MXPA02000355A - Cold-plasma treatment of seeds to remove surface materials - Google Patents

Abstract

Seeds are treated in a cold plasma in a reaction chamber to etch the surface of the seeds to remove surface materials, such as fungicides and insecticides, or to disinfect the surfaces. The cold plasma process is carried out using etch gases which do not harm the seeds and for selected periods of time sufficient to remove surface materials without necessarily affecting the viability of live seeds after treatment. Tumbling the seeds while exposing the seeds to the plasma allows the surfaces of the seeds to be etched uniformly.

Description

PLASMA TREATMENT FRIED IN SEEDS TO REMOVE SURFACE MATERIALS FIELD D I: THE INVENTION This invention is generally related to the field of plasma processing of materials and particularly to the treatment of plasma in seeds.

BACKGROUND OF THE INVENTION Seeds produced by commercial seed companies are commonly treated with insecticides and fungicides to improve the survival rate and germination of the planted seed. Fungicides and pes ticides can be applied to the seed in a dry or wet form. A dry treatment involves the application of the active ingredient in an inert powder that can contain additives to prevent particle agglomeration or "adhesions" to improve adhesion to the surface of the seed. The adhesion of the dry particles to the surface of the seed is a complex process that involves molecular forces and physically traps small particles. Both the molecular forces and the physical entrapment of the particles depend strongly on the size of the particle. The molecular forces of adhesion are very high per unit area and depend essentially on the surfaces that are in current contact. The rough surfaces have areas of low contact and, as a consequence, the forces Molecules generally play a less important role in the adhesion between said surfaces. The physical entrapment of the active particles is also related to the particle size. The porosity of the seed surfaces should be comparable with the average particle size to obtain an efficient trapping of the seed particles. Wetting agents can also be used to allow the active powder materials to be applied to the seeds using a mixture treatment. These treatments are carried out in a low-volume, low-volume liquid form, but still have the disadvantage that the seeds must generally be dried afterwards, which increases the cost of the treatment process. The result of these treatments, in the way they are carried out, is a fairly high concentration of active ingredients on the surfaces of the seed, which, of course, improves the usefulness of these seeds when planted in the normal course. However, for various reasons, large quantities of treated seeds may or may not be used to plant themselves within a period of time when the seeds have been treated. Very often, seed companies treat more seeds than they expect to be used during a planting season to ensure the availability of seeds in a subsequent season if there is an intervening harvest failure. In most years, the additional seed is not planted. During Prolonged storage periods of time, the active ingredients in the surface treatments may degrade, leading to the formation of secondary compounds that are not active for the intended purpose of the surface treatment. However, these pollutants can have quite high levels of toxicity. Thus, said treated aged seed is not acceptable for use as seed for planting or for human or animal food. The chemical removal in wet of the contaminate: it is by fungicides, pesticides or insecticides of the seeds could require large quantities of liquids (water, solvents or gánicos) and expensive drying technologies. In addition, the combination of prolonged periods of time and treatments of liquids can facilitate the penetration of the chemicals contained in the surface inside the seeds, potentially damaging or killing the seeds. Seed with cracks or embryos exposed, as by damage caused by threshing or by ventilation, can absorb even higher amounts of the toxins contained in the surface.

SUMMARY OF THE INVENTION According to the present invention, the seeds are treated by exposing them to a cold plasma to chemically attack the surface of the seeds to remove the surface materials, such as fungicidal or insecticidal chemicals, and / or to disinfect the surface. The cold plasma chemical attack process can carried out using chemical etching gases that are not harmful to the seeds themselves, and for periods of time sufficient to remove surface materials such as chemicals or other contaminants without significantly affecting the viability of the seeds after treatment. The plasma treatment processes can be carried out under conditions that allow the removal of a selected thickness of surface material from the seeds, with precision. In addition, because the plasma treatment process is carried out under dry conditions, there is no need to add moisture to the seeds during the treatment process, and the moisture can still be removed from the seeds during the plasma treatment. A plasma process In accordance with the invention, it has several advantages over liquid-based treatment processes for the detoxification of seeds or the removal of surface materials thereof, because large amounts of liquid, such as solvents, are not available. Necessary, and only small amounts of gas phase materials are required, the process has much less environmental impact than liquid-based processes. Due to the very low pressures under which plasma reactions develop, minimal amounts of plasma gases are required to support the plasma discharge.

