Patent Application
20090101172
The invention relates to a system and method of extraction of organic chemical compounds with toxic properties from polyurethane foam filters (PUF) in which they are retained, wherein the analytes of interest are gaseous atmospheric contaminants present in the ambient air. More specifically, it is described how to extract those chemical compounds from the filters in a mechanical and automatic manner, as a way to increase the quality of this analytical procedure.
At present time, there are not equipments in the market with these characteristics, and the procedures recommended in the literature or by the international environmental agencies are approached using classic methods and equipments, those usually used in analytical chemistry to extract analytes from materials and/or solid matrices such as PUF, using Soxhlet equipment (e.g. method EPA-3540). These equipments use large amount of solvents (measured in liters), long times of extraction (12 hours or days) and high energy expenses. Furthermore, they are not automatized, needing the presence of an operator for security reasons. The other existing alternative is to do the same extraction procedure in a manual form, which also implies the presence of an operator and the realization of repetitive mechanical movement that can lead to work related health problems (tendonitis). All the procedures previously described have low levels of efficiency, reproducibility and repetitiveness, and they also have low efficiency of extraction of the contaminants of interest.
In the document of de R. Niehaus, B. Scheulen, H. W. Dürbeck. (1990), Sci. Total Environ, 99:163-172. “Determination of airborne polycyclic aromatic hydrocarbons using a filter/adsorbed combination”, it is described a glass apparatus for the extraction of analytes from a PUF, by manual compression and decompression of a PUF immersed in organic solvent. The glass apparatus has a cylindrical form, surrounded by a concentric double sleeve, with a superior and inferior opening for hot water circulation inside the sleeve as a manner to increase the temperature in the cylinder and facilitate the extraction of analytes from the PUF. The investigation compares the efficiency of the traditional procedure with this new concept of extraction with solvent, using manual compression and decompression of a PUF. The work does not mention the automatization of any step of the process, or the optimization of the extraction procedure considering frequency of compression and decompression, extraction program (intervals between pressure application and pauses and total time of extraction), reproducibility, repetitiveness, quantity and sequence of solvents, and also the consideration of using solvent sweeping, among others.
As a consequence, it is necessary to automatize the extraction procedure, to allow the reduction of solvent volume to milliliters, the time to minutes and to obtain superior extraction efficiencies, and notably improving the reproducibility and security of operation, all factors that also lead to an important reduction of costs
The objective of this work is to develop a system of extraction of organic chemical compounds with toxic properties, such as Polycyclic Aromatic Hydrocarbons (PAHs) and Polychlorinated Biphenyls (PCBs), contaminants present in gaseous atmospheric samples (ambient air). The air samples are made up of a solid phase mixture consisting of particulate matter (PM), and a gaseous phase. The devices for taking air samples collect the samples on different types of filters, using polyurethane foam filters (PUF) to retain the gaseous phase, which is extracted using organic solvents. The invention is aimed to develop a mechanical and automatic method to extract analytes from those filters, in order to increase the extraction efficiency, and the reproducibility and repetitiveness of the analytical procedure; using a reduced volume of solvents and shorter time of extraction (cost reduction).
The automatic extraction system of gaseous atmospheric contaminants (for example PAHs PCBs) retained in PUF, comprises two devices with complementary functions:
The first one is an extraction device, which allows the extraction of chemicals of interest using a sequence of organic solvents where the PUF must be immersed. The process of extraction is based on compression and decompression cycles of the PUF using a mechanical-pneumatic piston, which is assisted by valves and oil-free compressors that are regulated by a PLC, which permits the automatic programming of the desired sequence to achieve maximum extraction efficiency. The device design takes into account luminous and acoustic security signals to indicate the end of the process, and also filters and eliminators of possible residues that could contaminate the extraction process. This device is useful to prepare the sample material (PUF) for gases present in atmospheric aerosols, to clean the PUF before usage in sampling and after sampling, and also to extract the compounds of interest retained in the filter. The second device, complementary to the previous one, consists of a hermetic container with entrance and exit valves which allow drying the cleaned PUF, from the previous process, by means of solvent sweeping with hot ultra-pure gaseous N2, eliminating the solvent to obtain a dry PUF. The process of cleaning a drying of the PUF is chromatographically certified and the PUF is stored in a hermetic container to avoid posterior contamination.
