US3501964A - Assembly for injecting liquid samples into the chamber of a gas chromatography apparatus - Google Patents

Description

E. L. DRUMMOND ErAL 3,501,964

March 24, 1970 ASSEMBLY FOR INJECTING LIQUID SAMPLES INTO THE CHAMBER OF A GAS CHROMATOGRAPHY APPARATUS 2 Sheets-Sheet 1 Filed March 29, 1968 INVENTORS Edward L. Drummond Michael E. Drummond W WfM ATTORNEYS March 24, 1970 L. DRUM ND Er AL 3,501,964

ASSEMBLY FOR ECTING LIQ SAMPLES INTO THE CHAMBER OF A GAS CHROMATOGRAPHY APPARATUS I 2 Sheets-Sheet 2 Filed March 29, 1968 |0O\ a Zl0 K36 916 92 V F 4 z 2 INVENTORS EdwardL. Drummona M/bhae/E Drummond BY W/ W W United States Patent 3,501,964 ASSEMBLY FOR INJECTIN G LIQUID SAMPLES INTO THE CHAMBER OF A GAS CHROMA- TOGRAPHY APPARATUS Edward L. Drummond and Michael E. Drummond, Bryn Mawr, Pa., assignors to Drummond Instrument Company, Broomall, Pa., a corporation of Pennsylvania Filed Mar. 29, 1968, Ser. No. 717,097 Int. Cl. G01n 1/14 U.S. Cl. 73425.6 14 Claims ABSTRACT OF THE DISCLOSURE An assembly for injecting liquid samples into the chamber of a gas chromatography apparatus which includes a high pressure line and a low pressure line connected at one end to a source of carrier gas. A valve permits selective gas flow from either gas line to an injector. The injector includes a disposable hypodermic syringe unit extending from a body portion having a longitudinal bore in communication with the syringe unit. A movable member is positioned in a transverse bore communicating with the longitudinal bore, for inducing the flow of liquid into the syringe unit. A valve controls the flow of gas to the longitudinal 'bore.

OBJECTS AND DESCRIPTION OF DRAWINGS It is an object of this invention to provide an assembly for injecting liquid samples into the chamber of a gas chromatography apparatus in a manner to eliminate any contamination by small amounts of air.

Another object is to provide an assembly of the character described which enables reproducible results to be obtained by accurate metering and pressurized injection.

A further object is to provide an injector comprising a pistonless hypodermic syringe which expels a fluid sample under gas pressure, that portion of the syringe touched by fluid being disposable, to eliminate cleaning and contamination problems.

A further object is to provide an injector having a capillary tube and hypodermic needle which are made as a disposable unit for facility in removing the unit after use and replacing it with a fresh unit.

A still further object is to provide an assembly for injecting liquid samples into the chamber of gas chromatography apparatus wherein pressure regulating means are provided for selectively admitting gas under high or low pressure, and valve means are provided for controlling the fiow of gas to, and inducing the flow of a liquid sample into, the tube and needle unit.

Other objects will be manifest from the following description of the presently preferred forms of the present invention, taken in conjunction with the appended drawings wherein:

DESCRIPTION OF FIGURES OF DRAWING FIGURE 1 is a schematic view illustrating the assembly of the present invention.

FIGURE 2 is a perspective view of the injector forming a part of the present invention.

FIGURE 3 is a top plan view of the injector.

3,501,964 Patented Mar. 24, 1970 DESCRIPTION OF FORM OF INVENTION OF FIGURES 1 TO 6 The assembly of the present invention is basically a pistonless hypodermic syringe, with gas pressure replacing the piston or the plunger of a conventional syringe, the gas pressure providing high velocity reproducible injection. The syringe working parts are primarily a tube and needle unit, comprised of a precision bore capillary glass tube secured to a stainless needle. This unit is preferably of a low cost disposable type, eliminating cleaning and contamination problems, or breakage of more expensive standard syringes.

As shown to advantage in FIGURE 1, the assembly of the present invention comprises a supply source of an inert carrier gas, such as nitrogen, which is designated 10. Gas source 10 is connected by a line 12 to a low pressure regulator 14 which may be of conventional type, for delivering the gas through a low pressure line 16 to a suitable valve .18. Regulator 14 admits gas to line 16 in a range of l to 8 pounds per square inch over the pressure of the sampled material, a pressure of five pounds per square inch having been found satisfactory for purposes of the present invention.

