O NDEVICE AND METHOD FOR THE DETECTION OF MICROPLASTICS IN AQUATIC ENVIRONMENTSTECHNICAL FIELD

[0001] The present disclosure relates to a device and method for the detection of microplastics in aquatic environments.BACKGROUND

[0002] Microplastics are pervasive pollutants in aquatic environments, posing significant risks to marine life and human health. Traditional methods for detecting these plastics are often time-consuming and lack the sensitivity required for microplastic detection.

[0003] Microplastics are emerging contaminants of global concern, with significant implications for environmental and human health. These plastic particles, typically defined as less than 5 mm in size originate from a variety of sources. They can be primary plastics, such as microbeads in personal care products and industrial abrasives, or secondary plastics, resulting from the breakdown of larger plastic debris due to weathering and degradation processes.

[0004] The pervasive nature of microplastics in aquatic environments has been well- documented. They are found in oceans, rivers, lakes, and even in drinking water. The persistence and bioaccumulation of these plastics pose threats to marine life, as they can be ingested by a wide range of organisms, from zooplankton to fish and birds. Once ingested, microplastics can cause physical harm, induce toxicological effects, and facilitate the transfer of pollutants and pathogens along the food chain, ultimately impacting human health.

[0005] Despite the growing recognition of the hazards associated with microplastics, their detection and quantification in aquatic environments remain challenging. Current methodologies often involve labour-intensive and time-consuming processes that maylack the sensitivity required for detecting microplastics. Moreover, the diversity in shape, size, and chemical composition of these plastics complicates their identification and quantification.

[0006] Traditional methods for detecting microplastics involve steps such as visual inspection under a microscope, which is subjective and limited to larger particles. More sophisticated techniques include Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, scanning electron microscopy (SEM) and mass spectrometry (MS).

[0007] The Fourier transform infrared spectroscopy (FTIR) is commonly used to identify the polymer type of microplastics by analysing their infrared spectra.

[0008] The Raman spectroscopy offers molecular-level identification and is more sensitive to smaller particles. Nonetheless, its application is often limited by fluorescence interference and the need for extensive sample preparation.

[0009] The scanning electron microscopy (SEM) provides detailed imaging of plastic particles' surface morphology but requires vacuum conditions and is not suited for routine analysis of water samples. This technique does not give any information related to chemical identification alone.

[0010] The mass spectrometry (MS) techniques like pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) are used for detailed chemical analysis. These methods are powerful but involve complex sample preparation and are generally not suitable for high-throughput analysis. This technique does not give any information related to the particle size.

[0011] Document CN114770800A discloses a micro-plastic particle screening and separating device and method combining deterministic lateral displacement and dielectrophoresis. The device comprises a deterministic lateral displacement sorting device based on micro-plastic particle size difference screening and a dielectrophoresis sorting device based on micro-plastic particle dielectric property screening. In the microcolumn array channel, micro-plastic particles with the diameter larger than that of the micro-column collide and generate lateral displacement when passing through the micro-column, the motion trail is changed, micro-plastic particles with the diameter smaller than that of the micro-column do not generate lateral displacement aftercolliding with the micro-column, still flow along the original streamline, pass through a deterministic lateral displacement sorting area, and then are separated from the microcolumn array channel. And the micro plastic particles with large size difference move to different outlets. Direct current dielectrophoresis is applied to a separation area of the dielectrophoresis separation device, four external electrodes act in a micro-channel to generate a non-uniform electric field, and micro plastic particles with small size difference after being separated in the area can enter different sample outlets so as to realize screening and separation of the micro plastic particles. As the sorting in the document is based on two process, deterministic lateral displacement and dielectrophoresis, the design of the microfluidics is different from the one now disclosed.

[0012] Document US10254229B2 discloses a hand-held microfluidic testing device is provided that includes a housing having a cartridge receiving port, a cartridge for input to the cartridge receiving port having a sample input and a channel, where the channel includes a mixture of Raman-scattering nanoparticles and a calibration solution, where the calibration solution includes chemical compounds capable of interacting with a sample under test input to the cartridge and the Raman-scattering nanoparticles, and an optical detection system in the housing, where the optical detection system is capable of providing an illuminated electric field, where the illuminating electric field is capable of being used for Raman spectroscopy with the Raman-scattering nanoparticles and the calibration solution to analyze the sample under test input to the cartridge. The sorting method in the referred document is different from the one that will be disclosed, and the SERS detection is focused on polymer molecules and not polymer particles.

