U.S. patent application number 13/477990 was filed with the patent office on 2012-11-29 for multi-dopant permeation tube.
This patent application is currently assigned to DSA DETECTION LLC. Invention is credited to Tim Burton, Stephen Scott Milt.
Application Number | 20120298856 13/477990 |
Document ID | / |
Family ID | 47218598 |
Filed Date | 2012-11-29 |
United States Patent
Application |
20120298856 |
Kind Code |
A1 |
Burton; Tim ; et
al. |
November 29, 2012 |
MULTI-DOPANT PERMEATION TUBE
Abstract
Aspects and embodiments of the present invention are directed to
spectrometry systems and for apparatus and methods for delivering
dopants to same. In one example, there is provided a dopant
delivery device configured to supply dopants to a spectrometry
system comprising a tube including a first chamber and a second
chamber, a first dopant source included in the first chamber, and a
second dopant source included in the second chamber.
Inventors: |
Burton; Tim; (Danvile,
NH) ; Milt; Stephen Scott; (Winchester, MA) |
Assignee: |
DSA DETECTION LLC
North Andover
MA
|
Family ID: |
47218598 |
Appl. No.: |
13/477990 |
Filed: |
May 22, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61490701 |
May 27, 2011 |
|
|
|
Current U.S.
Class: |
250/282 |
Current CPC
Class: |
G01N 27/622 20130101;
H01J 49/0422 20130101 |
Class at
Publication: |
250/282 |
International
Class: |
B01D 59/44 20060101
B01D059/44 |
Claims
1. A dopant delivery device configured to supply dopants to a
spectrometry system comprising: a tube including a first chamber
and a second chamber; a first dopant source included in the first
chamber; and a second dopant source included in the second
chamber.
2. The dopant delivery device of claim 1, wherein the first chamber
is defined by a wall of the tube, a first plug inserted into a
portion of the tube proximate a first end of the tube, and by a
second plug inserted into the tube at a position remote from the
first end of the tube.
3. The dopant delivery device of claim 2, wherein the second
chamber is defined by the wall of the tube, a third plug inserted
into a portion of the tube proximate a second end of the tube, and
by the second plug.
4. The dopant delivery device of claim 3, wherein a bore is defined
in one of the first plug and the third plug.
5. The dopant delivery device of claim 1, wherein the first dopant
source comprises dichloromethane liquid.
6. The dopant delivery device of claim 5, wherein the wall of the
tube defining the first chamber is permeable to dichloromethane
vapor.
7. The dopant delivery device of claim 1, wherein the second dopant
source comprises an ammonia solid.
8. The dopant delivery device of claim 7, configured to emit both
dichloromethane vapor and ammonia vapor.
9. The dopant delivery device of claim 6, configured to provide a
visual indication of an expiration of the supply of one of the
first dopant source and the second dopant source.
10. The dopant delivery device of claim 9, wherein the visual
indication includes a visual indication of a fluid level of the
dichloromethane liquid.
11. The dopant delivery device of claim 9, wherein the visual
indication includes a visual indication of a color of an indicator
material.
12. The dopant delivery device of claim 1, coupled to the
spectrometry system.
13. A method of supplying a plurality of dopants to a spectrometry
system comprising: loading a first quantity of a first dopant into
a first chamber of a dual-mode dopant tube, a remaining quantity of
the first dopant visually ascertainable through a wall of the first
chamber; loading a second quantity of a second dopant into a second
chamber of the dual mode-dopant tube, the second quantity of the
second dopant having an expected time for depletion greater than an
expected time for depletion of the first quantity of the first
dopant; loading the dual-mode dopant tube into a dopant tube port
of the spectrometry system; and heating the dual-mode dopant tube,
resulting in the release of a portion of the first dopant and a
portion of second dopant from the dual-mode dopant tube and in to
the spectrometry system.
