US3915677A - Injector and septum for gas chromatographic apparatus and other equipment - Google Patents

Injector and septum for gas chromatographic apparatus and other equipment Download PDF

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Publication number
US3915677A
US3915677A US374952A US37495273A US3915677A US 3915677 A US3915677 A US 3915677A US 374952 A US374952 A US 374952A US 37495273 A US37495273 A US 37495273A US 3915677 A US3915677 A US 3915677A
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septum
injector
needle
syringe
channel
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US374952A
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English (en)
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Asbjorn Oppegaard
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
    • G01N30/02—Column chromatography
    • G01N30/04—Preparation or injection of sample to be analysed
    • G01N30/16—Injection
    • G01N30/18—Injection using a septum or microsyringe
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D15/00—Separating processes involving the treatment of liquids with solid sorbents; Apparatus therefor
    • B01D15/08—Selective adsorption, e.g. chromatography
    • B01D15/10—Selective adsorption, e.g. chromatography characterised by constructional or operational features
    • B01D15/14—Selective adsorption, e.g. chromatography characterised by constructional or operational features relating to the introduction of the feed to the apparatus

Definitions

  • An injector arrangement in which an injector chamber is provided with at least two septa.
  • the injector is for gas chromatographic apparatus and other equipment where a sample is to be introduced through a hollow needle which is pushed through a septum.
  • the two or more septa are arranged in relative positions so that the hollow needle first penetrates one septum whereby the tip of the needle enters the interior of the injector chamber. Thereafter, the needle is forced through a second septum whereupon the tip of the needle appears on the outside of the chamber, where the needle can be cleaned. After the cleaning action, the needle is retracted so that the tip is returned to the interior Of the injector chamber where the injection process can then proceed.
  • a septum through which the sample is introduced with a syringe.
  • a septum is usually in the form of a disc of elastomer material installed in a suitable injector support. This septum separates the detection system from the environment, but the sample may be introduced by perforation by the needle of the syringe.
  • the combination septum/syringe is in use for injection of gases, liquids and solids into the above mentioned types of apparatus. It is especially popular for liquids because it has a range of advantages in comparison with other methods: It is quick; the quantity to be injected can be easily chosen and adjusted with accuracy (100 2': 2 percent in the microliter range); precision of the quantity to be injected is suitable for many purposes (100 i 2 percent or better); and in the cases where this deviation is too large, internal standards can be used.
  • the present invention is based on the fact that many of the complications in turn are linked with problems which until now have been neglected. To simplify the further description the following will treat a particular instrument, a gas chromatograph, GC among the above mentioned group of apparatus.
  • Septum A septum-less injector is referred to (van Swaay, Bacon: Joum. Chrom. 19(1965) 604), but the use of it is complicated and its reliability is dubious under varying circumstances. Hence, in commercial GC, the syringe injection is nearly always combined with a septum.
  • the ideal septum has physical properties which maintain the seal during and after repeated perforations, even when there is a great difference in gas pressure between the two sides of the septum.
  • An ideal septum is also chemically inert; it neither takes up nor gives off substances. These physical and chemical properties should be maintained in a temperature range over several hundred degrees over an unlimited period of time.
  • Septa with improved sorption properties can be obtained by using materials such as PTFE, but because their sealing properties are rather poor, such materials are used only in a thin layer sandwich types. Due to reasons later discussed, the sandwich principle is not completely efficient in eliminating the sorption phenomena. By using certain types of rubber in the inner layers, in fact, the situation can be made worse.
  • Septum Bleed In the production of synthetic elastomer, the monomer is usually used with other organic substances with comparatively high vapor pressures. It is not surprising that the latter substances can appear in the finished product. When a septum is used in a G.C. a series of unpleasant symptoms can arise from the septum giving off substances. Examples of this are unstable conditions and the so-called ghostpeaks. To avoid such complications attempts have been made to modify the elastomer and to apply certain post treatments. This will, how ever, usually result in a loss of other important material properties.
  • the sandwich principle is not entirely efficient in eliminating the sorption phenomena, nor is it completely effective in dealing with bleed. Further details are given later.
  • the bleed characteristics of seven commercial septum types have been studied by Smith and Sorrells (Smith, Sorrells: Journ. Chrom. Sci. 9 (1971) 15).
  • the seven septum types studied include all major varieties such as homogeneous and sandwich types. None was judged to be satisfactory for sub-microgram analyses.
  • the septum temperature should be kept as low as possible. But on the other hand, at such low temperatures there is a likelihood for condensation of the injected substance to occur and this must be prevented.
  • a more radical injector modification can, however, be found. It prevents gas, which has been next to the septum, from entering into the column.
  • the carrier gas stream is divided into two. The main stream enters the column as normal while a side stream moves toward the septum and so out of the system.
  • This modification does not increase the dead volume of an injector, but the danger with such designs is clearly that parts of the sample can be lost. This is due to the expansion and back-flush; in other words, the sample is driven towards the septum and out, instead of going towards the column.
  • the needle of the syringe is especially important.
  • Syringe needles for GC use are usually made from stainless steel. Platinum is used only for extra special samples. Needles often have an outer diameter of 0.5 mm and an inner diameter of about 0.2 mm. Various needle tips can be obtained. Some manufacturers recommend a 17 bevel for ease of penetration, although bevels of 12 and 22 and needles with a 90 tapered tip are also available. Production techniques are advanced and special polishing operations produce needles with a smooth finish.
  • the needles often suffer from rough handling during use.
  • injectors are designed such that the needle can come up against various obstructions, such as edges and the ends of tubes.
  • the needle can thereby be bent or damaged, becoming rough and result in scraping.
  • a damaged needle results in a damaged septum.
  • the manner in which a syringe needle perforates the septum affects gas leakage to a great extent, and a septum perforated by a' bent rough needle has fewer chances of maintaining a tight seal.
  • Sorption of the sample on loose septum bits can take place freely in the analysis system.
  • the granules come in very close contact with the sample and the surface area of irregular shapes is decidedly large.
  • FIG. 1ac are sectional views and show the penetration of a hollow needle through the septa for cleaning and injecting into the injection chamber, in accordance with the present invention
  • FIG. 2 is a sectional view and shows the constructional details of an injector arrangement, in accordance with the present invention
  • the construction is based on the fact that bits of septum are torn out only when the needle is pushed in and not when it is retracted. This principle is illustrated in FIG. 1 and applies under different technical designs.
  • the upper septum II is first (a) perforated by the syringe needle 12, which is then rotated into a vertical position.
  • the syringe needle is then (b) pushed out from the inside through the lower septum 13.
  • the bits or rubber can then be removed from the needle tip which is now accessible, and the syringe, can be rinsed with an appropriate liquid. Having eliminated the contamination, the sample can be taken up into the syringe in the usual manner.
  • the needle tip is then drawn back through the lower septum, into the system again, and after being rotated to a horizontal position (c), the sample is injected without any danger of contamination from bits of septum material.
  • the needle After injection, the needle can remain in the upper septum and it can also be driven out through the lower septum.
  • the upper septum therefore, only needs to be perforated once and the lower septum a number of perforations usual for an injector.
  • FIG. 1 illustrates an injector after the above principle.
  • a septum 1 is applied to a rotating support 3 by means of a septum nut 2 having threads, not shown.
  • the rotating support 3 has assembled to it a clamping ring 4 with clamping bolts, not shown.
  • An ring 5 serves as a seal.
  • An injector block 6 is provided with a channel 7 leading to the column, and a channel 8 leading to the lower septum.
  • An injector arrangement for introducing samples into physical-chemical investigating apparatus by means of a syringe comprising in combination:
  • a rotating support mounted on said injector block and adapted to receive a syringe
  • said first, second and third channels being so arranged with respect to the axis of rotation of said rotating support that said first channel can be brought into alignment with said second channel and third channel respectively, by rotating said rotating support, whereby in a first position of said rotating support a syringe needle can pass through both said first septum and said second septum, and after cleaning and retraction of said needle from said second septum the rotating support is rotatable to a second position in which said needle can be introduced into said third channel along a predetermined line for injecting a sample through said needle.
  • the injector arrangement as defined in claim 1 including gas chromatographic apparatus communicating and cooperating with said third channel.
  • the injector arrangement as defined in claim 1 including a syringe connected to said needle and filled with said sample.

