A method for analyzing volatile organic compounds

Abstract

A method for analyzing volatile organic compounds is disclosed. The sensors that implement the method described in this invention provide selectivity necessary for analyzing real-world samples with low-cost, fast, small-form-factor, and high usability.

Description

[0001] PROVISIONAL APPLICATION FOR PATENT

[0002] INVENTION TITLE

[0003] A method for analyzing volatile organic compounds.

[0004] BACKGROUND OF THE INVENTION

[0005] Problem Solved: Each year, between 340,000 and 900,000 premature deaths can be linked to air pollution caused by releasing Volatile Organic Compounds (VOCs). An estimated 1.8 billion tons of VOCs are emitted to the global environment each year. Some VOCs cause serious adverse health effects even at the trace level concentration. For example, the EPA has identified 188 toxic air pollutants known or suspected to cause cancer or other serious health effects, such as reproductive effects, congenital disabilities, or adverse environmental effects.

[0006] Existing commercial sensors for detecting VOCs, such as photoionization detectors, are non-selective. Hence, they are not suitable for detecting carcinogenic / toxic VOCs, e.g., benzene and toluene. Also, the current selective detecting technologies, such as gas chromatography mass spectrometry are bulky, expensive, sluggish, and require a skilled / trained operator.

[0007] The sensors that implement the method described in this invention provide selectivity necessary for analyzing real-world samples with low-cost, fast, small-form-factor, and high usability.

[0008] DETAILED DESCRIPTION OF THE INVENTION

[0009] As stated above, each year, between 340,000 and 900,000 premature deaths can be linked to air pollution caused by releasing Volatile Organic Compounds (VOCs). An estimated 1.8 billion tons of VOCs are emitted to the global environment each year. Some VOCs cause serious adverse health effects even at the trace level concentration. For example, the EPA has identified 188 toxic air pollutants known or suspected to cause cancer or other serious health effects, such as reproductive effects, congenital disabilities, or adverse environmental effects. The invention claimed here solves this problem.

[0010] This invention allows development of sensor-based VOC monitoring solutions with features such as selectivity, low-cost, fast, small form factor that do not require skilled / trained operators to detect unsafe levels of carcinogenic / toxic VOCs.

[0011] The claimed invention differs from what currently exists. The sensors that implement the method described in this invention provide selectivity necessary for analyzing real-world samples with low-cost, fast, small-form-factor, and high usability. This invention is an improvement on what currently exists. The sensors that implement the method described in this invention provide selectivity necessary for analyzing real-world samples with low-cost, fast, small-form-factor, and high usability.

[0012] The existing solutions that are low-cost, fast, and easy to use, do not have the required selectivity, therefore cannot detect the presence of carcinogenic / toxic VOCs with the presence of background compounds. The selective solutions are expensive, bulky, slow and require a tra ined / skil led operator.

[0013] The sensors that implement the method described in this invention provide selectivity necessary for analyzing real-world samples with low-cost, fast, small-form-factor, and high usability.

[0014] Also, this invention can be used to produce personal VOC exposure monitors, environmental VOC monitors, explosive and chemical weapon detectors, drug detectors, drug use monitors, exhaled breath analyzers for medical diagnosis, human detectors, and process monitors.

[0015] The invention claim is:

[0016] 1. Provide a sample comprising: one or more analytes of interest; and optionally, one or more additional compounds other than the one or more analytes of interest, adjust a temperature of a polymer waveguide to the first temperature threshold; contact the polymer waveguide with the sample; whereby one or more analytes of interest and the one or more additional compounds, if present in the sample, are captured and concentrated in the polymer waveguide; transmit light through the polymer waveguide to provide a first optical output; detect the first optical output with an optical detector;

[0017] 2. Heat the polymer waveguide, whereby one or more compounds in the waveguide are desorbed from the polymer waveguide at different desorption rates; transmit light through the polymer waveguide to provide multiple time series optical outputs during the desorption process; detect the outputs during desorption process with an optical detector; wherein the optical detector is a spectrometer or a photodetector and the first and time series optical outputs during desorption process comprise optical intensities.

[0018] 3. Determine an absorption measurement of compounds present in the waveguide at a given time at given a temperature using the intensity of the light transmitted through a clean waveguide at 25°C 10(0,25), the intensity of the light transmitted through the VOC exposed-waveguide t seconds after at T°C lvoc( t,T ), and the intensity of the light transmitted through the clean waveguide after t seconds at T°C lclean(t,T) as A(t,T)=loglO (lvoc(t,T) ) / IO(O,25) )- loglO (lclean(t,T) ) / IO(O,25) ); 4. Analyze the sample by analyzing the absorption measurements using an artificial intelligent method where absorption measurements of known sample compositions are used for training;

[0019] Relationship Between The Components:

[0020] Step 1 pre-concentrates the compounds in a polymer waveguide that improves the limit of detection of the compounds analyzed in Step 4.

[0021] Step 1 captures an optical output of the compounds present in the waveguide that have optical absorbance in the measured optical wavelength range that is used in the analysis in Step 4. The compounds present in the waveguide are representative of their concentrations in the exposed sample.

