Note: Descriptions are shown in the official language in which they were submitted.
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INJECTION MODULE
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of and priority to US
Provisional
Patent Application No. 63/088,073 filed October 6th, 2020, under the title
INJECTION SYSTEM. The content of the above patent application is hereby
expressly incorporated by reference into the detailed description hereof.
FIELD
[0002] The specification relates to an injection module, a method of
analyzing
a sample, a device having the injection module and an analytical system having
the
injection module.
BACKGROUND
[0003] Gas Chromatography (GC) is a separation technique of complex
mixtures based upon the chemical and physical properties of the individual
components such as molecular weight, boiling point, polarity, degree of
saturation
etc. A sample mixture is injected into a column with either a solid adsorbent
or thin
film liquid phase coating on the inside of the column referred to as the
stationary
phase. A carrier gas, known as the mobile phase, is passed through the column.
The individual chemical components are pushed via the carrier gas and pass
through the column at different rates depending on their interaction with the
stationary phase. The individual chemicals can then be identified and
quantitated.
Both compositional and trace analysis by GC are used in modern industry for
process control, to predict physical characteristics and maintain product
quality.
[0004] Sample mixtures are introduced into the GC column with
various
techniques depending on their phase. Permanent gases such as He, Hz, 02, Ar,
Nz,
CH4, CO, CO2, C2H5, C2H4, C2I-12 and H25 are already in the gas phase and can
be
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injected directly via headspace syringe or gas sampling valve. Moving up in
molecular weight are mixtures of C3s and C4s referred to as Liquified
Petroleum
Gases (LPGs). These are gases at Normal Temperature and Pressure (NTP) but can
be condensed by application of pressure. LPGs can be introduced into a GC via
high-pressure liquid sampling valves (LSVs). C5 and higher are liquids at NTP
and
can be introduced into a GC via LSV or liquid syringe. Both high-pressure
liquids
and atmospheric liquids are vaporized prior to or within the separation column
in
order to flow with the carrier gas and interact with the stationary phase. All
three of
these types of samples may contain thousands of compounds at trace levels, but
it
is the majority percentage compositional compounds which determine the phase
of
the overall mixture.
[0005] When an LSV is used to inject a high-pressure liquid
sample into a gas
stream, the sample is pressurized to ensure it remains in a single phase. The
pressure required to keep the sample in single phase is determined by the
composition of the sample and the temperature of the liquid sampling valve.
Referencing phase diagrams of C3-C4 mixtures (Figure 1)
(https://www.engineeringtoolbox.com/propane-butane-mix-d 1043. html,
incorporated herein by reference) shows that a minimum working range around
10bar or 150psi at 30 C will ensure that the sample stays in the liquid phase.
It is
common to increase the pressure to ensure all components are in the liquid
phase,
for example between 400 and 1000psi. This approach is commonly used for the
compositional GC analysis of high-pressure propane, butanes, pentanes, natural
gas liquids, condensates and even crude oil.
[0006] When the liquid valve is actuated, the liquid volume
trapped in the
sample loop at 400 psi is placed in series with the carrier gas flow. Carrier
gas
head pressures are generally between 5-50ps1, depending on the interior
diameter
and length of the column and carrier gas chosen. The LPG sample is now
vaporized, either by heated zone or by pressure drop. The resultant vaporized
sample is then pushed by the flowing carrier gas stream onto the column for
chromatographic separation. This technique is limited to characterizing only
the
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lighter compounds in the sample mixture due to incomplete vaporization of the
heavy compounds. It is very difficult to accurately characterize sample
composition
beyond C30 with a traditional liquid valve injection because the heavy
components
fall out of phase (remain liquid) the moment the majority of the lighter
components
are vaporized. This is referred to as mass discrimination. Vaporization of the
liquid
sample does not occur until the sample is moved into the heated zone and is
close
to or directly on-column. Heavy compounds can be analyzed separately from
light
compounds by first dissolving the sample in Carbon Disulfide (CS2). This
solvent is
both toxic and flammable. In addition, this approach requires separating the
sample in two or three fractions, each processed and analysed on different
instruments.
[0007] There is a need in the art for an injection module which
can be used
for injecting a sample for analysis and keeping the sample in liquid phase
when the
valve is actuated, and to help address some of the challenges of injection of
a
sample or where the sample can contain compounds having a broad range of
boiling points. In addition, there is a need in the art for a method for
analyzing a
sample containing compounds having a broad range of boiling points. Moreover,
there is a need in the art for a device having the injection module or an
analytical
system having the injection module as disclosed herein.
SUMMARY OF THE INVENTION
[0008] In one aspect, the specification relates to an injection
module having:
[0009] - an injection valve having a sample inlet port, a mobile
phase inlet
port, a waste port, a column port and a sample loop;
[0010] the injection valve configurable from a first position to a second
position,
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[0011] the first position directing fluid flow from the sample
inlet port to the
sample loop, and from the sample loop to the waste port, and also directing
fluid
flow from the mobile phase inlet port to the column port, and
[0012] the second position directing fluid flow from the sample
inlet port to
the waste port, and also directing fluid flow from the mobile phase inlet port
to the
sample loop, and from the sample loop to the column port;
[0013] - a restriction tubing having a valve end and a column
end, the valve
end coupled to the column port of the injection valve, and the column end
configured for coupling to a column; wherein the restriction tubing is
configured for
reducing separation of a sample into a gas phase and a liquid phase when the
injection valve is in the second position.