[0013] Document US2023285969A1 discloses a microfluidic device for isolating a microparticle from a heterogeneous sample includes a first microfluidic chamber containing a first chamber inlet; a plurality of first chamber outlets in fluid connection with the first chamber inlet; and a loop. The microfluidic device further contains a second microfluidic chamber containing a second chamber inlet and a plurality of second chamber outlets in fluid connection with the second chamber inlet. The second microfluidic chamber contains a loop. In some embodiments, the first and second microfluidic chambers include from about 1 loop to about 50 loops; or from about 2loops to about 25 loops; or from about 5 loops to about 15 loops. A first chamber outlet or a plurality of first chamber outlets is in fluid connection with the second chamber inlet. A method for removing a microparticle from a heterogeneous sample, and a water purification system and method use the microfluidic device. The sorting method in the referred document is different from the one that will be disclosed and therefore does not allow a in situ measurement.

[0014] Document CN112903655 discloses a new technology in the technical field of environmental pollutant detection, and particularly relates to a single micro / nano plastic detection method based on a Raman spectrum technology. The method is based on a surface enhanced Raman spectrum technology, a surface enhanced Raman substrate adopts a composite film obtained by sputtering Au on an anodic aluminium oxide (AAO) film, and detection of micro / nano plastic is realized; wherein the thickness of the gold sputtered on the AAO film is 30-70 nm, and the preferable thickness is 50 nm. During detection, an object to be detected is filtered by the composite membrane and detected under a Raman instrument, and a baseline is deducted from an obtained spectrum to obtain a Raman signal of the micro / nano plastic; then the position of the Raman signal peak is analysed to judge whether the micro-plastic exists or not and judge the type of the micro-plastic. The method disclosed by the invention is relatively good in universality, has the advantages of rapidness, accuracy, stability and the like, and can be used for effectively detecting micro-plastics in samples such as environment and food, and has great application prospects. The difference to the technology now disclosed is the use of Raman scattering instead of SERS, which reduce the dependence on the reproducibility of SERS substrate and integration on this in the microfluidic device. Interestingly, they did not exploit the capacity of the SERS substrate for the concentration of plastics by filtration.

[0015] Document CN115979778 discloses a micro-nano plastic detection method based on a photothermal effect and relates to the field of micro-nano optics. The micro-nano plastic serves as one of four types of new pollutants specified by the state, and an efficient detection method is urgently needed at present. According to the method disclosed by the invention, a strong photo-thermal trap is formed in a solution through a photo-thermal effect by utilizing resonance absorption of the gold nanoparticles on785nm laser, so that the micro-nano plastic can be efficiently enriched and captured. The enriched micro-nano plastic can be detected through a surface enhanced Raman spectroscopy (SERS) technology, so that the detection of the low-concentration micro- nano plastic is realized. The method solves the problem that the existing means cannot effectively enrich and detect the micro-nano plastic in a large range, provides a new detection means for monitoring the micro-nano plastic in the water environment and detecting the micro-nano plastic in the food industry, and has a wide application prospect.

[0016] Document CN117092087 discloses a method for separating nano-plastics and a method for identifying the nano-plastics and belongs to the technical field of microplastic detection. The method for separating the nano-plastics comprises the steps that nano-silver colloid is added into a container, and then a solution to be detected and a polymethyl methacrylate solution dissolved in ethyl acetate are sequentially added into the container; injecting ethyl acetate into the bottom of the mixed solution; after the ethyl acetate is volatilized, the SERS substrate is obtained, and the nano plastic in the solution to be detected is transferred to the surface of the SERS substrate. According to the method for separating the nano plastic, during preparation through liquid-liquid interface self-assembly, the nano plastic is migrated to the substrate under the hydrophobic and lipophilic interaction force in a two-phase system, the enrichment efficiency is high, the sample loss is small, the nano plastic in the sample is separated by adopting the method for separating the nano plastic, and the separation efficiency is high. The sensitivity of subsequent nano-plastic identification can be remarkably improved, and a reliable method is provided for analysing trace nano-plastic in the environment. In comparison to the technology now disclosed, the device and method now disclosed allow a minimum sample preparation and avoid the use of filters thank to the selection of the tubing length and flow for the size separation, reducing the risk of clogging due to the big particles.

