WO2016025714A1 - Capteur de chloropicrine - Google Patents

Capteur de chloropicrine Download PDF

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Publication number
WO2016025714A1
WO2016025714A1 PCT/US2015/045057 US2015045057W WO2016025714A1 WO 2016025714 A1 WO2016025714 A1 WO 2016025714A1 US 2015045057 W US2015045057 W US 2015045057W WO 2016025714 A1 WO2016025714 A1 WO 2016025714A1
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Prior art keywords
chloropicrin
sensor
reduced substrate
blue
sodium
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PCT/US2015/045057
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English (en)
Inventor
Gang Sun
Sanaz GHANBARI
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The Regents Of The University Of California
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Publication of WO2016025714A1 publication Critical patent/WO2016025714A1/fr

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N31/00—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods
    • G01N31/22—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using chemical indicators

Definitions

  • Detection of chemical agents at diluted concentrations is important for the safety of workers in certain areas such as farm workers in the field, soldiers in the field, hospital workers, chemists in production plants and the like.
  • One illustrative class of potentially harmful chemical agents is fumigants.
  • Fumigants are pesticides in the form of gas that are heavier than air and have the ability to spread to all areas and surfaces. Highly volatile, fumigants are used to sterilize soil before planting crops such as potatoes, carrots and strawberries. Fumigant exposure can cause a variety of adverse health effects, ranging from simple irritation of the skin and eyes to more severe effects such as affecting the nervous system, mimicking hormones causing
  • chloropicrin is a powerful pesticide used in agriculture to sterilize the soil either by itself or in combination with other chemicals. Chloropicrin is also used as a chemical warfare agent. It acts as an oxidizing agent and is toxic if ingested or inhaled. In particular, chloropicrin oxidizes the iron in hemoglobin, causing a condition known as methemoglobinemia in which there is a high level of methemglobin in the blood.
  • Leucomethylene blue is a well-known and widely used oxidation-reduction chemical reaction indicator that may be used to detect oxidizing agents.
  • LMB oxidation-reduction chemical reaction indicator
  • MB methylene blue
  • U.S. Patent No. 4,526,752 discloses an oxygen indicator for packaging in which MB is used as an indicator of package tampering.
  • the '752 patent is herein incorporated by reference in its entirety.
  • the '752 patent describes MB packaged in its reduced LMB form such that if the package is tampered with and exposed to oxygen, the LMB is oxidized and turns blue.
  • Methylene blue can be returned to its reduced, colorless state by applying a reducing agent.
  • the '752 patent recites an oxygen indicator for use in an atmosphere free of oxygen comprising a substrate carrying, in leuco state, a dye free of reducing agents and being capable of irreversibly reacting with oxygen.
  • the dye is characterized as being reactive with oxygen to change from the leuco state to the colored state and reactive with a reducing agent to change from the colored state to the leuco state.
  • the disclosure further recites an indicator wherein the dye is methylene blue and an indicator wherein the dye is new methylene blue.
  • the '811 patent discloses an oxygen indicator that comprises at least one dyestuff, at least one alkaline substance and at least one reducing agent.
  • the '811 patent recites a solid state oxygen color-change indicator for indicating the presence or absence of oxygen in gas comprising a solid mixture.
  • the dyestuff is selected from the group consisting of Methylene Blue (C.I. Basic Blue 9) and New Methylene Blue (C.I. Basic Blue 24).
  • Methylene blue is also commonly used to test for reducing agents present in milk due to bacteria growth.
  • WO 2003021252 Al describes a sensor for oxidizing agents comprising an irreversible indicator for detecting oxidizing agents, or in particular an oxygen indicator, comprising at least one redox-sensitive dyestuff, at least one semiconductor material and at least one electron donor. This indicator is activated by exposure to light of about 200-400 nm. That invention also relates to a UV light detector.
  • FumiDetec 200 is a multi-gas/multi-sensor detector for the identification of toxic fumigation gases in containers that gives out an electric reading of several different toxic gases including chloropicrin.
