U.S. patent application number 15/013109 was filed with the patent office on 2017-08-03 for apparatus and method for measuring a gas.
The applicant listed for this patent is Jonathan David LOWY. Invention is credited to Jonathan David LOWY.
Application Number | 20170219543 15/013109 |
Document ID | / |
Family ID | 59386539 |
Filed Date | 2017-08-03 |
United States Patent
Application |
20170219543 |
Kind Code |
A1 |
LOWY; Jonathan David |
August 3, 2017 |
APPARATUS AND METHOD FOR MEASURING A GAS
Abstract
In a measuring method for measuring an atmospheric concentration
of a compound, such as a volatile organic compound (VOC), an
adsorptive element is provided within a target atmosphere for a
period of time to allow adsorption of a compound of interest for
measurement, and then removed from the target atmosphere, and
placed within a closed measuring space. The adsorptive element is
heated within the measuring space to cause de-adsorption of the
compound into the closed measuring space, and a concentration of
the de-adsorbed compound is measured. A concentration of the
compound in the target atmosphere is determined based on the
concentration of the compound within the closed measuring space.
The adsorptive element may be formed of an adsorptive material such
as carbon fibers, cellulose or other adsorptive materials, and a
binder. The adsorptive element may be optimized for adsorption of a
specific compound.
Inventors: |
LOWY; Jonathan David;
(Auckland, NZ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LOWY; Jonathan David |
Auckland |
|
NZ |
|
|
Family ID: |
59386539 |
Appl. No.: |
15/013109 |
Filed: |
February 2, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y10T 436/216 20150115;
G01N 1/405 20130101; G01N 1/2273 20130101; Y10T 436/25875 20150115;
G01N 1/2226 20130101; G01N 33/0047 20130101; G01N 1/2214
20130101 |
International
Class: |
G01N 33/00 20060101
G01N033/00 |
Claims
1. A method for measuring an atmospheric concentration of a
compound, comprising steps of: providing an adsorptive tag within a
target atmosphere for a period of time to allow adsorption of a
compound of interest for measurement, wherein the adsorptive tag
comprises a substrate, a heating element disposed on or within the
substrate and an adsorptive element disposed on the substrate over
the heating element; removing the adsorptive tag from the target
atmosphere after said period of time, and placing the adsorptive
tag within a closed measuring space with electrical contacts of
said heating elements brought into connection with an electrical
power source; heating the adsorptive element to cause de-adsorption
of the compound of interest into the closed measuring space;
measuring a concentration of the de-adsorbed compound of interest
within the closed measuring space; and determining a concentration
of the compound of interest in the target atmosphere based on the
concentration of the compound of interest within the closed
measuring space.
2. The method of claim 1, wherein said adsorptive element is a
carbon based adsorptive element.
3. The method of claim 1, wherein said adsorptive element comprises
a plurality of carbon particles.
4. The method of claim 3, wherein said plurality of carbon
particles comprises carbon nano particles.
5. The method of claim 4, wherein said carbon nano particles are
carbon nano tubes.
6. The method of claim 1, wherein said adsorptive element is a
cellulose based adsorptive element.
7. The method of claim 6, wherein said cellulose based adsorptive
element is coated with a polypyrrole/silver nitrate
preparation.
8. The method of claim 1, wherein said adsorptive element is an
alumide based adsorptive element.
9. The method of claim 1, wherein said adsorptive element comprises
a plurality of silver nanoparticles.
10. An adsorptive tag for collecting and releasing a measurement
sample, comprising: a substrate; a heating element disposed on or
within said substrate; positive and negative electrical contacts
disposed on said substrate and electrically connected with said
heating element; and an adsorptive element disposed on said
substrate over said heating element; wherein said substrate is
adapted for placement within a measuring device with said
electrical contacts in contact with electrical terminals provided
in the measuring device.
11. The adsorptive tag of claim 10, wherein said adsorptive element
is a carbon based adsorptive element.
12. The adsorptive tag of claim 10, wherein said adsorptive element
comprises a plurality of carbon particles.
13. The adsorptive tag of claim 12, wherein said plurality of
carbon particles comprises carbon nano particles.
14. The adsorptive tag of claim 13, wherein said carbon nano
particles are carbon nano tubes.
15. The adsorptive tag of claim 10, wherein said substrate is a
fabric substrate.
16. The adsorptive tag of claim 15 wherein said heating element is
a wire heating element woven into said fabric substrate.
17. The adsorptive tag of claim 10, wherein said adsorbing element
is adapted for adsorption of a volatile organic compound (VOC).
