Preparation of pre-labeled adsorbent filters for the evaluation of pollutant sampling in liquid and gaseous matrices

Abstract

A filtration and adsorbent sampling and enrichment system is described, the system comprising a stationary phase and a sampling and / or enrichment standard, confined within a closed enclosure, the stationary phase consisting of a felt of activated carbon fibers having a micro-mesoporous structure and a specific surface area of about 1500 m2 / g, and methods for obtaining the system and related methods for analyzing organic and inorganic analytes using the system.

Description

Field of the Invention

[0001] The present invention relates to the field of environmental sampling of pollutants and more precisely of analytes dispersed in a fluid matrix. In particular, the present invention relates to filtration and adsorption systems previously spiked with reference standards and to their use for simultaneously sampling organic and inorganic compounds in liquid and gaseous matrices. Background Art

[0002] Air sampling of semi-volatile organic compounds is carried out by placing a sampling standard on a filter or on an absorbent / adsorbent material capable of intercepting the vapor fraction of the analyte not intercepted by the filter. For example, the sampling system may consist of: an air sampler equipped with a quartz fiber filter with a diameter of 102 mm, followed by an absorbent made of polyurethane foam (PUF) 50 mm thick with a density of 0.022 g / cm 3 The sampling time range can range from several hours up to weekly sampling, depending on whether the sampling is carried out indoors or outdoors, with a flow rate equal to 225 l / minute, for a total of approximately 2200 m 3 of air.

[0003] Table 1 below compares the outdoor and indoor sampling methods of the U.S. Environmental Protection Agency (EPA) and the International Standard Organization (ISO) for dibenzofuran and polychlorinated (PCDD / F), polybrominated (PBDD / F) dibenzo-p-dioxins and brominated or chlorinated pesticides and polychlorinated biphenyls (PCB). All methods in Table 1 use the same capture and sampling system.

[0004] Table 1

[0005]

[0006]

[0007] The use of sampling standards is defined as a basis by ISO 16000 13A and 14A and EPA Method TO9A. In fact, a sample is only valid for quantification when the recovery percentage of the standard falls within a predetermined range. Although EPA TO 4A does not require spiking, only by using this step can the sampling validity of these analytes (the same evaluation as in ISO 16000 13 and 14) be ensured.

[0008] The capture media to which the sampling standards are added can vary: polyurethane foam (PUF) in ISO 16000 Method 13, or filters in EPA TO-9A (EPA TO-9A, "Method TO-9A: Determination Of Polychlorinated, Polybrominated And Brominated / Chlorinated Dibenzo-p-Dioxins And Dibenzofurans In Ambient Air", EPA Method, No. January, pp. 1-94, 1999); EPA TO-4A, "Method TO-4A: Compendium of Methods for the Determination of Toxic Organic Compounds in Ambient Air Second Edition Compendium Method TO-4A Determination of Pesticides and Polychlorinated Biphenyls in Ambient Air Using High Volume Polyurethane Foam (PUF)", EPA Method, No. January, pp. 1-53, 1999; ISO / DIS 16000-13, "ISO / DIS 16000-13 - Indoor Air - Part 13: Determination of total (gas and particle-phase) polychlorinated dioxin-like biphenyls and polychlorinated dibenzo-p-dioxins / dibenzofurans — Collection on sorbent-backed filters", 2007; I.16000-14, "ISO / DIS 16000-14 - Indoor air - Part 14: Determination of total (gas and particle-phase) polychlorinated dioxin-like biphenyls (PCBs) and polychlorinated dibenzodioxins / dibenzofurans (PCDDs / PCDFs) - Extraction, clean-up and analysis by high resolution ga", 2007.

[0009] All of the above methods require that the filters and PUFs are also spiked with extraction standards for calculating the recovery of the sampling standards. The filter and adsorption trapping media are extracted together with a solvent in a Soxhlet extractor and the time depends on the method. The extract is then purified and the analytes are separated by class, usually using preparative chromatography techniques. The purified and separated fractions are concentrated to a few μl and a third standard is added prior to instrumental analysis. This third standard, also known as the syringe standard, is an analyte or mixture of known quantity and 100% recovery.

[0010] In the sampling of organic micropollutants from industrial emissions, even in the case of long-term sampling, the standards (e.g., EN 1948-1,4,5 EPA TO23) require a sampling system consisting of three separate compartments: a filtration system, an adsorbent / absorbent system, and a condensation system. The filtration system may be absent, in which case the capture of particulate matter occurs directly on the adsorbent / absorbent system. However, in both cases, there are sampling standards, and they can be labeled either on-site (at the measurement site) or previously in the laboratory. In the second case, there is an additional uncertainty variable in the measurement due to possible losses of the standards during the time interval elapsed between laboratory labeling and on-site sampling. These losses are even more evident if the standards are added to the filter rather than the adsorbent / absorbent system. After adding the sampling standards to each of the three capture systems, additional errors may be encountered when comparing the same analyte on the three capture systems. In fact, the losses of the standards due to degradation or volatilization occur in different ways in the three systems, and the comparison also varies. For example, parts 1-2-3-4-5 of EN 1948, which are dedicated to the methods for sampling polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzo-p-furans (PCDFs), and polychlorinated biphenyls (PCBs), specify different media to be labeled according to the expected concentration.

[0011] Adding the standards directly at the sampling site reduces the errors caused by degradation and volatilization of the standards during transportation. However, it is still difficult to automate the actual operation of adding the standards: undoubtedly, the variables that have the greatest impact on this parameter include the stability of the standards, the reproducibility of the operator, the subjective execution of the labeling between one operator and another, and the atmospheric and environmental conditions under which the process is carried out. In emission sampling, the environment is usually full of dust and contaminated with the analytes to be measured. Conducting the labeling in such an environment increases the risk of overestimating the pollutants in the emissions due to the contamination of the sampling filter during environmental exposure during the labeling process.

[0012] On-site labeling also significantly increases the time required to prepare the measurement campaign. This is even more evident when sequential sampling systems are involved, whose on-site labeling makes the operation slow, laborious, error-prone, and exposes the operator and the surrounding environment to the risk of contamination.

[0013] For liquid matrices, filters or sorbents can be used for sampling or enrichment. The support is known in the art and consists of a filter on which silica particles derivatized with octadecyl or octyl groups (ENVI-DiskTM, Sigma Aldrich) are dispersed. These particles are commonly used for the solid-phase extraction of organic compounds from aqueous samples, i.e., analytes dispersed in an aqueous matrix (E.G. Amvrazi and T.A. Albanis, “Multiresidue method for determination of 35 pesticides in virgin olive oil by using liquid-liquid extraction techniques coupled with solid-phase extraction clean up and gas chromatography with nitrogen phosphorus detection and electron capture detection,” J. Agric. Food Chem., vol. 54, no. 26, pages 9642–9651, 2006, doi: 10.1021 / jf061375s).