None of these equipments can be found in the market today. The original and automatized form of extraction of analytes from those PUF filters allows overcoming many of the typical deficiencies of the traditional systems and is a step forward in the state of the art related to extraction systems for solid samples, and especially for the previously described use.
Therefore, one of the main objectives of the present invention is to provide an automatic extraction system of gaseous atmospheric contaminants (like PAHs and PCBs) with toxic properties, from polyurethane foam filters (PUF) that comprises:
Wherein, the automatic extraction device comprises:
The mechanic-pneumatic piston permits to carry out the procedure of compression and decompression, this is accomplished by compression of ambient air using an oil-free pressure pump with Teflon membrane, which sends the compressed air through rapid connection tubes of the entrance valve in the piston; the lubrication of the piston is accomplished with a minuscule layer of oil formed on the piston rod, which comes from an oil deposit that allows the formation of an air aerosol containing very small oil particles in suspension. Two measures have been implemented to avoid any possible contamination from the oil of the system: the first one lies in the Teflon fastener located at the inferior end of the piston rod, which has a small sealed conicity in its superior piece, thus the conicity traps any possible drop from the layer of oil that might fall from the piston rod and avoids the contamination of the inferior end of the Teflon fastener; besides, the two parts that form the Teflon fastener are independent, consequently the contamination avoidance by this route is guaranteed, preventing the accidental contamination of rod of the glass compression blade that works over the PUFs; and the second measure is an oil trap located at the end of the tube that connects the rapid connection of the exit valve for compressed air of the piston with the trap; this washable and takedown trap is connected to an exit to eliminate the residual compressed air from the system to the exterior in a definitive manner; furthermore, the pneumatic piston has a regulation screw at the entrance and exit of the compressed air, those screws can mechanically regulate the movement of the piston rod and thus, fit the glass container for PUF extraction to different types of PUF (different sizes and densities), to different extraction solvents volumes, and different extraction procedures as well; this regulation can also control the magnitude of pressure applied to the PUF during the compression and expansion steps with the purpose of improving the efficiency of extraction; the mechanical-pneumatic piston uses compressed air to work, hence an exit tube transports the pressurized air to the piston entering through the valve, the return air exits through the valve and is leaded by a tube to the entrance in the control unit; to lubricate the piston, a device mixes the air, which has been compressed by the oil-free pressure pump with Teflon membrane, with a small amount of oil, the air thus prepared is transported to an solenoid valve, which is connected to an exit tube directed to the piston, the residual air that is discarded once has passed through the piston, exits the control unit through a tube and reaches the oil trap.
The control unit controls numerous solenoid valves, which permit to perform the movement of the piston by means of a PLC, this digital microprocessor has a LCD screen and allows the programming of different PUF extraction procedures by means of increasing the compression, based in a higher or lower pressure of the piston controlling the amount of air being compressed, furthermore the control unit has a series of electronic elements such as differentials, acoustic and luminous alarms that indicate the ending of an operation sequence and thus they permit to determine the time intervals for pressure versus pauses, and the total time of extraction; it allows the use PUFs with different thickness and/or densities; it allows additionally compressing the PUF to leave it as free as possible of extraction solvents, among others.
The metallic support consists of a cylindrical duraluminium support screwed to an iron base inserted in a plastic platform, which allows fixing the mechanical-pneumatic piston to the cylindrical fastener of the extraction system; the cylinder has in its upper part a fastener screw, which allows the regulation of the height at which the fastener support of the mechanical-pneumatic piston will be placed; the mechanical-pneumatic piston is screwed and secured to the cylindrical support on a small sheet metal, regulation screws allow controlling the movement of the piston rod; plastic circular clamps support the glass container for PUF extraction, from its upper and also from its lower part; the plastic circular clamps have two parts, one that surrounds the cylinder, with a winged thread bolt for fastening and security and a second part that surrounds the glass container for PUF extraction.