[0014] In a second aspect, the specification relates to a method
of analyzing a
sample having multiple phases using an injection module as disclosed herein,
the
method containing the steps of:
[0015] - injecting the sample into the sample loop;
[0016] - transporting the sample from the sample loop to the
column while
maintaining a pressure and/or a temperature on the sample for reducing
separation
of a sample into a gas phase and a liquid phase;
[0017] - separating the sample in the column; and
[0018] - detecting constituents of the sample.
[0019] In a third aspect, the specification relates to an
analytical device for
analysis of a sample, the analytical device having:
[0020] - an injection module as disclosed herein;
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[0021] - a column for separation of constituents of the sample,
wherein one
end of the column is in fluid communication with the injection module; and
[0022] - a detector coupled to a second end of the column for
detecting the
constituents of the sample.
[0023] In a fourth aspect, the specification relates to an analytical
system for
analysis of a sample having:
[0024] - an injection module as disclosed herein;
[0025] - a column for separation of constituents of the sample;
and
[0026] - a detector for detecting the constituents of the sample;
[0027] - a mobile phase delivery system; and
[0028] - a computer system having a program for executing a
method for
analysis of the sample.
[0029] Reference will now be made, by way of example, to the
accompanying
drawings which show example embodiments of the present application, and in
which:
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Reference will now be made, by way of example, to the
accompanying
drawings which show example embodiments of the present application, and in
which:
[0031] Figure 1 shows a phase diagrams of C3-C4 mixtures;
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[0032] Figure 2 shows a schematic of an analytical device having
the injection
module in accordance with the specification;
[0033] Figure 3 shows an embodiment of an injection valve in
different
positions;
[0034] Figure 4 shows an example of an injection system in accordance with
the specification;
[0035] Figure 5 shows a High Pressure Liquid Sample Valve, flush
mounted to
MGCI (arrow "A") and the LSV column port is vertically oriented down into the
MGCI (arrow "B");
[0036] Figure 6 shows a restriction tubing (arrow) mounted in the column
oven, coupled to column and connected to detector;
[0037] Figure 7 shows a Certificate of Analysis of 1m1 of Supelco
5000ppm
ASTM 2887 Quantitative Calibration Solution used to spike the butane sample;
[0038] Figure 8 shows comparative chromatograms of three samples;
[0039] Figure 9 shows a schematic of a second analytical device having the
injection module in accordance with the specification;
[0040] Figure 10 shows a connection of a mobile phase restriction
tubing to a
mobile phase system tubing;
[0041] Figure 11 shows connection to an injection valve in
accordance with a
second embodiment;
[0042] Figure 12 shows setup of a restriction tubing from the
injection valve
in accordance a second embodiment; and
[0043] Figure 13 shows a chromatogram obtained by analysis of a
sample
using a second embodiment of the injection module.
[0044] Similar reference numerals may have been used in different figures
to
denote similar components.
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DESCRIPTION OF EXAMPLE EMBODIMENTS
[0045] The specification relates to an injection module 10 that
can be used for
analysis of a sample having different constituents, and where some of the
constituents of the sample can exist in multiple phases, such as, for example
and
without limitation, a gas phase and a liquid phase.
[0046] As noted above, for example and without limitation, butane
exists as a
gas at normal temperature and pressure (NTP), however, at high pressures,
butane
liquefies. Analyzing, for example and without limitation, a sample containing
butane and longer hyrdocarbons can be challenging, as reduction in pressure
can
lead to separation of butane from the other constituents in the sample,
leading to
mass discrimination; and potentially, with some longer hydrocarbons going from
a
liquid phase to a solid phase, making their analysis even more challenging.
[0047] The injection module 10 disclosed herein can help to
retain sufficient
pressure on the sample to reduce separation of the sample constituents that
have
different vapor pressures. In one embodiment, for example and without
limitation,
the injection module 10 helps to retain the sample in a liquid phase, by
reducing
separation of the sample into a gas phase and a liquid phase. An embodiment of
the injection module is shown in Figure 2, described further herein.
[0048] According to one aspect, the specification relates to an injection
module 10 having:
[0049] - an injection valve 12 having a sample inlet port 14, a
mobile phase
inlet port 16, a waste port 18, a column port 20 and a sample loop 22;
[0050] the injection valve 12 configurable from a first position
to a second
position,
[0051] the first position directing fluid flow from the sample
inlet port 14 to
the sample loop 22, and from the sample loop 22 to the waste port 18, and also
directing fluid flow from the mobile phase inlet port 16 to the column port
20, and
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[0052] the second position directing fluid flow from the sample
inlet port 14 to
the waste port 18, and also directing fluid flow from the mobile phase inlet
port 16
to the sample loop 22, and from the sample loop 22 to the column port 20;
[0053] - a restriction tubing 24 having a valve end 26 and a
column end 28,
the valve end 26 coupled to the column port 20 of the injection valve 12, and
the
column end 28 configured for coupling to a column 30; wherein the restriction
tubing 24 is configured for reducing separation of a sample into a gas phase
and a
liquid phase when the injection valve is in the second position.
[0054] The injection valve 12 used in the injection module 10
disclosed herein
is not particularly limited, and can be varied depending upon design and/or
application requirement. Moreover, the injection valve 12 (sometimes also
referred
to as sampling valves), as used for purposes of chromatographic purification,
should be known to a person of ordinary skill in the art. The injection valve
12
selected should be able to withstand the pressure applied for purification of
the
sample using the method as disclosed herein. In one embodiment, for example
and
without limitation, the injection valve 12 is a six-port rotary valve. In a
further
embodiment, for example and without limitation, the six-port rotary valve is a
liquid
sampling valve as shown in Figure 3.