[0014] Alternatively, organic compounds can be solid-phase extracted from aqueous matrices using EmporeTM systems manufactured by 3M, which consist of adsorbent particles (such as divinylbenzene spheres or silica spheres derivatized with octadecyl or octyl groups or carbon) embedded within a polytetrafluoroethylene lattice. EmporeTM disks are commonly used for the solid-phase extraction of organic compounds from liquid matrices (W.M.G.M. Van Loon, F.G. Wijnker, M.E. Verwoerd, and J.L.M. Hermens, “Quantitative Determination of Total Molar Concentrations of Bioaccumulatable Organic Micropollutants in Water Using C18 Empore Disk and Molar Detection Techniques,” Anal. Chem., vol. 68, no. 17, pages 2916–2926, 1996, doi: 10.1021 / ac951136w), as passive samplers or enrichment systems in situations such as groundwater or wastewater monitoring (L. Pinasseau et al., “Calibration and field application of an innovative passive sampler for monitoring groundwater quality,” Talanta, vol. 208, no. June 2019, p. 120307, 2019, doi: 10.1016 / j.talanta.2019.120307; L. Mutzner et al., “Passive samplers to quantify micropollutants in sewer overflows: accumulation behaviour and field validation for short pollution events,” Water Res., vol. 160, pp. 350–360, 2019, doi: 10.1016 / j.watres.2019.04.012), and as passive samplers for airborne organic micropollutants (C. Sánchez, H. Carlsson, A. C. Crescenzi and R. Batlle, “Determination of nitroaromatic compounds in air samples at femtogram level using C18 membrane sampling and on-line extraction with LC-MS,” Anal. Chem., vol. 75, no. 17, pages 4639–4645, 2003, doi: 10.1021 / ac034278w; J. D. Tamburro, C. Crescenzi, and H. Carlsson, “Air sampling with Empore solid phase extraction membranes and online single-channel desorption / liquid chromatography / mass spectrometry analysis: Determination of volatile and semi-volatile organophosphate esters,” J. Chromatogr. A, vol. 1129, no. 1, pages 1–8, 2006, doi: 10.1016 / j.chroma.2006.05.086).

[0015] "Sandwich" filters such as the Atlantic SPE diskTM (Horizon Technologiy) are also known, where the adsorbent material is positioned between two layers of quartz or paper. The adsorbent material can be silica microspheres derivatized with, for example, octadecyl, styrene / divinylbenzene, or a combination of N-vinylpyrrolidone and divinylbenzene, and it is used for solid-phase extraction of organic compounds from aqueous matrices (C.C. Leandro, D.A. Bishop, R.J. Fussell, F.D. Smith, and B.J. Keely, "Semiautomated determination of pesticides in water using solid phase extraction disks and gas chromatography-mass spectrometry," J. Agric. Food Chem., vol. 54, no. 3, pages 645–649, 2006, doi: 10.1021 / jf051874d).

[0016] U.S. Patent No. 3,002,823 discloses a silica gel chromatography for separating compounds of different molecular weights in an aqueous phase. It is a particulate gel without a filler, composed of a three-dimensional molecule bonded to an aliphatic group (3 to 10 carbon atoms), and the content of its -OH groups is at least equal to 12% of the dry weight of the gel. The latter is obtained by polymerizing an organic substance (without a filler, having -OH groups) with an organic substance containing a halogen group or an epoxy group.

[0017] U.S. Patent No. 4,118,316 discloses a gel chromatography for separating compounds of different molecular weights using a porous silylated silica support functionalized with quaternary ammonium groups.

[0018] U.S. Patent No. 4,539,399 discloses silica gel functionalized with cyclodextrin by binding to silanols, which can be used in thin-layer chromatography.

[0019] All supports known and described so far in the art can be pre-labeled with sampling standards, which can be analytes similar to the target analyte, or analytes identical to the analyte to be sampled but with labeled atoms, i.e., isotopes different from those already found in the sample.

[0020] European Patent Application No. 13801779.3 discloses a filter made of quartz fiber or glass fiber or sintered silica, which is silanized with (Si-O)n-Si-Rm groups, where -(Si-O)- is the functionalized surface part and R is a functional group suitable for retaining analytes present in liquid and gaseous matrices, while n and m are integers, where n + m = 4, n > 0, m > 0, having a dust retention percentage greater than 80% for dust with a diameter greater than 0.3 μm, a thickness of 0.01 - 50 mm, and an area of 0.1 to 2500 cm2.

[0021] Italian Patent No. 102015000041855, corresponding to International Patent Application No. PCT / IB2016 / 054644, discloses stationary phases for the analysis of organic and inorganic compounds, gases and vapors. In particular, these include volatile organic compounds (VOCs), semi-volatile organic compounds (SVOCs) and mercury vapor. The stationary phase consists of carbon fibers, which are active and inactive, possibly functionalized or coated, in the form of a bundle of carbon fibers, which can be tangled, wound, woven, stranded, spun parallel, interlaced, woven in the form of a tube, woven in the form of a disc, tangled in the form of a tube, tangled in the form of a disc. It further describes a method for analyzing analytes, which includes capturing the analytes on the stationary phase, recovering the analytes by desorption and quantifying the analytes.

[0022] In Italian Patent No. 102015000041855, corresponding to International Patent Application No. PCT / IB2016 / 054644, three problems were not taken into account. The first problem is the problem of separation of the material fibers, which can lead to loss of the adsorbent material and make it difficult to use activated carbon fibers (ACFs) to produce a stable, effective and renewable adsorbent substrate. In addition, the released fibers, due to their size and the possible presence of toxic compounds on them, can cause harm to the operator if inhaled or ingested after sampling. The second problem is the characterization of the activated carbon fibers (ACFs) used, since not all activated carbon fibers (ACFs) can ensure good analytical performance and some of them are more difficult to manipulate and handle than others. The last problem is the problem of dispensing standards in a uniform, automatic, reproducible and precise manner, a topic that is very important for obtaining reliable data on the success of the sampling itself, especially if the above dispensing has to be carried out on a large surface.