18. The adsorptive tag of claim 17, wherein said VOC is
ethylene.
19. The method of claim 10, wherein said adsorptive element is a
cellulose based adsorptive element.
20. The method of claim 19, wherein said cellulose based adsorptive
element is coated with a polypyrrole/silver nitrate preparation.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an apparatus and method for
measuring a concentration of an aerosolized or gaseous compound,
such as a volatile organic compound (VOC), in an atmosphere, and
more particularly an apparatus and method using an adsorptive
collecting element for collection and measurement of the VOC.
BACKGROUND
[0002] The ability to measure an atmospheric concentration of an
aerosolized or gaseous compound, such as a volatile organic
compound, at relatively low levels, has practical and useful
applications, but presents technological challenges.
[0003] For example, ethylene is a ubiquitous problem in the fresh
produce supply chain. However, measurements of the gas are rarely
taken and even more rarely relied upon. Even when used, such
measurements often yield highly unreliable results.
[0004] While ethylene emitted from produce can be correlated to a
degree of ripeness of the produce, almost all ripeness testing is
performed using either manual examination by skilled hands, or by
destructive cell collapse compression tests wherein cell load
capacity is directly proportional to and calibrated to ripeness.
Both entail high labour cost, high fruit loss and relatively low
accuracy. And, neither test method is informative about the early
stages of ripeness, so these methods simply don't work as
predictors.
[0005] Ethylene control is commonly used across many sectors, but
is not typically used for ripeness analysis. And, it is believed
that analysis of any VOCs other than ethylene, such as heavier
compounds relating to flavor and scent that appear to be present in
trace quantities at early phases in the development post-harvest,
is unknown, although such other VOCs are believed to provide rich
data about fruit condition. Improved measurement capability and
sensitivity, such as in a range of 10-30 parts per billion
atmospheric, can provide useful tools for early and mid stage fruit
analysis.
[0006] PPM sensors for, for example, ethylene and a range of other
VOCs, are cheap, reliable and simple to use, whereas known sensors
suitable in a parts per billion (PPB) range are both expensive and
unreliable.
[0007] Precision sensors that can test PPB atmospheres cost $10 k
and upwards to $1M and take minutes to hours to take single
readings, usually by means of long slow flow or super precise
measurement tools such as gas chromatography-mass spectrometry
(GCMS) and photo acoustic spectrometry. These methods are only
suited to very low volume testing.
[0008] Hence, a low cost and accurate method and apparatus for
measuring low PPB atmospheric concentrations of a substance such as
a volatile organic compound is desired.
[0009] It is therefore an object of the present invention to
provide an apparatus and method for measuring a concentration of a
volatile organic compound (VOC) in an atmosphere, and in particular
for performing such measurements at low concentration levels.
SUMMARY
[0010] The present invention exploits an adsorptive tendency of
certain materials, such as carbon, to capture an aerosolized or
gaseous substance within an atmosphere, for providing the adsorbed
sample to a test device. For example, an adsorptive element may be
provided in a fruit box or storage environment to collect a sample
of a volatile organic compound or a gas related to a ripeness, or
other developmental aspect, of fruit, wherein the adsorptive
element may be subsequently removed to a test device.
[0011] The apparent surface area of an adsorber of the invention is
significantly larger than the physical exterior of the adsorber
patch, so that a capacity for adsorption of a substance is greatly
increased. For example, a carbon adsorber in one embodiment of the
invention has an effective surface area significantly greater than
a typical fruit box (including fruit surfaces), providing a
substantially greater surface area for adsorption than the physical
external dimensions of the adsorber itself.
[0012] When desorbed by heating in a small, closed volume, the
adsorbed gasses are released suddenly and raise the concentration
in the small test volume to levels that are much higher than the
original atmosphere. This presents as the adsorber as acting as an
intermediary concentrator or amplifier. It has been found that
concentration levels in the test chamber are 300 to 1000 or more
times the original atmospheric concentration. It is believed that
concentration levels in the test chamber as high as 10,000 times
the original atmospheric concentration may be achieved.
[0013] This enables readings in parts per million (PPM) that
represent atmospheres whose VOC levels are in parts per
billion.
[0014] Thus a low cost PPM sensor can be used for measurement of
the collected sample, providing a baseline for interpolation back
to a measurement of an atmosphere whose concentration levels are
significantly less concentrated.
