US3407647A - Chromatography - Google Patents

Description

Oct. 29, 1968 T. R. LYNN 3,407,647

CHROMATOGRAPHY Filed May 24, 1965 2 Sheets-Sheet 1 I I INVENTOR Theodore R. Lynn I i D-ZZLOWNQ mom? ATTORNEYS Oct. 29, 1968 T. R. LYNN 3,407,647

CHROMATOGRAPHY Filed May 24, 1965 2 Sheets-$heet 2 30 MlNUTE RUN INJECTOR HEHTER TEMPERHTURQ 340C sHMPLE METHYL ESTERS or I FHTTY R6105 (BUTTERFHT) SRMPLE SIZE -zcc I 30 MINUTE RUN INJECTOR HEQTEK TeMPERnTuRE- 340C snMPLE METHYL ESTERS 0F FHTTY FICID$(BUTTERFHI) snM'PLE sue 25 cc CIG INV ENT OR Theodore R. Lqnn BY Diblo Mnm ATTORNEYS United States Patent M 3,407,647 CHROMATOGRAPHY Theodore R. Lynn, 98 Meadow St., Wallingford, Conn. 06492 Filed May 24, 1965, Ser. No. 457,936 3 Claims. (Cl. 73---23.1)

ABSTRACT OF THE DISCLOSURE A system for providing a vaporized sample to a gas chromatography column. The system includes a vaporizing chamber into which there is forced under high pressure an atomized sample which is then vaporized and carried into the chromatography column by a carrier gas under low pressure.

This invention relates to chromatography and more particularly to a new and improved method and apparatus for introducing a sample into a gas chromatography column.

Chromatography is defined as those processes which allow the resolution of mixtures by effecting separation of some or all of the components in concentration zones or in phases different from those which were originally present, irrespective of the force causing the mixtures to move from one place to the other. Chromatography is a physical method of separation, in which components to be separated are distributed between two phases, one of these phases constituting a stationary bed of large surface area, the other being a fluid that percolates through or along the stationary bed. Gas chromatography is distinctive in that one of the phases is a gas which acts to transport the various solutes through a fixed solvent bed. More particularly in gas chromatography, a sample of the material to be separated is introduced into a column which contains a selective adsorbent. A carrier gas is directed into the column to tend to force the sample material through the column. The adsorbent attempts to hold the constituents of the sample, whereas the stripping gas tends to pull them through the column. This results in the several constituents of the fluid mixture traveling through the column at different rates of speed, depending upon their affinities for the stationary phase. The column effluent thus consists initially of the carrier gas alone and the individual constituents of the fluid mixture appearing at later spaced time intervals. It is common practice to detect these constituents by means of a thermal conductivity analyzer which compares the thermal conductivity of the carrier gas carrying some of the constituents with the thermal conductivity of the carrier gas directed to the column.

For a more complete explanation of chromatography, reference should be had to the text Gas-Liquid Chromatography by S. Dal Nogare and R. S. Juvet, Jr., published by lnterscience Publishers, 1962, and copyrighted by John Wiley & Sons of New York and London.

In the practice of gas chromatographic analysis of liquid materials, it is common practice to introduce a sample of the compound to be analyzed into a heater unit, such as a flash heater, which is coupled to the gas chromatography column. The prior art has generally utilized hypodermic syringes to supply the sample to the flash heater unit. As chromatography science progressed, larger sample amounts were introduced in order to prepare appreciable compounds but, due to poor vaporization of the sample introduced into the heater as a stream or slug of liquid, poor separation efiiciency resulted. Efforts to overcome the low efliciency separation have included the use of larger diameter or longer length chromatograph columns, but these have not altogether solved the efli- BAflLM'Z Patented Oct. 29, 1968 ciency problem which is particularly critical when high boiling materials are to be analyzed. In this situation, the length of time that it takes to convert the entire sample to a gas is greater than or appreciable in comparison with the time required by the chromatograph column to separate some of the constituents of the sample. When this occurs, the separation efficiency deteriorates since a portion of some of the later-converted but faster-separating consituents will interfere with the collection and de tection of some of the slower-separating constituents. Thus, the faster-separating, higher boiling point constituents will mask the slower-separating constituents and prevent some constituents from being recovered or analytically measured.

In view of the foregoing, a new and improved method and system for introducing a sample was necessary to improve the separating efiiciency of gas chromatography systems. Further, new and improved means were required to prevent faster separating sample constituents from masking slower separating sample constituents.