14. An apparatus configured to supply dopants to a spectrometry
system comprising: a first chamber coupled to a second chamber; the
first chamber configured to retain a first dopant source and to
release a first dopant from the first dopant source from an
internal volume of the first chamber; and the second chamber
configured to retain a second dopant source and to release a second
dopant from the second dopant source from an internal volume of the
second chamber.
15. The apparatus of claim 14, wherein the first chamber includes a
wall contiguous with a wall of the second chamber.
16. The apparatus of claim 14, wherein a wall of the first chamber
is formed of a material different from a material of which the
second chamber is formed.
17. The apparatus of claim 14, wherein the first chamber has a
dimension which differs from a corresponding dimension of the
second chamber.
18. The apparatus of claim 14, configured to be mounted in a port
of the spectrometry system and to deliver the first dopant and the
second dopant into the spectrometry system from within the port.
Description
RELATED APPLICATIONS
[0001] This application claims priority under 35 U.S.C.
.sctn.119(e) to U.S. Provisional Application Ser. No. 61/490,701,
titled "MULTI-DOPANT PERMEATION TUBE," filed on May 27, 2011, which
is herein incorporated by reference in its entirety.
BACKGROUND
[0002] 1. Field of Disclosure
[0003] Aspects and embodiments of the present disclosure are
directed to spectrometry systems and for apparatus and methods for
delivering dopants to same.
[0004] 2. Discussion of Related Art
[0005] Ion mobility spectrometers (IMS) and ion trap mobility
spectrometers (ITMS) are used to detect and identify trace amounts
of airborne chemicals. These types of spectrometers are sometimes
employed to detect explosives or narcotics. Ammonia and
dichloromethane (DCM) are used as dopants that enable the transport
of sampled materials within an IMS or ITMS spectrometer. These
dopants are used to accept a transfer of charge created during
ionization of a carrier gas used to carry a sample through the
spectrometer. Ionization of the carrier gas is thus reduced,
reducing the amount of spectrometer detector readings that might
otherwise occur due to ionized carrier gas and increasing the
signal to noise ratio of the spectrometer. A dopant may be
introduced to a carrier gas by flowing the carrier gas around a
permeation tube which releases a controlled concentration of a
dopant into the carrier gas. In the current state of the art, a
spectrometer uses two separate permeation tubes to convey the
ammonia gas (positive ion dopant) and DCM (negative ion dopant)
inside the spectrometer.
SUMMARY
[0006] Aspects and embodiments of the present disclosure include a
device used for introduction of dopants, for example, ammonia and
dichloromethane (DCM), into a spectrometry system, such as an ion
mobility spectrometer or ion trap mobility spectrometer and to
spectrometry systems including such devices.
[0007] In accordance with an aspect of the present disclosure there
is provided a dopant delivery device configured to supply dopants
to a spectrometry system. The dopant delivery device comprises a
tube including a first chamber and a second chamber, a first dopant
source included in the first chamber, and a second dopant to source
included in the second chamber.
[0008] In accordance with some embodiments, the first chamber is
defined by a wall of the tube, a first plug inserted into a portion
of the tube proximate a first end of the tube, and by a second plug
inserted into the tube at a position remote from the first end of
the tube. In some embodiments, the second chamber is defined by the
wall of the tube, a third plug inserted into a portion of the tube
proximate a second end of the tube, and by the second plug. In some
embodiments, a bore is defined in one of the first plug and the
third plug.
[0009] In accordance with some embodiments, the first dopant source
comprises dichloromethane liquid. In accordance with some
embodiments, the wall of the tube defining one of the first chamber
and the second chamber is permeable to dichloromethane vapor. In
accordance with some embodiments, the second dopant source
comprises an ammonia solid.
[0010] In accordance with some embodiments, the dopant delivery
device is configured to emit both dichloromethane vapor and ammonia
vapor.
[0011] In accordance with some embodiments, the dopant delivery
device is configured to provide a visual indication of the
expiration of the supply of the first dopant source and of the
expiration of the supply of the second dopant source. In some
embodiments, the visual indication includes a visual indication of
a fluid level of the dichloromethane liquid. In some embodiments,
the visual indication includes a visual indication of a color of an
indicator material.
