Gas inlet system for isotope ratio spectrometer
First Claim
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.
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Accused Products
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.
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Citations
22 Claims
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1. A method of coupling an analyte gas to an isotope ratio spectrometer, comprising:
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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. - View Dependent Claims (2, 6, 7, 8, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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3. A method of coupling an analyte gas to an isotope ratio spectrometer, comprising:
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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.
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4. A method of coupling an analyte gas to an isotope ratio spectrometer, comprising:
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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. - View Dependent Claims (5, 9, 10, 11, 12, 13)
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Specification