DEVICE AND METHOD FOR DETERMINING MEMBRANE PERMEABILITY.

Abstract

A device and method specifically designed to measure the permeability of volatile organic compounds (VOCs) in porous materials used in the pharmaceutical, food, agricultural, medical, textile, and cosmetic industries. The invention allows for the simple measurement of the permeability of various VOCs through plastic materials used in food packaging, preformed with synthetic and natural polymers. This will enable food technologists to model and design packaging materials with selective permeability for food preservation. In the pharmaceutical industry, it will provide information for creating encapsulation materials that effectively protect medications with active ingredients sensitive to volatile compounds. For the agricultural industry, it will be possible to evaluate the permeability of porous greenhouse materials and assess its effect on the availability of volatile compounds beneficial to crops.In the medical industry, permeability can be evaluated in membranes designed for the selective control of volatile compounds. In the textile industry, permeability can be evaluated in special materials for the production of safety suits against volatile compounds that pose a health risk. In the cosmetics industry, permeability can be evaluated in materials for the optimized release of perfumery compounds.

Description

DEVICE AND METHOD FOR DETERMINING MEMBRANE PERMEABILITY TECHNICAL FIELD OF THE INVENTION This invention falls within the field of analytical chemistry, more specifically, it describes a device for determining the permeability of membranes made from any type of material and applied to a wide variety of products, so its industrial application can range from food, environmental to pharmaceutical. BRIEF DESCRIPTION OF THE INVENTION The present invention relates to an auxiliary device that allows the evaluation of the permeability capacity of various volatile organic and inorganic compounds in a permeable membrane; specifically, it relates to an instrument that, together with the gas chromatography technique, allows the direct analysis in a headspace of volatile compounds that can pass through a membrane under study. BACKGROUND No evidence has been found of any device, apparatus, or process that supports the evaluation of the permeability of volatile organic compounds through a membrane; however, it has been found that there are currently three methods mainly used to measure the permeability of some gases in membranes. The first method is manometric, meaning it relies on pressure differences to determine the permeability of the most common gases in air (oxygen, nitrogen, and carbon dioxide). This method is based on DIN 53380-2 and ISO 15105-1 standards for manometric measurements. These methods are generally used to measure the permeation rate. Specialized equipment, such as the toDP-C (Bruggér Feinmechanik GmbH, Germany), is commonly used to determine permeability. This equipment measures the pressure difference on both sides of the membrane caused by the flow of a gas, and then uses this data to determine the permeability of the desired membrane. A second method involves forced flow of a specific carrier gas. This method is based on DIN 53380-3. Equipment is used to determine the permeability of a specific gas; oxygen and nitrogen are the most commonly used. The method's principle is to force a specific flow of carrier gas through a membrane and then measure it as it passes through the membrane. Nitrogen is introduced on one side of the membrane and oxygen on the other. The oxygen is then detected, and sensors on the other side of the membrane determine the flow. Due to the high pressure used, this test is not suitable for fragile semipermeable membranes. A third method is gravimetric, which determines the water vapor transmission rate (WVT) and water vapor permeability. The method is based on ASTM-96, which proposes using a gravimetric method that considers weight differences. A container with a material that has a high capacity to adsorb moisture, such as sodium hydroxide or calcium chloride, is placed in a closed system at a constant relative humidity. Finally, the containers are weighed and the water vapor permeability is determined. The difference between the methods mentioned above and the device presented here lies mainly in the fact that the compounds to be determined in this device can be of any nature, whether volatile organic compounds related to flavor and aroma, unlike the methods based on DIN 53380-2 and ISO 151054 standards, since these only allow the measurement of gases of specific humidity levels such as: oxygen, carbon dioxide and nitrogen.It is also worth mentioning that in the present invention it is possible to evaluate the permeability of a complex mixture of volatile gases in a single experiment, because the volatile compounds accumulate in the capture chamber of the device (3), which allows them to be recovered and subsequently analyzed by highly sensitive gas chromatography techniques, unlike the second method based on the DIN 53380-3 standard, which only allows the permeability of one gas to be evaluated at a time, and also requires the use of the flow of another carrier gas.Furthermore, the present invention allows for the evaluation of any semipermeable membrane regardless of its mechanical properties (hardness, elongation at break, extensibility, among others) since it is not necessary to apply pressure caused by a forced flow of a carrier gas, unlike the carrier gas method based on DIN 53380-3, which cannot be applied to membranes with weak mechanical properties or fragile structures. Another important aspect to highlight in the case of the system of the present invention is that it is not necessary to apply a forced flow or use any chemical agent