[0012] In accordance with some embodiments, the dopant delivery
device is coupled to the spectrometry system.
[0013] In accordance with another aspect of the present disclosure,
there is provided a method of supplying a plurality of dopants to a
spectrometry system. The method comprises loading a first quantity
of a first dopant into a first chamber of a dual-mode dopant tube,
a remaining quantity of the first dopant visually ascertainable
through a wall of the first chamber, loading a second quantity of a
second dopant into a second chamber of the dual mode-dopant tube,
the second quantity of the second dopant having an expected time
for depletion greater than an expected time for depletion of to the
first quantity of the first dopant, loading the dual-mode dopant
tube into a dopant tube port of the spectrometry system, and
heating the dual-mode dopant tube, resulting in the release of a
portion of the first dopant and a portion of the second dopant from
the dual-mode dopant tube and in to the spectrometry system.
[0014] In accordance with another aspect of the present disclosure,
there is provided an apparatus configured to supply dopants to a
spectrometry system. The apparatus comprises a first chamber
coupled to a second chamber. The first chamber is configured to
retain a first dopant source and to release a first dopant from the
first dopant source from an internal volume of the first chamber.
The second chamber is configured to retain a second dopant source
and to release a second dopant from the second dopant source from
an internal volume of the second chamber.
[0015] In accordance with some embodiments, the first chamber
includes a wall contiguous with a wall of the second chamber.
[0016] In accordance with some embodiments, a wall of the first
chamber is formed of a material different from a material of which
the second chamber is formed.
[0017] In accordance with some embodiments, the first chamber has a
dimension which differs from a corresponding dimension of the
second chamber.
[0018] In accordance with some embodiments, the apparatus is
configured to be mounted in a port of the spectrometry system and
to deliver the first dopant and the second dopant into the
spectrometry system from within the port.
BRIEF DESCRIPTION OF DRAWINGS
[0019] The accompanying drawings are not intended to be drawn to
scale. In the drawings, each identical or nearly identical
component that is illustrated in various figures is represented by
a like numeral. For purposes of clarity, not every component may be
labeled in every drawing. In the drawings:
[0020] FIG. 1 is a side view of a dopant delivery device in
accordance with an embodiment of the present disclosure;
[0021] FIG. 2 is an end view of the device of FIG. 1; and
[0022] FIG. 3 is a schematic illustration of the dopant delivery
device of FIG. 1 coupled to a spectrometry system.
DETAILED DESCRIPTION
[0023] This disclosure is not limited in its application to the
details of construction and the arrangement of components set forth
in the following description or illustrated in the drawings. The
disclosure is capable of other embodiments and of being practiced
or of being carried out in various ways. Also, the phraseology and
terminology used herein is for the purpose of description and
should not be regarded as limiting. The use of "including,"
"comprising," "having," "containing," "involving," and variations
thereof herein is meant to encompass the items listed thereafter
and equivalents thereof as well as additional items.
[0024] An embodiment of a dopant delivery device in accordance with
the present disclosure is illustrated in FIG. 1, indicated
generally at 100. This device may be referred to as a dual-mode
dopant tube. The device includes a tube 1. In some embodiments, the
tube is formed from a material, such as polytetrafluoroethylene
(PTFE), which is permeable to certain dopants, such as
dichloromethane. In some embodiments, the tube wall is formed of a
solid, non-porous material, and in other embodiments, the tube may
include one or more pores or apertures on at least a portion of the
tube wall. In some embodiments, the tube 1 is visually transparent
or translucent. In one embodiment, the tube 1 has a diameter of
about 0.5 inches (about 1.27 cm) and a thickness of about 0.03
inches (about 0.076 cm), and is divided into two one-inch long
chambers 5, 6, although the tube may be sized to accommodate or
adapt to different spectrometry systems. A tube formed of PTFE and
having a length of one inch (2.54 cm), a diameter of 0.5 inches
(1.27 m), and a wall thickness of 0.03 inches (0.076 cm) will
permeate dichloromethane at a rate of about 4,600.+-.460 nanograms
per minute (ng/min) at a temperature of 30.degree. Celsius at
atmospheric pressure. Different materials, dimensions and/or
thicknesses of the tube 1 could be utilized to achieve a desired
permeation rate of dichloromethane. In some embodiments, the tube 1
may include markings, for example, score marks, which may provide
an indication to a user of an amount of dopant present in the tube.
