Gas Samples

Sample Submission

Samples should be submitted in either 4 mm or 6 mm break seals (borosilicate or quartz glass) for easiest processing along with the pressure of the gas contained therein.

For δ³⁷Cl and δ⁸¹Br dual inlet analysis, the EIL requests aliquots of pure CH₃Cl and CH₃Br gas respectively. CH₃Cl and CH₃Br can be generated from both aqueous and gaseous samples by following the methodology described by Shouakar-Stash et al. (2005a) and (2005b).

Tips for sampling, labelling and shipping

Equipment

The Environmental Isotope Lab can process a number of different pure gasses using dual inlet isotope ratio mass spectrometry. The EIL utilizes several DI-IRMS systems including a Micromass IsoPrime, a Thermo Delta V Plus and a Thermo 253. Pure gas aliquots can be measured directly against internationally calibrated standard for high precision results.

Quality Assurance / Quality Control (QA/QC)

• Duplicate Analysis: Minimum 20% duplicate analysis. The result obtained must be within the specification of ≤0.2‰.
• Calibrated Standards: Each run incorporates a set of calibrated standards prepared according to identical treatment (IT) principle. The results obtained for the standards run are statistically evaluated and must be with the specification.

References

SHOUAKAR-STASH, O., Frape, S. K., and Drimmie, R. J. Determination of inorganic chlorine stable isotopes by continuous flow isotope ratio mass spectrometry. Rapid Communications in Mass Spectrometry. 2005;19:121–€“127.

SHOUAKAR-STASH, O., Frape, S. K., and Drimmie, R. J. Determination of bromine stable isotopes using continuous-flow isotope ratio mass spectrometry. Analytical Chemistry. 2005;77:4027-4033.

SPOELSTRA, J., Schiffa, S.L., Hazlett, P.W., Jeffries, D.S., Semkin, R.G. et al. The isotopic composition of nitrate produced from nitrification in a hardwood forest floor. Geochimica et Cosmochimica Acta. 2007;71: 3757–€“3771

THODE, H. G., Monster, J. and Dundford, H. B. Sulphur isotope geochemistry. Geochimica et Cosmochimica Acta. 1961;25:159-174.

Sample Submission

Samples should be sealed in a vial using a gas tight septum without headspace, 12 mL exetainer vials are preferred but most vials with gas tight septum are appropriate for methane isotope analyses.

Minimum detection limits are in the range of 1 nmol of carbon and 2 nmol of hydrogen. In a 12 mL vial at atmospheric pressure this is equivalent to ~2 ppm of methane. Clients must provide the individual gas concentrations ahead of analyses.

Tips for sampling, labelling and shipping

Equipment

Compound specific δ¹³C and δ²H in C1-C3 gas mixtures can be measured on low concentration samples utilizing a specially modified preconcentrator (Yarnes, 2013) interfaced with a GasBench II, a GC Isolink and a Thermo MAT253 continuous flow mass spectrometer.

Quality Assurance / Quality Control (QA/QC)

• Duplicate Analysis: Minimum 20% duplicate analysis. The result obtained must be within the specification of ≤0.2‰.
• Calibrated Standards: Each run incorporates a set of calibrated standards prepared according to identical treatment (IT) principle. The results obtained for the standards run are statistically evaluated and must be with the specification.

References

YARNES, C. δ¹³C and δ²H measurement of methane from ecological and geological sources by gas chromatography/combustion/pyrolysis isotope-ratio mass spectrometry. Rapid Communications in Mass Spectrometry. 2013;27(9):1036-1044.

Sample Submission

The preferred option for the submission of bulk gasses is glass or stainless steel with a gas tight septum. A sample list with available species and concentrations is required.

Tips for sampling, labelling and shipping

Equipment

The analysis of bulk gasses for δ¹³C measurements is determined through combustion conversion through a 4010 Elemental Analyzer (Costech Instruments, Italy) coupled to a Delta Plus XL (Thermo-Finnigan, Germany) continuous flow isotope ratio mass spectrometer (CFIRMS).

Quality Assurance / Quality Control (QA/QC)

The δ¹³C data (δ¹³C IRMEA / VPDB column) is the corrected delta value, reported in per mil (‰) units, against the primary reference scale of Vienna Pee Dee Belemnite (VPDB).