[0055] As shown in Figure 3, the injection valve 12 has a sample
inlet port 14,
a mobile phase inlet port 16, a waste port 18, a column port 20 and a sample
loop
22. The sample inlet port 14, a mobile phase inlet port 16, a waste port 18, a
column port 20 and a sample loop 22, disclosed and used in the injection valve
12,
disclosed herein, can be, for example and limitation, similar to a liquid
sampling
valve (LSV) typically employed in high pressure liquid chromatography (H PLC).
[0056] The injection valve 12 can be configured from a first position
(position
A' in Figure 3) to a second position (Iposition B' in Figure 3). In the first
position,
the sample inlet port 14 is in fluid communication with the sample loop 22, at
one
end of the sample loop 22, and the opposing end of the sample loop 22 is in
fluid
communication with the waste port 18. Hence, any sample injected in the sample
inlet port 14 would travel into the sample loop 22, filling the sample loop
22, and
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with the excess exiting out from the waste port 18. In addition, in the first
position, the mobile phase inlet port 16 is in fluid communication is in fluid
communication with the column port 20; and where the column port 20 is in
fluid
communication with a column 30. Hence, the mobile phase flows from the mobile
phase inlet port 16 and exits from the column port 20 towards the column 30.
[0057] Once the sample is filled in the sample loop 22, the
injection valve 12
can be actuated to move from the first position ('position A' in Figure 3) to
the
second position ('position B' in Figure 3). The means for actuation of the
injection
valve 12 is not particularly limited, and should be known to a person of skill
in the
art. In the second position, the mobile phase inlet port 16 is in fluid
communication
with the sample loop 22, and the other end of the sample loop 22 is in fluid
communication with the column port 20, which is in fluid communication with
the
column 30. Hence, upon actuation of the injection valve 12, the mobile phase
pushes the sample from the sample loop 22 to exit from the column port 20,
towards the column 30. In addition, in the second position, the sample inlet
port
16 is in fluid communication to the waste port 18, and directs any flow from
the
sample inlet port 14 towards the waste port 18.
[0058] Positioned between the injection valve 12 and the column
30 is a
restriction tubing 24, with one end ('valve end') 26 of the restriction tubing
24
coupled to the injection valve 12 at the column port 20, permitting fluid flow
from
the injection valve 12 that exits from the column port 20 to fluidly flow in
the
restriction tubing 24 from the valve end 26 towards a column end 28 of the
restriction tubing 24. The column end 28 of the restriction tubing 24 is
coupled to a
column 30, permitting fluid flow from the restriction tubing 24 to exit from
the
column end 28 of the restriction tubing 24 into the column 30.
[0059] The restriction tubing 24 used or selected for use in the
injection
module 10 helps to ensure that sufficient pressure is maintained on the sample
to
reduce or limit separation of the sample constituents into multiple phases,
such as
a gas phase and a liquid phase. Hence, the restriction tubing 24 has
specifications
that it can withstand the pressure of the fluid flowing through the
restriction tubing
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24. In one embodiment, the restriction tubing 24 is selected such that the
pressure
drop from the valve end 26 to the column end 28 of the restriction tubing 24
is
sufficiently low to reduce, and preferably avoid, separation of a sample into
a gas
phase and a liquid phase in the restriction tubing 24. In a further
embodiment, the
restriction tubing 24 is selected such that the fluid pressure at the column
end 28 of
the restriction tubing 24 lies within the pressure limits of the column 30
being used
for separation of the sample. In another further embodiment, the restriction
tubing
24 is selected such that the mobile phase has a flow rate within the flow rate
limits
of the column 30 and detector 68 being used for analysis of the sample.
[0060] In one embodiment, for example and without limitation, the
restriction
tubing 24 is selected to have a dimension, such as, for example and without
limitation, an internal diameter and/or length, to maintain sufficient
pressure on the
sample to limit or prevent separation of the sample constituents into a gas
phase
and a liquid phase, while the sample is in the injector valve 12. In one
embodiment, for example and without limitation, the restriction tubing 24 is
selected to have a dimension, such as, for example and without limitation, an
internal diameter and/or length, to maintain sufficient pressure on the sample
to
limit or prevent separation of the sample constituents into a gas phase and a
liquid
phase, till the sample constituents are within a heating zone, such as, for
example
and without limitation, inside an oven of a gas chromatography (GC) device. As
such, as the sample flows from the injector valve 12 into the restriction
tubing 24,
when the sample reaches a portion of the restriction tubing 24 inside a
heating
zone (such as a GC oven), some separation of the sample constituents can
occur.
Although not ideal, once inside the heating zone, the sample constituents will
encounter the heat inside the heating zone and can be vaporized, and carried
by
the mobile phase on to the column 30 for separation. In another embodiment,
for
example and without limitation, the restriction tubing 24 is selected to have
a
dimension, such as, for example and without limitation, an internal diameter
and/or
length, to maintain sufficient pressure on the sample to limit or prevent
separation
of the sample constituents into a gas phase and a liquid phase, prior to
positioning
of the sample on to the column. In a further embodiment, for example and
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without limitation, the restriction tubing 24 is selected to have a dimension,
such
as, for example and without limitation, an internal diameter and/or length, to
maintain sufficient pressure on the sample to limit or prevent separation of
the
sample constituents into a gas phase and a liquid phase, to attain one or more
conditions as described above, and wherein the sample contains constituents
having a carbon length of C4 and C14, C4 and C20, C4 and C25, C4 and C30, C4
and C40,
or C4 and C40+.
