U.S. patent number 4,038,055 [Application Number 05/621,404] was granted by the patent office on 1977-07-26 for gas chromatograph for continuous operation with infrared spectrometer.
This patent grant is currently assigned to Block Engineering, Inc.. Invention is credited to Reginald Tobias, Antonio Varano.
United States Patent |
4,038,055 |
Varano , et al. |
July 26, 1977 |
Gas chromatograph for continuous operation with infrared
spectrometer
Abstract
An improved gas chromatograph for "on line" use with absorption
spectrum analyzers, particularly, infrared spectrometers. The new
chromatograph has been adapted for compatibility with a variety of
absorption spectrum analysis instruments from the standpoint of
cycling time, dimensions, thermal characteristics and convenience
in handling extremely small and highly reactive chemical sample
materials.
Inventors: |
Varano; Antonio (Philadelphia,
PA), Tobias; Reginald (Watertown, MA) |
Assignee: |
Block Engineering, Inc.
(Cambridge, MA)
|
Family
ID: |
24490029 |
Appl.
No.: |
05/621,404 |
Filed: |
October 10, 1975 |
Current U.S.
Class: |
96/102; 96/104;
219/400 |
Current CPC
Class: |
G01N
30/74 (20130101) |
Current International
Class: |
G01N
30/74 (20060101); G01N 30/00 (20060101); B01D
015/08 () |
Field of
Search: |
;55/67,197,386,267
;23/232C ;73/23.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Adee; John
Attorney, Agent or Firm: Slater, Jr.; Robert L.
Claims
We claim:
1. An improved gas chromatograph in combination with an absorption
spectrum analyzer, the chromatograph comprising upper and lower
cojoined chambers, the lower chamber having measured dimensions,
the absorption spectrum analyzer having a measured dimension test
sample well, the chromatograph lower chamber being dimensioned to
fit within the test sample well; the upper chamber being thermally
insulated, provided with heating and thermostat means, the
chromatograph further comprising a chromatograph column and an
injection port, the column being mounted within the upper chamber
and connected at its input to the injection port; a detector, a
sample cell and a plurality of valves, the detector cell and at
least two multiport valves being mounted juxtaposed to a heated
thermostated metal plate means positioned within the lower chamber;
the cell, when mounted to the aforesaid plate being positioned
transversally of the lower chamber, short tubular connections
between, respectively, the column and valves between the detector
and valves, and between the cell and valves, whereby, eluted sample
materials emitted by the column may be entrained and momentarily
retained within the sample cell, the chromatograph lower chamber
with the transverse sample cell being positioned within, yet
thermally insulated from the analyzer test sample well, while
absorption spectrum analysis procedures are completed.
2. The apparatus combination of claim 1 above wherein the
absorption spectrum analyzer is an infrared spectrometer.
3. The apparatus combination of claim 1 above, a flow restrictor,
wherein at least one valve port connects to the flow restrictor and
the restrictor connects to exhaust into the atmosphere, whereby the
chromatograph column pressure measured at the output of the column
and the sample cell pressure may be maintained during operation at
gauge pressures greater than one atmosphere.
4. The combination apparatus of claim 1, wherein the upper chamber
heating means is comprised of means for heating and circulation of
heated air through the chamber.
5. The combination device of claim 4, wherein the chromatograph
column is wound into a flat spiral and mounted within the thermally
insulated upper chamber with the axis of the flat spiral at right
angles to the vertical.
6. The combination apparatus of claim 5 above, wherein there is a
second chromatograph column, the second column being wound into a
flat spiral and mounted juxtaposed and coaxially with the first
column within the upper chamber whereby the first column is an
analytic column and the second column is a reference column and
both columns are maintained in identical thermal condition with the
heated air circulating about them.
7. The combination apparatus of claim 1 above, wherein the heated
thermostated plate means positioned within the lower chamber is
comprised of a first and a second matching plates, the plates being
recessed respectively to accommodate enclosed mounting of two
thermal conductivity detectors within the juxtaposed plates,
external surfaces upon the plates for mounting the two multiport
valves, and an external concavity for mounting the sample cell, the
valves and cell when mounted to the plates being in thermal contact
therewith, and heater coils and thermostat means juxtaposed to the
plates to maintain the plates assembled with the detectors, valves
and sample cell within a specified temperature range, whereby the
chromatograph components mounted within the lower chamber and
adjacent to the absorption spectrum analyzer are maintained within
a specified operating temperature, but the adjacent analyzer is not
excessively heated by the chromatograph.
