Compound Specific Isotope Analysis (CSIA)

Sample Submission

Normal procedures for VOC collection should be followed. Analysis requires two (2) 40 ml VOC vials per compound per analysis for δ²H and δ¹³C or four (4) 40 mL VOC vials per compound for δ³⁷Cl (i.e. if you want to analyze TCE, cis-DCE and trans-DCE in one sample for both δ¹³C and δ³⁷Cl, then please collect 3x2+3x4=18 vials per sample).

• Use 40 ml VOC type open cap vial with Teflon/silicon septa. Make sure the Teflon side faces towards the sample.
• Purge the well three volumes before collecting your sample.
• Do not filter.
• Add the preservative. Either ZnCl₂ or acidification (acidify using HNO₃ or HCl) are recommended.
• Cap without headspace in the vials.
• Keep samples cold (<4°C) at all times and ship insulated with cold pack packs (e.g. ship in cooler with ice packs).
• Clear tape on labels can help preserve sample information during shipping.
• Please provide major ion geochemistry and other compounds of note that may be in solution.

Waterloo Membrane Sampler (WMS™) analysis is available for sampling of VOC vapour concentrations at no additional cost. Samples should be taken in duplicate (for chemistry and for isotopic analysis) and the chemical concentration of the analyte of interest and other significant compounds present in the sorbent must be provided.

Tips for sampling, labelling and shipping

Equipment

• δ¹³C: Compound-specific stable carbon isotope ratios are determined using a purge and trap gas chromatography combustion isotope ratio mass spectrometry (PT-GCC- IRMS) system. The PT-GCC-IRMS system consisted of CDS 7000E/7300/7400/7500 Purge and Trap/Thermal Desorption System equipped with a proprietary VOC selective analytical trap (CDS Analytical, Oxford, PA, USA) a Trace GC (Thermo Scientific, Bremen, Germany), a GC-Combustion III interface, and a Thermo Scientific Delta V Advantage isotope ratio mass spectrometer (Thermo Scientific, Bremen, Germany).
• δ²H: Compound-specific Hydrogen isotope ratios were determined in the Environmental Isotope Laboratory of the University of Waterloo using a PT-GC- IRMS system. The PT-GC-IRMS system consisted of CDS 7000E/7300/7400/7500, Purge and Trap/Thermal Desorption System (CDS Analytical, Oxford, PA, USA), a Trace GC (Thermo Fisher Scientific, Bremen, Germany), a GC –Combustion III interface operating at 1450°C for deuterium and a Delta plus XP isotope ratio mass spectrometer (Thermo Fisher Scientific, Bremen, Germany)
• δ³⁷Cl: Continuous flow isotope ratio mass spectrometry coupled with gas chromatography (GC–CF-IRMS) is used to separate compounds on-line and directly measure the Cl stable isotopic ratios of the ionized fragments. For pure phase samples, a vapour phase of the chlorinated solvent is injected directly into an Agilent 7890 Gas Chromatograph (Agilent Technologies Inc., Santa Clara, CA, USA) coupled to a Thermo Delta V Mass Spectrometer (Thermo Fisher Scientific, Bremen, Germany). A Teledyne Tekmar Purge and Trap (PT) (Teledyne Tekmar, Mason, OH, USA) is used to extract the compounds from aqueous solutions which are released to an Agilent 7890 Gas Chromatograph (Agilent Technologies Inc., Santa Clara, CA, USA) coupled to a Thermo Delta V Mass Spectrometer (Thermo Fisher Scientific, Bremen, Germany). Alternatively, aqueous solutions can be extracted and injected using a CTC PAL (CTC Analytics AG, Zwingen, Switzerland) Solid-Phase Microextraction (SPME) fiber assembly (Supelco Inc., Bellefonte, PA, USA) into an Agilent 7890 Gas Chromatograph (Agilent Technologies Inc., Santa Clara, CA, USA) coupled to a Thermo Delta V Mass Spectrometer (Thermo Fisher Scientific, Bremen, Germany).

Quality Assurance / Quality Control (QA/QC)

Duplicate Analysis:

• δ¹³C and δ²H: Minimum 20% duplicate analysis – repeat again if not within specification; if still not within specification – trouble shoot with standard.
• δ³⁷Cl: Minimum 3 separate duplicate analyses are performed from 2 separate sample vials with additional samples repeated if statistical variation not within specification with all relevent information being reported to the client.

Calibrated Standards:

δ¹³C and δ²H: Standards are analyzed every fourth analysis.

δ³⁷Cl: At least 30% of samples in a given run are calibrated standards (prepared offline and characterized against international standards), these are bracketing the samples and prepared at variable concentrations to account for time drift and linearity.

References

GOLI, O., Górecki, T., Mugammar, H. T., Marchesi, M. and Aravena, R. Evaluation of the suitability of the Waterloo Membrane Sampler for sample preconcentration before compound-specific isotope analysis. Environmental Technology and Innovation. 2017;7:141-151.

HUNKELER, D., and Aravena, R. Determination of compound-specific carbon isotope ratios of chlorinated methanes, ethanes, and ethenes in aqueous samples. Environmental Science and Technology. 2000;34:2839-2844.

SHOUAKAR-STASH, O., Drimmie, R. J., Zhang, M., and Frape, S. K. Compound-specific chlorine isotope ratios of TCE, PCE and DCE isomers by direct injection using CF-IRMS, Applied Geochemistry. 2006;21:766–781.

SHOUAKAR-STASH, O., Frape, S. K., Aravena, R., Gargini, A., Pasini, M. and Drimmie, R. J., Analysis of compound-specific chlorine stable isotopes of vinyl chloride by Continuous Flow-Isotope Ratio Mass Spectrometry (CF-IRMS). Environmental Forensics. 2009;10(4):299-306.

ZWANK, L., Berg, M., Schmidt, T. C. and Haderlein, S.B. Compound-specific carbon isotope analysis of volatile organic compounds in the low-microgram per liter range. Analytical Chemistry. 2003;75:5575-5583.