For to example, each score mark may indicate a specific volume of
the tube. A user may fill the tube with a dopant until the volume
of the dopant reaches a score mark indicating a desired quantity of
dopant. A user may periodically check the quantity of a dopant
which is visibly discernable through the wall of the tube by
checking the level of the dopant against the score marks on the
tube. For dopants which are not visibly discernable through the
wall of the tube 1, a user may remove a plug 3 enclosing the dopant
in the dopant chamber to check the amount of remaining dopant
remaining therein.
[0025] The tube 1 is separated into two chambers, a first chamber 5
and a second chamber 6, separated by a plug 3 which may be secured
in place by a collar 2. Additional plugs 3 may seal the ends of the
tube 1. The plugs 3 may be formed as short rods having a diameter
approximately equal to the inside diameter of the tube 1, or in
some embodiments, from about 5% to about 10% greater than the
inside diameter of the tube 1. The plugs 3 may be formed from a
material such as virgin PTFE or one or more other resilient
materials which may be chemically resistant to dopant sources which
are to be used in the dopant delivery device. The plugs 3 may
provide an interference fit inside the tube 1. Collars 2 may exert
a compressive force on the outside surface of the tube 1 and
facilitate securing the plugs 3 in place within the tube 1. The
plugs 3, alone or in combination with the collars 2, may seal the
various sections of the tube, thereby preventing leakage of gas or
liquid from the chambers of the tube 1 and/or preventing cross
contamination between the sealed chambers 5, 6 of the tube 1.
[0026] The plug 3 at the outside end of the chamber 6 may include
one or more bores 4 (illustrated in FIG. 2) formed in the plug 3.
The bores may provide for the controlled release of a dopant from
the second chamber 6, which is incapable of permeating the walls of
the tube 1. For example, anhydrous ammonium carbamate powder 7 may
be placed in the second chamber 6 to produce ammonia gas when
heated to, for example, a temperature of about 30.degree. Celsius.
The ammonia gas may exit the second chamber 6 through the bores 4.
The provision of two bores 4, each with a diameter of about 1/32 of
an inch (about 0.079 cm), with a total opening surface area of
1.53.times.10.sup.-3 inches.sup.2 (about 9.87.times.10.sup.-3
cm.sup.2), will provide for permeation to of ammonia gas from the
second chamber 6 at a rate of about 9,000.+-.900 ng/min. Different
bore sizes and/or different numbers of bores could provide for
different permeation rates as desired. Other ammonia producing
compounds may be utilized in addition to, or in place of the
anhydrous ammonium carbamate powder 7. Additional and/or other
chemical sources may be present in the second chamber 6 to provide
additional and/or different dopants.
[0027] In some embodiments, one or more pores or apertures may be
provided in the wall of the first chamber 5 and/or the second
chamber 6 to allow for the permeation of dopant gas therethrough.
In some embodiments, dopants placed in each of the first chamber 5
and the second chamber 6 may produce gasses capable of permeating
through the material of the walls of the tube and no bores, pores,
or apertures would be needed in either of the first chamber 5 or
the second chamber 6.