[0061] By selecting the appropriate restriction tubing 24 that
maintains
sufficient pressure on the sample, the sample can move from the injection
valve 12
to the column 30, while limiting separation of the sample constituents in gas
and
liquid phases. This can be analogous to a cold on-column injection, where a
sample
is positioned on the column before separation of the constituents is
initiated.
However, with the injection module 12 disclosed herein, a sample having
different
vapor pressures can be analyzed. In one embodiment, for example and without
limitation, the injection module 12 can be used for characterization of liquid
petroleum gases (LPG) containing hydrocarbons, for example and without
limitation, up to C120.
[0062] Without being bound to a particular theory, as noted
herein,
maintaining sufficient pressure on a sample above the vapor pressure of the
lowest
boiling point constituent of the sample can help to maintain the constituents
of the
sample in a single phase, which for instance, is the liquid phase. Temperature
also
has an impact, and as such, the temperature should be considered and
controlled,
along with pressure to reduce, and limit, separation of a sample into a gas
phase
and a liquid phase.
[0063] When injecting a sample using the injection module 10 disclosed
herein, the injection module 10 is selected to withstand the pressure required
for
reducing, and preferably limiting, separation of a sample into a gas phase and
a
liquid phase. In a further embodiment, the injection module 10 can be
maintained,
or positioned to limit exposure to any heat source, to limit temperature
variation
thereby limiting separation of the sample into gas and liquid phases.
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[0064] In a further embodiment, during the injection process, as
the sample
is carried by the mobile phase from the injection valve 12, via the
restriction tubing
24, to the column 30, the temperature of the mobile phase, injection module
10,
analytical device 64 having the injection module 10 or system 70 having the
analytical device 64 with the injection module 10, can be controlled to limit,
and
preferably avoid, separation of the sample into gas and liquid phases prior to
the
sample coming in contact with the column 30. In another further embodiment,
the
temperature can be controlled by avoiding heating of the mobile phase,
injection
module 10, analytical device 64 having the injection module 10 or system 70
having the analytical device 64 with the injection module 10, before the
sample
reaches the column 30. Once the sample reaches the column 30, the column 30
can be heated to assist with separation of the constituents of the sample.
[0065] In still another embodiment, during the injection process,
as the
sample is carried by the mobile phase from the injection valve 12, via the
restriction tubing 24, to the column 30, the pressure of the mobile phase,
injection
module 10, analytical device 64 having the injection module 10 or system 70
having the analytical device 64 with the injection module 10, can be
controlled to
limit, and preferably avoid, separation of the sample into gas and liquid
phases
before the sample reaches the column.
[0066] The time the sample takes from the injection valve 12 to reach the
column 30 can be determined based on the flow rate and distance between the
injection valve 12 and the column 30. This time required for the sample to
reach
the column 30 from the injection valve 12 can be determined by a person of
skill in
the art.
[0067] The dimensions, such as, length and internal diameter of the
restriction tubing 24 used can be determined based on the pressure required to
maintain the sample in a single fluid phase till it reaches the column 30, or
near the
column 30 in a heated zone, where sufficient heat can be provided to mobilize
the
constituents of the sample to allow for analysis of the constituents. In an
embodiment, the dimensions of the restriction tubing 24 take into account the
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pressure limits of the column 30, such that the mobile phase pressure at the
column end 28 of the restriction tubing 24 is within the limits of the column
30. In
a further embodiment, the dimensions of the restriction tubing 24 take into
account
the flow rate of the mobile phase achieved, such that the flow rate of the
mobile
phase in the column 30 and at the detector 68 are within the limits of the
column
30 and the detector 68, to allow separation and detection of the constituents.
Such
calculation of the dimensions of the restriction tubing are not particularly
limited,
and should be known or can be determined by a person of skill in the art. To
assist
with better understanding such a calculation, disclosed herein is an example.
[0068] In one embodiment, the restriction tubing is selected to having an
internal diameter that is narrower than an internal diameter of the column to
which
the restriction tubing is configured for coupling. In another embodiment, the
internal diameter and/or length of the restriction tubing is selected for
maintaining
sufficient pressure for reducing separation of a sample into a gas phase and a
liquid
phase when the injection valve in the second position.
[0069] In one embodiment, the injection valve 12 is further
provided with a
first waste tubing 32 having a first end 34 coupled to the waste port 18, and
a
second end 36 coupled to a waste valve system 38 (Figure 2). Excess sample can
be directed to the waste port 18 of the injection valve 12 in both the first
and
second positions of the valve. The first waste tubing 32 used is not
particularly
limited, and standard tubing utilized in separation devices for directing
waste
should be known to a person of skill in the art.
[0070] The waste valve system 38 used with the injection module
10
disclosed herein, is provided with a first waste valve 40 coupled to the
second end
36 of the first waste tubing 32. Also provided in the waste valve system 38 is
a
second waste tubing 44 coupled at one end to the first waste valve 40,
permitting
fluid flow from the first waste tubing 32 to the second waste tubing 44, when
the
first waste valve 40 is open (or actuated). In addition, the waste valve
system 38
is provided with a second waste valve 42, coupled to the second end of the
second
waste tubing 44. The second waste valve 42 permitting fluid flow from the
second
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waste tubing 44 to an outlet 46 upon actuation (or opening) of the second
waste
valve 42.