[0023] The scientific publication Cerasa et al. 2020, "Validation studies on activated carbon fibre passive sampler for PCDD / Fs and PCBs in water", Chemosphere, Jan; 239:124666. doi:10.1016 / j.chemosphere.2019.124666. Epub 2019 Aug 25 describes the use of pre-labeled carbon fiber adsorbent membranes in aqueous matrices and shows the possibility of also using activated carbon fiber (ACF) adsorbents in this matrix and in air. The material has not been spiked with isotope-labeled standards and / or sampling standards. The characteristics of the activated carbon fiber (ACF) are shown in the table.

[0024] Table 2

[0025]

[0026] In particular, Cerasa et al. 2020 reported data for validating activated carbon fiber (ACF) membranes as alternatives to standard liquid / liquid extraction techniques for the quantitative adsorption and desorption of PCDD / Fs and PCBs in water. Validation was carried out according to the requirements of the standard methods EPA 1613 and EPA 1668, which envision liquid / liquid extraction techniques; then the results of the adsorption and desorption of pollutant classes from activated carbon fiber (ACF) were compared with those of the L / L of the standards added to the water. In Cerasa et al. 2020, these methods did not include spiking the adsorbent membrane with isotope-labeled homolog standards prior to extraction or enrichment. Isotope-labeled standards in water were used to obtain quantitative results, thus simulating sampling with labeled homologs; in fact, using standards of natural homologs would likely result in altered results due to interferences already present in the water.

[0027] Technical issues

[0028] The role of the sampling standard is to evaluate the possible loss of the analyte during the same sampling period. Such loss may be due to breakthrough of the filtration / adsorbent system, reaction with substances present in the sampling matrix, evaporation or degradation processes that may occur during the time elapsed between sampling and subsequent chemical analysis. Sampling of the analyte can be both passive and active: in the first case, the analyte reaches the enrichment system by diffusion, and in the second case, the analyte reaches the enrichment system by using a pump. For very dilute analytes, it is necessary to sample a large amount of matrix in order to be able to exceed the limit of quantification (LOQ): in these cases, active sampling on the enrichment system (also called the capture system) is actually mandatory to perform sampling in a reasonably short time (i.e., between 24 and 300 hours). The ideal capture system completely retains the analyte and allows the rest of the matrix to pass through; a real capture system retains a good percentage of the analyte, as well as other compounds (interferents) present in the matrix. A high sampling volume can lead to breakthrough of the capture system, while a high interferent value can degrade the target analyte. The addition of the sampling standard is used to evaluate such deviations. The efficiency of the enrichment system is defined as the ratio of the amount of analyte collected to the total amount of analyte passing through it. The capacity of the enrichment system is defined as the maximum amount of analyte that the enrichment system can retain before becoming saturated and losing / changing the efficiency of the enrichment system.

[0029] Therefore, the sample obtained consists of an enrichment system with the analyte, interferents, and the sampling standard that defines the goodness of the same sampling. Each sampling is related to the value of the sampling capacity. The analyte is extracted from the sample using a selected solvent mixture such that the maximum amount of analyte and the minimum amount of interferents are extracted. The sampling standards will be extracted in a similar way, as they will be chosen to have a chemical / physical behavior similar to that of the analyte, and in the case of isotopically labeled compounds, they will have an equivalent chemical / physical behavior. Further purification of the extract may be required before analysis. An alternative to solvent extraction is thermal desorption, where the interaction of the analyte with the analyte is weak, volatile at the operating temperature, the desorption enthalpy is less than the energy required to degrade the analyte, and the interferents are less volatile or absent.

[0030] Therefore, the analyte sampling method envisages introducing known concentrations of sampling standards (possibly isotopically labeled), which are compounds similar to the analyte to be sampled or the isotopically labeled analyte itself, onto the capture system in a step called sampling labeling before sampling.

[0031] The labeling step is carried out before the sampling system is transported to the measurement site or is carried out temporarily during sampling.

[0032] Unfortunately, in the sampling devices known in the art, there is a loss of sampling standards, which can alter the accuracy of the sampling itself. Losses can occur due to evaporation processes that occur during the time elapsed between the preparation of the standards, sampling, and subsequent chemical analysis. Sampling standard losses can also occur when handling the system in an inappropriate location that is potentially dangerous to the operator.

[0033] The choice of adsorbent is also crucial for the correct sampling of analytes present in the matrix. Insufficient adsorbent does not guarantee obtaining a homogeneous and representative sample, a feature that is essential for being able to provide accurate analytical data. Therefore, the material selected must be able to quantitatively adsorb the analytes present in the sample, without being affected by environmental disturbances or significant sample losses, where the reference percentage is determined by the method used.

[0034] The same inventors themselves have confirmed that the device described in Patent 102015000041855 can be implemented by using materials that are not easily fiber-separated through their confinement / encapsulation, so as to be able to pre-label it with reference standards without causing the drawbacks found in the devices known in the art.

[0035] The proposed technical solution makes it possible to overcome the problems of the devices known in the art, facilitate the sampling operation in measurement activities, avoid handling chemicals in inappropriate locations (both for the safety of the operator and to ensure the quality of the standards handled outside a controlled environment, such as a possible chemical laboratory), and reduce both the loss of reference analytes and the loss of analytical artifacts.

[0036] Therefore, the present inventors have designed a filtration / adsorbent system capable of retaining semi-volatile organic and inorganic standard compounds, which ensures the sampling / enrichment evaluation of analytes from a fluid matrix in the presence or absence of particulate matter. The pre-labeled sampling standard system has a high capacity to quantitatively retain the unchanged standards during the time elapsed between adding the standards to the system and using the standards. In this way, a higher recovery rate can be obtained from the sampling standards, thereby reducing measurement uncertainty and improving the precision and accuracy of the method.

[0037] Another technical problem solved by the present invention is the technical problem of stripping / fiber separation.