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analysing Biological Materials (AREA)
  • Sampling And Sample Adjustment (AREA)
US374952A 1972-06-30 1973-06-29 Injector and septum for gas chromatographic apparatus and other equipment Expired - Lifetime US3915677A (en)

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NO02344/72A NO129368B (da) 1972-06-30 1972-06-30

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US3915677A true US3915677A (en) 1975-10-28

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4010648A (en) * 1975-10-01 1977-03-08 Harris Sr Rano J Adapter unit for use in sampling fluid specimens
EP0126885A1 (en) * 1983-05-20 1984-12-05 Becton Dickinson and Company System for locating a vial
US4928541A (en) * 1988-02-05 1990-05-29 Solinst Canada Limited Groundwater sampling apparatus
US20020102185A1 (en) * 2001-01-31 2002-08-01 Shimadzu Corporation Automatic sampler and needle for the same
FR2838826A1 (fr) * 2002-04-17 2003-10-24 Inst Francais Du Petrole Methode et dispositif pour l'injection de gaz par une seringue dans un appareil d'analyse
US6638346B1 (en) * 1999-10-29 2003-10-28 Thermo Finnigan Italia S.P.A. Vaporization injector

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2584397A (en) * 1945-10-03 1952-02-05 Louis K Pitman Apparatus for transferring liquid from one container to another
US3205711A (en) * 1963-04-11 1965-09-14 Microtek Instr Inc Sample injection in gas chromatography

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2584397A (en) * 1945-10-03 1952-02-05 Louis K Pitman Apparatus for transferring liquid from one container to another
US3205711A (en) * 1963-04-11 1965-09-14 Microtek Instr Inc Sample injection in gas chromatography

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4010648A (en) * 1975-10-01 1977-03-08 Harris Sr Rano J Adapter unit for use in sampling fluid specimens
EP0126885A1 (en) * 1983-05-20 1984-12-05 Becton Dickinson and Company System for locating a vial
US4928541A (en) * 1988-02-05 1990-05-29 Solinst Canada Limited Groundwater sampling apparatus
US6638346B1 (en) * 1999-10-29 2003-10-28 Thermo Finnigan Italia S.P.A. Vaporization injector
US20020102185A1 (en) * 2001-01-31 2002-08-01 Shimadzu Corporation Automatic sampler and needle for the same
US7175812B2 (en) * 2001-01-31 2007-02-13 Shimadzu Corporation Automatic sampler and needle for the same
FR2838826A1 (fr) * 2002-04-17 2003-10-24 Inst Francais Du Petrole Methode et dispositif pour l'injection de gaz par une seringue dans un appareil d'analyse

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Publication number Publication date
NO129368B (da) 1974-04-01

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