The process conditions of the plasma can be selected so that the species of pia ma penetrate and interact only with the uppermost layers of a seed, without affecting the rest of the same. Plasma species can efficiently interact with surface ca- pable molecules, and despite the nature of these molecules, molecular (chemical attack) fragmentation of surfaces can be carried out. Various plasma process parameters, such as plasma coupled energy, gas pressure and trituration time, can be selected to suit the etching rate and the nature of the gas phase components that result after the treatment. Molecular molecules or fragments that result from the chemical attack process usually so? Gas phase components that can be easily removed from the system. Depending on the nature of the plasma gases used, which may be inert or reactive gases (eg, argon, CF4, air, oxygen, water vapor, etc.), rates of chemical attack and the chemical nature of the components resulting volatiles (toxic or non-toxic derivatives) can also be controlled or adapted to the specific process requirements. The gas phase components generated by the plasma resulting from the process can be easily trapped and used if they constitute hazardous waste or, if not, can be released into the environment. In a preferred method for treating seeds according to the invention, the seeds to be treated are put into a reaction chamber, the reaction chamber is evacuated at the base level, and a selected source gas is supplied to the chamber reaction and a selected pressure is established in it. The gas can be provided from an external gas source and selected to produce a desired etching characteristic and not a deposit during the process. The gas can constitute water vapor emitted from the seeds themselves as the pressure within the reaction chamber is reduced below the atmospheric pressure.

In addition, multi-step processes can be carried out. For example, initial cold plasma may be ignited in the water vapor that evolved from the seeds, and the seeds may be exposed to this plasma for a selected period of time.

Then an external gas can be introduced into the reaction chamber and the cold plasma ignited in the external source gas. The gas in the chamber can be ignited by coupling RF energy to the gas in the chamber in several ways, including capacitive coupling and inductive coupling. In addition, RF energy can be coupled in pulses to the plasma in the reaction chamber. Virtually any type of seed can be treated in accordance with the present invention. The invention has particular application to corn seeds which are conventionally treated with insecticides and funcids. After the treatment according to the present invention to chemically attack with plasma the chemicals found on the surface of the same, corn and other seeds can be used for animal feed, or can be re-treated with insecticides, etc. , later so that the miles are properly treated to be used later in a planting season The gases that can be used according to the present invention can be any of the different reactive gases that can perform a chemical etching of plasma in a cold plasma process. For example, gases may be used in the process, including but not limited to argon, CF4, air, oxygen, water vapor, and mixtures of these. The cold plasma treatment according to the present invention can also be employed to reduce the amount of foreign flakes and dust that are intermixed with the seed by physical ablation of said materials or by oxidation, thereby providing a seed product with cleaner volume with less dust (possibly carrying toxic particles) than is typically the case with seeds of normal volume. A chemical plasma cold attack process according to the invention can also be carried out on both treated and untreated seeds, to remove all or part of the seed surface layers for various purposes, including affecting germination rates. of the seed, changing, for example, the water absorption characteristics of the seed surfaces. The process of chemical etching with plasma can be carried out to remove the selected depths of the surface layers of the seed, including, if desired, the total removal of the pericarp.

Other objects, features and advantages of the invention may be apparent from the following detailed description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic view of the plasma reactor system for carrying out the present invention. Figure 2 is a chromatogram of the surface chemicals detected in corn seeds before and after the plasma treatment according to the invention, Figure 3 is a portion of the chromatogram of Figure 2 showing the peak for d-4-tetrahydrophthalimide Figure 4 is a portion of the chromatogram of Figure 2 showing the peak for Captano 50W.

