Gas inlet system for isotope ratio spectrometer

Patent metadata

Field	Value
Publication number	US-10408747-B2
Application number	US-201816163436-A
Country	US
Kind code	B2
Filing date	Oct 17, 2018
Priority date	Nov 8, 2013
Publication date	Sep 10, 2019
Grant date	Sep 10, 2019

Abstract

A gas inlet system for an isotope ratio spectrometer and a method for coupling analyte gas to an isotope ratio spectrometer are disclosed. A variable volume reservoir is located between a supply of analyte gas and a spectrometer. The reservoir's internal volume is controllably adjusted at a pre-determined rate to generate a defined flow of analyte gas or mixture to or from the reservoir. Analyte gas and carrier gas are taken up by the reservoir on increasing the reservoir's internal volume and then expelled from the reservoir to the spectrometer on decreasing the reservoir's internal volume. An open split can be used together with the reservoir to facilitate splitting away and hence dilution of analyte within the reservoir. A method for cleaning the gas inlet system is provided, which involves flushing the system with carrier gas.

First claim

What is claimed is:

1. A method of coupling an analyte gas to an isotope ratio spectrometer, comprising:
supplying a first analyte gas to a variable volume reservoir of a gas inlet system;
expanding the variable volume reservoir so as to take up the first analyte gas into the reservoir;

expelling, by compressing the variable volume reservoir, the first analyte gas, or a first analyte mixture containing the first analyte gas, from the reservoir at a controlled flow rate, by controllably adjusting the volume inside the variable volume reservoir at a predetermined rate;
directing a flow of the said first analyte gas or first analyte mixture to the spectrometer at the controlled flow rate; and
selectively supplying a carrier gas to the spectrometer and/or to the variable volume reservoir;
wherein the reservoir is expanded at a rate faster than the rate of supply of the first analyte gas so as to create a vacuum within the reservoir and thereby to suck in substantially all of the first analyte gas supplied by a first analyte gas supply during a sample uptake period wherein a part of the carrier gas passes to the variable volume reservoir so as to dilute the concentration of the first analyte gas in the reservoir.

2. The method of claim 1 , wherein at least a part of the carrier gas passes to an open split located upstream of the spectrometer and/or the variable volume reservoir.

3. A method of coupling an analyte gas to an isotope ratio spectrometer, comprising:
supplying a first analyte gas to a variable volume reservoir of a gas inlet system;
expanding the variable volume reservoir so as to take up the first analyte gas into the reservoir;
expelling, by compressing the variable volume reservoir, the first analyte gas, or a first analyte mixture containing the first analyte gas, from the reservoir at a controlled flow rate, by controllably adjusting the volume inside the variable volume reservoir at a predetermined rate;
directing a flow of the said first analyte gas or first analyte mixture to the spectrometer at the controlled flow rate, wherein at least a part of the carrier gas passes to an open split located upstream of the spectrometer and/or the variable volume reservoir;
diluting the first analyte gas once the variable volume reservoir has taken it up by:
isolating the variable volume reservoir from a supply of the first analyte gas;
compressing the reservoir by a known amount so as to expel a proportion of the first analyte gas to the spectrometer and to expel the remaining portion of the first analyte gas to the open split;
subsequently expanding again the variable volume reservoir to or by a predetermined amount, at a speed which is smaller than the difference between the uptake of the spectrometer and the carrier gas flow, so as to cause carrier gas to be drawn into the variable volume reservoir and to dilute the first analyte gas therein;
wherein the predetermined amount of expansion of the reservoir is selected on the basis of the subsequently desired dilution/concentration of the first analyte gas.