8. An improved gas chromatograph comprising an upper chamber and a
lower chamber, the chambers being cojoined metal enclosures
thermally insulated respectively one from the other, the
chromatograph further comprising a chromatograph column and an
injection port, the column being mounted within the upper chamber
and connected at its input to the injection port heat generating
means mounted within the upper chamber, adapted to maintain the
column at an elevated temperature; a detector, a sample cell and a
plurality of multiport valves, the detector cell and at least two
multiport valves being mounted juxtaposed to a heated, insulated
and thermostated metal plate means, the metal plate means being
positioned within the lower chamber; the cell, when mounted to the
aforesaid plate being positioned transversally of the lower
chamber, short tubular connections between respectively, the column
and valves, between the detector and valves, and between the cell
and valves, whereby eluted sample materials emitted by the column
may be entrained and momentarily retained within the sample cell,
the chromatograph lower chamber enclosure with the transverse
sample cell mounted therein thermally insulated from the upper
chamber heat source, whereby absorption spectrum analysis
procedures may be performed upon sample materials entrained within
the cell without communicating excessive heat from the
chromatograph through the lower chamber enclosure into juxtaposed
absorption spectrum analysis equipment.
Description
CROSS REFERENCES TO RELATED APPLICATIONS
Certain portions of the apparatus and method of the present
invention are not our invention but are the inventions of TOMAS
HIRSCHFELD and DAVID BROWN, as defined in the claims of their
applications, Ser. No. 553,989, filed Feb. 28, 1975, and TOMAS
HIRSCHFELD and HAROLD MC NAIR, as defined in the claims of their
application, Ser. No. 553,990, filed Feb. 28, 1975. The above
referenced applications are assigned to the assignee of the present
invention.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to gas chromatograph devices, and
specifically pertains to a compact improved gas chromatograph
device for "on line" use in combination with absorption spectrum
analyzers, particularly, infrared spectrometers.
2. Description of the Prior Art
Chromatograph elution of a mixture of sample vapors is a common
laboratory procedure. The separated sample components issue from
the chromatograph column at a rate determined by many factors,
among which is the carrier gas flow velocity. The efficiency of the
chromatographic separation is dependent upon operation of the
column at, or very near, the optimum carrier gas velocity for the
given column conditions. The most efficient chromatographs emit
well spaced eluted sample mixture components characterized by
narrow peak widths as shown on chromatograph charts. That is,
eluted samples are preferably issued from the chromatograph column
in the briefest time interval measured from leading edge to
trailing edge of peak.
On the other hand, absorption spectrum analyzers require a fixed,
and in a given spectrometer, an irreducible period of time to scan
the sample through the selected frequency range, process and record
the resultant data. The infrared spectrometer is, at present, the
most widely used laboratory chemical identification absorption
spectrum analyzer.
The time of response of presently available infrared spectrometers
is approximately an order of magnitude longer than the presently
available efficient gas chromatograph output peak transit time. As
a consequence, these two instruments are not normally compatible
when directly connected one to another, but may be used in
combination for the separation and identification of chemical
compounds only by skillful and time consuming manipulations
performed by qualified technicians. Previous practice has comprised
catching and storing in separate sample cells the eluted sample
peaks issuing from a chromatograph column, then placing the
separate sample cells, one by one, in the spectrometer for the
required time to complete the spectrometer analysis. "On line"
operation of a gas chromatograph in combination with an absorption
spectrum analyzer, such as an infrared spectrometer, has for full
spectrum range analysis, not been feasible to this date.
Because of the cumbersome procedures for wide frequency band
absorption spectrum analysis of eluted samples, a practice referred
to as analysis, "on the fly" has been developed. The eluted sample
peak is passed through the spectrometer "on the fly" and absorption
spectra data is recorded, as may be obtained in the brief interval
of time the sample material requires to pass the windows of a flow
through sample cell. An experienced analytical chemist can utilize
the fragmentary absorption spectrum "fly" data to provide useful
sample compound identification clues. The "fly" spectrometer
analysis is a compromise and a limited value substitute for the
full frequency spectrum scan analysis.
Additional problems attend present practices for combining gas
chromatographic devices with absorption spectrum spectrometers,
particularly, infrared spectrometers. Sample compounds issue from
chromatograph columns at elevated temperatures. Present
chromatographs require bulky ovens and temperature control
paraphernalia. The higher temperatures of the chromatograph, if
mounted adjacent to an infrared spectrometer without special heat
shielding, would interfere with the operation of the
spectrometer.