[0017] These facts are disclosed in order to illustrate the technical problem addressed by the present disclosure.GENERAL DESCRIPTION

[0018] The present disclosure relates to a device and method for the detection of microplastics in aquatic environments.

[0019] The present invention aims to provide a comprehensive solution by combining advanced separation techniques with sensitive analytical methods, which by changing the principle of sorting, it is possible to identify "in situ" the microplastics and sort it by size without human intervention.

[0020] There is an urgent need for more efficient, sensitive, and high-throughput methods for detecting microplastics in aquatic environments. An ideal detection system should have an efficiently collect and process samples, allowing for rapid and comprehensive sample collection and preparation to handle the wide range of plastic sizes and types present in aquatic environments, separate and concentrate plastics, i.e. use innovative separation techniques to isolate microplastics from other particulates and organic matter in the water, precisely identification and quantification of plastics, using advanced analytical techniques that provide both qualitative and quantitative data on the types and quantities of plastics present, with high sensitivity and specificity.

[0021] The present technology addresses these needs by integrating a comprehensive detection system that combines efficient sample collection, innovative separation and digestion processes, and advanced analytical methods. This system aims to overcome the limitations of current methodologies by providing a robust, high-throughput solution capable of detecting and quantifying microplastics in situ with high accuracy and reliability. The present technology can also calculate a relative quantification of microplastics inside of the device for the detection of microplastics in aquatic environments, which means that it is possible to give a relation positive spectra / total spectra acquired. Along this description, it is considered that a positive spectrum is related to plastic identification.

[0022] An aspect of the disclosure comprises a device for the detection in situ of microplastics in aquatic environments comprising: an inlet and an outlet; a separation unit, within said inlet and outlet, with at least two arrays of micropillars separated from each other; a sample container, coupled to the inlet of the separation unit, comprisingan aeration system; a detection unit aligned substantially perpendicularly to the separation unit; wherein the inlet comprises a coiled tube comprises a length from 25 cm to 125 cm; wherein the separation unit comprises a flow rate comprised from 10 pL / min to 150 pL / min, preferably from 50 pL / min to 150 pL / min, to promote particles separation according to their sizes due to an axial spreading of the particles along the direction of the laminar flow.

[0023] In an embodiment, the detection unit of the device is aligned perpendicularly to the separation unit.

[0024] In an embodiment, the interpillar distance from consecutive micropillars of the device is from 0.25 pm to 150 pm, preferably 0.5 pm to 125 pm, more preferably from 0.75 pm to 100 pm.

[0025] In an embodiment, the distance between the at least two arrays of micropillar arrays of the device is from 0.5 mm to 1.2 mm, preferably 0.7 mm to 1.0 mm, more preferably from 0.8 mm to 0.9 mm.

[0026] In an embodiment, the each of the at least two arrays of micropillar arrays of the device comprises a width of 0.1 mm to 1.0 mm, preferably from 0.3 mm to 0.7 mm.

[0027] In an embodiment, the micropillar of the device comprises a length of 1 pm to 150 pm, preferably from 25 pm to 125 pm, more preferably from 50 pm to 100 pm.

[0028] In an embodiment, the coiled tube of the device comprises a length of 40 cm to 100 cm, preferably from 60 cm to 80 cm.

[0029] In an embodiment, the channel height of the device is from 10 pm to 100 pm, preferably from 25 pm to 75 pm, more preferably from 45 pm to 55 pm.

[0030] In an embodiment, the detection unit of the device comprises a Raman spectroscopy or micro-infrared Spectroscopy for the chemical composition analysis of microplastics.

[0031] In an embodiment, the detection unit of the device includes data processing software capable of quantifying the amount of microplastics in the sample based on the spectroscopic data.

[0032] In an embodiment, the device further comprises an integrated user interface that displays real-time analysis results.

[0033] In an embodiment, the micropillar array of the device is cylindrical-shaped.

[0034] It is also described a method for detection in situ of microplastics in aquatic environments using the described device, comprising the following steps: preparation of the device for the detection in situ of microplastics in aquatic environments; preconcentration, size sorting and detection of microplastics in environmental water samples.BRI EF DESCRIPTION OF TH E DRAWINGS

[0035] The following figures provide preferred embodiments for illustrating the disclosure and should not be seen as limiting the scope of invention.