Gas source 10 is also connected through a line 20 to a high pressure regulator 22 of conventional type, which delivers the gas through a high pressure line 24 to a standard valve 26. Regulator 22 is set to deliver gas through line 24 in a range of l to pounds per square inch over the pressure of the gas chromatography chamber, a pressure of 60 pounds per square inch having been found to be suitable for carrying out the objects of the present invention.

Pressure lines 16 and 24 are connected by feeder lines 28 and 30 respectively to a single line 32 in which is located a valve 34, the latter valve being connected by a line 36 to an injector generally designated 38.

Referring now to FIGURES 2 and 4, it will be seen that injector 38 generally comprises a substantially cylindrical body portion 40, having a nipple 42 extending from one longitudinal terminal thereof, and an elongated tube and needle support 44 extending from the other longitudinal terminal. A uniform bore 46 extends axially through nipple 42 and the major portion of body portion 40. At a point adjacent the terminal of body portion 40 proximate nipple 42, there is provided a transverse bore 48 which is adapted for the reception of an induction screw assembly 50.

As shown to advantage in FIGURES 4 and 5, induction screw assembly 50 includes a fitting 52 secured to body portion 40 by bolts 54 at the locus of transverse bore 48. A screw member 56 extends through fitting 52 into transverse bore 48, the inner terminal of screw 56 being reduced in diameter and extended to provide a stop 58 which positively limits the entry of the screw into transverse bore 48. Screw member 56 is threaded at 60 for engagement with complemental threaded portions of the transverse bore, indicated at 62, for permitting the induction screw to be partially withdrawn from the transverse bore to the desired degree in order to induce intake of the sample. Operation of screw 56 is facilitated by an operating knob 64. Scaling means such as an O-ring 66, is positioned between fitting 52 and screw 56.

At a point substantially spaced from induction screw assembly 50, a conical section of body portion 40- is cut out for the reception of a complemental shut off valve assembly 68 for selectively permitting passage of gas through the balance of the body portion. Any suitable non-displacement type valve may be employed for this purpose, a stopcock valve being illustrated, which includes a substantially conical body 70 complementing the shape of the recess body portion 40, which in turn is provided with a bore 72 which is selectively in communication with, but of smaller diameter than, bore 46. Stopcock 70 is provided with an extension 74 beyond body portion 40, the terminal of which is threaded at 76 for the reception of a nut 78. A convolute spring 80 is interposed between nut 78 and body portion 40. The opposite end of the stopcock is provided with a handle 82 for facilitating the opening and closing of the stopcock in a well known manner.

Beyond stopcock 68 body portion 40 is provided with a restricted passage 84, which permits passage of the gas therethrough, the restriction serving to preclude the backing up of fluid into the body portion of the injector under certain pressure conditions resulting from insertion of the needle through the septum of the gas chromatograph, and thus preventing contamination. As shown in FIGURE 4, a gastight rubber fitting 86 is set in the terminal of body portion 40 and is provided with a bore 88 in communication with restricted passage 84.

Elongated support 44 includes a cylindrical disc portion 90 having an axial bore 92. A semi-cylindrical support 94 extends from disc 90, the flat portion of which is provided with a longitudinal groove 96 which is coextensive with the length thereof. Adjacent the longitudinal recess are a plurality of graduation markings 98.

Support 44 is adapted for the reception of a hypodermic syringe unit generally designated 100 which includes a stainless steel hypodermic needle 102 which is epoxyed or secured in any other suitable fashion as indicated at 104 to a capillary tube 106 which is disposed in longitudinal recess 96, and extends rearwardly through bore 92 of cylindrical disc 90 and bore 88 of gastight rubber fitting 86. A removable clamp plate 108 extends transversely of the terminal of needle support 44 remote from body portion 40 for engaging and holding the hypodermic syringe unit in position, the clamp plate being removably held in position by a screw member 110.

It is a salient feature of the present invention to provide a hypodermic syringe unit which is of a disposable variety comprising a low cost economical hypodermic needle and a precision redrawn glass capillary tube which is also of low cost for ready disposal. In this way, cleaning of these parts is eliminated, as is the problem of contamination of the parts contacted by the fluid which is drawn into the hypodermic syringe.

OPERATION In use of the assembly of the present invention, the injector needle 102 is immersed in the sample to be drawn into capillary tube 106, at which time valve 68 is open and induction screw assembly 50 is screwed in, with valves 18 and 34 open. Low pressure regulator 14 is adjusted to provide a gentle bubbling rate through the sample, arate of five pounds per square inch having been found satisfactory. This purges the air from the system and replaces it with the carrier gas. Valves 18 and 34 are then closed.