DETAILED DESCRIPTION OF THE INVENTION The present invention is related to the removal of cold plasma from material of the > surfaces of the seeds. If desired, said process can be carried out without significantly affecting the viability of the seeds. Cold plasmas are non-thermal plasmas without equilibrium. The temperatures of the plasmas are atmospheric temperatures close to normal and generally well below the boiling point of water. In comparison, hot plasmas are thermal plasmas with equilibrium. In a cold plasma, the kinetic energy of the electrons in the plasma is high, while the kinetic energy of the molecular and atomic species is low. On the other hand, in the hot plasma, the cynenetic energy of all species is high. As a result, organic materials would be damaged or destroyed in hot plasma. It has been found, according to the present invention, that the treatment of appropriate cold plasma of living material, such as seeds, not only does not destroy the seeds, but allows the seeds to remain viable, so that they can germinate when planted under appropriate conditions. Referring to Figure 1, an exemplary cold plasma reactor system, which can be used to carry out the invention, is generally shown at 10. Reactor system 10 includes a cylindrical reaction vessel 11 (eg formed Pyrex® glass, 1 m long and 10 cm internal diameter) which is closed at both ends by means of disc-shaped stainless steel end seal assemblies 12 and 13. The sealing assemblies 12 and 13 are mounted on mechanical supports 16 and 17 which couple the sealing assemblies 12 and 13 to allow rotation of the reaction vessel 11 about its central axis, i.e. the central axis of the reaction vessel. cylindrical. Ferrofluidic feeders 19 and 20 of hollow cylinder extend through the assembly assemblies 12 and 13, respectively, to allow the introduction of the gas into the reaction chamber and the exit of the gas out of the same. An outer, copper, outer, semi-cylindrical electrode 21 is connected to the power source 22, and a copper electrode 24, similar, lower, cylindrical exterior, is connected to ground (illustrated at 25). The two electrodes 21 and 24 conform closely to the cylindrical exterior of the reaction vessel 11, are separated ligthly from it, and together they extend over the outermost outermost portion of the reaction vessel, but separate from each other at their edges. enough distance to avoid loading or discharging between the two electrodes 21 and 24. The above electrode arrangement is only one example of the many arrangements of appliances that can be used to couple power to the plasma. For example, a central internal electrode (not shown) can be extended within the reaction chamber along the central axis instead of using external electrodes. The present invention allows the surface of the seeds to be chemically etched with cold plasma provided from a variety of source gases. The source gases may be contained in containers 26, for example, storage tanks. The source gases in the containers 26 can be a variety of gases (eg, argon, ammonia, air, oxygen, CF4, etc.) which are typically compressed under pressure. The source gas pu may also be provided from other sources, solid or liquid, which are properly volatilized, and may comprise aerosols of liquid or solid particles, such as water vapor, all of which will be referred to herein as "gas". The gas flow of a source cylinder 26 can be controlled by needle valves and pressure regulators 27 that can be operated manually or automatically. The gas passing through the control valves 27 is transported along the supply lines 28, via flow rate controllers 30 to a gas mixing chamber 31 (eg, preferably stainless steel). . An MKS 32 pressure gauge (eg, Baratron) is connected to the mixing chamber 31 to verify the pressure of the same. A supplementary valve 33 is connected to the mixing chamber 31 to allow selective ventilation of the chamber as necessary. The mixing bed 31 is connected to the feeders 19 which are directed to the interior of the reaction vessel 11. For example, a controller 34 can be used to control an activation motor 35 which is coupled to the reaction vessel 11 to provide the controlled activation of the reaction vessel 11 in rotation, The