It is therefore an object of this invention to provide a new and improved gas chromatography method and apparatus.

It is a further object of this invention to provide a new and improved method for introducing a sample into a gas chromatography system.

Another object of this invention is to provide a new and improved means for introducing a sample into a gas chromatography system.

Still another object of this invention is to provide a new and improved gas chromatography apparatus which has the capability of separating the constituents of samples greater in amount than prior art samples, without sacrificing resolution efficiency.

Other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.

The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, and the apparatus embodying features of construction, combination of elements and arrangement of parts which are adapted to effect such steps, all as exemplified in the following detailed disclosure and the scope of the invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description, taken in connection with the accompanying drawings, in which:

FIG. 1 is a schematic representation of a chromatographic system including the sample introducing means in accordance with the teachings of this invention;

FIG. 2 is an enlarged schematic representation of the sample introducing system in accordance with this invention;

FIG. 3 is a graphical representation of a typical output signal from a chromatographic analyzer system without the novel features of this invention; and

FIG. 4 is a graphical representation of a typical output signal from a chromatographic analyzer system when the novel features of this invention are utilized.

Referring now to the drawings in detail and to FIGS. 1 and 2 in particular, there is shown a temperature stabilized housing 10 which has mounted therein a gas chromatography column 11 filled with a suitable packing material or adsorbent that selectively retards passage therethrough of the gaseous mixture to be analyzed. Positioned adjacent to the housing 10 is a heater unit 12, utilized to convert a sample to a gaseous form so that it may pass through tube 13 coupled to column 11. The heater element may be of the conventional electrical resistance type or may be of the more sophisticated microwave oven type, although, for the purposes of this invention, the electric heater type is preferred. The car rier gas is supplied from a suitable container 14 through a valve 15 by way of a tube 16 which is coupled to the heater unit 12. The sample i permitted to enter the vaporizing unit 12 by way of an opening 20. Also mounted in housing 10 is a sensor device 21 which preferably includes two thermistor-s which are disposed in thermal contact with the fluids flowing through a conduit 22 coupled to the carrier gas conduit 16 and to a conduit 23 coupled to the outlet end of the column 11. The sensor 21 provides an output signal representative of the difference in composition of the fluids flowing through the conduits 22 and 23 as sensed by separate thermistors in each detecting gas flow in each of the conduits. This in formation is then transmitted to a recorder-controller 24 which presents the recording of the difference in thermal conductivity of the fluids passing through each of the conduits as a result of the separation produced by the action of the column on the combined carrier gas and gaseous sample. Some of the newer chromatography equipment provide a controlled valve assembly 26 which is coupled by way of a conduit 28 to sensor 21. The valve assembly 26 is controlled from sequential signals provided by the recorder-controller 24 to selectively permit gaseous fluid to exit from a plurality of separate conduits 30-33. In this manner, upon the sensing of a constituent in the conduit 23, a selected valve is actuated in device 26 to permit fluid to exit from one of the conduits 30-33. Upon the sensing of the next constituent, a different valve is actuated to cause the fluid to exit through an other one of the conduits coupled to the valve device 26. This type of system is available from various manufacturers as, for example, The Wilkins Instrument and Research Inc., and The F. & M. Scientific Corporation.

The gas from container 14 is generally pumped through at a pressure such that the gas will continuously force the gasified sample through column 11. In order to introduce the sample through opening 20, an injecting nozzle 39 is utilized. The injecting nozzle is of a type such that when fluid is forced into it at a selected, predetermined pressure, it will open, but below this selected, predetermined pressure it will remain closed. This type of nozzle is commonly utilized on fuel injection systems for diesel engines and the like. The injector nozzle which may be utilized in this system can be a springloaded ball assembly set to release at a predetermined pressure. A pump 40 is provided in order to force a fluid sample through a conduit 41 coupled to the injection nozzle 39. This pump is itself coupled through a conduit 42 to a sample reservoir 43. The reservoir is coupled through a conduit 44 to a sample source.

Referring more particularly now to FIG. 2, there is disclosed, in an enlarged view, the heating unit 12 and the injecting nozzle 39. The heating unit 12 includes an electric heater 45 for gasifying a liquid sample 47 which is introduced by way of nozzle 39 into a chamber 48 in the interior of the heating unit. The type of material employed in column 11 and the carrier gas employed depend, to a large extent, on the composition of the fluid mixture to 'be analyzed. The column can be filled with an adsorption material such as charcoal, silica gel, and the like. The column can also be filled with an inner solid material such as crushed fire brick or diatomaceous earth, which is coated either with a solvent such as hexadecane or benzyl ether. Examples of suitable carrier gases include helium, hydrogen, carbon dioxide, nitrogen, argon and air. Suitable recorder systems can be found in Patent 2,977,472 issued to K. V. Kratochvil.