[0036] Figure 1: (A) Schematic representation of an embodiment of a device for the detection in situ of microplastics in aquatic environments, at left, and of their micropillars arrays at right side of the figure. (B) Top and lateral views of one microfluidic device, containing an array of pillars with different inter-distances. Size measures are represented in mm, if not indicated otherwise.

[0037] Figure 2: Photographic representation of parts of an embodiment of a device for the detection in situ of microplastics in aquatic environments, where (A) represents a photographic representation of an embodiment of the separation unit; and (B) represents a setup of the integration of the device for the detection in situ of microplastics in aquatic environments in a confocal Raman microscope for the preconcentration, separation by size and detection of microplastics. (C) Representative photograph of a setup of the integration of the device for the detection in situ of microplastics in aquatic environments in a portable Raman system with optical fibre configuration.

[0038] Figure 3: Photographic representation of bright-field images of 10 pm pillars array after injecting, at 100 pL / min, 2.5 mL of 100 mg / L of milled polyethylene (PE) microplastics dispersed in ultrapure water. These images were acquired using a confocal microscope with (A, B) 5x objective and (C, D) 20x objective.

[0039] Figure 4: Photographic representation of (A) Photographic representation of an embodiment of the sample container coupled with an aeration system and PTFE tubing; (B) Photographs of polyethylene terephthalate (PET) and polypropylene (PP) suspensions; (C) Photographic representation of an aeration system working into the bottle to homogenize the plastic suspension.

[0040] Figure 5: Merged bright-field images of pillars' arrays acquired using a 5x objective after pumping (A) 2 mL of mixture of spherical polystyrene (PS) with size of 40, 25, 10, 8, 5, and 3 pm, (B) 15 mL of PET, (C) 16 mL of PE, and (D) 4 mL of PP. The arrows indicate the flow direction.

[0041] Figure 6: Photographic representation of (A) Bright-field image and (B) corresponding Raman spectrum of 100 mg / L PET <300 pm disperse in both ultrapure water and natural water from a River. The asterisks (*) indicate the characteristic peaks of PET.

[0042] Figure 7: Merged bright-field images of pillars' arrays acquired using a 5x objective after pumping (A) 3 mL of mixture of spherical PS with size of 40, 25, 10, 8, 5, and 3 pm and tyre microplastics. The dispersion was prepared in ultrapure water. (B) Raman spectrum was acquired using a confocal Raman microscope with a 20x objective. The power of 785 nm laser used was 1 mW. The asterisks (*) and hashes (#) indicate the characteristic peaks of PS and tyre, respectively. (C) Bright-field image was acquired using 5x after the acquisition of the Raman spectrum (0.5 s, 100 accumulation).

[0043] Figure 8: Photographic representation of bright-field images and Raman spectra of 100 mg / L of PE, PP, PET at micro scale range acquired and 1 pm polystyrene (PS) using 785 nm laser line. The backslashes ( / ), at signs (@), asterisks (*) and hashes (#) indicate the characteristic peaks of PE, PP, PET and PS, respectively.

[0044] Figure 9: Graphic representation of Raman spectra of PE < 200 pm, PS of size mixture of 40 - 1 pm, and PET< 300 pm at different concentrations acquired inside of an embodiment of the device for the detection in situ of microplastics in aquatic environments. The backslashes ( / ), asterisks (*) and hashes (#) indicate the characteristic peaks of PE, PET and PS, respectively.

[0045] Figure 10: (A) Graphic representation of representative Raman spectra of suspension injected into the device for the detection in situ of microplastics in aquatic environments of 100 mg / L PP <200 pm, 5 mg / L PS 1 pm and a mixture of 100 mg / L PP <200 pm + 5 mg / L PS 1 pm; (B) Bright field images of the accumulation of PS 1 pm in the 1 pm pillars' array by injection of PS alone and mixed with PP. (C) Bright field images of pillars' arrays after injection of a mixture of 100 mg / L PP <200 pm + 5 mg / L PS 1 pm. The at signs (@) and hashes (#) indicate the characteristic peaks of PP and PS, respectively.

[0046] Figure 11: Raman analysis and the bright-field images of microplastics in (A) wastewater and (B) run-off water using a confocal Raman microscope. PS and PET with different size ranges were detected.DETAILED DESCRIPTION

[0047] The present disclosure relates to a device and method for the detection of microplastics in aquatic environments.