reaction vessel 11 can be rotated by the drive motor 35 at various selected rotational speeds (eg, 30-200 rpm). The second feeder 20 is connected to a camera ejection 37, which is selectively coupled by means of ejector valves 38, 39 and 40, to ducts for expelling, to the atmosphere or to an appropriate recovery system or other waste route, the exhaust gases within the chamber of expulsion 37. A liquid nitrogen trap 42 can be connected to an ejection line 43, which extends from chamber 37 through means of a stainless steel pipe 44. The trap 42 can be formed, for example, of stainless steel (25 mm internal diameter). A mechanical pump 45 is connected through a large cross-sectional valve 46 by means of a tube 47 to the trap 42 to selectively provide a vacuum suction in the reactor system 10 to evacuate the interior of the reaction vessel. at a selected level. It is preferred that the vacuum pump and associated connections allow the pressure in the reaction chamber within the vessel to be selectively reduced to 30 mT. The power source 12, preferably, is an RF energy source (eg, 13.56 MHz, 1,000W) which, when activated, provides RF energy between the electrodes 21 and 24 to capacitively couple the RF energy to the gas in the reaction chamber inside the reaction vessel 11. Conventional coils for inductively coupling the RF energy to the plasma can also be used (eg, a coil that extends around the reaction vessel 11). A Farraday cage 50 is preferably mounted around the outside of the reaction vessel to provide a protection Rf and to prevent accidental physical contact with the electrodes. The reactor vessel can be rotated by the drive motor 35 at various speeds of selected rotation (for example, 30-200 rpm), and it is preferred that the vacuum pump and associated connections allow the pressure in the reaction chamber within the vessel S3 to selectively reduce to 30 mT. The following are examples of commercial parts that can be incorporated into system 10: RF energy supply 22 (Plasma Therm Inc., RTE 73, Kresson, N.J. 08053, AMNS-3000E, AMNPS-1); vacuum mechanical pump 45 (Leibold-Heraeus / Vacuum Prod. Inc., Model: D30AC, Spectra Vac nc); pressure gauge 32 (MKS Baratron, Model: 622A01TAE); digitally controlled rotation system 34, 35 (CD motor, Model 4Z528, Dayton Electric Mfg. Co., controller DART Controls Inc.). In using the plasma treatment system 10 according to the present invention, it is orally preferred that the improved cleaning by the plasma of the reactor be carried out before the treatment to eliminate possible contaminants. An exemplary cleaning step includes introducing oxygen gas from one of the tanks 26 into the reaction chamber and igniting the plasma in the gas, for example, an energy level of 300W, a gas pressure of 250 mT, an oxygen flow velocity of 6 sccm and a typical cleaning period of 15 minutes. To carry out the treatment of the seeds according to the invention, the reactor is opened to allow access to the interior of the reaction vessel 11 d by connecting one of the vacuum sealing assemblies 19 or 20 of the cylindrical reaction vessel, and inserting the seeds on the inside of the container, followed by the resealing of the assemblies in an airtight vacuum coupling with the reaction vessel 1. Sealable ports can also be provided in the sealing assemblies. The pump 45 is operated to evacuate the plasma reactor to a desired base pressure level based on the water vapor originating from the seeds or the artificially supplied plasma gases and vapors. The desired gas is then introduced from the source vessels 26, and a desired gas pressure level is established in the reaction chamber. The RF energy supply 22 is then turned on (generally, it is preferred that the energy be supplied in pulses) to ignite the plasma in the gas introduced into the reaction chamber defined by the reaction vessel 11 and the end seal assemblies. and 13. To treat the seeds, it is preferred} The activating motor 35 operates to rotate the reaction chamber 11 to stir the seeds during the plasma reaction process so that all the surfaces of the seeds are exposed to the plasma for a relatively uniform period of time for r. ermit that the surfaces of the seeds can be chemically attacked uniformly.