The glass container for PUF extraction is built of borosilicate glass and has a mouth that permits the insertion of the PUF in the extraction system; this mouth is a ground glass conical female which fits an upper part consisting in a ground glass conical male that allows the hermetic closure of the extraction container to avoid solvent spills during the extraction; also and to avoid overpressures produced by the evaporated solvent during the process of compression and expansion of the PUF, the upper part is provided with a Teflon valve that can be opened at will during the process; furthermore, to introduce new portions of solvent or to change the extraction solvent, the same upper part is provided with a ground conical female, which has a ground conical male glass lid that allows the hermetic closure of the extraction container anew, once such solvent has been introduced; a glass male mouth with exterior thread permits joining the Teflon piece that works as guide for the rod of the compression blade so it can be inserted and moved in the right form and vertically inside the body of the glass container for PUF extraction; once the PUF has been extracted, the extraction solvent must be removed from the extraction container, for that purpose it is provided a Teflon valve joined to a ground glass conical male that allows a direct connection to the extraction container, thus when the Teflon valve is opened, the liquid is poured directly into a distillation round bottom flask that has a mouth compatible with the ground conical glass male, this glass male has an open hose connector, which permits to even up the pressures during the elimination of the extraction solvent from the extraction container, facilitating the flow of liquid to the distillation flask.
The drying device consists in a container for drying the PUF and a line to supply hot ultra-pure nitrogen (N2).
The drying device for the PUF comprises a lid that has an upper part with a wedge for coupling with the lower part and it has a groove where it can be placed a silicone o-ring. This o-ring is useful to hold tight and hermetic a transparent glass that is adjusted in the wedge between the upper and lower part of the lid and it is used as a window to observe the drying process; the lower part also has a groove to place a silicone o-ring similar to the previous one in form and function; in the center of the glass window there is a metallic male with an interior and exterior sweglook thread for connection to the hot N2 line by means of a sweglook nut, which allows the entrance of the N2 to the drying container for the PUF; this N2 entrance connection is hermetically sealed against the glass by means of a lock nut that has an exterior thread which permits to screw it to the metallic male, furthermore both pieces are sealed against the glass using o-rings with appropriate diameters; for the drying procedure, the PUFs are placed on a PUF support located inside the lower part of the drying container for the PUF, or body of the container; the lid and the body of the container are coupled by means of metallic fasteners, which can be adjusted to achieve maximum tightness, and consequently obtain an hermetic sealing of the drying container for the PUF.
The line of hot ultra-pure nitrogen (N2) supply consists of a N2 cylinder with a predetermined pressure, which is reduced using a secondary manometer at 400 kPa (4 bars), a pipe with N2 at 400 kPa (4 bars) reaches an extraction hood and connected to it by means of a needle valve for coarse flow regulation, which is at the same time connected to a needle valve for fine flow regulation; the line for hot nitrogen N2 supply is at the same time connected and regulated by the valve, the thermal regulation (9) of this line is achieved thanks to a blanket provided with electric resistances regulated and controlled by a thermostat, which keeps the temperature of this line at approximately 70° C.; in this manner the drying of the PUF is accomplished by means of removing the residual solvent retained in the PUF using a process of sweeping with N2, the heating of the N2 helps to evaporate the solvent and as a consequence notably reduces the drying time, and the N2 that has passed through the PUF is eliminated by a regulation valve through a hose to the interior of the extraction hood.
The PUF support consists of a first support for the PUF of a first diameter which rests on a metallic grid with perforations of 1 cm; the first support is supported by cylindrical legs that separate it from the second support which has the same dimensions of the first one, but used for PUFs with a second diameter, smaller than the first diameter; this second support is also rested on some cylindrical legs to separate it from the bottom of the drying container for the PUF.