It is common practice to operate gas chromatograph columns at
programmed elevated temperatures selected to assure proper
volatility of all elutant sample components. Abrupt temperature
changes of elutants, as these issue from a chromatograph column and
are caught and stored temporarily in sample cell containers
awaiting spectrometer analysis, may give rise to altered physical
states of the eluted samples. Rapid cooling of eluted samples may
result in condensation on the sample cell windows. All of the
foregoing effects adversely degrade the absorption spectrum
analysis data.
Reduction in the number of required hand manipulations of toxic and
dangerous materials during analysis and production quality control
procedures is an important safety advantage. No presently available
gas chromatograph provides compatible means for matching the
chromatograph output directly with an infrared spectrometer. As a
consequence, dangerous toxic elutants must be hand transferred from
the chromatograph output to a spectrometer sample cell. After the
spectrum analysis is completed, the toxic sample contents of the
sample cell must be cleared. All these presently required steps
involve separate hand manipulations and incur some element of
hazard. Continuous "on stream" management of dangerous materials
significantly reduces the risks of loss or dispersion of toxic
sample materials.
The incompatibility of presently available gas chromatographs and
infrared spectrometers is not only limited to time incompatibility.
The shear size and vertical dimensions of present chromatographs,
as compared with spectrometer sample cell dimensions, makes the
direct physical matching of chromatograph output to spectrometer
sample cell apparatus awkward. The different ambient temperature
requirements for operation of the two kinds of instruments, as
referred to above, further complicates "on line" matching of
presently available chromatographs and infrared spectrometers.
The chromatograph column emits large volumes of gaseous effluent,
some of which may be combined with portions of reactive corrosive
sample mixture vapors. Infrared spectrometers are sensitive complex
instruments easily damaged by corrosive chemicals. Direct physical
combination of the output of gas chromatograph devices with
infrared and other absorption spectrum spectrometers in the absence
of special precaution, risks corrosion and damage to sensitive
spectrometer working parts.
There is, accordingly, a need for a gas chromatograph device that
may be conveniently and compatibly combined directly with
absorption spectrum analyzer equipment. Particularly, there is a
present need for a compact easily operated gas chromatograph
suitable for "on line" combination with infrared spectrometers.
OBJECTS AND ADVANTAGES OF THE PRESENT INVENTION
A first object of the present invention is to provide a compatible
general purpose gas chromatograph for "on line" combination
operation with absorption spectrum spectrometers.
Another object of the present invention is to provide an easily
operated gas chromatograph having dimensions, thermal properties
and operating time characteristics compatible with juxtaposed
mounting to and simultaneous "on line" operation with, presently
available laboratory infrared spectrometers.
Still another object of the present invention is to provide a
compact compatible gas chromatograph wherein the column output is
connected directly to a sample cell means within an absorption
spectrum spectrometer.
Yet another object of the present invention is to provide a
compact, safe gas chromatograph having means for compatibly
matching the chromatograph operation time to the response time of
presently available infrared spectrometers.
These and other objects and advantages of my invention will be
evident from the drawings, specification and claims below.
SUMMARY OF THE INVENTION
An improved novel gas chromatograph for combination with absorption
spectrum analyzers, particularly, infrared spectrometers. The
chromatograph adapted to be compactly mounted; the various
chromatograph components are separately thermostated and thermally
insulated from one another and from excessive transfer of heat to
adjacent equipment. A valved flow through sample cell is positioned
transversely within the chromatograph and adapted to provide "on
line" test sample material for "on line" absorption spectrum
analysis. Means for adjusting the chromatograph time response to a
rate compatible with absorption spectrum analysis procedure rates,
particularly for infrared spectrometer frequency scan cycle rate is
provided in the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view, partially cutaway, of a preferred
embodiment of my invention.
FIG. 2 is a cross section plan view taken on the plane 2--2 of the
embodiment of my invention shown in FIG. 1.
FIG. 3 is a schematic flow diagram of the embodiment of my
invention shown in FIGS. 1 and 2.
DESCRIPTION OF THE INVENTION
A partially cutaway perspective view of a preferred embodiment of
our invention is shown in FIG. 1, wherein an absorption spectrum
analyzer 10 is shown in fragmentary form. For purposes of the
present description, the absorption spectrum analyzer used is an
infrared spectrometer. However, our combination of chromatograph
and absorption spectrum analyzer is intended to encompass within
the combination any spectrum analyzer chosen from the variety of
ultra-violet visible band, raman and other available absorption
spectrum analyzer instruments. The infrared spectrometer 10, shown
in the illustrations, is provided with a test sample well 12, into
which a test sample cell is normally inserted for performing the
analysis procedure.