4. A method of coupling an analyte gas to an isotope ratio spectrometer, comprising:
supplying a first analyte gas to a variable volume reservoir of a gas inlet system;
expanding the variable volume reservoir so as to take up the first analyte gas into the reservoir;
expelling, by compressing the variable volume reservoir, the first analyte gas, or a first analyte mixture containing the first analyte gas, from the reservoir at a controlled flow rate, by controllably adjusting the volume inside the variable volume reservoir at a predetermined rate;

directing a flow of the said first analyte gas or first analyte mixture to the spectrometer at the controlled flow rate, wherein at least a part of the carrier gas passes to an open split located upstream of the spectrometer and/or the variable volume reservoir;
wherein the reservoir is expanded at a rate slower than the rate of supply of the first analyte gas so as to create a vacuum within the reservoir and thereby to suck a part, but not all, of the first analyte gas being supplied by a first analyte gas supply during a sample uptake period.

5. The method of claim 4 , further comprising determining the first analyte gas concentration within the variable volume reservoir when the first analyte gas concentration is present therein.

6. The method of claim 1 , comprising determining the concentration of the first analyte gas within the variable volume reservoir by:
connecting the variable volume reservoir to an opening once the first analyte gas has been taken up into the reservoir;
decreasing the volume of the reservoir to a known amount by expelling a part of the contents of the reservoir to the opening; and
determining the concentration of the first analyte gas using the spectrometer.

7. The method of claim 1 , further comprising:
isolating the variable volume reservoir from the spectrometer and from a supply of the first analyte gas, once the reservoir has taken up first analyte gas through expansion of the reservoir;
compressing the volume of the reservoir following the said isolation of the reservoir, until the pressure of the gas within the reservoir reaches a chosen pressure; and
connecting the variable volume reservoir to the spectrometer for expulsion of at least a part of the contents of the reservoir thereto.

8. The method of claim 1 , further comprising:
determining an optimum equilibrium flow into the spectrometer.

9. The method of claim 4 , wherein at least a portion of the first analyte gas not sucked into the variable volume reservoir is sucked into the spectrometer.

10. The method of claim 4 , wherein the open split receives a flow of first analyte gas from the first analyte gas supply in excess of the sum of the input flow rate of the first analyte gas into the variable volume reservoir and the input flow rate of the laser analyzer.

11. The method of claim 4 , further comprising determining the first analyte gas concentration within the variable volume reservoir when the first analyte gas concentration is present therein.

12. The method of claim 11 , wherein the step of determining the first analyte gas concentration comprises calculating the concentration based upon measurement or inference of flow rates and volumes within the gas inlet system.

13. The method of claim 11 , wherein the step of determining the first analyte gas concentration comprises inferring the concentration of the gas within the reservoir based upon the concentration of the first analyte gas which does not enter the variable volume reservoir as it is expanded.

14. The method of claim 1 , comprising determining the concentration of the first analyte gas within the variable volume reservoir by:
connecting the variable volume reservoir to an opening once the first analyte gas has been taken up into the reservoir;
decreasing the volume of the reservoir to a known amount by expelling a part of the contents of the reservoir to the opening; and
determining the concentration of the first analyte gas using the spectrometer.

15. The method of claim 14 , wherein the opening is a second open split, the method further comprising:
isolating the variable volume reservoir from the spectrometer whist the volume of the reservoir is being decreased to the known amount, and
connecting the variable volume reservoir to the spectrometer subsequently.

16. The method of claim 1 , further comprising:
isolating the variable volume reservoir from the spectrometer and from a supply of the first analyte gas, once the reservoir has take

Assignees

• Thermo Fisher Scient Bremen Gmbh

Inventors

• Schlueter Hans-Juergen
• Schwieters Johannes
• Wapelhorst Eric
• Krummen Michael

Classifications

• G01N2030/8411

  Intermediate storage of effluent, including condensation on surface · CPC title

• G01N30/7206

  interfaced to gas chromatograph (interfaces in general for introducing or extracting samples to be analysed with specially adapted mass spectrometer, see H01J49/04) · CPC title

• G01N30/84

  Preparation of the fraction to be distributed · CPC title

• G01N21/3504 Primary

  for analysing gases, e.g. multi-gas analysis · CPC title

• H01J49/0422

  for gaseous samples (interfaces to gas chromatographs G01N30/7206) · CPC title