Because the seeds are exposed to a dry gas during the plasma treatment, there is no need to introduce additional moisture into the seeds, and due to the evacuation of the chamber to a pressure below atmospheric, some removal of moisture of the seeds during the plasma process, if desired.

After a selected period of time has elapsed to sufficiently remove a selected material from the On the surface of the seeds, the energy supply is added 22. The pump 45 then operates to evacuate the chamber to suck out the remaining source gases and any secondary product. These can be vented to the atmosphere or disposed of properly. Atmospheric air, or other selected gas, is then introduced into the chamber to bring the pressure in the reaction chamber to normal atmospheric pressure. One of the sealing assemblies 12 or 13 is then opened to allow the removal of the treated seeds. If desired, the plasma treatment processes can be stopped periodically to allow samples of the seeds to be collected for analytical and biological evaluations. In addition to the preferred RF plasma reaction apparatus mentioned above, the invention can be carried out using other plasma treatment apparatus including plasma reactors RF static inductive or capacitively coupled, CD discharge reactors and atmospheric pressure barrier discharges. Said apparatuses are not preferred for certain applications of the invention.

Static reactors can provide non-uniform treatment of seeds or other material. Discharges of atmospheric pressure usually require a narrow electrode space, and generally can not expose the surfaces of the seed (or other particulate matter) uniformly to the discharge. Additionally, due to the nature of seed particles, etc., the ability to use vacuum tight seals is limited, which can result in pollution problems. The barrier discharge processes are also less efficient due to the short ibre trajectory of the plasma particles, and consequently, the rapid recombination of the active species in the gas phase. The active species of the plasma, including charged and neutral species, have energies compatible with the chemical bonds of the organic compounds, and consequently, these species can break molecules and therefore can generate active molecular fragments, such as: atoms, free radicals, ions of any polarity, etc. These molecular fragments, aided by electrons and autumns, generate a specific gas phase and recombination reaction mechanisms that can lead to the formation of roe macromolecular molecular structures, and to the extraction of volatile molecular fragments, low molecular weight r of substrates of origin. By controlling the external plasma parameters (energy, pressure, flow velocity, etc., and internal parameters (energy distribution and neutral species, particle densities, etc.) these processes can be adapted for the purposes of the present invention so that the predominant fragmentation processes to chemically attack the seed surface material. Other factors such as molecular stresses, gas composition, and pest characteristics can significantly influence the nature of the reaction mechanisms. by plasma. Carbon tetrafluoride plasmas do not deposit fluorinated macromolecular layers under common cold RF plasma conditions due to the intense etching effects associated with the high atomic concentrations of fluorine generated by plasma. However, the presence in the gas mixture of the fluorine scavengers (eg, hydrogen) allows deposition of the macromolecular layers. There are species, which, due to their molecular structures, can never deposit macromolecular layers, such as oxygen, chlorine, ammonia, nitrogen, etc. In the present invention, source gases (including mixtures) are used under process conditions that result in the chemical etching of the surface instead of the surface deposit. As an example of the removal of the cold plasma from the surface material of the seeds according to the invention, the plasma cleaning of treated maize D with Captan 50W, a commercially available brand of agricultural fungicide, was performed in the reaction apparatus of plasma 10 as described above. The seeds were treated in a two-step process. The first step uses a plasma generated from water vapor emitted from the seeds. The second step uses an oxygen gas from an external source where the plasma is ignited. During this surface cleaning process, the following conditions were used: RF energy of 20 W; pressure in the 600 mT plasma reactor; temperature in the reactor of 25 ° C; Oxygen flow rate of 2 sccm; and treatment times of 15 or 30 minutes for the water vapor plasma and 15 minutes for the oxygen plasma. At the end of the plasma cleaning step, the corn seeds were removed from the reactor and stored in unsealed polyethylene bags until analytical work was carried out on the corn.

