Method of chemical analysis and apparatus for such analysis

• US 3,897,679 A
• Filed: 07/03/1972
• Issued: 08/05/1975
• Est. Priority Date: 05/18/1970
• Status: Expired due to Term

• Current Assignee: Lloyd V. Guild
• Original Assignee: Lloyd V. Guild
• Inventors: Guild, Lloyd V.
• Primary Examiner(s): Queisser, Richard C.
• Assistant Examiner(s): Roskos, Joseph W.
• Application Number:
  US05/268,924
• Time in Patent Office: 1,128 Days
• Field of Search: 73/23.1,61.1C 210/31C,198C
• US Class Current: 73/61.52
• CPC Class Codes: B01L 7/00 Heating or cooling apparatus autoclaves B01J3/04; Heat insulating devices
• CPC Class Codes: B05B 11/1087 Combination of liquid and air pumps
• CPC Class Codes: G01N 30/00 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 G01N3/00, G01N5/00, G01N7/00, G01N9/00, G01N11/00, G01N13/00, G01N15/00, G01N17/00, G01N19/00, G01N21/00, G01N22/00, G01N23/00, G01N24/00, G01N25/00, G01N27/00, G01N29/00 take precedence
• CPC Class Codes: G01N 30/08 using an enricher
• CPC Class Codes: G01N 33/0011 Sample conditioning preparing specimens for investigation G01N1/28

Abstract

There is disclosed a method, particularly useful in studying pollution, for concentrating components, under investigation, of a fluid, in a concentrator including a tube having in it a selective adsorbent for the components, such as a molecular sieve or diatomaceous earth impregnated with silicone oil. A measured relatively large quantity of the fluid is transmitted through the tube and the components in the fluid are adsorbed. The adsorbent is then heated rapidly to a predetermined temperature at which the component is desorbed and passed through measuring apparatus such as a chromatograph or analyzed in a spectrophotometer. As the fluid passes through the concentrator the component is deposited progressively along the length of the adsorbent from the fluid input end of the concentrator to its output end. The quantity of the adsorbent in the concentrator is so set that a readily measurable quantity of component can be deposited from the fluid along less than the whole length of the adsorbent. The method is particularly useful where the component sought is of such low concentration in the fluid that the quantity of component in a moderate quantity of fluid is below the detecting limit of the measuring instrument. Since there is substantially no component in any of the fluid emitted from the output end of the concentrator, the concentration of the component in the fluid can be determined from the indication of the measuring instrument and the known quantity of the fluid transmitted through the concentrator. There is also disclosed a novel concentrator and apparatus in which the adsorbent is heated by passing high current through the tube so that the adsorbent is rapidly heated to the predetermined temperature. The current may be automatically turned off when this temperature is reached.

Claims

1. Apparatus for measuring the quantity of a component in a concentrator, said concentrator including a tube composed of electrically-conducting material having therein an adsorption medium for selectively adsorbing said component from a fluid passing through said medium, said component remaining adsorbed in said medium so long as the temperature of said medium is below a predetermined magnitude and being desorbed when the temperature of said medium is at least at said predetermined magnitude, the said apparatus including:

component measuring means, means for connecting said concentrator to said measuring means so that said component, when desorbed from said Medium, flows into said measuring means, electrical means, to be connected to said tube, for conducting current of the order of hundreds of amperes through said tube, for supplying a large quantity of heat to said medium in a short time interval for heating said medium to a temperature at least of said predetermined magnitude in a short interval of time of the order of about 10 seconds so that said component is desorbed and transmitted through said measuring means as a pulse, and control means connected to said heating means, including temperature-responsive means, directly responsive to the temperature of said medium, for controlling the heating of said desorbing medium to terminate the supply of heat after said interval of time.

2. The apparatus of claim 1 wherein the heating means includes a transformer having a primary connected to a power supply, and a secondary connected to the tube to conduct current through said tube, the transformer having a high primary-to-secondary turns ratio so that the current of the order of several hundred amperes is conducted through said tube and said tube is heated at least to the predetermined temperature in said short time interval, and the control means includes means, responsive to the temperature-responsive means, for permitting the secondary to conduct current so long as the temperature of the medium is below the predetermined temperature and to interrupt the current when the medium reaches the predetermined temperature, whereby the component flows through the measuring means as a pulse.