Leaving the needle immersed in the sample, induction screw is unscrewed to increase the internal volume and draw the liquid up to the desired graduation 98 on the needle support such as, for example, 3 /2 lambda. Needle 102 is then removed from the sample and induction screw 50 is further unscrewed until the bottom of the liquid sample column is visible in glass capillary tube 106. By adjusting screw 50 until the bottom of the liquid is at gradation 1, the 1 lambda is subtracted from the reading at the top of the column to give the actual precise measurement of the sample to be injected. For example, if the top of the fluid column reads 6, subtract 1 lambda, so that the accurate measurement of the liquid sample is 5 lambda. The induction screw is then screwed until the top of the liquid sample column reaches the original reading on the graduation scale, for example, 3 /2 lambda. This places the end of the sample at the end of the needle, expelling all air.

After this step, valve 68 is closed, limiting the internal volume of the liquid, and retaining it while the needle is inserted through the diaphragm of the chromatography apparatus.

Next, valves 34 and 26 are opened, admitting an empirically determined pressure of a higher value then that in the chamber of the chromatography apparatus, all the way in the line to valve '68. Valve 26 is then shut, trapping a definite volume of gas at high pressure. Injection is then accomplished by opening stopcock 68, and because the pressure head goes through at high sp ed carrying the bulk of the sample, this is sprayed in atomvizer fashion into the chamber. Following this, the remainder of the trapped gas flows through at diminishing pressure and speed, effectively wiping the tube walls by evaporation. This effects substantially sample injection instead of leaving a film on the walls of the syringe.

After use, the hypodermic syringe unit 100 is readily removed by loosening clamp plate 108, and withdrawing capillary tube 106 from rubber fitting 86. The contaminated capillary tube and needle unit is then replaced by a new unit and the assembly is ready for injection of the next sample.

DESCRIPTION OF FORM OF INVENTION OF FIGURE 7 In FIGURE 7 there is illustrated a modified form of the assembly of the present invention, wherein parts which are similar to the parts of the invention illustrated in FIGURE 1 are identified by like, primed numbers. In accordance with this form of the invention, the injection gas is matched in temperature to the gas within the chamber or to any other desired temperature. To effect this purpose, a heater 110' is inserted in the gas line at any desirable point, such as line 32', prior to its entry into injector 38'.

What we claim is:

1. A gas chromatography sample injection assembly for injecting a sample into a gas chromatography chamber comprising:

(a) a gas line,

(b) a gas source in communication with one terminal of said gas line,

(c) an injector in communication with the opposite terminal of the gas line,

(d) Valve means for selectively admitting gas in said gas line to said injector, and

(e) movable means in communication with the gas receiving bore of said body portion for selectively increasing the internal volume of the gas-receiving bore to induce the flow of a measureable amount of liquid sample into the injector when said valve means is closed.

2. The gas chromatography sample injection assembly of claim 1, wherein:

(a) said gas line includes a pair of feeder lines connected in parallel at one end to said gas source and at the other end to said injector,

(b) a low pressure regulator in one of said feeder lines, and

(c) a high pressure regulator in the other of said feeder lines.

3. The gas chromatography sample injection assembly of claim 2, wherein:

(a) said low pressure regulator permits passage of gas to said injector in the range of 1-8 p.s.i. over the sampled material.

4. The gas chromatography sample injection assembly of claim 2 wherein:

(a) said high pressure regulator permits passage of gas to said injector in the range of 1-75 p.s.i. over the gas chromatogrphy chamber.

'5. A gas chromatography sample injection assembly for injecting a sample into a gas chromatography chamber comprising:

(a) a pair of gas lines, r

(b) a carrier gas source connected to a terminal of each of said gas lines,

(c) a low pressure regulator in one of said gas lines,

(d) a high pressure regulator in the other of said gas lines,

(e) an injector in communication with said lines, and

(f) valve means for selectively passing gas into said injector, said injector including,

(g) a body portion having a longitudinal bore extending therethrough and a transverse bore in communication with the longitudinal bore,

(h) an induction screw assembly mounted in the transverse bore, said assembly including,

(i) a screw member movable into and out of the longitudinal bore of said body portion,

(j) a shutoff valve rotatably mounted in said body portion,

(k) said shutoff valve including a transverse passage selectively aligned with the longitudinal bore of said body portion,

(1) an elongated support extending from a terminal of said body portion,

(m) said support having a longitudinal groove coextensive with the length thereof,

(11) a hypodermic syringe unit positioned in the longitudinal groove of said support, said hypodermic syringe unit including,

(o) a sample-receiving tube,

(p) a hypodermic needle fixed to one terminal of said sample-receiving tube,

(q) the opposite terminal of said tube being aligned with the longitudinal bore of said body portion,

(r) graduation markings on said support adjacent said hypodermic syringe unit, and

(s) a clamp removably attached across a terminal of said support for engaging and holding said hypodermic syringe unit in position.