The control samples of maize treated with Captan and the samples of maize cleaned with plasma and tr bound with Captan were extracted with alcohol (ethanol), and the contents of the solution were analyzed by gas chromatography-mass spectroscopy (GC-MS) , to allow the Captan concentrations of the seed surfaces of the samples to be evaluated. The untreated and treated seeds (10 pieces of corn per sample) were extracted for 10 minutes with 10mL of ethyl alcohol. One μL of solution was injected into a Hewlett-Packard GC-6890 + / MSD 5973 system for gas chromatographic separation (GC) and mass spectrographic identification of the chemicals. The data obtained from the chromatographic analyzes are summarized in the following Table 1, &. * Í? * Í ¡.S- water vapor for 15 minutes followed by the treatment of water vapor plasma du 15 minutes at 67; and for the previous treatment followed by an additional oxygen plasma treatment of 15 minutes in 68. The results of these experiments show that the level of Captan of corn treated with plasma can be reduced to very b [levels]. Seeds that were timed to remove Captan from seed surfaces were then subjected to germination tests to determine the effect of plasma treatment on ^ 10 germination. The germination tests were carried out on seeds treated with Captano having a normal storage of one year; in seeds of the same lot that were treated with plasta in accordance with the present invitation to remove from the Captano service material; and semi-ones that were treated with plasma and that were later treated by Captano. The percentage of germination, range of germination for the samples and range of difference for the three types of samples under hot and cold germination conditions are shown in the following Table 2. 20 ntjfeASiBME - ,. ..

Claims (13)

1. A method of treating seeds comprising a) igniting a cold plasma in a gas from a gas source and manning the plasma under conditions that provide chemical attack by means of the plasma and not the deposit of the plasma; b) exposing the seed s to the plasma for a selected period of time to chemically etch the seed surfaces with plasma to remove the surface material from the seeds; and c) stir the seeds as they are exposed to the plasma to thereby allow the surfaces of the seeds to be attacked uniformly.

2. The method according to claim 1, wherein the stirring of the seeds is carried out in a plasma reactor with cylindrical walls having a central axis rotating the reactor around its axis.

3. The method according to claim 1, wherein igniting the plasma in the gas is carried out by capacitively coupling the RF energy to the gas.

4. The method according to claim 3, wherein the RF energy is provided at a frequency of 13.56 MHz. The method according to claim 1, wherein igniting the plasma in the gas is brought to out inductively coupling RF energy to gas.

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The method according to claim 1, wherein the seeds to be treated are corn seeds.

7. The method according to claim 1, wherein the RF energy is coupled in pulses to the plasma in the reaction chamber.

The method according to claim 6, wherein the frequency of the RF energy coupled to the plasma in the chamber is approximately 13.56 MHz.

9. The method according to claim 1, which further includes applying moisture to the seeds treated to germinate the seeds.

10. The method according to claim 1, wherein the gas in which the plasma is delivered is water vapor emitted from the seeds.

11. The method according to claim 1, wherein the gas in which the plasma is entangled is oxygen.

12. The method according to claim 1, wherein the gas in which the plasma is released is selected from the group consisting of argon, air, CF4, ammonia, oxygen, water vapor and mixtures thereof.

13. A method for treating seeds that comprises: a) introducing seeds; to be treated in a reaction chamber; b) evacuate the reaction chamber to a base level;

c) supplying gas to the reaction chamber and establishing a gas pressure selected therein; d) lighting a cold plasma in the gas in the chamber so that the plasma provides a chemical attack and not a deposit of the plasma and exposing the seeds to the plasma for a selected period of time to chemically attack the surfaces of the seeds with plasma to remove the surface material from the seeds; and e) stir the seeds while they are exposed to the plasma to thereby allow the surfaces of the seeds to be attacked uniformly. The method according to claim 13, wherein igniting the plasma in the gas in the chamber is carried out by capacitively coupling the RF energy in the gas in the chamber. 15. The method according to claim 14, wherein the RF energy is provided at a frequency of 13.56 MHz. 16. The method according to claim 13, wherein the igniting the plasma in the gas in the chamber. it is carried out by inductively coupling the RF energy to the gas in the reaction chamber. 17. The method according to claim 13, wherein the seeds to be treated are corn seeds. 18. The method according to claim 13, wherein the RF energy is coupled in pulses to the plasma in the reaction chamber.