  • the Sensidyne #172S Chloropicrin Detector Tube detects chloropicrin in the 0.05 to 16 ppm range and operates on the following reaction: Chloropicrin + CrOs + H 2 S0 4 ⁇ COCI 2 and COCI 2 +Nitro-benzyl pyridine ⁇ DYESTUFF.
  • the Draeger Chloropicrin Tubes provide a colorimetric assay that can detect chloropicrin in the range of 0.1 to 2 ppm.
  • Any useful tool for detection of chemical agents should provide a rapid, sensitive and visible response to chemical agents. Further, such a detection tool should be easy to manufacture and easy to use for a worker who can be potentially exposed to chemical agents (e.g., oxidizing agents).
  • chemical agents e.g., oxidizing agents.
  • the detection of oxidizing agents such as fumigants is not trivial because they are highly reactive and have low molecular weights.
  • the present invention provides methods, kits and sensors for rapid detection of chloropicrin and other chemical agents (e.g. , oxidizing agents) in the air or atmosphere at low concentrations.
  • chemical agents e.g. , oxidizing agents
  • the present invention provides a method for detecting chloropicrin in the environment, the method comprising: contacting a reduced substrate with chloropicrin to form an oxidized form of the substrate; and detecting a change in light absorbance.
  • the present invention provides a kit for detecting chloropicrin, the kit comprising: a reduced substrate; and an optional color chart for quantification of chloropicrin.
  • the present invention provides a sensor for detecting chloropicrin, the sensor comprising: a reduced substrate; and an optional color chart for quantification of chloropicrin.
  • kits and sensors can optionally comprise an additive such as a reducing agent when the reduced substrate is instead an oxidized substrate.
  • Suitable reducing agents include, but are not limited to, sodium hydrosulfite (Na 2 S 2 0 4 ) or sodium thiosulfate (Na 2 S 2 0 3 ).
  • the present invention detects a trace amount of chloropicrin in air at a level that is below 100 parts per billion.
  • the present invention comprises a reduced liquid substrate into which ambient air can be introduced using a syringe or a syringe pump. Color changes in the liquid can be immediately observed if there is a trace amount of an oxidizing agent in the introduced air.
  • the oxidizing agent is chloropicrin.
  • the reduced substrate is leucomethylene blue (LMB).
  • the oxidizing agent is chloropicrin and the reduced substrate is LMB
  • the LMB interacts with the chloropicrin and is oxidized by the chloropicrin. When oxidized by the chloropicrin, the solution turns color (e.g. blue).
  • Leucomethylene blue is an oxidation-reduction chemical reaction indicator.
  • LMB oxidation-reduction chemical reaction indicator.
  • MB interacts with a reducing agent and gains electrons, it becomes colorless.
  • MB in its oxidized state, MB is blue and in its reduced state, LMB is clear.
  • the present invention provides a sensor comprising a vial containing a solution of 2 mL of 0.03% MB and 2 mL of 1% sodium carbonate solution containing 0.5% sodium hydrosulfite.
  • Sodium hydrosulfite acts as a reducing agent, which makes the MB in the vial become clear.
  • LMB when exposed to air containing chloropicrin (e.g., via a syringe and needle method in which the air is injected into the vial or by directly exposing the solution to the environment), the LMB in the solution is oxidized by the chloropicrin and turns blue. As the concentration of chloropicrin increases, the solution in the vial becomes darker blue.
  • the senor can detect trace amounts of chloropicrin in the air, including amounts less than 100 ppb (e.g., 10-50 ppb).
  • the solution in the vial can be returned to its initial clear color by adding a reducing agent (e.g., sodium hydrosulfite (Na 2 S 2 0 4 ) or sodium thiosulfate (Na 2 S 2 0 3 )).
  • a reducing agent e.g., sodium hydrosulfite (Na 2 S 2 0 4 ) or sodium thiosulfate (Na 2 S 2 0 3 )
  • the sensor further comprises a color chart for quantification of chloropicrin in the air.
  • FIG. 1 illustrates the chemical structure of chloropicrin.
  • FIG. 2 illustrates the toxicity mechanism of chloropicrin that results in
  • FIG. 3 illustrates the reduction of methylene blue to leucomethylene blue.