[0038] In fact, systems known in the art for using activated carbon fibers (ACF) for analytical purposes suffer during processing from a loss of fiber cohesion from the material itself, resulting in fiber separation and a consequent non - quantifiable loss of adsorbent material. This physical characteristic ensures that the use of activated carbon fiber filters (ACF) as, for example, sampling systems is strongly restricted because their structural integrity cannot be guaranteed. In fact, during the membrane washing step before sampling, the release of fibers of variable size into the cleaning solvent can already be observed, which is usually carried out in the same way as the extraction. When handling the filter itself, fiber separation is also macroscopically visible, releasing material on the support on which the filter is placed or on the gloves used by the operator. The released fibers have the same adsorption characteristics as the source material. This event results in a non - reproducible and non - quantifiable loss of the sampling standard added to the membrane at time t = 0, which can have implications for workplace safety as well as a non - reproducible and non - quantifiable loss of the sample. The fiber separation of activated carbon fibers (ACF) is non - quantifiable because it depends on subjective handling and, as a result, the recovery percentage of the sampling standard will be highly variable. The fibers released from activated carbon fibers (ACF) can affect the portion of the material to which the sampling standard has been added. The recovery percentage of this standard is the basis for validating quantitative analysis and will therefore be affected by variables that are completely out of control, which can render a correctly performed sampling useless. The processing can involve the simple packaging of pre - labeled membranes or their transportation and use. Fiber separation in the sampled filters or in filters to which the standard has simply been added can also lead to occupational health problems. These fibers, rich in potentially toxic analytes, can easily disperse in the air and can therefore be inhaled or inadvertently ingested by the operator during all filter - handling procedures.

[0039] Fiber loss (also known as stripping) can occur not only during the filter treatment step but also during the sampling or extraction step. In the first case, fiber loss can lead to not only an underestimation of the sampling standard but also an irrecoverable sample loss and an absolute loss of the adsorbent medium capacity. In the second case, the extraction efficiency can be very low and completely uncontrollable. In fact, each fiber in the filter has exactly the same adsorption capacity as the original membrane, and if present even in trace amounts in the extract, they will tend to passively adsorb natural compounds and standards. This occurs in any type of liquid extraction and can lead to an incorrect assessment of the sampling and extraction standards as well as the target analyte itself. Whenever activated carbon fibers (ACF) as such are used in the field of analysis, the above problems arise. It should be emphasized that this drawback cannot be simply solved by ultracentrifugation followed by extraction of the deposited fibers, since the size of the fibers themselves causes them to always remain suspended, making some separation of the particles impossible. In addition, even in the case of a successful separation between the extract and the residual fiber impurities, the partitioning kinetics of the analyte between the filter fibers and the extraction solvent are unknown, and variable recoveries of the analyte and sampling standards are sometimes obtained.

[0040] In the present invention, this technical problem is solved as follows: encapsulating and / or confining the adsorbent membrane to avoid any loss of part of the activated carbon fibers (ACF), providing protection on all sides of the membrane, different from other types of confinement where the adsorbent is located between two filters (sandwich system) or dispersed in another device. These latter two types of systems actually cannot guarantee that the released fibers do not disperse during the treatment of the filter. Therefore, the proposed solution envisages encapsulating / confining the activated carbon fibers (ACF) membrane by including all solutions having the following characteristics: they do not interfere with sampling, by not significantly increasing its impedance or reducing the adsorption capacity of the material itself, they are compatible with the matrix to be sampled, they do not represent competitors of the analyte and do not create sampling artifacts, they are compatible with the extraction or treatment techniques in the laboratory (therefore they are not thermally unstable or degradable by pressure or due to the action of solvents). In addition, it is designed to adapt to the sampling instrument in terms of shape, thickness, and orientation.

[0041] Therefore, encapsulation / confinement avoids leakage or loss of parts of the activated carbon fibers (ACF) membrane in terms of micro / macro dimensions, ensures no loss of the sampling standard, and enables accurate quantitative analysis of the real sample. It further ensures easier handling of the activated carbon fibers (ACF) membrane. The encapsulation process ensures excellent airtightness and resistance to chemical and physical stresses and does not interfere with the sampling system.

[0042] Another advantage is the fact that it can also act on a microscale without having an adverse effect on the materials inside the enclosure. It is possible to implement the restriction system without altering the stability of the standards previously added thereto and to ensure that the standards can also be added after sealing without competing with the activated carbon fiber (ACF).

[0043] Depending on the application and the extraction system, the restriction material can be pre-washed with a solvent.

[0044] Another element considered in the following invention is the choice of ACF type, whose chemo-physical properties vary based on the degree of activation and thus on the industrial process they have undergone. By increasing the degree of activation, the technical methods for non-analytical purposes have more stringent parameters, which increase the specific surface area, the adsorption capacity and the purity of the adsorbent, but also make it more fragile. The result is that the material has lower cohesion, facilitating the separation of its fibers.

[0045] Object of the Invention

[0046] The above technical problem is solved by providing a filtration and adsorbent sampling and enrichment system comprising

[0047] a stationary phase consisting of a felt fabric of activated carbon fibers having a micro-mesoporous structure and a specific surface area of about 1500 m 2 / g

[0048] and a sampling and / or enrichment standard, confined within a closed enclosure.

[0049] Another object of the present invention is a method for preparing a filtration and adsorbent sampling and enrichment system comprising a stationary phase and a sampling and / or enrichment standard, the stationary phase consisting of a felt-type fabric of activated carbon fibers having a micro-mesoporous structure and a specific surface area of about 1500 m 2 / g, confined within a closed enclosure.

[0050] Another object of the present invention is a method for analyzing organic and inorganic analytes by using a filtration and adsorbent sampling and enrichment system comprising a stationary phase and a sampling and / or enrichment standard, the stationary phase consisting of a felt-type fabric of activated carbon fibers having a micro-mesoporous structure and a specific surface area of about 1500 m 2 / g, confined within a closed enclosure.

[0051] With reference to the experimental examples and the attached drawings, further features of the present invention will become apparent from the following detailed description. Description of the Drawings

[0052] Figure 1The figure shows the comparison of the average recovery percentages of the mixture of 13 C PCB congeners added to QFF (quartz fiber filter) and ACF (activated carbon fiber) filters after exposure at 35 °C for 24 h. The Y-axis is R% (recovery percentage), and the X-axis is 13 C-labeled PCB congeners (L, labeled).

[0053] Figure 2 The figure shows the comparison of the average recovery percentages of the mixture of 13 C PCDD / F congeners added to QFF (quartz fiber filter) and ACF (activated carbon fiber) filters after exposure at 35 °C for 24 h. The Y-axis is R% (recovery percentage), and the X-axis is 13 C-labeled PCDD / F congeners.

[0054] Figure 3 The figure shows the comparison of the average recovery percentages of the sampling standards of 13 C PCB congeners added to QFF (quartz fiber filter) and ACF (activated carbon fiber) filters wrapped and sealed with aluminum after exposure to an average temperature of 23.5 °C and a relative humidity of 55.9% for 15 days. The Y-axis is R% (recovery percentage), and the X-axis is 13 C-labeled PCB congeners (L, labeled).