6. The gas chromatography sample injection assembly of claim 5, wherein:

(a) said low pressure regulator is in the range of 1-8 p.s.i. over the sampled material, and

(b) said high pressure regulator is in the range of 1-75 p.s.i. over the gas chromatography chamber.

7. The gas chromatography injection assembly of claim 5, with the addition of (a) means for heating the gas prior to entry into the injector, to match the temperature of the injector gas to the gas within the chamber.

8. A gas chromatography sample injection assembly for injecting a sample into a gas chromatography chamber comprising:

(a) a gas line,

(b) said gas line including a pair of feeder lines in parallel,

(c) a gas source in communication with a terminal of each of said feeder lines,

(d) a low pressure regulator in one of said feeder lines,

(e) a high pressure regulator in the other of said feeder lines,

(f) an injector, and

(g) means for selectively admitting gas from the free terminal of each of said feeder lines to said injector.

9. The gas chromatography sample injection assembly of claim 8, wherein:

(a) said low pressure regulator permits passage of gas to said injector in the range of 1-8 p.s.i. over the sampled material.

10. The gas chromatography sample injection assembly of claim 8, wherein:

(a) said pressure regulator permits passage of gas to said injector in the range of 1-75 p.s.i. over the gas chromatography chamber.

11. A gas chromatography sample injection assembly for injecting a sample into a gas chromatography chamber comprising:

(a) a gas line,

(b) a gas source in communication with one terminal of said gas line,

(c) an injector in communication with the opposite terminal of the gas line,

(d) said injector including a body portion,

(e) said body portion having a gas-receiving bore in communication with said gas line,

(f) an elongated support extending from said body portion,

(5.!) a tubular sample-receiving member and hypodermic needle positioned on said support,

(h) said tubular member and hypodermic needle having longitudinal bores in communication with the gas-receiving bore of said body portion,

(i) means for drawing a liquid sample through said hypodermic needle into said tubular sample-receiving member,

(j) valve means for selectively admitting and stoping the flow of gas to said sample receiving member and hypodermic needle,

(k) an induction screw assembly mounted in a transverse bore of said body portion, the transverse bore being in communication with the gas-receiving bore of said body portion,

(1) said induction screw assembly having a fitting fixed to said body portion proximate the transverse bore, and

(m) a screw member inserted in each fitting and engaged with a part of the body portion wall defining the transverse bore,

(n) said screw member being selectively movable through the transverse bore with respect to said fitting and into the gas-receiving bore, for selectively increasing the internal volume of the gas-receiving bore to induce the flow of a measureable amount of liquid sample into said injector when said valve means is closed.

12. The gas chromatography sample injection assembly of claim 11, wherein:

(a) said tubular sample-receiving member and hypodermic needle are of unitary construction and removable from said support for disposal and ready replacement.

13. The gas chromatography sample injection assembly of claim 11, wherein:

(a) said tubular member is a capillary tube, and with the addition of,

(b)' a longitudinal groove coextensive with the length of said support, in which groove the capillary tube and needle are placed, and

7 8 (c) a clamp removably engaged with said support for References Cited gigventing movement of the capillary tube and nee- UNITED STATES PATENTS 14. The gas chromatography sample injection assem- 3,297,558 1/1967 Hinquist' bly of claim 11, wherein said valve means comprises 5 3,304,784 2/1967 a stopcock rotatably mounted in said body por- 3,401,564 9/1968 Hrdl 73-421 tion and extending across the longitudinal bore 3412'613 11/1968 Brown et (b'g fg k b d d th t LOUIS R. PRINCE, Primary Examiner sai stopcoc eing provi e W1 a ransverse bore which may be selectively aligned with the lon- 10 POST Asslstant Exammer gitudinal bore of said body portion to permit pas- Us, (:1, X R sage of gas through the stopcock. 222-425

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