[0015] According to one embodiment of the present invention, use of
sensitized adsorber as a collector provides an
amplification/sensitivity increase in collection of a VOC to be
measured within an atmosphere of interest for measurement, such
that using open atmosphere adsorption followed by limited volume
closed atmosphere de-adsorption allows for measurements of the VOC
in the atmosphere of interest at significantly lower levels than
possible by conventional direct measurement of the atmosphere of
interest. These and other features, aspects, and advantages of the
present invention will become better understood with regard to the
following description, appended claims, and accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a flowchart showing a method for measuring an
atmospheric concentration of a volatile organic compound using an
adsorptive element.
[0017] FIG. 2 illustrates an embodiment of an adsorptive element of
the present invention.
[0018] FIG. 3 is a diagrammatic depiction of an adsorptive tag
including a substrate, heating element and adsorptive element.
[0019] FIGS. 4a-4d illustrate certain possible configurations of an
adsorptive tag.
[0020] FIG. 5 is a diagrammatic view of a measuring device adapted
to receive an adsorptive tag in a closed measuring space.
DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS
[0021] Referring to FIG. 1, a measuring method for measuring an
atmospheric concentration of a compound, such as a volatile organic
compound (VOC), can be broadly described as comprising steps of:
providing an adsorptive element within a target atmosphere for a
period of time to allow adsorption of a compound of interest for
measurement; removing the adsorptive element from the target
atmosphere, and placing the adsorptive element within a closed
measuring space; heating the adsorptive element to cause
de-adsorption of the compound of interest into the closed measuring
space; measuring a concentration of the de-adsorbed compound of
interest within the within the closed measuring space; and
determining a concentration of the compound of interest in the
target atmosphere based on the concentration of the compound of
interest within the closed measuring space.
[0022] An adsorptive element 201 of the invention is, in one
embodiment, a carbon mass, which may be formed of carbon particles
203 such as carbon fibers, carbon nanofibers, carbon nanotubes and
the like. The carbon particles 203 may be formed into a disk or
"pill" in certain embodiments. The disk or pill may be cast from a
wet slurry comprising the carbon particles 203 and a binder 205.
Suitable binders 205 include, but are not limited to, water soluble
phase change polymers, such as poly vinyl acetate, or wood glue. In
certain embodiments, a wet slurry includes carbon particles with
poly vinyl acetate at about 2-8% of the weight of the
particles.
[0023] Polysiloxanes as well as polyvinylalcohol are also suitable
binders. Copper oxide (CuO) may be included, such as for example a
mixture of carbon nanofibers, CuO and polyvinylalcohol. In a
mixture of carbon nanofibers, together with CuO (at about 6-18% of
the weight of the nanofibers) and polyvinylalcohol (at about 15% of
the weight of the nanofibers), a resulting adsorber has been found
effective to detect ethylene in less-than 100 ppb
concentrations.
[0024] It is advantageous that a ratio of the carbon particles 203
to the binder 205 is such as to maximize porosity of the disk
(hence maximizing an exposed surface area of the carbon particles
203), while at the same time minimizing shedding of the carbon
particles 203. It can be recognized that if too much of the binder
is used, the disk becomes insufficiently porous for good
adsorption, while if too little of the binder is used, the disk may
be prone to spalling, releasing loose carbon particles into the
environment. Prevention of spalling becomes especially desirable if
the adsorptive element is used in proximity to food items.
[0025] In addition to a carbon based adsorber, other adsorbing
materials may be used. For example, in certain embodiments an
adsorber may be formed of cellulose, cellulose coated with silver
particles, silver nitrate, a mixture of polypyrrole and silver
nitrate, silver nanoparticles or the like. For example, cellulose
may be coated with mixture of polypyrrole and silver nitrate at
about 0.1M concentration. Cellulose based adsorbers have been found
effective to detect ethylene at as low as 10 ppb concentrations,
when the sample is heated at 100-125.degree. C.
[0026] Similarly, an adsorber may be formed of alumide, alumide
coated with silver particles, silver nitrate, a mixture of
polypyrrole and silver nitrate, silver nanoparticles or the like.
Further, mesoporous silica is another suitable adsorbant.
[0027] An ionic liquid may be incorporated to further enhance
adsorption. For example, in the case of ethylene, an ionic liquid
used as an ethylene trapping agent aides in ionization of silver
nanoparticles (to Ag+), which binds to electron donor groups in
ethylene, helping to remove ethylene from the surrounding
atmosphere.