  • FIG. 4 illustrates the half and net reactions of sodium dithionite and methylene blue.
  • FIG. 5 illustrates the half and net reactions of methylene blue and chloropicrin if chloropicrin is fully reduced.
  • FIG. 6 illustrates an embodiment of an optimized concentration of methylene blue.
  • FIG. 7 illustrates an embodiment of an optimized amount of sodium hydrosulfite as a reducing agent.
  • FIG. 8A illustrates different concentrations of 5 mL of chloropicrin directly injected as a liquid into 4 mL 0.03% methylene blue + 2 mL 1% sodium carbonate solution containing 0.5%) sodium hydrosulfite.
  • FIG. 8B illustrates a resulting light intensity spectrum of a chloropicrin solution.
  • FIG. 9A illustrates the concentration spectra of varying concentrations of chloropicrin when exposed as a gas to a solution containing 0.5mL 0.03% methylene blue + 0.5mL 1%) Sodium carbonate solution containing 0.5%> sodium hydrosulfite.
  • FIG. 9B illustrates vials with dissolved methylene blue turning colorless upon addition of a reducing agent, and resulting color change when exposed to varying
  • FIG. 10A illustrates the light absorbance spectra from vials containing 0.5 mL (0.03, 0.015, 0.0075, 0.003%) methylene blue + 0.5 mL 1% sodium carbonate solution containing 0.5% sodium hydrosulfite + 8 10000 ppm chloropicrin in acetone.
  • FIG. 10B shows the color intensity of vials containing 0.5 niL (0.03, 0.015, 0.0075, 0.003%) methylene blue + 0.5 mL 1% sodium carbonate solution containing 0.5% sodium hydrosulfite + 8 10000 ppm chloropicrin in acetone.
  • FIG. 1 1 illustrates chloropicrin sensitivity at an RA/MB molar ratio of 4.5.
  • FIG. 12A illustrates the storage stability of an exemplary sensor comprising 2 mL 0.03% methylene blue + 2 mL 1% sodium carbonate solution containing 0.5% sodium hydrosulfite stored in air in accordance with an embodiment of the present invention.
  • FIG. 12B shows a vial containing 2 mL 0.03% methylene blue + 2 mL 1% sodium carbonate solution containing 0.5% sodium hydrosulfite after incubating seven days in air in accordance with an embodiment of the present invention.
  • FIG. 13A illustrates stability of the reduced substrate at various RA/MB molar ratios when prepared in standard atmospheric conditions.
  • FIG. 13B illustrates stability of the reduced substrate at various RA/MB molar ratios when prepared under an atmosphere of N 2 .
  • FIG. 14A illustrates the reversibility of an exemplary sensor for chloropicrin in accordance with an embodiment of the present invention.
  • FIG. 14B illustrates the light absorbance at 670 nm with the reversibility of an exemplary sensor for chloropicrin.
  • the present invention provides for the detection of chloropicrin in the ambient environment at much lower levels than other commercially available tests for chloropicrin.
  • the methods, kits and sensors provided herein detect oxidizing agents in low concentrations (e.g., ppm or ppb concentrations), including trace concentrations below 100 ppb.
  • oxidizing agents e.g., ppm or ppb concentrations
  • trace concentrations e.g., ppm or ppb concentrations
  • These methods, kits and sensors are safe, non-toxic, inexpensive, easy to manufacture and easy to use. They are also quick, highly sensitive and provide results that are easy to observe and unexpectedly are based on the mild oxidizing potential of chloropicrin.
  • This invention provides methods, kits and sensors for rapid detection of oxidizing agents (e.g., fumigants, agents of chemical warfare, and the like) and development of sensors that can rapidly identify and quantify chemical agents (e.g., fumigants, agents of chemical warfare, oxidizing agents, and the like).
  • oxidizing agents are gas phase oxidizing agents.
  • the oxidizing agent is chloropicrin.
  • the methods, kits and sensors are acceptable for a wide range of monitoring activities, including monitoring exposure levels in rural, industrial and residential areas.