Our improved gas chromatograph comprises an upper chamber 16
cojointed to a specially dimensioned lower chamber 18. The lower
chamber is of such dimension that it readily fits into the infrared
spectrometer sample test well 12. The instrument industry has set
standards for dimensions of fittings and accessories which are now
widely adapted. Accordingly, our chromatograph may be readily
combined with spectrum analysis equipment produced by most
manufacturers. FIG. 2 shows the embodiment of the present
invention, illustrated in FIG. 1 as seen in a cross section on
plane 2--2. The relationship of the lower chamber 18 and the
spectrometer test sample well 12 is readily visualized in FIG. 2.
The upper chamber 16 is comprised of an inner liner 22, thermally
insulated with packing insulation 24 between an outer panel 26 and
the inner liner 22. The upper chamber 16 is mounted within a
panelled frame 30 to provide rigidity to the whole assembly and to
provide a base for mounting various other component parts of the
chromatograph which will be described below.
The upper chamber 16 is provided with a curved baffle 28, mounted
within but separated from the inner liner 22 in the upper portion
of the chamber 16. The baffle 28 is provided with a number of small
openings, 29a, 29b, 29c, for the flow of heated air into the
interior region of the chamber 16 from the space between the baffle
28 and the inner liner 22. The means for heating the air in the
space between the baffle 28 and the inner liner 22 will be
described below.
Another opening, square in shape, in the baffle is provided at 31.
A hinged rectangular air duct 40 provides both cool air intake and
hot air exhaust flow from the interior of the chamber, depending
upon the position of the hinged duct. The hinge 41 is mounted in a
bracket 41a attached to the exterior of the inner liner 22. In FIG.
2, the solid line for the duct 40 shows it positioned to exhaust
hot air from the interior of the chamber 16; the broken line
illustration of the duct 40 shows it positioned to draw cool air
into the space between the baffle 28 and the inner liner 22. In
this latter position, the hinged rectangular duct 40 closes the
square opening 31 in the baffle. Thus, the cool air is shunted
above the baffle 31 where it is heated.
The hinged duct 40 is held in the desired position by the action of
a solenoid 32 which actuates an extension arm 33. The extension arm
33 is attached to the hinged duct a distance below the hinge
pivotal axis. Small movement of the solenoid armature and its
extension arm will drive and hold the hinged duct to the respective
cooling or heating cycle position depending upon the direction of
the armature movement.
A thermostat 42 is mounted in the outer panel extending to the
interior of the chamber 16. A small motor 34 is mounted external of
the chamber 16, the shaft of which extends within the chamber and
rotates a squirrel cage fan 35. The fan 35 is mounted within a fan
housing 35a, positioned between the baffle 28 and the inner liner
22. A heating element 38 is mounted in the outflow portion of the
fan housing. The thermostat 42 with its control means, not shown in
the drawings, may be preset to actuate the solenoid 32, fan motor
34 and the heating element 38 to maintain the interior of the
chamber at any prescribed temperature. Both heating and cooling
cycles are provided within the automated temperature control
system. Thus, the chamber 16 is a finely controlled temperature hot
air oven for maintaining the chromatograph columns at the desired
temperatures for optimal operation of the chromatograph.
The chromatograph is provided with two identical packed
chromatograph columns, the first or analytic column 50, and the
second or reference column 52 each, respectively, being coiled into
a flat spiral. The spirals are positioned coaxially adjacent to one
another within the interior of the upper chamber 16. Circulated
thermostatically controlled warm air within the chamber maintains
both columns at the pre-specified temperature throughout the
respective lengths of the spirals. The spiraled juxtaposed
positioning of the columns within the oven chamber 16 allows for
equal and constant heating with less radiated heat loss into the
environment about the chromatograph.
An injection port 56 is mounted to extend partially through the
panelled frame 30 and partially into the chamber 16. The injection
port is connected to the input of the analytic column 50. The
injection port is separately thermostated, insulated and heated by
means of a conductive heating coil 58.
FIG. 3 is a schematic drawing representative of the embodiment of
our invention illustrated in FIGS. 1 and 2. The connections between
the various components of the chromatograph may be readily seen in
FIG. 3.