[0055] Figure 4 The figure shows the comparison of the average recovery percentages of the sampling standards of 13 C PCDD / F congeners added to QFF (quartz fiber filter) and ACF (activated carbon fiber) filters wrapped and sealed with aluminum after exposure to an average temperature of 23.5 °C and a relative humidity of 55.9% for 15 days. The Y-axis is R% (recovery percentage), and the X-axis is 13 C-labeled PCDD / F congeners.

[0056] Figure 5 The figure shows the comparison of the average recovery percentages of the sampling standards of 13 C PCDD / F congeners added to the encapsulated ACF (activated carbon fiber) type ACN 15 wrapped and sealed with aluminum after 7 days, 30 days (1 month), and 90 days (3 months) at an ambient temperature of approximately 20 °C and a chiller temperature of approximately 4 °C. The Y-axis is R% (recovery percentage), and the X-axis is 13 C-labeled PCDD / F congeners used as sampling standards.

[0057] Figure 6Figure shows the average recovery percentage comparison of the sampling reference standards of 13 C PCB congeners added to the encapsulated ACF (activated carbon fiber) type ACN 15 wrapped and sealed with aluminum after 7 days, 30 days (1 month), and 90 days (3 months) at an ambient temperature of about 20 °C and a chiller temperature of about 4 °C. The Y-axis is R% (recovery percentage), and the X-axis 13 The

[0058] Figure 7 Schematically shows the preparation of an ACF filter type ACN 15 encapsulated with an aluminum edge. Detailed Description

[0059] Definitions

[0060] Within the meaning of the present invention, carbon fiber (CF) refers to a material composed of fibers with a diameter of about 5 - 10 microns and mainly composed of carbon atoms.

[0061] Within the meaning of the present invention, activated carbon fiber (FCA) is a fibrous carbonaceous adsorbent obtained by carbonization and activation of polymer fibers, preferably of the phenol - aldehyde or poly(acrylonitrile) (PAN) type, such as those described in Italian Patent Application No. 102015000041855 (incorporated by reference).

[0062] Within the meaning of the present invention, the sampled organic and inorganic compounds are all categories of target compounds for analytical chemistry. By way of example only, they can be polycyclic aromatic hydrocarbons, polychlorinated biphenyls, polychlorinated dibenzo - p - dioxins and polychlorinated dibenzofurans, chlorobenzenes, alkylbenzenes, alkanes, phthalates, polybrominated diphenyl ethers, perfluoroalkylated pharmaceuticals, active ingredients, perfluoroalkylated substances (PFAS - PFOA), metabolites, elements and mercury in bound forms, semi - volatile metal halides.

[0063] Within the meaning of the present invention, a sampling reference standard refers to any compound similar or analogous to the analyte to be sampled, or the analyte itself labeled with an isotope, which is added to the sampling system to reduce bias and measurement error and to evaluate the accuracy of the measurement.

[0064] The object of the present invention is a filtration and adsorbent sampling and enrichment system, which includes a stationary phase composed of a felt - type fabric of activated carbon fiber having a micro - mesoporous structure and a specific surface area of about 1500 m 2 / g

[0065] and sampling and / or enrichment reference standards,

[0066] confined within a closed enclosure.

[0067] If necessary, the activated carbon fiber can be functionalized or coated.

[0068] Preferably, the activated carbon fiber is coated with a coating selected from the group consisting of: squalene, methyl silicone OV-1, methyl silicone SE-30, methyl-phenyl-silicone (20% phenyl) OV-7, methyl-phenyl-silicone (50% phenyl) OV-17, cyanopropyl-methyl-phenyl-silicone OV-225, Carbowax 20M (polyethylene glycol), nitroterephthalate of PEG (FFAP), diethylene glycol succinate (DEGS).

[0069] Preferably, the felt is woven or non-woven.

[0070] Preferably, the felt is a felt of type ACN 15.

[0071] The term ACN 15 refers to a Kynol type non-woven felt having an SSA determined by iodine adsorption of 1500 m2 / g, mfibres 3.3 dtex, 80% non-crimped and 20% crimped for greater capacity.

[0072] The membrane of the present invention can be used for in-situ sampling of analytes by active or passive methods and can also be used for enriching samples from previously collected gaseous or liquid matrices.

[0073] In the latter case, if the method requires it, or if it is desired to lower the quantification limit of the collected sample, or if it is not possible to use ACF in the sampling step, the analytes present in the laboratory can also be enriched.

[0074] Another object of the present invention is a method for preparing a filtration and adsorbent sampling and enrichment system, the system comprising a stationary phase and sampling and / or enrichment standards, the stationary phase consisting of a non-woven felt fabric having a micro-mesoporous structure and a specific surface area of about 1500 m 2 / g of activated carbon fiber, confined within a closed enclosure, the method comprising the following steps:

[0075] a) Purifying the stationary phase to remove organic or inorganic impurities;

[0076] b) Drying the stationary phase obtained at the end of step a);

[0077] c) Adding sampling standards,

[0078] d) Encapsulating and closing the enclosure without using glue and / or adhesives.

[0079] Preferably, in step a), purification is carried out by solvent extraction or by treatment with acids and oxidants followed by washing with water (most preferably MilliQTM water).

[0080] Preferably, if purification is carried out with a solvent in step a), drying of the stationary phase in step b) is carried out under vacuum, or if purification is carried out by treatment with an acid and an oxidizing agent in step a), drying of the stationary phase in step b) is carried out by thermal dehydration.

[0081] In step c), the sampling standard is added to the membrane in a uniform, reproducible and accurate manner.

[0082] Preferably, in step c), the sampling standard is positioned on the stationary phase at n predetermined positions. Preferably, in step c), the sampling standard is positioned on the stationary phase by an automatic multi-head dispenser that is capable of dispensing the sampling standard onto the membrane at different speeds in a completely reproducible and automatic manner.

[0083] In the automatic dispenser, the stationary phase is positioned on a rotating disk or oscillating plate with an adjustable and constant speed. The sampling standard is distributed simultaneously as the membrane moves, thus ensuring a uniform distribution over the entire surface.

[0084] In the case of a rotating plate, the distribution of the sampling standard on the stationary phase can be concentric (n circles), or in the case of an oscillating plate or non-rotating movement, the distribution of the sampling standard on the stationary phase is in n lines (continuous or interrupted, crossing or non-crossing).

[0085] Preferably, the sampling standard is distributed with a quantitative precision equal to 10 μl ± 0.20 μl and a standard deviation of 0.1%.

[0086] Optionally, a stabilizer is added to the sampling standard in step c).

[0087] The process avoids loss of the sampling standard before measurement, thus during its storage and / or transportation.