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19. The method according to claim 18, wherein the frequency of the RF energy coupled to the plasma in the chamber is about 13.56 MHz. 20. The method according to claim 13, wherein the stirring of the seeds was carried out. in a plasma reactor with cylindrical walls having a central axis rotating the reactor around its axis. 21. The method according to claim 13, which further includes applying moisture to the treated seeds for

IO germinate the seeds. 22. The method according to claim 13, wherein the gas supplied in the reaction chamber is oxygen 23. The method according to claim 13, wherein the gas supplied to the reaction chamber is selected from the group 15 which consists of argon, air, CF4, ammonia, oxygen, water vapor, and mixtures thereof. The method according to claim 13, wherein the surface material removed from the seeds includes a material selected from the group that consists of fungicides, insecticides and

20 pesticides.

The method for treating seeds having a fungicidal, pesticidal or insecticidal coating, comprising: a) introducing seeds having a coating thereon of a material selected from the group consisting of

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fungicides, pesticides, insecticides and mixtures of these in a reaction chamber; b) evacuate the reaction chamber to a base level; c) supplying gas to the reaction chamber and establishing a gas pressure selected therein; d) lighting a cold plasma in the gas in the chamber so that the plasma provides a chemical attack and not a plasma deposit and exposing the plasma to the plasma for a selected period of time sufficient to chemically attack with plasma

^ 10 the surfaces of the seed 3 to remove the coating of surface material from the emulsions and convert the coating materials into gas phase components in the reaction chamber; and e) removing the gas phase components from the reaction chamber. 26. The method according to claim 25, wherein igniting the plasma in the gas in the chamber is carried out by capacitively coupling the RF energy to gas in the chamber. 27. The method according to claim 26, wherein

The RF energy is provided at a frequency of 13.56 MHz. The method according to claim 25, wherein turning on the plasma in the gas in the chamber is carried out by inductively coupling RF energy to the gas in the chamber. reaction chamber.

29. The method according to claim 25 wherein the seeds to be treated are corn seeds. 30. The method according to claim 25, wherein the RF energy is pulse-coupled to the plasma in the reaction chamber 31. The method according to claim 30, wherein at the frequency of the RF energy coupled to the plasma in the chamber is approximately 13.56 MHz. The method according to claim 25, which

10 further includes stirring the seeds while they are exposed to the plasma. The method according to claim 32, wherein the stirring of the seeds is carried out in a plasma reactor with cylindrical walls having a central axis rotating the reactor

15 around its axis 34. The method according to claim 25, wherein the gas supplied to the reaction chamber is oxygen. 35. The method according to claim 25, wherein the gas supplied to the reaction chamber is selected from the group consisting of argon, air, CF, ammonia, steam, oxygen.

^ and mixtures of these. 36. The method according to claim 25, wherein the gas supplied to the reaction chamber is water vapor emitted from the seeds, and after the period of time

25 selected to expose the seeds to the plasma, further comprises

evacuate the reaction chamber to a base level, supplying a source gas external to the reaction chamber and establish a selected gas pressure therein, and ignite a cold plasma in the external source gas so that the plasma provides a chemical attack and not a deposit of the plasma and exposing the seeds to the plasma for a selected period of time to chemically attack the seed surfaces with plasma to remove the additional surface material from the seeds

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SUMMARY 25

Seeds are treated with cold plasma in a reaction chamber to chemically attack the surface of the seeds to remove surface materials, such as fungicides and insecticides, or disinfect the surfaces. The cold plasma process is carried out using chemical etch gases that do not damage the seeds and for sufficient periods of time to remove the surface materials, necessarily affecting the viability of the live seeds after the treatment. Stir the seeds

- n, while exposed to asthma allows the surfaces of

10 the seeds are attacked uniformly

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