[0048] An aspect of the disclosure comprises a device for the detection in situ of microplastics in aquatic environments comprising: an inlet and an outlet; a separation unit, within said inlet and outlet, with at least two arrays of micropillars separated from each other; a sample container, coupled to the inlet of the separation unit, comprising an aeration system; a detection unit aligned substantially perpendicularly to the separation unit; wherein the inlet comprises a coiled tube comprises a length from 25 cm to 125 cm; wherein the separation unit comprises a flow rate comprised from 10 pL / min to 150 pL / min, preferably from 50 pL / min to 150 pL / min, to promote particles separation according to their sizes due to an axial spreading of the particles along the direction of the laminar flow.

[0049] In an embodiment, the detection unit of the device is aligned perpendicularly to the separation unit, for better results.

[0050] In an embodiment, the interpillar distance from consecutive micropillars of the device is from 0.25 pm to 15 pm, preferably 0.5 pm to 125 pm, more preferably from 0.75 pm to 100 pm, for better results.

[0051] In an embodiment, the distance between the at least two arrays of micropillar arrays of the device is from 0.5 mm to 1.2 mm, preferably 0.7 mm to 1.0 mm, more preferably from 0.8 mm to 0.9 mm, for better results.

[0052] In an embodiment, the each of the at least two arrays of micropillar arrays of the device comprises a width of 0.1 mm to 1.0 mm, preferably from 0.3 mm to 0.7 mm, for better results.

[0053] In an embodiment, the micropillar of the device comprises a length of 1 pm to 150 pm, preferably from 25 pm to 125 pm, more preferably from 50 pm to 100 pm, for better results.

[0054] In an embodiment, the coiled tube of the device comprises a length of 40 cm to 100 cm, preferably from 60 cm to 80 cm, for better results.

[0055] In an embodiment, the channel height of the device is from 10 pm to 100 pm, preferably from 25 pm to 75 pm, more preferably from 45 pm to 55 pm, for better results.

[0056] In an embodiment, the detection unit of the device comprises a Raman spectroscopy or micro-infrared Spectroscopy for the chemical composition analysis of microplastics, for better results.

[0057] In an embodiment, the detection unit of the device includes data processing software capable of quantifying the amount of microplastics in the sample based on the spectroscopic data, for better results.

[0058] In an embodiment, the device further comprises an integrated user interface that displays real-time analysis results, for better results.

[0059] In an embodiment, the micropillar array of the device is cylindrical-shaped, for better results.

[0060] It is also described a method for detection in situ of microplastics in aquatic environments using the described device, comprising the following steps: preparation of the device for the detection in situ of microplastics in aquatic environments; preconcentration, size sorting and detection of microplastics in environmental water samples.

[0061] In the step of preparation of the device for the detection in situ of microplastics in aquatic environments, the user places the length tube in the inlet of the size-sorter and pre-concentrator. The tubing placed in the outlet can be any, but it should be enough to connect with a waste container. Then, the user places the device for the detection in situ of microplastics in aquatic environments in a confocal Raman microscope, as illustrated in Figure 2B, with, for example, 5x and 20x objectives. The 5x objective allows following the performance of the coating and the potential formation of bubbles. The 20x objective is utilized for the Raman measurement. The device can be placed in a portable Raman system with an optical fibre configuration with a working distance between a maximum of 4 mm and a minimum of 2 mm, and a spot size of <50 pm, which allows better integration with microfluidic chips, and offers mapping options and measurement of multiple samples in combination with XYZ automated stages, as illustrated in Figure 2C.

[0062] After this step, the user injects 1 mL of ethanol at 100 pL / min using a 5 mL-plastic syringe with a syringe filter, for example of nylon or aluminium oxide with 0.2 pm. The use of nylon or aluminium oxide was selected to avoid any release of fibres from the filter membrane as occurring with membranes made from glass fibre or cellulose. Then, a 1 mL of ultrapure water is injected at 100 pL / min using a 5 mL-plastic syringe with a syringe filter, for example of nylon or aluminium oxide with 0.2 pm. Next step is the functionalization of the tubing and device for the detection in situ of microplastics in aquatic environments by injecting 1 mL of 1% of hydroxypropyl methyl cellulose (HPMC) at 100 pL / min using a 5 mL-plastic syringe with a syringe filter, for example of nylon or aluminium oxide with 0.2 pm. HPMC coating reduces the non-specific adhesion / adsorption of microplastics, increasing thus their accumulation in the pillar arrays as shown in Figure 3. Then, the user removes the excess of HPMC by injecting 1 mL of ultrapure water at 100 pL / min using a 5 mL-plastic syringe with a syringe filter, for example of nylon or aluminium oxide with 0.2 pm.