[0088] For example, in the case of PCDD / F and PCB, 4% tetradecane is added to the nonane solution containing the sampling standard.

[0089] The sampling system is confined within a closed enclosure, where confinement is understood as a method of enclosing on all sides with a continuous material having a mesh size such that no fibers are released to the outside.

[0090] Preferably, the material of the enclosure is selected from the group consisting of natural or synthetic polymers, cellulose or silica-based sheets, wire meshes or combinations thereof.

[0091] More preferably, the material of the enclosure is selected from the group consisting of quartz fibers, polypropylene, nylon fibers, aldehyde fibers, phenolic fibers, amino fibers, vinyl fiber filters, cellulose fibers, cellulose derivatives and wire meshes of metals and combinations thereof.

[0092] The enclosure is sealed by techniques selected from the group consisting of stitching, thermal welding, chemical welding, electric welding, pneumatic welding, ultrasonic welding, bonding, melting, bending, stamping, riveting, sealing using an external enclosure, or sealing using an adhesive solvent, and the enclosure is never sealed using techniques involving the addition of any type of adhesive or glue.

[0093] The filter thus obtained is different from an encapsulated filter sandwiched between two filters.

[0094] The pre-labeled adsorbent filter with attenuated sampling standards can be stored at a temperature of 4 to 30 °C.

[0095] In one embodiment of the present invention, the adsorbent filter is an ACF filter, having a diameter of 102 mm, a thickness of 2 mm, and a surface area of approximately 1500 m2 / g.

[0096] Other embodiments may provide, for example, a rectangular shape (for high-capacity filters) or other shapes according to the usage requirements, or other diameters, such as 47 mm.

[0097] A method for analyzing organic and inorganic analytes by using a filtration and adsorbent sampling and enrichment system including a stationary phase composed of activated carbon fibers and sampling and / or enriching standards provides a step of capturing analytes on the filtration and adsorbent sampling and enrichment system, followed by steps of analyte extraction and quantification.

[0098] Common extraction techniques can be used to extract analytes from the filter.

[0099] A filtration and adsorbent sampling and enrichment system including a stationary phase composed of activated carbon fibers and sampling and / or enriching standards can be used for active or passive sampling of fluid, gaseous, gas, and liquid matrices.

[0100] Examples

[0101] Example 1

[0102] The comparison between ISO 16000 13 and 14 and EPA TO 4A and 9A reported in Table 1, known in the prior art, shows the addition of sampling standards on quartz fiber filters (QFF). In this study, the ability of quartz fiber filters to retain sampling standards and PCDD / F and PCB congeners without change over time was compared with that of encapsulated ACF filter type ACN-15.

[0103] Five 102 mm felt-type ACF filters were prepared, 2 mm thick, with an SSA of approximately 1500 m2 / g, and pre-washed in toluene. Among them, three QFFs and three ACF filters were pre-labeled with known amounts of sampling standards, containing 13 C 12 PCDD / F and PCB, and then encapsulated.

[0104] Since the sampling standards only included some homologues, it was decided to also use a more complete standards mixture 13 C 12 to evaluate the effect on the remaining compounds. Hypothetically, it might be related to the processes the compounds underwent after sampling during transportation to the laboratory. For this reason, among the remaining pre-washed filters, two QFFs and two ACF filters were labeled with known amounts of the standards mixture. Then the ACF filters were encapsulated. It was decided to evaluate the variable that had the greatest effect on compound volatilization, namely temperature.

[0105] For the ACN-15 type ACF filter, the porosity and its distribution were evaluated by BET analysis and the Langmuir equation, and it was determined that it had a microporous distribution as the main type with a slight presence of mesopores, which was the preferred type of ACF.

[0106] The type of ACF used was derived from the carbonization (activation) of novoloids in an inert atmosphere and was usually referred to in terms related to the BET number. In particular, ACF-15 was the activation level selected. The increase in surface area led to a higher percentage of the analyte adsorbed on the material, which could be explained by the increase in the absolute capacity of the material and the larger pore size. The presence of a higher porosity led to a different energy distribution of the analyte adsorbed on the material. The internal structure of the ACF was disordered, and the distance between the pores greatly affected the force of interaction between the adsorbate and the substrate. Compared with what would happen with ACF-20 and ACF-25, the ACF with a smaller surface area and a narrower porous structure ensured a more uniform substrate, and the analyte could be distributed on the substrate with a greater binding force (high-energy pores). In fact, in the latter cases, an analyte layer was generated upon contact with the substrate, and thus the interaction force between the analyte farthest from the surface and the adsorbent itself decreased sharply.

[0107] The adsorbent suitable for sampling must be able to work even under potentially adverse environmental conditions. Therefore, it was also important to evaluate the adsorption isotherms of the analyte at different temperatures. ACF-15 exhibited a slightly varying behavior from 25 °C to 150 °C, thus ensuring reproducible performance even under extreme conditions and at low concentrations.

[0108] Therefore, ACF-15 seems to be the best candidate and has a good surface area at the same time, which enables quantitative sampling of all concentrations of analytes present in the matrix. In addition, from a macroscopic perspective, as the degree of activation increases, the degree of fiber separation also increases, which is a negative characteristic of this type of adsorbent.

[0109] Filters with the mixed standard 13C12 PCDD / F and PCB

[0110] Two filters of ACF and QFF were exposed to a constant temperature of 35 °C for 24 h.

[0111] The data obtained are shown in Figure 1 and Figure 2 .

[0112] Filters with sampling standards

[0113] Six filters (3 of QFF and 3 of ACF) were labeled with 1000 pg of sampling standards 13 C 12 of PCDD / F and PCB. Then they were packaged in the same way: wrapped with aluminum pre-cleaned with DCM and sealed in an airtight package. The filters were placed at an average temperature of 23.5 °C (maximum 37.4 °C; minimum 9.8 °C) and an average relative humidity of 55.9% (maximum 89.3%; minimum 30.7%) for 15 days. Assuming the pre-labeled filters are transported during summer months, the temperatures considered are underestimated anyway. After exposure, the six filters were extracted separately to evaluate the R% of the standards. Figure 3 and Figure 4 show the average recovery % for PCDD / F and PCB.