[0071] In one embodiment, the waste valve system 38 disclosed
herein can
help to maintain the integrity of the sample by use of the first waste valve
40 and
second waste valve 42 in series. The waste valve system 38 operates by
actuation
of the first waste valve 40 to permit fluid flow from the first waste tubing
32 into
the second waste tubing 44, while ensuring that the second waste valve 42
remains
closed, and filling the second waste tubing 44. This can help to reduce or
limit
separation of the sample in to gas and liquid phases, by ensuring sufficient
pressure
is maintained on the sample. In the absence of a second waste valve 42, the
sample would be open to atmosphere leading to a sudden pressure drop,
resulting
in change in the constituents of the sample. Once the second waste tubing 44
is
filled, the first waste valve 40 closes, and the second waste valve 42 is
actuated to
open, allowing fluid in the second waste tubing 44 to exit from the outlet 46.
Again, by closing the first waste valve 40 and opening the second waste valve
42,
pressure can be maintained on the sample to reduce or limit separation of the
sample in to gas and liquid phases in the injection module 12. In another
embodiment, for example, the waste valve system 38 operates such that only one
of the first waste valve 40 and the second waste valve 42 is open at any time.
[0072] In one embodiment, the injection module 10 is provided with a sample
tubing 48 having a first end 50 coupled to the sample inlet port 14, and a
second
end 52 for coupling to a sampling system 54, the sample tubing 48 configured
to
permit fluid flow from the sampling system 54 to the sample inlet port 14. The
sample tubing 48 disclosed herein is not particularly limited and should be
known or
can be determined by a person of skill in the art. The sample tubing 48 used
with
the injection valve 12 helps to ensure that sufficient pressure is applied on
the
sample to limit or avoid separation of the constituents of the sample into a
gas
phase and a liquid phase.
[0073] In one embodiment, the injection module 10 disclosed
herein is
provided with a mobile phase tubing 56 having a first end 58 coupled to the
mobile
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phase inlet port 16 and a second end 60 configured for coupling to a mobile
phase
system 62, the mobile phase tubing 56 configured to permit fluid flow from the
mobile phase system 62 to the mobile phase inlet port 16.
[0074] In another embodiment, the mobile phase tubing 56 is also
a tubing
that restricts flow of the mobile phase through the mobile phase tubing 56.
Hence,
the mobile phase tubing 56 is similar to the restriction tubing 24 disclosed
herein,
and is a second restriction tubing (or restricted mobile phase tubing 56). The
restricted mobile phase tubing 56, similar to the restriction tubing 24, helps
to
ensure that sufficient pressure is maintained on the sample to limit or avoid
separation of the sample constituents in gas and liquid phases.
[0075] Without being bound to a particular theory, when the
sample is in the
sample loop 22, and the injection valve 12 is actuated to move from the first
position to the second position, the mobile phase in the mobile phase tubing
56
should push the sample from the sample loop 22 towards the column port 20.
However, if the mobile phase pressure is below the phase separation line of
the
sample, the sample constituents can separate into gas and liquid phases. To
limit
or avoid separation of the sample constituents in to gas and liquid phases,
the
mobile phase should be at a higher pressure than the phase separation line of
the
sample constituents. This can be achieved by using a restricted mobile phase
tubing 56 that maintains sufficient pressure on the sample to limit or avoid
separation of the sample constituents in to gas and liquid phases.
[0076] The restricted mobile phase tubing 56 disclosed herein is
similar to the
restriction tubing 24 disclosed herein; and the reader is directed to the
description
of the restriction tubing 24 which is applicable to the restricted mobile
phase tubing
56, disclosed herein. Hence, in one embodiment, the restricted mobile phase
tubing 56 is configured for limiting separation of the sample constituents
into a gas
phase and a liquid phase when the injection valve is in the second position.
In
another embodiment, for example and without limitation, the internal diameter
and/or length of the restricted mobile phase tubing 56 is selected for
maintaining
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sufficient pressure for limiting separation of a sample constituents into a
gas phase
and a liquid phase when the injection valve 12 in the second position.
[0077] The injection module 10 disclosed herein can be coupled to
a mobile
phase system 62 for supplying a mobile phase. The mobile phase system 62 used
and disclosed herein is not particularly limited, and should be known to a
person of
skill in the art. In one embodiment, for the embodiment for example and
without
limitation, the mobile phase system 62 is provided with a mobile phase tank 72
having one or more regulators 74 for controlling mobile phase flow from the
mobile
phase tank 72. The one or more regulators 74 are coupled to a mobile phase
system tubing 76 that carries the mobile phase towards the injection valve 12.
Additional valves or control meters can be used depending upon design and
application requirements, and which should be known to a person of skill in
the art.
[0078] In one embodiment, for example and without limitation, the
restricted
mobile phase tubing 56, disclosed herein, is selected to having an internal
diameter
narrower than an internal diameter of a mobile phase system tubing 76 to which
the restricted mobile phase tubing 56 is configured for coupling.
[0079] The use of the injection module 10 disclosed herein is not
particularly
limited. In one embodiment, for example and without limitation, the injection
module 10, disclosed herein, is for use with an analytical device 64, wherein
the
device is, for example and without limitation, a gas chromatography (GC)
instrument. The injection module 10 can be provided as a stand alone part, or
part
of an analytical device 64, or a system 70 having the analytical device 64.
[0080] Gas chromatography (GC) is a known separation technique,
and used
in analytical chemistry for separating/or and analyzing compounds that can be
vaporized. Typical GC instruments include an injection module for injection of
a
sample, which is carried by a carrier gas on to a column, where the column is
placed in an oven. Separation of the constituents occurs in the column, which
exit
from the column and are detected by a detector. The detector is coupled to a
display, typically, a computer system having a monitor, to record and display
the
analysis of the sample. Depending upon the sample, different separation
methods
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involving column type, flow rate, and oven temperature, including heating ramp
rate, is employed for separation and/or analysis of a sample. Typically, an
analytical device, such as a GC, is provided with an injection module, a GC
oven
and detector. However, a system having the GC device, along with a computer
and
software, can be provided for separation and/or analysis of a sample.