[0063] In the step of pre-concentration, size sorting and detection of microplastics in environmental water samples, the user removes the syringe pump and integrate the tube from the inlet with a peristaltic pump; places the tubing from the peristaltic pump in the sample container by introducing it inside of PTFE tube. Importantly, the samplecontainer includes an aeration system to homogenize the distribution of the plastics independent of their physicochemical properties, as illustrated in Figure 4. The nature of the plastic as well as their size and shape, e.g. their distribution on the water column due to their density, have strong implications on the efficiency of the accumulation of plastics inside of the device for the detection of microplastics in aquatic environments, as illustrated in Figure 5. Additionally, the sample container and the PTFE tube must be pre-treated with 1% HPMC to reduce the non-specific adsorption. Once the system is fully assembled, the user turns on the aeration system and waits 1 min for the stabilization and better homogenization of the microplastic-containing water samples; the pumping of the sample starts at 100 pL / min. The volume pumped through the separation unit is terminated for the accumulation of particles observed using a Confocal Raman microscope. The minimum volume is 1 mL and the maximum volume is 15 mL. The quality of the water sample has a strong effect on the volume since samples with high content of suspended sediments and particulate organic matter provoke the saturation of the separation unit after passing 1 -2 mL of sample, as illustrated in Figures 6 and 7. Once the pumping is finished, the 5x objective is used to visualize the accumulation in the micropillars' arrays. For the analysis, the 20x objective is used to acquire Raman spectra in a confocal Raman. The device can be analysed using a portable Raman system with an optical fibre configuration, a working distance between a maximum of 4 mm and a minimum of 2 mm, and a spot size of <50 pm integrated with automated XYZ stages.

[0064] Along this specification, Raman spectroscopy, leveraging its ability to provide a detailed molecular fingerprint through the inelastic scattering of monochromatic light, was utilized to analyze the material's molecular composition and structural characteristics, employing a laser source, optical filters, a spectrometer, and a CCD detector to ensure precise and reproducible data that substantiates the invention's uniqueness and innovation.

[0065] Figure 1 illustrates a schematic representation of an embodiment of a device for the in situ detection of microplastics in aquatic environments involving one inlet and one outlet. The device for the detection of microplastics in aquatic environments is integrated by arrays of micropillars with different interdistance between pillars, i.e.interpillar distance, allowing the selection of what size range of microplastics will be accumulated and sorted. The Figure shows (A) 3D representative schemes for the full device for the detection of microplastics in aquatic environments and micropillars arrays and (B) top and lateral views of one microfluidic device, containing an array of pillars with different inter-distances.

[0066] Figure 2 illustrates (A) Photographic representation of an embodiment of the separation unit, which is possible to visualize the 4 micropillars arrays separated each other. The interdistance between pillars, i.e., interpillar distance, in these micropillars arrays are: 10, 5, 3 and 1 pm, respectively. (B) Setup of the integration of the device for the detection of microplastics in aquatic environments in a confocal Raman microscope for the preconcentration, separation by size and detection of microplastics.

[0067] Figure 3 illustrates bright-field images of pillars array with an interpillar distance of 10 pm after injecting, at 100 pL / min, 2.5 mL of 100 mg / L of milled polyethylene (PE) microplastics dispersed in ultrapure water. These images acquired using a confocal Raman microscope with (A, B) 5x objective and (C, D) 20x objective. The device for the detection in situ of microplastics in aquatic environments shown in A and C was not treated with 1% HPMC, while the device shown in B and D was tread with 1% HPMC. Clearly, the HPMC coating improve the accumulation of the PE microplastics into the device.

[0068] Figure 4 illustrates (A) Photographic representation of an embodiment of the sample container coupled with an aeration stone system and PTFE tubing. (B) Photographs of polyethylene terephthalate (PET) and polypropylene (PP) suspensions, which is clearly observed the different behaviour of both plastics. (C) shows the aeration system working into the bottle to homogenize the plastic suspension.