  • the present invention provides a method for detecting oxidizing agents, the method comprising, consisting essentially of, or consisting of: contacting a reduced substrate with an oxidizing agent to form an oxidized form of the substrate; and detecting a change in light absorbance.
  • the oxidizing agent is chloropicrin.
  • the reduced substrate is leucomethylene blue.
  • kits for detection of oxidizing agents comprising, consisting essentially of, or consisting of: a kit for detecting an oxidizing agent, the kit comprising: a reduced substrate; and an optional color chart for quantification of the oxidizing agent.
  • the oxidizing agent is chloropicrin.
  • the reduced substrate is leucomethylene blue.
  • a sensor for detecting oxidizing agents comprising, consisting essentially of, or consisting of: a sensor for sensing an oxidizing agent, the sensor comprising: a reduced substrate; and an optional color chart for quantification of the oxidizing agent.
  • the oxidizing agent is chloropicrin.
  • the reduced substrate is leucomethylene blue.
  • chloropicrin includes a chemical with CAS No. 76-06-2. Chloropicrin is also known as trichloronitromethane, PS, and nitrochloroform. The full IUPAC chemical name of chlrorpicrin is trichloro(nitro)methane.
  • a reduced substrate includes chemicals that when in the presence of an oxidizing agent oxidize to form a new chemical species.
  • a reduced substrate comprises a chemical that when oxidized produces a desired chemical property.
  • the desired chemical property may comprise an oxidized form of the reduced substrate that is detectable either through light absorption, the naked eye, or other spectroscopic means.
  • a reduced substrate can include leucomethylene blue.
  • the term "change in light absorbance" includes measuring the conversion of a reduced substrate to a detectable oxidized form of the reduced substrate.
  • the change in light absorbance comprises measuring the change in a detectable property of a reduced substrate after contacting the reduced substrate with an oxidizing agent.
  • detecting a change in light absorbance comprises measuring the conversion of leucomethylene blue by monitoring the change in absorbance at about 670 nm (e.g., 650-690 nm).
  • detecting a change in light absorbance comprises measuring the conversion of leucomethylene blue by monitoring the change in color of a sample and comparing it to a provided color chart.
  • Chloropicrin is a strong electrophile due to the presence of the chloride and nitro groups, as shown in FIG. 1. Consequently, it is capable of covalently binding with various proteins, DNA and other nucleophiles within the body.
  • the mechanism of toxic action for chloropicrin is not well understood, but may involve an oxidative reaction with biological thiols (R-SH), such as glutathione (GSH) and hemoglobin (Hb).
  • R-SH biological thiols
  • GSH glutathione
  • Hb hemoglobin
  • Chloropicrin also inhibits pyruvate and succinate dehydrogenase (enzymes for the respiratory system) possessing SH groups.
  • Hb is the iron-containing oxygen-transport in the red blood cells which iron is in the Fe 2+ state
  • methemoglobin is a form of Hb which the iron in the heme group is in the Fe 3+ state.
  • Hemoglobin is oxidized to methemoglobin by PS.
  • Methemoglobinemia occurs when iron atoms in hemoglobin become oxidized.
  • FIG. 2 illustrates the toxicity mechanism of chloropicrin that results in methemoglobinemia. During oxidation, the iron atom loses an electron to an oxidant and is converted from the ferrous state (Fe 2+ ) to the ferric state (Fe 3+ ).
  • Methylene blue is an oxidizing agent that is the treatment of choice for acquired methemoglobinemia.
  • Methylene blue is reduced to leucomethylene blue by erythrocyte methemoglobin reductase in the presence of nicotinamide adenine dinucleotide phosphate (NADPH). Leucomethylene blue then reduces methemoglobin to oxyhemoglobin, converting the ferric ion (Fe 3+ ) back to its oxygen carrying ferrous state (Fe 2+ ).
  • Methylene blue is a basic aniline dye. At room temperature, it appears as a solid, odorless, dark green powder that yields a blue solution when dissolved in water. Methylene blue is widely used as a redox indicator. LMB indicates the presence of oxidizing agents because it is oxidized by these compounds which causes a color change.