[0022] Step 2 generates optical outputs that are representative of the species, concentration and desorption rates of the compounds that is used in the analysis in Step 4.

[0023] Step 3 is used to convert the optical output to a signal that is representative of the compounds and their concentrations, that is used in the analysis in step 4.

[0024] How The Invention Works:

[0025] VOCs have high solubility in polymers such as PDMS (sensor core). Therefore, VOC concentration in the polymer waveguide is several orders of magnitude higher than the concentration of the compound in the exposed air. The analyte is absorbed and concentrated into the polymer waveguide at a fixed temperature. The concentrations in the waveguide and the exposed air can be described using the Nernst distribution law.

[0026] The optical absorption measurement of compounds present in the waveguide at a given time at a given temperature is expressed using the intensity of the light transmitted through a clean waveguide at 25°C 10(0,25), the intensity of the light transmitted through the VOC exposed-waveguide t seconds after at T°C lvoc( t,T ), and the intensity of the light transmitted through the clean waveguide after t seconds at T°C lclean(t,T) as A(t,T)=loglO (lvoc(t,T) ) / IO(O,25) )- loglO (lclean(t,T) ) / IO(O,25) ). Finally, the compound concentration is linearly related to the optical absorption (A) based on the Beer-Lambert.

[0027] Step 1 allows capturing an optical output that is representative of the sample that is exposed to the waveguide. Step 2 allows capturing an optical output that is representative of the compounds present in the waveguide during the desorption process. Step 3 allows converting the optical output to a signal that is representative of the optical absorbance due to the compound present in the waveguide.

[0028] Optical signal produced at different time and temperature points generates a signal that is representative of the optical absorbance of the compound present in the waveguide and additionally representative of the desorption rates of the compound present in the waveguide.

[0029] The optical signals collected at different time and temperature points represent the optical absorbance and desorption rates of compounds present in the waveguide and therefore related to the sample composition the waveguide was exposed to and are used as the input in the analysis in Step 4.

[0030] How To Make The Invention:

[0031] The method described in this invention is implemented on a polymer waveguide structure that is embedded or on the surface of a substrate. A light source (LED or broad band) is optically coupled to the waveguide on one end and an optical detector such as a spectrometer is connected on the other end. A heating element and a temperature sensor are used to achieve the desired temperature of the waveguide. Optionally, a cooling element can be used to lower the waveguide temperature.

[0032] Obtaining an optical output that is representative of the exposed sample is necessary.

[0033] Optical outputs during the desorption process are necessary to achieve higher selectivity.

[0034] Step 1 can be done at a lower temperature to improve capturing of highly volatile compounds.

[0035] Optical output measurements can be taken at different or / and multiple wavelength bands to improve selectivity.

[0036] How To Use The Invention:

[0037] The method described in this invention can be implemented on polymer waveguide structure that is embedded or on the surface of a substrate. A light source (LED or broad band) is optically coupled to the waveguide on one end and an optical detector such as a spectrometer is connected on the other end. A heating element and a temperature sensor are used to achieve the desired temperature on the waveguide. Optionally, a cooling element can be used to lower the waveguide temperature. A sensing device that implements the method described in this invention enables detection of hazardous volatile organic compound levels at a lower cost, faster response times, smaller form factor and higher usability.

[0038] Additionally: This invention can be used in applications that require analysis of volatile organic compounds such as but not limited to detection of explosives, chemical weapons, drugs, medical diagnosis using VOCs in exhaled breath and other bodily fluids, process monitoring, environmental monitoring, and detection of use of drugs and other substances.

[0039] Also, it can create personal VOC exposure monitors, environmental VOC monitors, explosive and chemical weapon detectors, drug detectors, drug use monitors, exhaled breath analyzers for medical diagnosis, human detectors, and process monitors.

Claims

The invention claim is:

1. Provide a sample comprising: one or more analytes of interest; and optionally, one or more additional compounds other than the one or more analytes of interest, adjust a temperature of a polymer waveguide to the first temperature threshold; contact the polymer waveguide with the sample; whereby one or more analytes of interest and the one or more additional compounds, if present in the sample, are captured and concentrated in the polymer waveguide; transmit light through the polymer waveguide to provide a first optical output; detect the first optical output with an optical detector;2. Heat the polymer waveguide, whereby one or more compounds in the waveguide are desorbed from the polymer waveguide at different desorption rates; transmit light through the polymer waveguide to provide multiple time series optical outputs during the desorption process; detect the outputs during desorption process with an optical detector; wherein the optical detector is a spectrometer or a photodetector and the first and time series optical outputs during desorption process comprise optical intensities.

3. Determine an absorption measurement of compounds present in the waveguide at a given time at given a temperature using the intensity of the light transmitted through a clean waveguide at 25°C 10(0,25), the intensity of the light transmitted through the VOC exposed-waveguide t seconds after at T°C lvoc( t,T ), and the intensity of the light transmitted through the clean waveguide after t seconds at T°C lclean(t,T) as A(t,T)=loglO (lvoc(t,T) ) / IO(O,25) )- loglO (lclean(t,T) ) / IO(O,25) );4. Analyze the sample by analyzing the absorption measurements using an artificial intelligent method where absorption measurements of known sample compositions are used for training;