to evaluate permeability. This allows for determining the rate of transmission of volatile compounds and thus observing the natural behavior of these gases.Unlike the third method based on the ASTM-96 technique, which relies on determining how much water vapor permeates the membrane, which is forced through and captured by a moisture adsorption agent, this invention aims to evaluate the permeability of volatile compounds released from a water system. A sample of a certain size, such as raisins, is used to evaluate biological materials. BRIEF DESCRIPTION OF THE FIGURES Figure i. Process diagram and usage diagram for solid-phase microextraction. A process diagram and usage diagram for solid-phase microextraction is shown, which uses the solid-phase microextraction method, in which a fiber is exposed to adsorb the volatile organic compounds from the chamber (4) of the device. Finally, the fiber is introduced into the gas chromatograph coupled to the mass spectrometer to resorb the analytes and analyze the data. Figure 2. Process diagram and usage method with direct injection. A process diagram and usage method with direct injection is shown: in which 1 pf of the volatile organic compounds are collected from the chamber (4) of the device. In this usage method, a gas syringe with a capacity of 5 ml is used. Subsequently, the syringe is inserted into the gas chromatograph connected to the mass spectrometer and the volatile organic compounds are injected. Figure 3. Process diagram and method of use with continuous system'. It shows the process diagram and method of use with a continuous system in which a high-pressure capillary tube is used connected to the chamber (4) of the device and to the inlet of the gas chromatograph injector attached to the mass spectrometer, a constant flow of helium of 1 ml / min was maintained by connecting the device to a gas tank. Figure 4 Top view of the device for determining membrane permeability. Figure 5. Side view of the device for determining membrane permeability Figure S. Perspective view of the device for determining membrane permeability. Figure 7; Longitudinal cross-section view of the device for determining membrane permeability. DETAILED DESCRIPTION OF THE INVENTION The present invention consists of a device for determining the permeability of membranes made of any type of material, where said device comprises: a main chamber (0) consisting of a container made of a non-reactive and impermeable material in which samples will be placed. This chamber has a support for the membrane to be analyzed, and also has a slot for the membrane. rm e reops oompuesiua voiátii-ss osancio re recamare íl) se enraretea unida a una aenunun moeriRi interconectada (4), ia cual es un pieza hueca que tiene la fini de captura ios complejos volatilees que pasen a través de la membrana (13), donde donde dicha recamara (4) cuenta con un septo de roma de muestra (5) para recoger en.This space contains volatile compounds that passed through the membrane (2), a purge septum (6) for injecting gas and purging, the chamber (4). Wherein also said chamber (4) is complementary with the chamber (T) and these are assembled by holding them together with the help of a plurality of fastening means (7). Which may be wing nuts, so that a hermetic seal can be given, preferably the present device may also have a heating system (8).which can be made up of any type of heat generating element, such as a plurality of 10 electrical resistors, which allows control of the internal temperature, which can also include the installation of a regulator (9) which can range from 10 °C to 100 °C, likewise to verify the temperature various instruments can be implemented such as a digital display (Jo) that shows the internal temperature of the device, all controlled by an on / off system ^.11 and a power supply (12) which is recommended to be 110 W. The device can be used as an adjunct to a gas chromatograph (15). Preferably, the device is used with the solid-phase microextraction technique; however, it can be used in ways such as direct syringe injection (16) and continuous injection. Gas chromatography coupled to mass spectrometry is used to determine, with high precision, both qualitatively and quantitatively, volatile compounds that permeate through membranes. However, it can be used as an auxiliary in any other volatile sampling technique in the headspace of gas chromatography; on the other hand, the chromatograph can be equipped with the detector that is convenient for the detection of volatile compounds. The procedure for using the device includes the following steps: 1 A known quantity of sample is placed in the chamber (1) of the device, 2. The membrane (13) to be studied is placed in the membrane support (2), positioning the packing (3) on the upper edge of the chamber (1). It should be noted that the membrane must be at least the same size as the surface area of ​​the membrane support (2). 3. The second tecamara is placed (4.i for the capture of volatiles and is adjusted with the airtight sealing system by means of the fastening means (7) that make up.. 4. The septum (5) for sampling is opened, helium gas from the tank (14) is injected into the septum (6) and the septum (5) is closed, which is where the sampling is carried out. Or, an equilibrium time is allowed depending on the type of membrane. P. The concentration of volatile organic compounds is analyzed in the gas chromatograph chamber using a solid-phase microexpiration system. Injection is performed with a 3-gauge syringe for gases or in a continuous system with a high-pressure hose to capture the volatile organic compounds and subsequently inject the samples into the gas chromatograph coupled to the mass spectrometer. Example 1. Evaluation of the permeability of volatile compounds through an edible membrane An edible memory was analyzed with the following characteristics: density - 0.0148 gf / cmL, area - 50 cm², thickness - 0.04 mm, moisture content - 15%. In addition, a mixture of alkenes C₆-C₆ was used at a concentration of 1000 μg / mL in hexane. 