[0114] Figures 1 - 4 The data reported in

[0115] show that the adsorbent medium (QFF) commonly used for PCDD / F and PCB air sampling does not have the same ability to hold the sampling standards, let alone the standard mixture remaining unchanged over time. Temperature was judged to be the most influential parameter in this process, and it seems to change the original concentration of the standards fixed on the adsorbent medium. Figure 3 and Figure 4 ) show that the ACF filters subjected to thermal stress maintain a satisfactory average R%, so they can be used as if they were freshly added sampling standards regardless of the temperature ( Figure 1 and Figure 2)。The same does not apply to quartz fiber filters, which were treated in exactly the same way as the ACF filters and showed satisfactory recovery rates only for the higher molecular weight fractions.

[0116] This shows how vulnerable quartz fiber filters would be to errors and underestimation if they were pre-labeled, and could lead to significant losses of sampled analytes.

[0117] Example 2

[0118] In the case of the ISO 16000 13A method, the felt-type ACF fiber filter ACN 15 was cut to a diameter of 102 mm, a thickness of 2 mm, and an SSA of approximately 1500 m2 / g. This method is designed to sample PCDD / F and PCB, and for this reason, tetradecane was added to the nonane solution containing the sampling standards.

[0119] Optimal conditions were determined in order to locate the PCDD / F and PCB sampling standards on the ACN 15 type ACF membrane and then encapsulate them. After that, the capture system was stored on aluminum sheets pre-washed with dichloromethane (DCM) and sealed in an airtight bag.

[0120] By evaluating two of the factors that affect the system's ability to keep the standards unchanged: temperature and time, the packaging film was allowed to stand.

[0121] It was decided to evaluate exposures of 7 days, 1 month, and 6 months; each test was carried out at two temperatures, both the ambient temperature of 22 °C and the freezer temperature of 4 °C. All tests were carried out in triplicate to ensure the reproducibility of the results.

[0122] The results are shown in Figure 5 and Figure 6 in.

[0123] The data reported so far shows that ACF has the ability to keep the concentration of the standards added to it unchanged for up to 6 months. This allows the assumption that multiple filters can be prepared and used at a distance.

[0124] Example 3

[0125] Based on the research on activated carbon fiber as an enrichment or sampling medium in water (Cerasa et al. 2020, Validation studies on activated carbon fibre passive sampler for PCDD / Fs andPCBs in water, Chemosphere, Jan; 239:124666. doi:10.1016 / j.chemosphere.2019.124666. Epub 2019Aug 25), it can be shown that the filter can also be used for aqueous matrices. In fact, in "Validation studies on activated carbon fibre passive sampler forPCDD / Fs and PCBs in water", the material was evaluated as suitable according to the requirements of ISO 1613B and 1668B methods (for PCDD / F and PCB respectively).

[0126] The object of the present invention does not exclude its use in aqueous matrices. In the present embodiment, it relates to the micropollutants PCDD / F and PCB, but generally does not exclude the possibility of extension to other micropollutants. The hypothesis can be a passive system, such as one of the POCIS (Polar Organic Chemical Integrative Sampler), and the ACF filter (encapsulated) is very suitable for passive sampling in waterways. In addition, if inserted into an SPE cartridge, its use as an active enrichment system can be evaluated, where water samples in the cartridge are flushed by a pump, as in the case of "Innovative rapid SPE for the extraction of PCDD / Fs and dl-PCBs in aqueous sample D preliminary assessment".

[0127] Therefore, the pre-spiked sampling standards on the ACF allow streamlining the on-site process by a simple operation of inserting the filter into an enclosure prepared for the adsorbent medium. The presence of the standards enables the correction of errors due to losses and any breakthrough related to the sampling water volume. The results show that in one possible method, the pre-packaged ACF filter spiked with sampling standards, in the shown embodiment PCDD / F and PCB, is able to retain these compounds unchanged for up to 6 months. The recovery percentages estimated from the replicates enable the filter with the pre-spiked standards to be considered usable.

[0128] Example 4

[0129] To evaluate the importance of the stripping phenomenon, the quantitative results of 3 encapsulated ACF filters were compared with 3 ACF filters used as such.

[0130] The encapsulation involves placing the ACF between two quartz filters, which are surrounded by two aluminum rings, all of the aluminum rings having a diameter of 102 mm and an SSA greater than 1500 v·m2 / g.

[0131] Sampling standards of PCDD / F and PCB in nonane stabilized in tetradecane were added to all the membranes in the ACF (those encapsulated prior to sealing).

[0132] The membranes thus packaged were processed by sampling in simulated ambient air. In this regard, all the membranes were stored on aluminum sheets for a short time (less than 1 hour), transported to an ambient air monitoring station, installed on a high-volume sampler (Echo Hi-Vol Tecora), and the sampler was started for only 5 minutes at a flow rate of 200 l / min. Then the membranes were placed on aluminum sheets and transported to the laboratory. This experiment was used to evaluate the possible losses due to the stripping of ACF fibers. During the experiment, for the unsealed membranes, visual observation was made of the residual fibers on both the aluminum sheets used for transportation and storage and the filter holder grid of the high-volume sampler. All the membranes were extracted in a Soxhlet using a quartz filter sleeve. After inserting the unsealed ACF membranes into the sleeve, additional fiber losses in the air and outside the sleeve were recorded. The samples were spiked with 13 C 12 -labeled PCDD / F and PCB extraction standards. After 36 hours of thermal extraction in toluene, the extracts were concentrated, and for the samples of unsealed membranes with quartz filters and aluminum ferrules, some residual fibers were shown in the test tubes. Therefore, it was necessary to filter the samples, and in order not to change the experiment, the solutions from the sealed ACF samples were also filtered, although they did not require filtration. Filtration was carried out using a 47 mm quartz filter, and the residue was then eluted with an additional 5 ml of toluene.

[0133] The data reported show that the sampling standards found on the unsealed adsorbents were on average approximately 10% lower for both PCBs and PCDD / F.

[0134] Table 3

[0135]

[0136] Table 4

[0137]

[0138] More significant differences in the R% of the extraction standards were observed. This difference (about 20% for PCDD / F and even about 30% for PCB) can be precisely attributed to the adsorption of the fibers transported by toluene during the Soxhlet extraction step. These free fibers present on the extract adsorb the standards, and filtration after elution / washing with 5 ml of toluene is not sufficient to recover the target analytes.

[0139] Table 5

[0140]

[0141] Table 6

[0142]

[0143] Example 5

[0144] Although the experimental tests were carried out on a hand-made laboratory prototype, an industrialized system was used for the preparation implementation, and the product gave the same results as in Example 4.