  • the present invention is based on the unexpected discovery that LMB can be used to detect chloropicrin at much lower levels than other commercially available tests or assays for chloropicrin.
  • the method of the present invention comprises: contacting a reduced substrate (e.g., LMB) with an oxidizing agent to form an oxidized form of the substrate; and detecting a change in light absorbance.
  • the reduced substrate when oxidized, undergoes a detectable change in light absorbance when exposed to an oxidizing agent.
  • the detectable change is in the visible spectrum of light wavelengths (e.g., a visible change in color). In some embodiments, the detectable change is not in the visible spectrum of light wavelengths (e.g. , a detectable change in IR or UV wavelengths of light).
  • the oxidizing agent is chloropicrin and the reduced substrate is leucomethylene blue (LMB).
  • LMB leucomethylene blue
  • a vial contains a solution of 2 mL of 0.03% MB and 2 mL of 1% sodium carbonate solution containing 0.5% sodium hydrosulfite. Sodium hydrosulfite acts as a reducing agent, which makes the MB in the vial become clear LMB.
  • the LMB in the solution When exposed to air containing chloropicrin (e.g., via a syringe and needle method in which the air is injected into the vial or by directly exposing the solution to the environment), the LMB in the solution is oxidized by the chloropicrin and turns blue as it becomes MB. As the concentration of chloropicrin increases, the solution in the vial becomes darker blue.
  • the sensor can detect trace amounts of chloropicrin in the air, including amounts less than 100 ppb.
  • the sensitivity of the present invention to an oxidizing agent is dependent on the molar ratio between reduced substrate (RS) and reducing agent (RA) used.
  • the molar ratio RA/RS can be between about 0.5 - and about 30.
  • Non-limiting examples of the RA/RS ratio are 1 , 2, 3, 3.5 4, 4.1 , 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5, 5.5, 6, 7, 8 , 9 ,10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30.
  • the RA/RS ratio is between about 4 to about 6.
  • a vial contains a solution of 2 mL of 0.03% MB and 0.68 mL of 1% sodium carbonate solution containing 0.5% sodium hydrosulfite (RA/RS of 10.38).
  • a vial contains a solution of 2 mL of 0.03% MB and 0.27 mL of 1% sodium carbonate solution containing 0.5% sodium hydrosulfite (RA/RS of 4.122).
  • a vial contains a solution of 2 mL of 0.03% MB and 0.3 mL of 1% sodium carbonate solution containing 0.5% sodium hydrosulfite (RA/RS of 4.5).
  • a vial contains a solution of 2 mL of 0.03% MB and 0.34 mL of 1% sodium carbonate solution containing 0.5%> sodium hydrosulfite (RA/RS of 5.190).
  • the reduced substrate is prepared in inert atmospheric conditions which can include one or more inert gases. In some embodiments, the reduced substrate is prepared in an N 2 atmosphere. In some embodiments, the reduced substrate is prepared under standard atmospheric conditions. In some embodiments, the reduced substrate is stored under inert atmospheric conditions which can include one or more inert gases. In some embodiments, the reduced substrate is stored under N 2 atmospheric conditions. In some embodiments, the reduced substrate is stored under standard atmospheric conditions.
  • a container e.g., a vial
  • a solution of between 0.1 mL to about 10 mL e.g., 0.1 , 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 , 2, 3, 4, 5, 6, 7, 8, 9, or 10 mL
  • a solution of between 0.1 mL to about 10 mL e.g., 0.1 , 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 , 2, 3, 4, 5, 6, 7, 8, 9, or 10 mL
  • the container can also contains about 1-10 mL of a l%-5% sodium carbonate solution containing 0.5% -2% sodium hydrosulfite.
  • a reducing agent e.g., sodium hydrosulfite (Na 2 S 2 0 4 ) or sodium thiosulfate (Na 2 S 2 0 3 ).
  • the methods, kits, and sensors described herein are advantageous because they are reversible and can be reused.
  • the methods, kits and sensors further comprise a color chart for quantification of chloropicrin in the air, atmosphere or environment.