[0069] Figure 5 illustrates the particle accumulation under aeration into the device of(A) a mixture of spherical polystyrene (PS) with size of 40, 25, 10, 8, 5, and 3 pm, (B) <250 m PET, (C) <200 pm PE, and (D) <200 pm PP after injecting a volume of (A) 2 mL,(B) 15 mL, (C) 16 mL, and (D) 4 mL, respectively. The efficiency of the accumulation inside the device depended on the nature of the plastic and its size and shape. PS particles, which were dispersed in the whole water column, accumulated efficiently under any conditions: 1) pumping without shaking or aeration, 2) using a peristaltic pump or asyringe pump, or 3) pumping with aeration. However, accumulating the other three plastics, PET, PP, and PE, was only possible when the plastic was pumped with aeration using a peristaltic pump.

[0070] Figure 6 illustrates (A) Bright-field image and (B) corresponding Raman spectrum of 100 mg / L PET <300 pm disperse in both ultrapure water and natural water from a river and subsequently their injection to the device for the detection in situ of microplastics in aquatic environments for their pre-concentration and Raman analysis. Asterisks in the figure indicate the characteristic peaks of PET. All spectra were processed by subtracting glass fingerprint and correcting the baseline.

[0071] Figure 7 illustrates (A) merged bright-field image and (B) the corresponding Raman spectrum of a mixture of spherical PS of 40, 25, 10, 8, 5, and 3 pm and tyre microplastics dispersed in ultrapure water after injecting 3 mL of this mixture into the device. In this case, the higher accumulation was observed in the 1 m interdistance pillar' array, as illustrated in Figure 7A. In the presence of tyre microplastics and organic matter, the power of the laser had to be reduced to avoid the formation of bubbles due to the degradation of these particles. Figure 7B shows that the Raman spectrum involves both characteristic peaks of PS (peaks centered at 997 and 1027 cm4) and tire (like amorphous carbon). However, a bubble formation was produced as shown in Figure 7C, which impacts the selection of the laser power and consequently the sensitivity of the final system.

[0072] Figure 8 illustrates bright-field images and Raman spectra of 100 mg / L of PE, PP, PET at micro scale range and 1 pm polystyrene (PS) acquired using 785 nm laser line. Slash, at signs, asterisks and hash indicate the characteristic peaks of PE, PP, PET, and PS, respectively. All spectra were processed by subtracting glass fingerprint and correcting the baseline.

[0073] Figure 9 illustrates Raman spectra of PE < 200 pm, PS of size mixture of 40 - 1 pm, and PET< 300 pm at different concentrations acquired inside of the device for the detection in situ of microplastics in aquatic environments using 785 nm laser line. Slash, asterisks and hash indicate the characteristic peaks of PE, PET, and PS, respectively. All spectra were processed by subtracting glass fingerprint and correcting the baseline.

[0074] Figure 10 illustrates (A) Representative Raman spectra of suspension injected into the device for the detection in situ of microplastics in aquatic environments of 100 mg / L PP <200 pm, 5 mg / L PS 1 pm and a mixture of 100 mg / L PP <200 pm + 5 mg / L PS 1 pm. Suspensions were prepared in ultrapure water. All spectra were processed by subtracting glass fingerprint and correcting the baseline. At signs and hash indicate the representative Raman peaks of PP and PS, respectively. (B) Bright field images of the accumulation of PS 1 pm in the pillars' array with an interpillar distance of 1 pm by injection of PS alone and mixed with PP. (C) Bright field images of pillars' arrays with interpillar distances of 10.5 and 3 pm after injection of a mixture of 100 mg / L PP <200 pm + 5 mg / L PS 1 pm.

[0075] Figure 8 shows the bright-field image and the corresponding Raman spectrum of 4 different microplastics: polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), and polystyrene (PS), demonstrating the capacity of our system to detect both aromatic (PET and PS) and aliphatic (PE and PP) plastics. The minimum concentration detected inside the microfluidic chamber is: PS: 14 pg / L; PET : 16 - 26 pg / L; PE: 54 pg / L; PP: 45 pg / L. Figure 9 shows the importance of the integration of the aeration system in the limit of detection. Additionally, mixture of microplastics can be identified by the system presented here, as indicated in Figure 10.