[0028] In use, the first chamber 5 may be partially filled with a
quantity of dichloromethane 8 or some other dopant source, while
the second chamber 6 is at least partially filled with a quantity
of anhydrous ammonium carbamate powder or other dopant source. The
dopant source used in chamber 5 may in some embodiments be
dichloromethane with a purity of about 99.8% or above, mixed with
amylene. The dopant source in chamber 5 may provide negative ion
dopants for use in an IMS or ITMS detector, while the dopant source
in chamber 6 may provide a positive ion dopant for use in an IMS or
ITMS detector.
[0029] In some embodiments, the amount of a first dopant source
whose depletion may readily be gauged by observation, for example,
by visual observation through a wall of the tube 1, may be included
in one of chambers 5 or 6 while a second dopant source whose
depletion may not be readily gauged by observation may be included
in the other one of the chambers 5 or 6. The amount of the dopants
added to the chambers may be calibrated such that the dopant source
whose depletion may readily be gauged by observation is provided in
a quantity such that this dopant will be depleted prior to the
depletion of the dopant source whose depletion may not be readily
be gauged by observation. For example, in the first chamber 5,
dichloromethane may be provided as a liquid, a level of which may
be visually ascertained through the wall of the tube 1. In the
second chamber 6, ammonium carbamate powder may be provided. During
use, the ammonium carbamate powder may decompose and coat the
inside of the tube 1, or a residual amount of ammonium carbamate
powder may be left on the inside of the tube 1, thus obscuring an
accurate visual reading of the remaining amount. An amount of
ammonium carbamate may be loaded into the chamber 6 that exceeds
the lifetime of the dichloromethane liquid loaded into the chamber
5, so that the limiter of the useful lifetime of the dopant
delivery device comprising the tube 1 is the dichloromethane. This
allows the user to quickly ascertain the remaining useful lifetime
of the dopant delivery device by observing the dichloromethane side
of the tube 1 only.
[0030] In some embodiments, one or more additional mechanisms for
determining a remaining useful lifetime or the presence of one or
more dopants in the first chamber 5 and/or the second chamber 6 may
be provided. For example, a portion of the wall of the tube 1 may
be coated or surrounded with an indicator material which reacts by,
for example, changing color in the presence of a particular dopant
or a gaseous form of a particular dopant. Alternatively or
additionally, a color changing strip including the color changing
indicator material may be included in one of the chambers of the
tube 1. The color of the indicator material may change when the
dopant has become depleted, providing for a user to visibly
ascertain if a dopant to which the color changing indicator
material reacts remains in the tube 1 or not. In other embodiments,
a time-sensitive indicator material which changes color over time
in the presence of a particular dopant may be provided in one of
the chambers of the tube 1 or on or surrounding a wall of the tube
1. An amount of dopant may be added to the tube 1 which would
expect to become depleted in a time corresponding to the time it
would take the time-sensitive indicator material to change color.
The color of the time-sensitive indicator material may change when
the dopant has become depleted, providing for a user to visibly
ascertain if a dopant to which the time-sensitive indicator
material reacts remains in the tube 1 or not.
[0031] In some embodiments, the tube 1 may be provided with a
single chamber into which a plurality of dopant sources may be
added, at least one of which having a volume which may be
ascertained, visually or otherwise, through the wall of the tube 1.
In such embodiments, the plurality of dopant sources may be
compatible, for example, not reacting with one another or
inhibiting the production of dopants from one another.
[0032] In further embodiments, the two chambers 5, 6 may be formed
from different tubes and joined together. The material(s) of which
the tubes defining the chambers 5, 6 may be the same, or in other
embodiments, different. For example, one of the tubes defining one
of the chambers 5, 6 may be formed from PTFE while the other tube
is formed from a different polymer, for example, perfluoroalkoxy
(PFA), fluorinated ethylene-propylene (FEP), or polyvinylidene
fluoride (PVDF). In some embodiments, one or more dimensions, for
example a wall thickness, length, or diameter of one of the
chambers 5, 6, may differ from one or more dimensions of another of
the chambers 5, 6. In some embodiments, one or both of the tubes
defining the chambers 5, 6 may have solid, non-porous walls, and in
other embodiments, one or both of the tubes defining the chambers
5, 6 may have porous walls. In further embodiments, the chambers 5,
6, are not limited to being tubes, but may have any suitable shape
conducive to the storage of one or more dopant sources and the
release of one or more dopants.