  • the reduced substrate is selected from the group of
  • leucomethylene blue a compound comprising a Fe 2+ ion, iodide paper, sodium 2,6- dibromophenol-indophenol, sodium 2,6-dichlorophenol-indophenol, thionine, indigo tetrasulfonic acid, indigotrisulfonic acid, indigo carmine, indigomono sulfonic acid, phenosafranin, Safranin T, neutral red, leucoberbelin Blue I, leucocrystal violet,
  • LMB leucomethylene blue
  • leucomalachite green or leuco xylene cyanole FF.
  • leucomalachite green or leuco xylene cyanole FF.
  • LMB leucomethylene blue
  • MB methylene blue
  • the present invention comprises a kit for detecting oxidizing agents.
  • the kit comprises: a reduced substrate; and an optional color chart for quantification of the oxidizing agent.
  • the oxidizing agent is chloropicrin.
  • the reduced substrate is leucomethylene blue.
  • the present invention provides a sensor for detecting chloropicrin, the sensor comprising a container, the container comprising a solution containing a reduced substrate.
  • the sensor comprises a vial containing a solution of 2 mL of 0.03% MB and 2 mL of 1% sodium carbonate solution containing 0.5% sodium hydrosulfite.
  • sodium hydrosulfite acts as a reducing agent, which makes the MB in the vial clear.
  • the LMB in the solution is oxidized by the chloropicrin and turns blue.
  • the sensor can detect trace amounts of chloropicrin in the air, including amounts less than 100 ppb.
  • the solution in the container can be returned to its initial clear color by adding a reducing agent (e.g. , sodium hydrosulfite (Na 2 S 2 C"4) or sodium thiosulfate (Na 2 S 2 0 3 )).
  • a reducing agent e.g. , sodium hydrosulfite (Na 2 S 2 C"4) or sodium thiosulfate (Na 2 S 2 0 3 )
  • the sensor further comprises a color chart for quantification of chloropicrin in the air.
  • the container is a vial.
  • the container is wearable (e.g., as a badge, wristband or the like).
  • the reduced substrate solution is basic.
  • the pH of the reduced substrate solution can range from about 7 to about 9, from about 9 to about 1 1 , or from about 1 1 to about 13 or more.
  • the pH of the solution can be greater than 7, 8, 9, 10, 1 1 , 12, 13, or higher.
  • the pH is about 8.5, 8.7, 8.9, 9.1 , 9.3, 9.5, 9.7, 9.9, 10.1 , 10.3, 10.5, 10.7, 10.9, 1 1.1 , 1 1.3 or about 1 1.5.
  • the present invention provides a color chart for rapid determination of assay results.
  • the color chart is calibrated based on the molar ratio of reducing agent to reduced substrate (RA/RS molar ratio).
  • the color chart is a look-up table. In another non-limiting example the color chart is a
  • comparison chart Users can compare assay results to the provided chart(s) and to a reference control to measure the presence of an oxidizing agent. For example, there is a reference chart or color chart with various concentrations of chloropicrin exposed to LMB. The color intensity is listed next to the concentration of chloropicrin. In this manner, an unknown concentration amount in the field can be compared to the reference chart to determine the concentration of the unknown.
  • kits and sensors can optionally comprise an additive such as a reducing agent and an oxidized substrtate is provided (e.g., MB).
  • Suitable reducing agents include, but are not limited to, sodium hydrosulfite (Na 2 S 2 C"4) or sodium thiosulfate (Na 2 S 2 0 3 ).
  • the present invention detects a trace amount of chloropicrin in air at a level that is below 100 parts per billion.
  • the chloropicrin sensor can detect chloropicrin concentration levels between about 1 ppb to about 1000 ppm, 1 ppb to about 1000 ppb, about 1 ppb to about 500 ppb, about 0.1 ppb to about 500 ppb, 0.1 ppb to about 50 ppb, about 50 ppb to about 200 ppb, about 0.1 ppm and about 1000 ppm, about 100 ppm and about 500 ppm, or about 10 ppm to about 50 ppm.
  • the present invention comprises a reduced liquid substrate in a sealed vial or container into which ambient air can be introduced, for example using a syringe or a syringe pump.