A carrier gas reserve, normally a pressurized tank (not
illustrated), of helium, nitrogen or other suitable carrier gas is
connected to the carrier gas inlet 60 of the injection port 56, and
also to the input of the reference column 52. It is common practice
to heat the carrier gas by some convenient means prior to its
flowing into the reference column. While the direct connection
between the carrier gas reserve and the reference column 52 as
shown in the schematic FIG. 3 does not show preheating, such
preheating procedure is conventional and often necessary for the
proper functioning of the instrument.
The effluent gases emitted from the coiled columns 50 and 52,
respectively, flow through valve means 64, 66 and into thermal
conductivity detectors 68 and 70. From the reference detector 70,
the gases flow through a stop valve 72 and a restrictor 74. From
the analytic detector 68, the gases flow through a stop valve 76
and into a test sample cell 90 described below. The valves 64, 66
72 and 76, associated with the column effluents are referred to as
column valves; and other valves described below associated with the
test sample cell are referred to as sample cell valves. The column
valves and the sample cell valves are combined, respectively, and
form multiport column valve 86 and cell valve 96. The mounted
positioning of the multiport valves 86 and 96 may be visualized by
reference to FIGS. 1 and 2.
The test sample cell 90 is mounted transversely of the chamber 18.
The test sample well 12 of the infrared spectrometer 10 permits
insertion of a test sample cell within a beam of infrared radiation
generated within the spectrometer. The test cell 90 is a hollow
metal or glass chamber, windowed 92, 94, at either end. The windows
are sealed to the chamber and are made of material reasonably
transparent at the wavelengths of radiation to be used in the
analysis. In infrared analysis, crystalline sodium chloride or
sodium bromide are common window materials.
When the lower chamber 18 is set within the infrared spectrometer
sample test well, the transversely mounted sample cell 90 is
coaxial with and intercepts the spectrometer's infrared beam. This
arrangement may be readily visualized by reference to the
illustrations.
Extraneous heat, radiated or conductively transported into the
spectrometer will interfere with the infrared absorption spectrum
analysis. Accordingly, the insertion of the lower chamber 18 into
the spectrometer sample test well requires care that excessive heat
generated by the chromatograph operation does not interfere with
the spectrometer operation. On the other hand, the eluted sample
vapors issuing from the analytic column 50 must be maintained at a
sufficiently high temperature to maintain a vapor state and prevent
condensation on the cell windows and within the connecting tubes.
The chromatograph thermo conductivity detectors 68 and 70 are
adversely responsive to ambient temperature changes. To meet these
diverse conditions, we have provided a novel mounting with thermal
control of the component parts mounted thereto. Two heavily walled
plates or castings 100, 102 contoured to provide, when juxtaposed,
a recess 104 within which the two detectors 68 and 70 are mounted.
Surfaces are provided on the plates 100, 102 for mounting in
thermal contact the multiport column valve 86 and the multiport
cell valve 96. Valve stems 86a and 96a, respectively, extend beyond
the panelled frame 30 for convenient control of the valves. The
sample cell 90 is also mounted to the plates 100 and 102 in
controlled thermal contact. The plates 100, 102 comprise a sizable
heat sink which is warmed by means of a heater coil 106. Radiant
heat emitted from the heated plates 100, 102 is insulated from the
adjacent spectrometer components by means of heat shielding 108.
All tubular connections from the columns, the detectors, sample
cell and to atmospheric exhaust pass through the respective valves
86 and 96 as described above. The desired temperature of the gases
issuing from the columns may be maintained and yet by means of the
thermostated shielded heat sink plates 100 and 102, no excess
extraneous heat is communicated to the spectrometer.
Our improved chromatograph in combination with absorption spectrum
analyzers may firstly be utilized in conventional chromatographic
procedures. Secondly, used on the "fly" for rapid partial analysis.
And finally and thirdly, used in a stop flow mode with high
pressure procedures. In the latter pressurized chromatograph
method, the restrictors 74, 78 and 80 may be utilized in accordance
with the methods and apparatus described in the inventions of
HIRSCHFELD and MC NAIR, Ser. No. 553,990, filed Feb. 28, 1975 and
HIRSCHFELD and BROWN, Ser. No. 553,989, filed Feb. 25, 1975 and
other related applications. In conventional chromatographic
procedures and "fly" analysis, the flow restrictors 74, 78 and 80
would normally be removed or preset at the open position.
The foregoing description and drawings are intended as merely
illustrative of our invention, the scope of which is set forth in
the following claims.
* * * * *