[0081] When provided with a sample having constituents that have
varying
vapor pressures, and can be in different phases under NTP, an injection module
10,
as disclosed herein, can be used in an analytical device 64, which can be a GC
instrument. The GC instrument 64 can be provided as a stand alone unit, or
provided as part of a system 70, having a computer with software installed.
The
software can be programmable to control the pressure of the mobile phase, flow
rate, and temperature, along with time, at which the oven should be heated. In
accordance with the disclosure herein, in one embodiment, upon injection of a
sample into the injection valve 12, the valve can be actuated to direct the
sample
towards the column 30, while maintaining the temperature of the oven to limit
and/or avoid heating the column. The pressure applied and/or maintained on the
sample, due to the bore width of the restriction tubing 24 being narrower than
the
column for limiting or avoiding separation of the sample in a gas phase and a
liquid
phase, moves the sample on to the column 30. Once on column 30, in one
embodiment, heat can be applied to the column 30, by ramping up the
temperature
in the GC oven. This can lead to separation of the constituents of the sample,
which are detected at the detector, and can be displayed with the help of the
system 70 and software.
[0082] Disclosed herein below are different embodiments, along
with a
description of the figures, to assist with further understanding of the
injection
module 10, device 64 and method for separation and/or analysis of a sample.
[0083] In one embodiment, the technique uses the carrier gas
pressure at the
injection valve 12 to be above the evaporation pressure of all constituents of
the
sample, which can be LPG. In one embodiment, for example and without
limitation,
this can be achieved by placing two pressure restrictions in the system (Fig.
2).
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One mobile phase restriction tubing 56 can be between the carrier gas flow
controller 78 and the injection valve 12, and a second restriction tubing 24
can be
between the injection valve 12 and the GC capillary column 30. In a particular
embodiment, the later restriction can flow through an injector, which can be,
for
example and without limitation, a modified GC injector (MGCI). The first
restriction
56 can help prevent the sample from vaporizing and expanding backwards towards
the flow controller 78. The second restriction 24 can help to ensure the
sample
remains in a pressurized liquid state until it is deposited at the head of the
column
30.
[0084] Once the sample reaches the head of the column, the MGCI and the
GC oven can be heated simultaneously to convert the sample to gas allowing it
to
flow trough the column 30 for separation and analysis. The second restriction
24,
MGCI, all connections and the column 30 can be heated up to 430 C in order to
elute all heavy hydrocarbons present in the sample. In one embodiment, the
injection valve 12 itself is not heated but insulation is placed between the
injection
valve 12 and the injector to prevent heat from the injector to reach the
injection
valve 12. In a particular embodiment, the injection valve 12 is maintained at
a
consistent temperature at the point of injection. This can allow calculation
of the
evaporation pressure required to keep the sample in single phase. In a further
embodiment, sample can travel from the injection valve 12 onto a column 30,
where the restriction tubing 24 is coupled directly to a column 30 using a
union 80,
and without having to pass through a MGCI.
[0085] In one embodiment, for example and without limitation, as
per Figures
2, 4, 5 and 6, two pieces of narrow Inner-Diameter (ID) steel tubing (24, 56)
were
installed in series with the capillary column to raise the pressure up above
the
evaporation point of the sample. The first length of tubing (56) was 4' x
1/16" x
0.005" ID SS. It was installed between the 100psi flow controller 78 to the
carrier
gas IN 16 connection on the injection valve 12. The temperature of this piece
is
not particularly limited, as directly contact with sample is unlikely. This
first piece
56 can help to prevent the sample from vaporizing and expanding backwards up
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towards the flow controller 78. The second length of tubing 24 was 12' x 1/32"
OD
x 0.005" ID. It was installed from the column port 20 on the injection valve
12 and
routed vertically down through the programmable temperature valve (PTV)
injector.
The lengths and diameters of the tubing 24, 56 were chosen so the total length
of
16' x 0.005" ID would yield 10m1/min of Argon at 100psi. The relative lengths
were
chosen because they were commercially available in pre-cut lengths and would
give
a pressure of approximately 84psi at the injection valve 12. This was above
the
evaporation pressure of the butane sample which was analyzed. Argon was
chosen as the carrier gas because it is inert, inexpensive and has the highest
backpressure with the lowest linear velocity, but Helium or Nitrogen should
also
work.
[0086] The injection valve 12 was mounted so that the orientation
of the
column port 20 connection on the injection valve 12 was facing vertically
down.
The injection valve 12 was flush mounted into the top of the PTV injector, so
the
steel line could be heated as close to the valve as possible to prevent a cold
spot.
However, this is not necessary, and the injection valve 12 can be placed
further
away from the oven, to avoid heating the sample, which can lead to separation
of
the sample constituents in to different phases. The 12' x 1/32" tubing 24
passed
through the PTV injector but was not connected with any unions or glass
inserts.
The PTV was solely used as a heating/cooling zone so that the temperature of
the
tubing could be accurately controlled very close to the injection valve 12.
The 12' x
1/32" 24 was coiled and mounted in the column oven of the gas chromatograph
and connected with a zero dead volume union 80 to the capillary column 30
which
was a 10m x 0.53mm x 1.0um MXT-1 from Restek. Both the narrow bore steel
tubing and the capillary column should be able to safely withstand up to 430 C
in
order to elute the potential heavy hydrocarbons in the sample. The calculated
head
pressure at the column 80 is around 2.2p5i at 30 C and 10m1/min Argon flow.