  • the present invention provides a reduced liquid substrate in a container with a semi-permeable membrane, valve or other device through which ambient air can pass. Color changes in the liquid can be immediately observed if there is a trace amount of an oxidizing agent in the introduced air.
  • the oxidizing agent is chloropicrin.
  • the reduced substrate is
  • LMB leucomethylene blue
  • the oxidizing agent is chloropicrin and the reduced substrate is LMB
  • the LMB interacts with the chloropicrin and is oxidized by the chloropicrin.
  • the LMB turns blue as it becomes MB.
  • kits comprise instructions for using the kits and an optional color chart, reference chart or look-up table that provides a correlation between color and/or color intensity and the amount of the oxidizing agent.
  • the sensors comprise instructions for using the sensors and an optional color chart that provides a correlation between color and/or color intensity and the amount of the oxidizing agent.
  • Chloropicrin 's ⁇ was determined using a SHE (Standard hydrogen electrode) technique. The results below demonstrate that chloropicrin has a mild oxidizing potential.
  • SHE Standard hydrogen electrode
  • FIG. 4 shows the net and half reactions involved in producing the reduced substrate.
  • the reducing potential of sodium dithionite is used to reduce methylene blue into its colorless leucomethylene blue form.
  • This diagram demonstrates that two moles of methylene blue are reduced for every mole of sodium dithionate as each reduction of sodium dithionate transfers four moles electrons and each oxidation of methylene blue transfers two moles electrons.
  • FIG. 5 shows the net and half reactions when chloropicrin encounters the reduced substrate, leucomethylene blue. For each reduction of chloropicrin, there is one oxidation of leucomethylene blue.
  • This example shows optimizing the concentration of methylene blue for the use in a sensor designed to detect chloropicrin.
  • seven samples containing 1 mL of methylene blue at various concentrations (3, 0.3, 0.03%) were added to different volumes (3, 1.5, 0.5 mL) of a 0.5%> sodium dithionite solution dissolved in 1% sodium carbonate.
  • the results of this experiment can be seen in FIG. 6.
  • a number of solutions tested (see samples 1, 2, 4-7) produced no color change, or produced a precipitate.
  • Sample 3 however, produced a colorless solution with no precipitate.
  • Sample 3 is one condition where the reduced form of MB (i.e., LMB) can be used as a reduced substrate to detect the presence of chloropicrin.
  • the conditions of sample 3 were 1 mL of 0.03% MB and 0.5 mL of a 0.5% sodium dithionite solution dissolved in 1% sodium carbonate.
  • This example shows optimizing the amount of reducing agent for the use in a sensor designed to detect chloropicrin.
  • four different volumes (0.25, 0.5, 1, 1.5 mL) of a 0.5% solution of sodium dithionite dissolved in 1% sodium carbonate were titrated into 2 mLs of 0.03% MB.
  • the resulting mixtures were then monitored over time (1 hr) for their change in physical properties.
  • the results of this experiment can be seen in FIG. 7.
  • Sample 1 immediately turned light blue, while sample 2 turned blue over the time of the experiment. Samples 3 and 4, on the other hand, remained colorless over the tested time intervals.
  • FIG. 8A shows the results of this experiment, where the reduced substrate can readily detect 2 ppb chloropicrin (see spectra of 2 ppb Chloropicrin in FIG. 8B).
  • the reduced substrate was prepared by mixing 0.5 mL of 0.03% methylene blue and 0.5 mL of 1% sodium carbonate solution containing 0.5% sodium hydrosulfite. This resulted in a RA/MB molar ratio of 30.
  • FIG. 9 A shows the absorbance decrease as the amount of chloropicrin added in the atmosphere was reduced from 0.48 mg to 0.015 mg. Even at 0.015 mg, the presence of chloropicrin was still readily detectable.
  • the chart above the graph shows the calculation of the molar ratio of reducing agent (RA) and methylene blue (MB) (RA/MB). In this experiment, the reduced substrate was prepared with a RA/MB molar ratio of 30.
  • FIG. 9B shows the vials of each respective trial are pictured showing the visible color change to the naked eye. Each spectrum was measured after at least 45 seconds to ensure that chemical equilibrium had been established.