Referring now to FIGS. 3 and 4, there is shown graphical illustrations of the output electrical signal gained from recorder 24 as a result of the gasified sample passing through column 11. FIG. 3 represents the prior art injection of the liquid sample into a heater unit without the use of the invention described herein. The chromatography apparatus of FIG. 1 was run for 30 minutes and the heater temperature was set at 340 C. The sample was squirted into the heater unit 12 by a prior art syringe and were methyl esters of fatty acids, in this case butter fat, and the sample size was 1 cc. The graph shown in FIG. 3 represents the output signal from the recorder 24. The peaks in the graph indicate the passage of various constituents which were sensed 'by sensor 21. In FIG. 4 the chromatography apparatus was also run for 30 minutes and the heater temperature set at 340 C. A butter fat sample of the same type tested in the graph of FIG. 3 was also utilized but, in this case, a sample of 25 cc. was utilized inasmuch as FIG. 4 represents the output signal when applicants invention, as shown in FIGS. 1 and 2, is utilized.

In the test shown in FIG. 4 the pump 40 was set to provide a liquid sample 47 at a pressure of 1800 lb./p.s.i. to the nozzle 39. The nozzle was set to prevent any liquid from passing and entering the heater unit 12 until a pressure greater than 1800 lb./p.s.i. was reached. At this time the injector nozzle opened and a liquid sample was forced into the heater unit 12. The sample was forced under such a pressure that it was presented to the cavity 48 of heater unit 12 as an atomized spray rather than the common cohesive liquid squirt provided by the prior art devices. In comparing FIG. 4 to FIG. 3, it is noted that the peaks representing the various constituents are much narrower in width, thus representing greater separation capability with applicants invention. Further, as can be seen from FIG. 4 when compared to FIG. 3 the separation efiiciency is greater and there is less masking of one constituent by another, since the peaks and the bases of the spikes are further from each other along the base line. Moreover, the constituents C16 and C18 appear as small particles, represented in FIG. 4 by peaks, whereas in FIG. 3 there is very little which can be seen. In both examples of FIGS. 3 and 4 nitrogen gas was used as an inert carrier and was forced by way of example only, into the heater unit 12 at a pressure of 40 lb./p.s.i. The results obtained with applicants invention are apparent from the FIG. 4 graph, wherein a sample size twenty-five times greater than that capable of being run or processed with prior art sample squirting syringes was processed by utilization of applicants invention. Even with the increased sample size, better sample-separation reso lution was obtained by utilizing applicants invention. The invention provides a means for furnishing a vaporized sample to a chrom-atograph column at a time interval generally less than the separation rate of the fastest separating constituent of the sample being analyzed. This occurrence is due principally to the ability of an atomized sample to be gasified at a much faster rate than that ordinarily obtainable with a liquid which has been squirted in.

Thus, by the use of an injector nozzle 39, which only permits a sample to exit therefrom when the sample is forced into the nozzle at greater than a predetermined pressure which opens the nozzle and much greater than the carrier gas pressure, a sample is atomized such that the liquid entering the chamber 48 is divided into a fine spray of minute particles. This is cliflerent from the prior art sample injecting systems wherein the liquid was squirted into a chamber without being broken up or atomized into a fine particle spray and only at a pressure just above the pressure of the carrier gas.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in carrying out the above method and in the construction set forth without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

What is claimed is:

1. A chromatography apparatus .for separating a fluid mixture into a plurality of constituents, comprising a block having first inlet means and an outlet means defining a heating chamber therein, second inlet means provided in said block adjacent said first inlet means, an injection nozzle connected to said first inlet means, a chromatography column coupled to said outlet means, means connected to said second inlet means for providing a carrier gas to said chamber, and heating means for heating said chamber.

2. A chromatography apparatus according to claim 1,

coupled between said source of fluid and said fluid injection nozzle.

References Cited FOREIGN PATENTS 37/ll,949 8/1962 Japan.

818,703 8/1959 Great Britain.

RICHARD C. QUEISSER, Primary Examiner.

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