[0028] As described above and with reference to FIG. 1, the
adsorptive element 201 in use is placed in a target atmosphere for
a time period during which the VOC will be adsorbed. Subsequently,
the adsorptive element 201 is removed from the target atmosphere,
placed within an enclosed, sealed measuring space, and heated to
cause de-adsorption of the collected VOC. In certain embodiments, a
heater may be incorporated within a sealed measuring space of a
measuring device, while in other embodiments a heater may be formed
together with the adsorptive element 201 such as in an adsorptive
tag 300.
[0029] A general arrangement for an adsorptive tag 300 is shown in
FIG. 3, wherein a substrate 301 is provided with an electrical
heating element 303 formed on or embedded in the substrate 301,
electrical contact elements 305 are disposed on the substrate 301
and in electrical connection to the heating element such that an
electrical current may be supplied to the electrical heating
element 303 from a sampling or measurement device, and an
adsorptive element 201 is disposed on the substrate 301 over the
heating element 303.
[0030] Referring to FIGS. 4a-4d, embodiments of a substrate 301
having an integral heating element are shown. Broadly speaking, the
heating element 303 comprises one or more heating wires formed on,
or embedded in, a substrate 301, and arranged such that an
adsorptive element 201 may be disposed on the substrate 301, over
the heating wires. In FIGS. 4a and 4b, a plurality of parallel
heating wires of the heating element 303 are provided and arrayed
such that positive and negative electrical contacts 305 may be
provided at opposite ends of the wire array of the heating element,
to provide an electric current for heating the heating wires of the
heating element 303. In FIG. 4c, the heating element 303 comprises
a single heating wire, arranged in a meander pattern.
[0031] In certain embodiments, the substrate 303 may be a woven or
embroidered fabric, with the heating wires woven into the fabric
such that at least end portions of the heating wires are exposed
for electrical contact, defining electrical contact regions 305.
The electrical contact regions 305 are arranged to make electrical
contact with electrical terminals provided in a measuring
device.
[0032] Alternatively, shown in FIG. 4d, a substrate 301 may be
provided in the form of a circuit board substrate 401 with an
etched foil heating element matrix 403. It can be recognized that
porosity of the substrate, inherent to a fabric substrate, may
facilitate dispersion of the de-adsorbed compound from the
adsorbing element into the measuring space. Accordingly, apertures
405 may be formed through the circuit board substrate 401 to
similarly facilitate dispersion such dispersion.
[0033] In certain embodiments, the adsorptive element may be
optimized for adsorption of a particular compound, such as by
addition of electroactive dopants.
[0034] Referring to FIG. 5, a measuring device 500 is adapted to
receive an adsorptive tag 300 in a closed measuring space 505.
Within a body of the measuring device 500, a receiving space, or
measuring space 505 is defined, where in the measuring space 505 is
closed or closable such as by a cover 509. Within the measuring
space 505 is disposed a sensor 503 which is adapted for measurement
of a substance of interest, such as a volatile organic compound
(VOC). In an illustrated embodiment, proximate to or within the
measuring space 505, electrical terminals 507 are arranged to
correspond with electrical contact elements 305 of the adsorptive
tag 300 for supplying an electrical current to the heating element
of the adsorptive tag 300. In alternative embodiments, a heating
element may be disposed within the body of the measuring device
such that the measuring device may be used with an adsorptive
element or adsorptive tag lacking an integrated heating
element.
[0035] A control circuit is provided to activate the heating
element and the sensor 503, to obtain and display or report a
measurement of the substance of interest within the measuring space
505. Referring again to FIG. 1, an adsorptive element such as the
adsorptive tag 300 is placed within the measuring space 505, and
the measuring space 505 is then closed. Following closure of the
measuring space 505, the adsorptive element is heated, such as by
applying an electrical current to the heating element, to cause
de-adsorption of the compound of interest into the closed measuring
space. A measurement of a concentration of the de-adsorbed compound
of interest within the within the measuring space is taken by the
sensor 503, from which can be determined a concentration of the
compound of interest in the target atmosphere.
[0036] In view of the concentration, or amplification, of the
compound of interest in the target atmosphere achieved by the
adsorber, the concentration in the target atmosphere is determined
as a function of the measured concentration, and the expected
amplification. For example, considering an adsorber that achieves a
1000 times amplification, a measured value of 50 ppm would
correspond to a 50 ppm concentration in the target atmosphere.
Approximate amplifications resulting from this process are of the
order of 300 to over 1000 times, and may be as high as 10,000
times.
[0037] It will be understood that the above-described embodiments
of the invention are illustrative in nature, and that modifications
thereof may occur to those skilled in the art. Accordingly, this
invention is not to be regarded as limited to the embodiments
disclosed herein, but is to be limited only as defined in the
appended claims.
* * * * *