The other main objective of this invention is to provide an automatic method of extraction of gaseous atmospheric contaminants (for example PAHs and PCBs) with toxic properties, from polyurethane foam filters (PUF) where they are retained, that is composed of the following steps:
The chemical compounds extraction step using a sequence of organic solvents where the PUF must be immersed, by means of an extraction process based in compression and decompression cycles of the PUF; it is accomplished by means of a mechanical-pneumatic piston; a control unit for solenoid valves, which allow controlling the piston movement; a metallic support; and a glass container for PUF extraction fastened to such metallic support. Such mechanical-pneumatic piston permits to carry out the compression and decompression procedure, this is accomplished by compression of ambient air using an oil-free pressure pump with Teflon membrane, which sends the compressed air through tubes to the rapid connection of the entrance valve in the piston; the lubrication of the piston is accomplished with a minuscule layer of oil formed on the piston rod, which comes from an oil deposit that allows the formation of an air aerosol containing very small oil particles in suspension. Two measures have been implemented to avoid any possible contamination from the oil that works over the PUFs; and the second measure is an oil trap located at the end of the tube that connects the rapid connection of the exit valve for compressed air of the piston with the trap; this washable and takedown trap is connected to an exit to eliminate the residual compressed air from the system to the exterior in a definitive manner; furthermore, the pneumatic piston has a regulation screw at the entrance and exit of the compressed air, those screws can mechanically regulate the movement of the piston rod and thus, fit the glass container for PUF extraction to different types of PUF (different sizes and densities), to different extraction solvents volumes, and different extraction procedures as well; this regulation can also control the magnitude of pressure applied to the PUF during the compression and expansion steps with the purpose of improving the efficiency of extraction; the mechanical-pneumatic piston uses compressed air to work, hence an exit tube transports the pressurized air to the piston entering through the valve, the return air exits through the valve and is leaded by a tube to the entrance in the control unit; to lubricate the piston, a device mixes the air, which has been compressed by the oil-free pressure pump with Teflon membrane, with a small amount of oil, the air thus prepared is transported to an solenoid valve, which is connected to an exit tube directed to the piston, the residual air that is discarded once has passed through the piston, exits the control unit through a tube and reaches the oil trap.
The control unit controls numerous solenoid valves, which permit to perform the movement of the piston by means of a PLC, this digital microprocessor has a LCD screen and allows programming of different forms of PUF extraction by means of increasing the compression, based in a higher or lower pressure of the piston controlling the amount of compressed air, furthermore the control unit has a series of electronic elements such as differentials, acoustic and luminous alarms that indicate the ending of an operation sequence and as a result they permit to determine the pressure time intervals versus pauses, and the extraction total time; it allows the use PUFs with different thickness and/or densities; it allows the compression of the PUF to leave it as free as possible of extraction solvents, among others.
The metallic support consists of a cylindrical duraluminium support screwed to an iron base inserted in a plastic platform, which allows fixing the mechanical-pneumatic piston to the cylindrical fastener of the extraction system; the cylinder has in its upper part a fastener screw, which allows the regulation of the height at which the fastener support of the mechanical-pneumatic piston will be placed; the mechanical-pneumatic piston is screwed and secured to the cylindrical support on a small sheet metal, regulation screws allow to control the movement of the piston rod; plastic circular clamps support the glass container for PUF extraction, from its upper and also its lower part; the plastic circular clamps have two parts, one that surrounds the cylinder, with a winged thread bolt for fastening and security and a second part that surrounds the glass container for PUF extraction.
The glass container for PUF extraction is built of borosilicate glass and has a mouth that permits the insertion of the PUF in the extraction system; this mouth is a ground glass conical female which fits an upper part consisting in a ground glass conical male that allows the hermetic closure of the extraction container to avoid solvent spills during the extraction; also and to avoid overpressures produced by the evaporated solvent during the process of compression and expansion of the PUF, the upper part is provided with a Teflon valve that can be opened at will during the process; furthermore, to introduce new portions of solvent or to change the extraction solvent, the same upper part is provided with a ground conical female, which has a ground conical male glass lid that allows the hermetic closure of the extraction container anew, once such solvent has been introduced; a glass male mouth with exterior thread permits joining the Teflon piece that works as guide for the rod of the compression blade so it can be inserted and moved in the right form and vertically inside the body of the glass container for PUF extraction; once the PUF has been extracted, the extraction solvent must be removed from the extraction container, for that purpose it is provided a Teflon valve joined to a ground glass conical male that allows a direct connection to the extraction container, thus when the Teflon valve is opened, the liquid is poured directly into a distillation round bottom flask that has a mouth compatible with the ground conical glass male, this glass male has an open hose, which permits to even up the pressures during the elimination of the extraction solvent from the extraction container, facilitating the flow of liquid to the distillation flask.
