The Sercon CryoGas: for automated, high precision H and C … · 2019. 11. 17. · The Sercon...

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The Sercon CryoGas: for automated, high precision δ 2 H and δ 13 C analysis of gaseous and dissolved methane Andrew C. Smith 1 *, Steve Welsh 2 , Helen Atkinson 2 and Melanie Leng 1 1 National Environmental Isotope Facility, British Geological Survey, Nottingham, NG12 5GG 2 Sercon Group, 3B, Crewe Trade Park, Gateway, Crewe CW1 6JT * email: [email protected] 1. Introduction: Methane is the third most important greenhouse gas af- ter water vapour and CO 2 , contributing 20% of all radia- tive forcing from the long lived green house gases. Isotopic analysis of carbon ( 13 C/ 12 C) and hydrogen ( 2 H/ 1 H) in methane, can tell us by which process the me- thane has been formed. Enabling us to understand where methane pollution is originating from and mitigate against it. The new Sercon CryoGas (Figure 1) is an automated system for the high precision, rapid throughput analysis of both carbon and hydrogen isotopes in methane. 2. Operation: Samples are introduced as a mixed gas, either atmosphere or an equilibrated headspace from water samples. In both hydrogen and carbon modes the CryoGas utilises cryogenic trapping, chemical gas clean up and gas chromatography to separate out air compo- nents (CO 2 , N, O 2 ) from methane (Figures 2 and 3). Pyrolysis is used for δ 2 H –CH 4 and combustion for δ 13 C-CH 4 analysis. Figure 1: The Sercon CryoGas and HS2022 mass spectrometer, this is the first Sercon instrument built specifically for the analysis of C and H in methane. 3 Results: Instrument precision on 150ml of air is <3for δ 2 H –CH 4 (Figure 4b) and <0.2for δ 13 C-CH 4 . The CryoGas can do unattended runs of either 21 samples of 150ml or >200 12ml samples at higher concentrations. Figure 3a) A typical δ 2 H –CH 4 in air output, with initial ref gas pulse followed by a >1 nano amp sample peak height. 3b) example data showing the CryoGas precision for 150ml of air and standards at 2000ppb CH 4 . Laboratory Air (±1.9‰) NGS1 (±2.7‰) External Air (±1.2‰) 1% CH 4 ref gas (±1.0‰) Position in Run δ 2 H-CH 4 (‰) 3b 3a Sample 2 H-CH 4 peak Standard gas injection Figure 2: Schematics of the CryoGas system in both carbon (top) and hydrogen (bottom) modes. Showing a se- ries of chemical and cryo traps as well as the configuration of GC columns/ vents for the separation of CH 4 from air components.

Transcript of The Sercon CryoGas: for automated, high precision H and C … · 2019. 11. 17. · The Sercon...

Page 1: The Sercon CryoGas: for automated, high precision H and C … · 2019. 11. 17. · The Sercon CryoGas: for automated, high precision δ2H and δ13C analysis of gaseous and dissolved

The Sercon CryoGas: for automated, high precision δ2H and δ

13C analysis of gaseous and dissolved methane

Andrew C. Smith1*, Steve Welsh

2, Helen Atkinson

2 and Melanie Leng

1

1 National Environmental Isotope Facility, British Geological Survey, Nottingham, NG12 5GG

2 Sercon Group, 3B, Crewe Trade Park, Gateway, Crewe CW1 6JT

* email: [email protected]

1. Introduction:

Methane is the third most important greenhouse gas af-

ter water vapour and CO2, contributing 20% of all radia-

tive forcing from the long lived green house gases.

Isotopic analysis of carbon (13

C/12

C) and hydrogen

(2H/

1H) in methane, can tell us by which process the me-

thane has been formed. Enabling us to understand

where methane pollution is originating from and mitigate

against it.

The new Sercon CryoGas (Figure 1) is an automated

system for the high precision, rapid throughput analysis

of both carbon and hydrogen isotopes in methane.

2. Operation:

Samples are introduced as a mixed gas, either atmosphere or an equilibrated

headspace from water samples.

In both hydrogen and carbon modes the CryoGas utilises cryogenic trapping,

chemical gas clean up and gas chromatography to separate out air compo-

nents (CO2, N, O2) from methane (Figures 2 and 3).

Pyrolysis is used for δ2H –CH4 and combustion for δ

13C-CH4 analysis.

Figure 1: The Sercon CryoGas and HS2022 mass spectrometer,

this is the first Sercon instrument built specifically for the analysis of

C and H in methane.

3 Results:

Instrument precision on 150ml of air is <3‰ for δ2H –CH4

(Figure 4b) and <0.2‰ for δ13

C-CH4.

The CryoGas can do unattended runs of either 21 samples of

150ml or >200 12ml samples at higher concentrations.

Figure 3a) A typical

δ2H –CH4 in air output,

with initial ref gas pulse

followed by a >1 nano

amp sample peak

height.

3b) example data

showing the CryoGas

precision for 150ml of

air and standards at

2000ppb CH4.

Laboratory Air (±1.9‰)

NGS1 (±2.7‰)

External Air (±1.2‰)

1% CH4 ref gas (±1.0‰)

Position in Run

δ2H

-CH

4 (

‰)

3b

3a Sample

2H-CH4

peak

Standard gas

injection

Figure 2: Schematics of the CryoGas system in both carbon (top) and hydrogen (bottom) modes. Showing a se-

ries of chemical and cryo traps as well as the configuration of GC columns/ vents for the separation of CH4 from air

components.