Of the total sample number dropped in an analytical run, no less than 20% are Std/Ref materials. These Std/Ref measurements are used in data normalization and to ensure daily mass spec precision and accuracy; also to assess linearity issues or mass spec drift throughout the duration of the run. With these QA/QC checks, an error of 0.2‰ δ¹³C is required for reportable data.

Sample Submission

For δ³⁴S analysis, the mass spectrometer requires ~0.03 mg of sulphur

Sampling poses no problem where only oxidized species are present; special precautions must be taken where reduction occurs or bacterial activity may occur. In the case of reduction, a small amount of cadmium or zinc acetate is added to the sample bottle before filling (filling is done as much out of contact with air as possible - i.e. the discharge tube must be at the bottom of the sample bottle). The Cd or Zn will fix the sulphide as CdS or ZnS a bright yellow and white precipitate respectively. Bacterial activity can be minimized by the addition of sodium azide during collection (Van Stempvoort, 1989). The sample can then be filtered through a 0.45 micron cellulose nitrate filter to collect the precipitate and the residual fluid can be processed for sulphate.

H₂S from wells can be collected in the field by directing the gas stream through a cadmium or zinc acetate solution where the sulphur precipitates as cadmium or zinc sulphide (Thode, 1958). Dissolved gas can be stripped from water by placing cadmium or zinc acetate in a collection bottle and flushing it slowly with the stream of water. The end of the tubing must be kept under the surface to prevent oxidation. Continue until no more precipitation occurs. The cadmium or zinc sulphide precipitate can then be dried and run directly for ³⁴S by EA-IRMS.

Tips for sampling, labelling and shipping

Equipment

The analysis of solid materials for ³⁴S isotope measurements is determined through combustion conversion of sample material to gas through an 4010 Elemental Analyzer (Costech Instruments, Italy) coupled to a Isochrom (Micromass UK) continuous flow isotope ratio mass spectrometer (CF-IRMS).

The δ³⁴S data (δ³⁴S RESULT / VCDT column) is the corrected delta value, reported in per mil (‰) units, against the primary reference scale of Vienna-Canyon Diablo Troilite meteorite (VCDT).

Data quality control is monitored and corrections made using an array of international reference material and in-house EIL standards (i.e. EIL-40 + 41 + 42) that are calibrated using certified international reference materials (IAEA-SO-5, IAEA-SO-6, NBS-127, NBS-123, IAEA-S1 to-S3) with values provided through CIAAW. Whenever possible we try to run like-against-like materials; sulphide Std/Ref materials with sulphide samples, sulphate Std/Ref materials with sulphate samples.

Sample and Standard materials are weighed into tin capsules with a few mg of ground WO₃ added to help in the conversion to SO₂ gas.

See δ³⁴S in EA-IRMS for more information.

Quality Assurance / Quality Control (QA/QC)

Of the total sample number dropped in an analytical run, in the order of 100-160 depending on the material type, every 5^th or 6^th sample is repeated and no less than 20% are Std/Ref materials. These Std/Ref measurements are used in data normalization and to ensure daily mass spec precision and accuracy; also to assess linearity issues or mass spec drift throughout the duration of the run. With these QA/QC checks an error of 0.3‰ δ³⁴S for standards are required for reportable data.

References

MORRISON, J., Fallick, T., Donelly, T., Leossen, M., St. Jean, G. and Drimmie, R. J. d34S measurements of standards from several laboratories by continuous flow isotope ratio mass spectrometry (CF-IRMS). Micromass UK Ltd. Technical Note 309. 1996.

REES, C. E. The isotopic analysis of sulphur and oxygen. In: McMaster University. Isotopic, Nuclear and Geochemical Studies Group. 1984;139.

THODE, H. G., Harrison, A. G. and Monster, J. Sulphur isotope fractionation in early diagenesis of recent sediments of North-East Venezuela. American Association of Petroleum Geologists Bulletin. 1960;44:1809-1817.

THODE, H. G., Monster, J. and Dundford, H. B. Sulphur isotope geochemistry. Geochimica et Cosmochimica Acta. 1961;25:159-174

VAN STEMPVOORT, D.R. The use of stable isotope techniques to investigate the sulphur cycle in upland forests of central and southern Ontario. PhD. Thesis. Waterloo, Canada: University of Waterloo;1989.