3. The apparatus of claim 1 wherein the electrical conductor is an additional tube of substantially the same material, wall thickness and inside diameter as the tube of the concentrator.

4. The apparatus of claim 3 wherein the temperature responsive means includes a thermocouple whose hot junction is substantially in point contact with the additional tube and whose wires diverge from said point contact at said hot junction.

5. The apparatus of claim 1 wherein the temperature-responsive means includes a thermocouple whose hot junction is connected to an electrical conductor which is substantially at the temperature of the medium, said hot junction being substantially in point contact with said conductor and the wires of said thermocouple diverging from said hot junction.

6. The apparatus of claim 3 wherein the temperature-responsive means includes a thermocouple whose hot junction is substantially in point contact with the electrical conductor and whose wires diverge from said hot junction.

7. Apparatus for measuring the quantity of a component in a concentrator, said concentrator including a tube having therein an adsorption medium for selectively adsorbing said component from a fluid passing through said medium, said component remaining adsorbed in said medium so long as the temperature of said medium is below a predetermined magnitude and being desorbed when the temperature of said medium is at least at said predetermined magnitude, the said apparatus including:

component measuring means, means for connecting said concentrator to said measuring means to transmit said component therethrough, said concentrator and measuring means forming a junction at the region where they are connected, means, to be connected to said tube, for heating said medium to a temperature at least of said predetermined magnitude so that said component is desorbed and transmitted through said measuring means, heating means for said measuring means, and heat-transfer means, thermally connected to said heating means, for transmitting heat to said junction to heat said concentrator at said junction.

8. The apparatus of claim 7 wherein the heat-transfer means includes means for concentrating the heat at the junction on the concentrator.

9. The apparatus of claim 7 wherein the junction includes a plate of low heat conducting material, and the heat-transfer means including a tube of heat conducting material thermally connected to said heating meAns and abutting the plate, the concentrator being connected to conduct the component through the plate and through the tube, the plate being perforated in the region where it is abutted by said tube to suppress lateral flow of heat from said tube along said plate.

10. The apparatus of claim 7 wherein the heat-transfer means includes a tube of thermally conducting material thermally connected to said heating means, the said apparatus also including means, to be connected to the concentrator, for transmitting the component through said thermally conducting tube to be heated by said tube.

11. Apparatus for measuring the quantity of a component in a plurality of concentrators, each said concentrator including a tube having therein an adsorption medium for selectively adsorbing said component from a fluid passing through said medium, the said apparatus including component-measuring means, means for connecting said concentrators in succession, each to transmit its said component, to said measuring means, means, connected to said connecting means, for supplying a carrier gas for carrying said component through said concentrator and through said measuring means, and means connected to said measuring means and responsive to the interruption of carrier-gas flow through a concentrator last connected to said measuring means for maintaining the flow of said carrier gas through said measuring means, during the intervals between connection of said last-connected concentrator and a successive concentrator to said measuring means.

12. A concentrator for concentrating, from a fluid for measurement, a measureable quantity of a component in said fluid, the said concentrator including a generally U-shaped tube having, along its length between a point near one end and a point near the opposite end, adsorbing means for adsorbing said component from said fluid as said fluid is passed through said adsorbing means, said one end of said tube being an inlet end into which said fluid is to be injected and said opposite end being an outlet end from which the resulting fluid is to be emitted, said component to be adsorbed only along a portion of the length of said adsorbing means from said inlet end, said tube having arms of different lengths, the shorter arm including the inlet end and the longer arm the outlet end, so that the inlet end may be distinguished from the outlet end.