Although not ideal because the LPG sample can vaporize somewhere upstream in
the 12' of tubing, but has been utilized to show proof of concept. The
injection
valve 12 itself was not mounted in an isothermal oven. However, there was some
insulation between the injection valve 12 and the top of the PTV to prevent
some
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heat bleed. When utilizing the method disclosed herein, the injection valve 12
can
be kept at a consistent temperature at the point of injection. This allows the
calculation of the evaporation pressure required to keep the sample in single
phase.
[0087] Figure 6 shows a Certificate of Analysis of lml of Supelco
5000ppm
ASTM 2887 Quantitative Calibration Solution used to spike the butane sample,
which were analyzed. The analysis is shown in Figure 7 which shows comparative
chromatograms of three samples.
[0088] First Chromatogram at the top of Figure 7 is: Butane
sample
pressurized up to 400p5i and injected via LSV directly into a 10m x 0.53mm x
1.0um MXT-1 Capillary column. The injection system disclosed herein is NOT
employed in this injection.
[0089] The chromatogram in the middle, as shown in Figure 7 is:
Butane
sample spiked with lml of a 5000ppm ASTM 2887 Calibration standard containing
n-hydrocarbons (HC) from C5-C44. The Butane sample is approximately 200m1,
giving an estimated concentration of 25ppm for each spiked hydrocarbon (HC).
The HCs should yield a similar height and area count response. However, only
HCs
up to C12 reached the detector. At 400psi the butane sample is in the liquid
phase
and acts as a solvent which solubilizes and carries the heavy hydrocarbons.
When
the LSV is actuated, the butane in the sample loop is in series with the
carrier gas
which is only flowing at around 2.5psi. Since 2.5psi is below the vapour
pressure
required on the phase diagram for butane at room temperature, it evaporates
and
most of the heavy hydrocarbons fall out of phase and are not pushed by the
carrier
gas to the detector.
[0090] The chromatogram at the bottom in Figure 7 is: Same spiked
butane
sample, however, the embodiment of the injection system disclosed herein has
now
been installed into the gas chromatograph. Now when the LSV actuates, the
400p5i
Butane moves into series with the carrier gas at approximately 84ps1. At this
pressure, the Butane sample stays in the liquid phase and keeps the heavier
hydrocarbons solubilized. The butane as a liquid droplet, is pushed by the
carrier
gas through the restriction and into the heated zone of the GC. As the butane
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moves through the restriction towards the capillary column, the pressure will
be
decreasing down to an estimated 2.5p5i at the top of the capillary column. The
HCs
are now within the heated zone of the GC which will ramp up to 430 C,
vaporizing
all components and selectively sending them to the detector. As illustrated in
the
results from the current setup, it can be possible to achieve effectively zero
mass
discrimination up to C34, approximately 25% mass discrimination at C36 and 50%
at
C40 =
[0091] Disclosed herein below is a second embodiment where the
injection
valve 12 is positioned away from the GC oven, and the restriction tubing 24
connects directly to a column 30 for separation.
[0092] Flush mounting the LSV over the PTV injector can cause
inconsistent
heat in the LSV. As the PTV heated during the analysis, the LSV would warm up
from the heat radiation. This can cause the Butane to partially evaporate
inside the
LSV when running the instrument multiple times leading to inconsistent
analyses.
[0093] Figures 9, 10, 11 and 12 relates to an embodiment where by
increasing the distance between LSV and PTV, to reduce the heat bleeding from
the
PTV to the LSV, was tested to improve the consistency of multiple analyses.
[0094] This allows to mount the LSV in an insulated oven for
consistent
temperature.
[0095] In the embodiment disclosed in Figures 9, 10, 11 and 12, a shorter
but
much narrower bore restrictor, and a longer and much narrower bore MXT
capillary
column was utilized. This allowed utilization of much higher pressures.
[0096] The goal was to keep the pressure at the head of the
column above
the 40 C Butane vapour pressure estimated at 60psi. This should keep all the
heavy hydrocarbons present in the sample to be solubilized in the liquid
butane,
until deposited on the head of the column.
[0097] The following specifications were utilized.
[0098] Argon carrier pressure at the regulator was ¨250psi.
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[0099] Pressure at the LSV at the point of injection was ¨160psi.
[00100] Pressure at the head of the column was ¨75 psi
[00101] Flow through the column was approximately 6m1/min at 30 C
[00102] In the embodiment disclosed in Figures 9, 10, 11 and 12, a
shorter but
much narrower bore restrictor, and a longer and much narrower bore MXT
capillary
column was used. The goal was to keep the pressure at the head of the column
above the 40 C Butane vapour pressure estimated at 60psi.
[00103] The following specifications were utilized.
[00104] Argon carrier pressure at the regulator was ¨250p5i.
[00105] Pressure at the LSV at the point of injection was ¨160psi.
[00106] As shown by the chromatographic analysis shown in Figure
13, the
embodiment disclosed in Figures 9, 10, 11 and 12, provided better mass
discrimination. In the embodiment disclosed in Figures 9, 10, 11 and 12, 0%
mass
discrimination was observed from C8-C4o, and 10% mass discrimination for C44
with
improved consistency from multiple injections.
[00107] Described herein below is an embodiment of a calculation
of the
restriction tubing dimensions for use in the injection module disclosed
herein. In
the embodiment below helium is used as an example. However, the specification
is
not limited to helium, and other gases, such as, for example and without
limitation,
argon, can be used, depending upon design and application requirements.
[00108] Step 1:
[00109] Look at sample matrix and phase diagram to determine
minimum
pressure and temperature within the injection system and the head of the
column.