100 ml of alkali solution were placed in chamber (1) where the samples were placed. Subsequently, the membrane (13) was placed on the membrane support (2). The packing (3) was then placed, and the chamber (4), in which the capture of volatile compounds would take place, was assembled. Next, the purging process was carried out in the sampling compartment with high-purity helium gas for a period of two minutes. This process consisted of opening the sampling septum (6) and injecting helium gas into the purge septum (6). The purity of the helium gas and the flow pressure were 99.9999% and 10 ml / min, respectively. The temperature was adjusted to 35°C, and an equilibrium time of 30 minutes was recorded. Subsequently, the qualitative and quantitative analysis of volatiles was carried out in the sampling chamber (4) by means of gas chromatography coupled to mass spectrometry, using the solid-state microextraction technique.An analysis was performed every hour for 5 h. The same system without placing the membrane was considered as a control (13). For the analysis by solid phase microextraction, a fiber (17) was used, which is a 50 / 30 pm capillary fiber (Dx / B i CAR / PDMS) assembled in a manual fiber cutter. The fiber (17) was heated for 10 min at a temperature of 230 °C prior to analysis; afterwards, the fiber (17) was placed in the capture chamber (4) for 5 min to adsorb the volatiles. Subsequently, a gas chromatograph was used, which had a capillary column of 5% phenyl 95% dimethyl polysulfoxane phase, 30 m in length, 0.32 mm ID, 0.25 µm film thickness and temperature limits between -10 to 30 / 350 °C. Helium gas was used at a flow rate of 1 ml / min at constant flow with a waiting time of 0.5 min at start. The column temperature was initially maintained at 35 °C for 2 min and then raised to 140 °C at 9 °C / min. remaining at this temperature for another 5 minutes.The injector temperature was 230 °C. A mass spectrometer with an electromagnetic sensor (70 eV) was used. The analysis of the 30-400 m² mass spectrometer and the injector temperature were 230 and 250 °C, respectively. The quantitative analysis of the substances that we are members of is a comparison of the spectra 00100030 00 of each use of the οκ-ηη ion with number 6 The masses were based on the NIST spectral mass data; a level of agreement greater than 90% was considered acceptable. The quantitative determination of the volatile compounds that permeated the membrane was carried out based on previously prepared standard curves, which were constructed in relation to a part of the dilutions of each compound and the area under the curve of the chromategrams generated respectively The membrane permeability was determined from the volatile compound transfer rate (VTCOR), which is obtained from the slope resulting from plotting the concentration of each volatile compound against time. Subsequently, the membrane permeability was calculated according to the following equation: Equation 1. Where: PER ~ Membrane permeability (ug / (s'm)) 15vtcov - rate of transfer of volatile compounds (pg / h) A = membrane transfer area (m2) e - membrane thickness (m) The results obtained are presented in Table 1 20 Table 1. Compound Name Transfer Rate Membrane Permeability (pg / h) (pg / (h*m)) Heptane (C1) 9.4877 9.094877 Octane (C2) 8.4148 0.084148 Nonane (C3) 7.6140 0.07614 Decane (C10) 7.3155 0.073155 Undecane (C1) 7.0286 0.070286 Dodecane (C12) 6.6193 0.066193 Tridecane (C13) 5.9274 0.059274 Tetradecane (C13) 5.2593 0.052593 Pentadecane (C12) 4.6181 0.046181 Hexadecane (C12) 3 8574 0.038574 Heptadecane (Ov) 3.3371 0.033871 Ociadecane (C?s) 3 0648 0.030648 Nonadecane (Ct«) 2.7182 0.027182 Cace mention cite chano etempa no asee be temoso como un asrñsmte Átete ¡nvention previously deserte, más Lite sounds be a eisíte:rte tes ds-sc: detailed to make it clearer: how it can be carried out in the particular case presented. But a technician in the field will find that depending on the membrane, small modifications obvious to someone versed in the subject will be required; therefore, these variations do not depart from the spirit of the present invention.

Claims

CLAIMS 1. A device for determining the permeability of membranes, characterized in that it comprises: a main chamber (T), which consists of a container made of a non-reactive and impermeable material in which samples emitting volatile compounds are placed, and which has: a support (2) for placing the semipermeable membrane (13) to be analyzed; and a slot for placing a packing (3). The chamber (1) is connected to: a second interconnected chamber (4), which is a hollow piece intended to capture the volatile compounds that pass through the membrane, and where said chamber (4) is held by a plurality of fastening means (3) and has: a sampling septum (5); a purge septum (6) for injecting gas and purging the chamber (41, wherein said chamber (4), and; a heating system (8).

2. The device for determining membrane permeability of claim 1 characterized in that the sample of volatile compounds used can be simple or complex.

3. The device for determining the permeability of membranes of claim 1, characterized in that the heating system (8) preferably operates on the basis of a plurality of electrical resistors.

4. The device for determining the permeability of membranes of claim 1 characterized in that the membrane can be selected from the group of semipermeable membranes based on natural and synthetic polymers that can be preformed and that have some degree of porosity.

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