  • the vials and spectra in FIG. 9 demonstrate the sensor's sensitivity to varying concentrations, allowing users to quickly and rapidly assess the concentration of chloropicrin in the surrounding environment.
  • FIG. 10 shows an experiment where reduced substrate was prepared using varying levels of methylene blue, but a constant amount of reducing agent. The reduced substrate solutions were then exposed to a constant amount of chloropicrin.
  • FIG. 10A shows the spectra intensities based on the RA/MB ratio
  • FIG. 10B shows the visual differences in light intensities. This results shows the lower the RA/MB ratio, the more sensitive the sensor is to chloropicrin, emphasizing the importance of the molar ratio in assay readout and sensitivity. This result also demonstrates the necessity of sensor calibration based on the RA/MB ratio to properly interpret assay results.
  • the reduced substrate was prepared by mixing 0.5 mL of 0.03% methylene blue and 0.5 mL of 1% sodium carbonate solution containing 0.5% sodium hydrosulfite in an N 2 atmosphere. This resulted in a RA/MB molar ratio of 4.5.
  • FIG. 11 shows the resulting spectra when various microgram amounts of chloropicrin evaporated in air are injected into a vial containing the reduced substrate with a RA/MB ratio of 4.5.
  • the results of this experiment demonstrate the sensor's ability to not only detect low amounts of chloropicrin but also to clearly report differences between low levels.
  • This example demonstrates the stability and reusability of the chloropicrin sensor.
  • the stability and shelf-life of the reduced substrate solution was studied by exposing the reduced substrate to normal atmospheric positions over 7 days. In this experiment, 2 mL of 0.03% methylene blue was mixed with 2 mL 1% sodium carbonate solution containing 0.5% sodium hydrosulfite (an RA/MB molar ratio of 30). The resulting reduced substrate solution was incubated in normal atmospheric conditions for seven days. Each day the spectrum of the solution was taken, and the results can be seen in FIG. 12. Even after 7 days, there is only a very low absorbance at 670 nm.
  • FIG. 11 shows one RA/MB molar ratio to detect lower concentrations of chloropicrin.
  • FIG 13 shows preparations of reduced substrate with varying RA/MB molar ratios that were stable for at least two hours. Stability was defined as having no visible color change, as determined by experimenter observation, or no visible absorbance peak in the visible range (about 390 nm - about 700 nm), as measured on a spectrophotometer.
  • FIG. 13A shows reduced substrate solutions that were prepared under standard atmospheric conditions
  • FIG. 13B shows reduced substrate solutions prepared under N 2 (g).
  • the lower limits of RA/MB stability for this particular reducing agent (sodium hydrosulfite) and reduced substrate (leucomethylene blue) was about 5.4 when incubated in standard atmospheric conditions, and about 4.1 when incubated in N 2 atmospheric conditions.
  • FIG. 14A shows an embodiment of the reduced substrate sensor described herein where the reduced substrate sensor is exposed to an amout of chloropicrin in the atmosphere, the sensor tuns blue to indicate its presence, and is then regenerated by adding 0.5%> reducing agent. The regenerated solution can be used again to test for the presence of chloropicrin.
  • the chart in FIG. 14B monitoring the absorbance at 670 nm shows the cycling of aborbance resulting from multiple cycles of chlorpicrin expsorue and regeneration.

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Abstract

La présente invention concerne des procédés pour détecter la présence d'un agent oxydant dans l'atmosphère par mise en contact d'un substrat réduit avec un agent oxydant pour former une forme oxydée du substrat et détecter une variation d'absorbance de lumière. La présente invention concerne également des kits et des capteurs pour détecter un agent oxydant dans l'atmosphère par la détection et la mesure de la variation de l'absorbance de lumière provoquée par la présence d'un agent oxydant. Dans des modes de réalisation particuliers, l'agent oxydant est la chloropicrine. Dans certains modes de réalisation, le substrat réduit est du bleu de leucométhylène.
PCT/US2015/045057 2014-08-14 2015-08-13 Capteur de chloropicrine WO2016025714A1 (fr)

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