Example 100% butane has a vapour pressure of approximately 55psi at 50 C. To
keep the butane sample in single phase during injection, the pressure in the
entire
system should be above 55 psi including at the LSV and at the head of the
capillary
column. To ensure partial vaporization doesn't occur, the minimum pressure can
be
increased up to 70psi. Once the sample has been deposited on the capillary
column,
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the oven can be heated up to 350 C at a linear ramp rate and selective
vaporization of all the heavy hydrocarbons that were dissolved in the butane
sample will occur over time. Using this technique, it is possible to analyze
up to Cso
hydrocarbons dissolved in butane.
[00110] Step 2
[00111] Using the Restek EZGC Flow calculator
https://ez.restek.com/ezgc-
mtfc, a 20m x 0.18mm ID x 0.4um MXT-1 column was chosen. The calculator
disclosed herein is not particularly limiting, and other calculators and
method of
calculation are available and should be known to a person of skill in the art.
The
column chosen is a metal column with a 100% PDMS phase and has a maximum
temperature of 400 C, so it will be capable of eluting n-hydrocarbons up to
C50.
According to the EZGC Flow Calculator (Table 1), the optimum carrier gas range
for
a 0.18mm ID column is between 1-1.4m1/min. However, 70psi head pressure leads
to 5.4m1/min carrier gas at the outlet leading to the FID, which is above our
optimum carrier gas range for a 0.18mmID column.
EZGC Flow Calculator
-`.
_ =
Helium
CW40111.1* _ ___________
Long 20.00
I noel- Diameter 0.18 win
Filiii Thickner,s 0.25 pm
Temperature 50.00 'C
- "
Optimum Range
Column Flow r nt 1 0 In 11 5.44 mLimin
Average Velocity 99.57 cm/sec
Holdup Time 0.33 min
Inlet Pressure psi 70.00 psi
Outlet PFessuce Cabs) 14.70 psi
Table 1.: Calculation of gas carrier range.
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[00112] The injection system is currently isobaric (meaning, one
cannot
pressure program to compensate for increasing viscosity of the carrier gas as
the
column oven heats during analysis). Therefore as the column heats up to 350-
400 C, the flow in the column will actually drop from 5.4nril/min at 50 C to
1.5m1/min at 400 C., which is very close to our optimum column flow range.
EZGC Flow Calculator
_______________________________________________________ - __ -
Helium
Length 2000. ri
Inner Diameter 0.18 ram
Film Thickness 025 pm
Temperature 400.00 c
rti*Ifell****1_1k - -
Optimum Range
Column Flow !ram 1.0 !a 1.4 158 fliJniir
mUrnin
Average Velocity 60.30 or/see
Holdup Time 0.55 min
Inlet Pressure psi 70.00 psi
Outlet Pressure (absS 14.70 psi
vorvit
Table 2: Calculation of flow in column after accounting for temperature.
[00113] Step 3:
[00114] In order to calculate the length and inner diameter of the
restrictor
that is coupled upstream of the capillary column, one can type the column flow
rate
at the FID in the Restek EZGC Flow Calculator. Keeping the temperature at 50 C
and the length at 1m (which is an easily purchased length for restrictor
tubing), one
can enter the various IDs that are available for restrictor tubing. Tubing IDs
of 10,
15, 20, 25, 30, 40, 50, 75, 100, 125, 180 and 250um are all available "off-the-
shelf". Using a 1m x 0.05mm tube gives us 230p5i head pressure in order to
deliver
5.4rn1/nnin at 50 C.
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EZGC Flow Calculator
=i
Helium
U6161.011ni
Length 1.00 m
I niier- Diameter 0.05 In m
Filin Thickness 0.25 inn
Temperature 50.00 .c
.
Optimum Range
Column Flow Mom 0.2 to 0..z 540 rn i
etL..rnirr
Average Velocity 459.62
Imsec
HUILILIp TIITIt 0.00 min
Inlet Pressure psi 230.08 psi
outlet Pressure (abs) 14.70 ps
=
Table 3.: Calculating the length and inner diameter of the restriction tubing.
[00115] Using a dual stage regulator to deliver 230psi into our
restrictor
tubing, a person of skill in the art should recognize that it will
approximately yield
70psi at the head of the capillary column and deliver 5.4m1/min carrier gas to
the
FID at 50 C. We can also estimate an approximate linear pressure drop along
the
length of the lm restrictor tube which is divided into a 1 foot and a 2 foot
length.
The pressure in the LSV can be estimated at 160-180ps1, which is above the
vapour
pressure of butane at 50 C and will prevent the vaporization of the sample
prior to
depositing on the head of the column.
[00116] Certain adaptations and modifications of the described
embodiments
can be made. Therefore, the above discussed embodiments are considered to be
illustrative and not restrictive.
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Table of reference numerals
No. Description No. Description
Injection module 62 Mobile phase system
12 Injection valve 64 Analytical device
14 Sample inlet port 66 sample
16 Mobile phase inlet port 68 detector
18 Waste port 70 System having 64
Column port 72 Mobile phase tank
22 Sample loop 74 Regulator for 72
24 Restriction tubing 76 Mobile phase system
tubing
26 Valve end of 24 78 Flow controller
28 Column end of 24 80 union
Column 82 PTV injector
32 First waste tubing 84 oven
34 First end of 32 86
36 Second end of 32 88
38 Waste valve system 90
First waste valve 92
42 Second waste valve 94
44 Second waste tubing 96
46 Outlet 98
48 Sample tubing 100
First end of 48
52 Second end of 48
54 Sampling system
56 Mobile phase tubing
58 First end of 56
Second end of 56
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