The step for drying the cleaned PUF, by means of solvent sweeping with hot gaseous ultra-pure N2, eliminating the solvent until the PUF is dry; it is accomplished with the use of a drying container for the PUF; and a line for hot gaseous ultra-pure nitrogen (N2) supply.
The drying container for the PUF comprises a lid that has an upper part with a wedge for coupling with the lower part and it has a groove to accommodate a silicone o-ring. This o-ring is useful to hold tight and hermetic a transparent glass that is adjusted in the wedge between the upper and lower part of the lid and it is used as a window to observe the drying process; the lower part also has a groove to accommodate a silicone o-ring similar to the previous one in form and function; the glass window has on its center a metallic male with an interior and exterior sweglook thread for connection to the hot N2 line by means of a sweglook nut, which allows the entrance of the N2 to the drying container for the PUF; this N2 entrance connection is hermetically sealed against the glass by means of a lock nut that has an exterior thread which allows screwing it to the metallic male, furthermore both pieces are sealed against the glass using o-rings of appropriate diameters; for the drying procedure, the PUFs are placed on a PUF support located inside the lower part of the drying container for the PUF, or body of the container; the lid and the body of the container are coupled by means of metallic fasteners, which can be adjusted to achieve maximum tightness, and consequently to obtain an hermetic sealing of the drying container for the PUF.
The line of hot ultra-pure nitrogen (N2) supply consists of a N2 cylinder with a predetermined pressure, which is reduced using a secondary manometer at 400 kPa (4 bars), a pipe with N2 at 400 kPa (4 bars) reaches an extraction hood and connects to it by means of a needle valve for coarse flow regulation, which is at the same time connected to a needle valve for fine flow regulation; the line for hot nitrogen N2 supply is at the same time connected and regulated by the valve, the thermal regulation of this line is achieved thanks to a blanket provided with electric resistances regulated and controlled by a thermostat, which keeps the temperature of this line at approximately 70° C.; in this manner the drying of the PUF is accomplished by means of removing residual solvent retained in the PUF using a process of sweeping with N2, the heating of the N2 helps to evaporate the solvent and as a consequence notably reduces the drying time, and the N2 that has passed through the PUF is eliminated by a regulation valve through a hose to the interior of the extraction hood.
The PUF support consists of a first support for the PUF of a first diameter which rests on a metallic grid with perforations of 1 cm; the first support is supported by cylindrical legs that separate it from the second support which has the same dimensions of the first one, for the PUFs with a second diameter, smaller than the first diameter; this second support is also rested on some cylindrical legs to separate it from the bottom of the drying container for the PUF.
Once the PUF has been cleaned and dried, it is necessary to store it so it does not get contaminated before it reaches the sampling location.
The automatic extraction equipment can be used for the extraction of PUFs which come from an ambient air sampling event, as well as to clean a PUF from residual contaminants originated from the manufacture process before its use in field sampling, and also as a form to guarantee that the PUF is clean at the time of taking the atmospheric sample.
The automatic extraction system for gaseous atmospheric contaminants (for example PAHs and PCBs) retained on PUF, comprises two devices with complementary functions.
The first one is an extraction device, which allows the extraction of chemicals of interest using a sequence of organic solvents where the PUF must be immersed. This device consists in an automatic extraction system for chemical compounds at trace level, contaminants present in gaseous atmospheric samples (ambient air).
The second device, complementary to the previous one, is a drying device for the PUF, which consists of a hermetic container with entrance and exit valves to allow drying the cleaned PUF, obtained from the previous process, by means of solvent sweeping with hot ultra-pure gaseous N2, eliminating the solvent until the PUF is dry. The process of cleaning and drying of the PUF is chromatographically certified and the PUF is stored in a hermetic container to avoid posterior contamination.