[0076] Figure 11 shows the identification of microplastics in real matrix: (A) wastewater and (B) runoff water. The plastics identified were PET and PS using a confocal Raman microscope, 20x, and a 785 nm laser line. No extra pre-concentration step was carried out since high concentrations of organic matter increased the matrix interference. However, the detection and identification of microplastics, specifically, PP, PE, PET, PS, nylon, PVC, and PVCD in natural water was possible by the combination of an extra preconcentration step and the accumulation inside of our device. The pre-concentration step consists in a cloud-point extraction procedure (CPE). Samples were subjected to CPE to pre-concentrate and eliminate part of the undesirable particulate organic matter and suspended sediments. Briefly, 40 mL of the water sample was dispersed in 4 mM Triton-X114 and incubated in pre-boiled water for 1 h. Then, the supernatant (surfactant-poor phase) was removed using glass Pasteur pipettes, and the pellet (surfactant-rich phase) was re-dispersed in 1 mL of ultrapure water. This surfactant-richphase was filtered by 0.2 pm anodise and washed using 4 mL ethanokwater (1:1) mixture. This last step removes the excess of Triton, allowing the Raman analysis. Finally, particles on the filters were dispersed in 2 mL water and accumulated inside of the device to be analyzed using a confocal Raman microscope.

[0077] The term "comprising" whenever used in this document is intended to indicate the presence of stated features, integers, steps, components, but not to preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0078] The disclosure should not be seen in any way restricted to the embodiments described and a person with ordinary skill in the art will foresee many possibilities to modifications thereof. The above-described embodiments are combinable.

[0079] The following dependent claims further set out particular embodiments of the disclosure.

Claims

C L A I M S1. A device for the detection in situ of microplastics in aquatic environments comprising: an inlet and an outlet; a separation unit, within said inlet and outlet, with at least two arrays of micropillars separated from each other; a sample container, coupled to the inlet of the separation unit, comprising an aeration system; a detection unit aligned substantially perpendicularly to the separation unit; wherein the inlet comprises a coiled tube comprises a length from 25 cm to 125 cm; wherein the separation unit comprises a flow rate comprised from 50 pL / min to 150 pL / min to promote particles separation according to their sizes due to an axial spreading of the particles along the direction of the laminar flow.

2. The device according to the previous claim, wherein the detection unit is aligned perpendicularly to the separation unit.

3. The device according to the previous claim, wherein the interpillar distance from consecutive micropillars is from 0.25 pm to 150 pm, preferably 0. 5 pm to 125 pm, more preferably from 0.75 pm to 100 pm.

4. The device according to any of the previous claims, wherein the flow rate in the separation unit ranges from 50 pL / min to 150 pL / min.

5. The device according to any of the previous claims, wherein the distance between the at least two arrays of micropillar arrays is from 0.5 mm to 1.2 mm, preferably 0.7 mm to 1.0 mm, more preferably from 0.8 mm to 0.9 mm.

6. The device according to any of the previous claims, wherein the each of the at least two arrays of micropillar arrays comprises a width of 0.1 mm to 1.0 mm, preferably from 0.3 mm to 0.7 mm.

7. The device according to any of the previous claims, wherein the micropillar comprises a length of 1 pm to 150 pm, preferably from 25 pm to 125 pm, more preferably from 50 pm to 100 pm.

8. The device according to any of the previous claims, wherein the coiled tube comprises a length of 40 cm to 100 cm, preferably from 60 cm to 80 cm.

9. The device according to any of the previous claims, wherein the channel height is from 10 pm to 100 pm, preferably from 25 pm to 75 pm, more preferably from 45 pm to 55 pm.

10. The device according to any of the previous claims, wherein the detection unit comprises a Raman spectroscopy or micro-infrared Spectroscopy for the chemical composition analysis of microplastics.

11. The device according to any of the previous claims, wherein the detection unit includes data processing software capable of quantifying the amount of microplastics in the sample based on the spectroscopic data.

12. The device according to any of the previous claims, further comprising an integrated user interface that displays real-time analysis results.

13. The device according to any of the previous claims, wherein the micropillar array is cylindrical-shaped.

14. A method for detection in situ of microplastics in aquatic environments using the device described in any of the previous claims, comprising the following steps:Preparation of the device for the detection in situ of microplastics in aquatic environments;Pre-concentration, size sorting and detection of microplastics in environmental water samples.

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