Gas inlet system for isotope ratio analyzer and method of determining an isotope ratio

Patent metadata

Field	Value
Publication number	US-9766219-B2
Application number	US-201414784877-A
Country	US
Kind code	B2
Filing date	Apr 9, 2014
Priority date	Apr 15, 2013
Publication date	Sep 19, 2017
Grant date	Sep 19, 2017

Abstract

A gas inlet system for introducing gas into an isotope ratio analyser, the gas inlet system including a reference system comprising: a first supply of a reference gas having a first known isotope ratio; a supply of a carrier gas, wherein the supplies of reference gas and carrier gas are each connected by respective reference and carrier gas lines to a first mixing junction where the reference gas and carrier gas combine; a mixing zone connected downstream of the first mixing junction wherein the combined reference gas and carrier gas mix together; an exit line for transporting the mixed gas from the mixing zone to the isotope ratio analyser; and an opening on the exit line, wherein the opening is downstream of the mixing zone. Also provided is a method of determining an isotope ratio.

First claim

The invention claimed is:

1. A gas inlet system for introducing gas into an isotope ratio analyzer, the gas inlet system including a reference system comprising:
a first supply of a reference gas having a first known isotope ratio;
a supply of a carrier gas,
wherein the supplies of reference gas and carrier gas are each connected by respective reference and carrier gas lines to a first mixing junction where the reference gas and carrier gas combine;
a mixing zone connected downstream of the first mixing junction wherein the combined reference gas and carrier gas mix together;
an exit line for transporting the mixed gas from the mixing zone to the isotope ratio analyzer; and
an opening on the exit line, wherein the opening is downstream of the mixing zone,
where the opening is open to the atmosphere and the pressure at the first mixing junction with the opening is close to the atmospheric pressure.

2. A gas inlet system according to claim 1 , the reference system further comprising a second supply of a reference gas having a second known isotope ratio, wherein the first and second supplies of reference gas may be each independently connected to the first mixing junction for mixing with the carrier gas.

3. A gas inlet system according to claim 1 wherein the reference gas is a substantially pure gas and the carrier gas is substantially free from the reference gas.

4. A gas inlet system according to claim 1 wherein the carrier gas flow to the first mixing junction is dynamically controllable by flow control means.

5. A gas inlet system according to claim 1 wherein the opening is in the form of an open capillary that is at least 0.5 mm in internal diameter and at least 5 mm in length.

6. A gas inlet system according to claim 5 wherein the flow rate through the open capillary is at least 0.5 ml/min.

7. A gas inlet system according to claim 1 wherein the mixing zone is at least 75 mm in length and at least 0.8 mm internal diameter.

8. A gas inlet system according to claim 1 wherein the mixing zone includes one or more bends and/or includes an angle along its length.

9. A gas inlet system according to claim 1 wherein the system further comprises a second mixing junction on the exit line from the mixing zone for mixing further carrier gas with the already mixed gas, the further carrier gas being supplied to the second mixing zone via a second carrier gas line.

10. A gas inlet system according to claim 9 wherein the carrier gas supplied to the second mixing junction is not dynamically controllable.

11. A gas inlet system according to claim 1 wherein the mixed gas that enters the analyzer comprises a CO 2 in air or CO 2 in nitrogen concentration in the range between about 200-1500 ppm.

12. An isotope ratio analyzer comprising the gas inlet system according to claim 1 .

13. A gas inlet system according to claim 12 wherein the isotope ratio analyzer is an isotope ratio mass spectrometer or an isotope ratio optical spectrometer.

14. A gas inlet system according to claim 12 wherein the isotope ratio analyzer is for determination of a concentration dependence of an isotope ratio measurement and/or determination of an isotope ratio dependence of the isotope ratio measurement.

15. A gas inlet system for introducing gas into an isotope ratio analyzer, comprising:
a supply of analyte gas;
an analyte gas line for transporting a flow of analyte gas from the supply of analyte gas;
a supply of carrier gas; and
a carrier gas line for transporting a flow of carrier gas from the supply of carrier gas;
wherein the analyte gas line joins the carrier gas line at an analyte-carrier junction to mix the analyte gas and the carrier gas, wherein the analyte-carrier junction is further connected to an exit gas line for transporting the mixed gas from the junction to the isotope ratio analyzer, wherein the analyte-carrier junction is positioned downstream of an opening on the carrier gas line, and wherein the opening is open to the atmosphere and the pressure at the analyte-carrier junction with the opening is close to the atmospheric pressure.

16. A gas inlet system according to claim 15 configured such that the flow rate of the analyte gas in the analyte line is lower than the flow rate of gas into the isotope ratio analyzer and the flow between the opening and the analyte-carrier junction is always towards the isotope ratio analyzer.

17. A gas inlet system according to claim 15 configured such that the flow rate of the analyte gas in the analyte line is higher than the flow rate of gas into the isotope ratio analyzer and the flow between the opening and the analyte-carrier junction is always towards the opening.

18. A gas inlet system according to claim 15 wherein the analyte gas is selected from the group consisting of: CO 2 , CH 4 , C 2 H 6 , C x H (2x+2) , water vapour, CO, small hydrocarbons, alcohols, aldehydes, NO x , N x O y , H 2 S, nitrogen, oxygen, and hydrogen.

19. A gas inlet system according to claim 15 wherein the carrier gas is selected from the group consisting of: air, nitrogen, helium and argon.

20. A gas inlet system according to claim 15 wherein the flow rate to the opening junction is at least 10 ml/min.

21. A gas inlet system according to claim 15 wherein the gas inlet system further includes a calibration system comprising: at least a first supply of a reference gas having a first known isotope ratio, wherein the supplies of reference gas and carrier gas are each connected by respective gas lines to a mixing junction where the reference gas and carrier gas combine; a mixing zone connected downstream of the mixing junction wherein the combined reference gas and carrier gas mix together; an exit gas line for transporting the mixed reference and carrier gas from the mixing zone to the isotope ratio analyzer; and an opening to atmosphere on the exit line from the mixing zone, wherein the opening is downstream of the mixing zone.

22. A method of determining an isotope ratio, comprising:
providing a reference gas at a first known isotope ratio;
measuring the isotope ratio of the reference gas with the first known isotope ratio at a plurality of concentrations in a carrier gas;
determining a concentration dependence of the isotope ratio measurements of the reference gas with the first known isotope ratio;
providing a sample gas of unknown isotope ratio and unknown concentration;
measuring the isotope ratio and concentration of the sample gas; and
correcting the measured isotope ratio of the sample gas by the determined concentration dependence.

23. A method of determining an isotope ratio according to claim 22 , wherein the method further comprises:
providing the reference gas at a second known isotope ratio;
measuring the isotope ratio of the reference gas with the second known isotope ratio, at one or more concentrations in the carrier gas that lie within the range of measured concentrations of the reference gas with the first known isotope;
determining an isotope ratio calibration from the measured isotope ratios of the reference gas with the first and second known isotope ratios; and
further correcting the measured isotope ratio of the sample gas by the determined isotope ratio calibration.

24. A method of determining an isotope ratio according to claim 22 wherein there is a single supply of reference gas with the first known isotope ratio, which is dynamically diluted with the carrier gas to provide the plura

Assignees

• Thermo Fisher Scient (Bremen) Gmbh

Inventors

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

Classifications

• G01N21/31

  Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry {(G01N21/72 takes precedence)} · CPC title

• G01N33/0011 Primary

  Sample conditioning (preparing specimens for investigation G01N1/28) · CPC title

• H01J49/0422

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