As schematically shown in
All the control system (003) of the solenoid valves (not shown) which permit to perform the movement of the piston is done with the help of a PLC, this digital microprocessor has a LCD screen and allows programming different PUF extraction procedures by means of increasing the compression, based on a higher or lower pressure of the piston controlling the amount of air being compressed. Furthermore, the pneumatic piston has a regulation screw at the entrance (305) and at the exit (306) of the pressurized air, the movement of the piston (106) rod can be mechanically regulated with these screws and in this form the glass container for PUF extraction (111) can be adjusted to different PUF characteristics (different sizes and densities); to different volumes of extraction solvent, and also to different extraction procedures. With this regulation it can also be modified the intensity of the pressure applied to the PUF during the compression and expansion steps, as a form to optimize the extraction efficiency. The control system as a whole, thus allows determining the pressure times versus pauses, and the total extraction time; it allows using PUFs with different thickness and/or density; it allows to additionally compressing the PUF to leave it as free as possible of the extraction solvent, among others. All this set of automatized actions permit, among other things, to significantly increase the possibility of optimizing the extraction procedure, taking into account parameters such as frequency of compression and decompression, program of extraction, reproducibility, repetitiveness, amount and sequence of solvents and solvents polarities, in a systematic and friendly manner.
The analytical procedures associated with this invention derive from the following activities:
The PUFs are commercialized with a great number of contaminants that are inherent to their fabrication process. This contamination is so important that the PUF in this condition (dirty) is not suitable to be used as an adsorbent filter in the sampling of atmospheric aerosols, in particular to retain organic chemical compounds in gaseous state present in this type of samples. In this way, before using the PUF for this purpose, it must be decontaminated, put differently it must be cleaned and its cleanliness must be certified by chromatographic techniques that assure no residual substances are left that could prevent a good interpretation of the chromatograms of the real samples once these have been extracted to identify and quantify the analytes of interest. The developed invention precisely consists in an automatic system for PUF (100) extraction, which can be used either for the cleaning procedure as well as the extraction of the PUF. For the cleaning procedure of the PUF, previous to its use under monitoring conditions, it is used a sequence of extraction solvents, for 4 steps of 15 minutes each. Each step is composed of 3 cycles of compression and decompression of the PUF lasting 5 minutes each; starting the cleaning in the first step using 80 ml of water with Mili-Q quality, and then, in the second step using 80 ml of acetone, in the third step using 80 ml of toluene, and finishing the last period with 80 ml of n-hexane.
The extraction procedure starts with the addition of 80 ml of the first solvent that is the most polar one: water (Mili-Q quality) directly in the glass container for PUF extraction (111). After this, the PUF is picked with tweezers and carefully placed in the interior of the same container (111). Then, the upper part (904) of the extraction container (111) is held and introduced through the mouth of the glass male (901) that has attached to it the Teflon piece (109) that works as a guide for the rod of the compression blade (108) so this can be introduced and moved in a proper and vertical form in the interior of the body (906) of the glass container for PUF extraction (111) which fits a ground glass conical male NS64/46, that allows hermetically closing the container.
The extraction adjustment depends on the type of cleaning to be performed, where cycles of compression and decompression of the PUF submerged in the different solvents permit to extract from this solid support (PUF) the impurities previously described. Once the extraction process has ended, the extracted solution is poured in a distillation flask and the solvent is reduced by evaporation in a rotary evaporatorator 30° C. of temperature and under vacuum, until a final volume of 1-2 ml. The extract obtained in this step is poured in a 5 ml conical vial in a quantitative form and the excess volume is reduced again, this time under a nitrogen current until nearly dryness. Afterwards, it is dissolved again in 50 μl of solvent and 1 μl of this solution is injected in capillary gas chromatography equipment (GC), using an appropriate chromatography detector, according to the contaminants (FID, ECD, MS) nature, to verify if the cleaning procedure has been carried out successfully. The judgment to determine if this objective has been achieved is resolved by analyzing the size (area under the curve) of the chromatographic peaks obtained from the extract injected in the GC. The area previously mentioned must be inferior to the threshold defined as the maximum allowed accomplishing the PUF cleanliness. This chromatographic analysis permits to certify each PUF by separate and guarantee its use under field conditions in an atmospheric sampling; furthermore it can be used later for the quantification of the analytes of interest adsorbed in the PUF, after the monitoring has been performed.