13. Apparatus for measuring the quantity of a component in a concentrator, said concentrator including a tube, composed of electrically conducting material, having therein an adsorption medium for selectively adsorbing said component from a fluid passing through said medium, said component remaining adsorbed in said medium so long as the temperature of said medium is below a predetermined magnitude and being desorbed when the temperature of said medium is at least at said predetermined magnitude, the said apparatus including:

component measuring means, means for connecting said concentrator to said measuring means so that said component, when desorbed from said medium, flows into said measuring means, an electrical conductor having the same resistance per unit length as said tube, a transformer having a primary connected to a power supply and a secondary, said transformer having a high primary-to-secondary turns ratio so that said secondary is capable of supplying high current, means for connecting said secondary, said tube and said electrical conductor in a heating circuit in which said secondary supplies said high current to heat said electrical conductor and said tube and, through said tube, to heat said medium to a temperature at least of said predetermined magnitude so that said component is desorbed and transmitted through said measuring means, and control means, including temperature-responsive means responsive to the temperature of said electrical conductor and also including means, responsive to said temperature-responsive means, for actuating said control means to interrupt the current through said tube When said medium reaches said predetermined temperature, whereby said component flows through said measuring means as a pulse.

14. Apparatus for measuring the quantity of a component in a plurality of concentrators, each said concentrator including a tube having therein an adsorption medium for selectively adsorbing said component from a fluid passing through said medium, the said apparatus including component-measuring means, means for connecting said concentrators in succession in a first gas flow circuit, each to transmit its said components to said measuring means, means connected to said connecting means for supplying a carrier gas to said first gas-flow circuit for carrying said component through said concentrator and into said measuring means, said first gas-flow circuit having a first impedance to said carrier-gas-flow, a second gas-flow circuit connecting said carrier-gas-supplying means directly to said measuring means, said second circuit having a second impedance to said carrier-gas-flow which is high compared to said first impedance, and valve means, responsive to the interruption of carrier-gas-flow through a concentrator, for confining gas flow through said second circuit to said measuring means during the intervals between successive connections of said concentrators to said measuring means.

15. The method of measuring with an instrument the quantity of a component in a fluid, said instrument producing an observable response only when said quantity exceeds a predetermined level, the said measurement being made with a concentrator having a tube including means for selectively adsorbing the said component from said fluid and from which the said component can be desorbed at a predetermined temperature, the said adsorbing means being disposed along the length of said tube from a position near one end to a position near the opposite end of said tube, the said method comprising removing the concentrator from the instrument, conducting a large quantity of said fluid through said concentrator, while said concentrator is maintained at a temperature substantially below said predetermined temperature to concentrate said component in said concentrator, the said fluid being injected in said one end of said tube and the component being adsorbed in said adsorbing means progressively along the length of said adsorbing means, from said one end, and the resulting fluid being emitted from said opposite end of said adsorbing means, there being sufficient adsorbing means along the length of said tube to adsorb said component at least up to said level without the emitted resulting fluid containing any substantial quantity of said component, connecting said concentrator to said instrument so that said component when desorbed from said adsorbing means flows into said instrument, said concentrator being connected with said one end, through which the fluid was injected, remote from said instrument and said opposite end nearest said instrument, and heating said concentrator at least to said predetermined temperature to desorb said component from said desorbing means and pass said desorbed component to said instrument, said instruments measuring the quantity of said component.

16. Apparatus for measuring the quantity of a component in a concentrator, said concentrator including a tube, composed of electrically conducting material, having therein an adsorption medium for selectively adsorbing said component from a fluid passing through said medium, said component remaining adsorbed in said medium so long as the temperature of said medium is below a predetermined magnitude and being desorbed when the temperature of said medium is at least at said predetermined magnitude, the said apparatus including:

component measuring means, means for connecting said concentrator to said measuring means so that said component, when desorbed from said medium, flows into said measuring means, an electrical conductor having the same resistance per unit length as said tube, power supply means capabLe of supplying high current, means for connecting said power-supply means, said tube and said electrical conductor in a heating circuit in which said power supply means supplies said high current to heat said electrical conductor and said tube and, through said tube, to heat said medium to a temperature at least of said predetermined magnitude so that said component is desorbed and transmitted through said measuring means, and control means, including temperature-responsive means responsive to the temperature of said electrical conductor and also including means, responsive to said temperature-responsive means, for actuating said control means to interrupt the current through said tube when said medium reaches said predetermined temperature, whereby said component flows through said measuring means as a pulse.