[0145] In particular, the method consists in preparing the material for the enclosure, which is usually in the form of a sheet in its original form. Each sheet is cut to the desired size, slightly larger than the size of the stationary phase, and placed on two matrices ready for thermoforming (a male matrix for forming the lid and a female matrix for forming the bottom), and then carried out by stamping. The stationary phase is placed on the thermoformed bottom, and then spiked with sampling / enrichment standards by a micro-droplet diffusion system with a high quantitative accuracy (quantitative accuracy: 10 μl ± 0.20 μl)

[0146] After placing the shielding enclosure inside the lid, a pre-welding step is carried out, blowing nitrogen into the controlled atmosphere conditions to eliminate any excess solvent until a continuous annular weld is obtained around the membrane. This is followed by a final weld around the circular edge of the central membrane in order to obtain good structural stiffness for the final product, making it easy to handle.

[0147] Example 6

[0148] At the same time, the ACF identified as having the most suitable activation degree ACN-15 was subjected to chemical-physical characterization. In particular, the analysis of the specific surface area according to the Brunauer Emmett and Teller (BET) method and the application of the Langmuir equation based on nitrogen absorption are reported below. Before the measurement, the samples were degassed with a nitrogen flow at 150 °C.

[0149] Nitrogen adsorption increases rapidly, and the resulting Langmuir isotherm corresponds to a type I isotherm: a completely microporous material. There are slight hysteresis points in the isotherm, indicating the presence of mesopores.

[0150] This dual aspect was confirmed by the results of the pore size distribution (PSD), which identified 1.2 nm (micropores) and 22 nm (mesopores) as the average diameters.

[0151] The active groups mainly attributed to the pore cavities were also characterized by Boehm titration (K.K. Beltrame, A.L. Cazetta, P.S.C. de Souza, L. Spessato, T.L. Silva, V.C. Almeida, Adsorption of caffeine on mesoporous activated carbon fibers prepared from pineapple plant leaves, Ecotoxicol. Environ. Saf. 147 (2018) 64–71. https: / / doi.org / 10.1016 / j.ecoenv.2017.08.034.).

[0152] Based on the literature data reported previously in Example 3, it is considered that the ACF of type ACN-15 in the tested table may have better performance. Not only because the SSA is easy to adsorb at 1500 even at low ACN concentrations compared to the SSA of 2000 m2 / g, but also because of the lower presence of acidic groups, which tend to coordinate water molecules and remove the active sites for adsorbing pollutants.

[0153] In which we found that the basic groups were significantly more compared to the total acidic groups composed mostly of phenolic groups.

[0154] Table 7

[0155]

Claims

1. A filtration and adsorbent sampling and enrichment system, the system comprising Stationary phase, said stationary phase consisting of a felt-like fabric of activated carbon fibers having a micro-mesoporous structure and a specific surface area of 1500 m 2 / g, said specific surface area being measured by the Brunauer Emmett and Teller method and the application of the Langmuir equation based on nitrogen absorption, and a sampling and / or enrichment standard positioned on the stationary phase, confined within a closed enclosure, where the confinement is by enclosing on all sides of the closed enclosure using a continuous material having a mesh size such that no fibers are released to the exterior.

2. The filtering and adsorbent sampling and enrichment system according to claim 1, wherein The activated carbon fiber is functionalized or coated.

3. The filtering and adsorbent sampling and enrichment system according to claim 1, wherein, The felt is woven or non-woven.

4. The filtering and adsorbent sampling and enrichment system according to claim 1, wherein, The enclosure is made of a material selected from the group consisting of: natural or synthetic polymers, silica substrates, wire meshes, or combinations thereof.

5. The filtration and adsorbent sampling and enrichment system according to claim 1, wherein, The enclosure is made of a cellulose substrate, wire mesh, or combinations thereof.

6. The filtration and adsorbent sampling and enrichment system according to claim 1, wherein, The enclosure is made of a material selected from the group consisting of: quartz fibers, polypropylene, nylon fibers, aldehyde fibers, phenolic fibers, amine fibers, vinyl fibers, cellulose fibers, cellulose derivatives, and wire meshes of metals, and combinations thereof.

7. Use of the filtration and adsorbent sampling and enrichment system according to any one of claims 1 - 6 for active or passive sampling of a fluid matrix.

8. Use according to claim 7, wherein, The fluid matrix is a gaseous or liquid matrix.

9. Use according to claim 7, wherein, The fluid matrix is a gas matrix.

10. A method for preparing the filtration and adsorbent sampling and enrichment system according to claim 1, said system comprising a stationary phase, said stationary phase being composed of a felt-like fabric of activated carbon fibers having a micro-mesoporous structure and a specific surface area of 1500 m 2 / g, and a sampling and / or enrichment standard positioned on the stationary phase, confined within a closed enclosure, The method comprises the following steps: a) purifying the stationary phase to remove organic or inorganic impurities; b) drying the stationary phase obtained at the end of step a); c) adding the sampling and / or enrichment standard; d) encapsulating and closing the enclosure without using glue and / or adhesives.

11. The method according to claim 10, wherein, In step a), the purification is carried out by solvent extraction or by treatment with acids and oxidants followed by washing with water.

12. The method according to claim 10, wherein, If the purification in step a) is carried out with a solvent, the drying of the stationary phase in step b) is carried out under vacuum, or if the purification in step a) is carried out by treatment with acids and oxidants, the drying of the stationary phase in step b) is carried out by thermal dehydration.

13. The method according to claim 10, wherein, In step c), the sampling and / or enrichment standard is added with a quantitative precision equal to 10 μl ± 0.20 μl.

14. The method according to claim 10, wherein, In step c), the sampling standard is positioned on the stationary phase at n predetermined positions.

15. The method according to claim 10, wherein, In step c), the sampling standard is positioned on the stationary phase by an automatic multi-head dispenser.

16. The method according to claim 15, wherein, In step c), in the automatic multi-head dispenser, the stationary phase is positioned on a rotating disk or an oscillating plate with an adjustable and constant speed.

17. The method according to claim 16, wherein, In step c), the sampling standard is distributed while moving with the membrane positioned on the rotating disk or oscillating plate.

18. The method according to claim 17, wherein, In step c), in the case of a rotating disk, the sampling standard is distributed concentrically.

19. The method according to claim 17, wherein, In step c), in the case of an oscillating plate, the sampling standard is distributed in n lines.

20. The method according to claim 10, wherein In step d), the enclosure is closed by a technique selected from the group consisting of: stitching, thermal welding, chemical welding, electric welding, pneumatic welding, ultrasonic welding, melting, bending, stamping, riveting, closing using an external closure, without adding any type of adhesive or glue.

21. The method according to claim 10, wherein, In step d), the enclosure is closed by a combined technique.

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