The process involved in this invention is a procedure for extraction of ambient air samples, where organic chemical contaminants present in the MP as well as a gaseous phase are considered, grouped under the category of semivolatile organic compounds (SVOCs). In the particular case of the equipment developed in this invention, the objective is to extract from a filter named PUF, where the gaseous phase of the aerosol sample is retained, compounds with toxic properties such as Polycyclic Aromatic Hydrocarbons (PAHs) and Polychlorinated Biphenyls (PCBs) and also other families of SVOCs. Once the sampling cartridge has arrived to the laboratory, the PUF is taken out of the PUF compartment with the use of tweezers and carefully placed in the extraction container for the PUF (111), to which previously had been added the first extraction solvents and a internal standard solution to control losses in this procedure and as a manner to be able to calculate the exact concentration of analytes of interest. For this purpose, the PUF is subjected to an extraction with organic solvents of different polarity, where compression and decompression cycles of the PUF submerged in the different solvents allow extracting the analytes of interest from this solid support (PUF), during 4 periods of 15 minutes each. Each step is composed of 3 compression and decompression cycles of the PUF lasting 5 minutes each; initiate the extraction using 80 ml of Toluene in the first three steps, and end the extraction using 80 ml of n-hexane in the last step. After each cycle, the solvent is poured from the extraction container for the PUF (111), by means of opening the Teflon valve joined to a conical ground glass male, which permits to connect a distillation round bottom flask directly to the extraction container, in this way when the Teflon valve is opened, the solvent is poured directly to a distillation flask that has a mouth compatible with the dimensions of the conical ground glass male, this glass male also has an open hose connector, which permits to even up pressures during removal of the extraction solvent from the extraction container, making easier the flow of the liquid to the distillation flask. At the end of the extraction, 320 ml of solvents will be accumulated in the distillation flask containing the analytes extracted from the PUF. The volume of the solvent contained in the distillation flask is reduced by evaporation in a rotary evaporatorator at 30° C. of temperature and under vacuum, until reaching a final volume of 1-2 ml. The extract obtained in this step is poured to a conical vial of 5 ml in a quantitative manner and the excess volume is reduced again, this time under nitrogen current until nearly dryness. Subsequently, it is dissolved once more in 100 μl of solvent and subjected to a purification process using packed column chromatography, with the purpose of eliminating unwanted compounds and selecting only those families of interest organic compounds. Once the fractions of interest have been obtained, the excess volume is reduced again under nitrogen current until nearly dryness. Afterwards, the extract is dissolved once more with 30-50 μl of solvent according to the concentration level and 1 μl of the extract is injected in the capillary gas chromatography equipment, using an appropriate chromatography detector, according to the nature of the contaminants (FID, ECD, MS) to carry out the identification and quantification of the analytes of interest.
As soon as a clean and dry PUF has been obtained, it is necessary to store it in such a way that it is not contaminated before reaching the sampling location. For this purpose, it is necessary to store the PUF wrapped in aluminium foil previously conditioned. The cleaning treatment for the aluminium foil consists in washing both faces of the material with acetone and drying it in a hood under absolute cleanliness conditions. Once the PUF has been wrapped in clean aluminium foil, it must be stored in a glass container with a hermetic lid. For greater security, the glass container is also wrapped in aluminium foil and stored in darkness. Only in this manner it can be assured a safe, and free of contamination storing of the PUFs before its final use in an atmospheric monitoring.
| Number | Date | Country | Kind |
|---|---|---|---|
| 588-2006 | Mar 2006 | CL | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/ES2007/070055 | 3/15/2007 | WO | 00 | 9/16/2008 |