[0033] In further embodiments, as illustrated in FIG. 3, the dopant
introduction apparatus 100 is coupled to, or mounted within an IMS
or ITMS detector 200. Samples are collected with sampling media,
such as sample traps or sample swabs made of PTFE-coated
fiberglass, paper, cloth, polyimide, or NOMEX.RTM. meta-aramid
material may be vaporized in the desorber 210. The vaporized
molecules then may pass through a semi-permeable membrane 220 and
into the detector. In an analysis chamber 230 of the spectrometer
the vaporized molecules are ionized so that they can be mobilized
through the detector by an electric field. The time of flight which
is the length of time it takes a substance to pass through the
detector, depends on the mobility of the ion, and hence the species
of the ion. Ions are detected as they hit the collector 240. The
detection events are processed through a pre-amplifier 250 and a
signal processor 260, and the resultant data displayed on a display
270, for example, a computer monitor. A carrier gas present in the
analysis chamber is circulated by a pump 280 through one or more
drying units 290 and a dopant chamber 300. The dopant delivery
device 100 is present in the dopant chamber 300, for example, in a
dopant tube port. The dopant delivery device 100 introduces dopants
into the carrier gas as the carrier gas circulates through the
apparatus. The dopant delivery device 100 may introduce dopants
into the carrier gas upon heating of the dopant delivery device to,
for example, a temperature of about 30.degree. Celsius. One or more
dopants may be introduced into the carrier gas by permeating
through a wall in a first and/or a second chamber of the dopant
delivery device 100. One or more dopants may be introduced into the
carrier gas by passing through a bore, aperture, or pore in a wall
of the first and/or the second chamber of the dopant delivery
device 100.
[0034] In accordance with further aspects of the present
disclosure, there is provided a method of supplying dopants to a
spectrometry system, for example, an IMS or an ITMS system.
Embodiments of the method may include providing a dual-mode dopant
tube such as that illustrated in FIG. 1 and FIG. 2, or as otherwise
described above. A first quantity of a first dopant, for example
DCM, may be loaded into a first chamber of a dual-mode dopant tube.
In some embodiments, the quantity of the first dopant is visually
ascertainable through a wall of the first chamber. The first
quantity of the first dopant may be measured out prior to the
addition of the dopant to the tube, or may be determined during the
loading of the dopant by, for example, comparing a level of the
dopant in the tube to markings on the tube, when present.
Embodiments of the method may further include loading a second
quantity of a second dopant, for example, ammonium carbamate, into
a second chamber of the dual mode-dopant tube. In some embodiments,
the second quantity of the second dopant may be measured out,
either prior to or during loading of the second dopant into the
second chamber, such that an amount of the second dopant is loaded
which has an expected time for depletion greater than an expected
time for depletion of the first quantity of the first dopant. The
dual-mode dopant tube may then be loaded into a dopant tube port of
the spectrometry system for use. The remaining quantity of one or
both of the dopants may periodically be checked by a user. In some
embodiments checking the remaining quantity of the first and/or
second dopant may include visually ascertaining a remaining
quantity of the first and/or second dopant through a wall of the
tube 1. In some embodiments, if a useful remaining quantity of one
of the dopants is observed, this may serve as an indication that a
useful remaining quantity of the other dopant also remains.
[0035] Having thus described several aspects of at least one
embodiment of this disclosure, it is to be appreciated various
alterations, modifications, and improvements will readily occur to
those skilled in the art. Such alterations, modifications, and
improvements are intended to be part of this disclosure, and are
intended to be within the spirit and scope of the disclosure.
Accordingly, the foregoing description and drawings are by way of
example only.
* * * * *