Sample Requirements for Water Isotopes
|δ2H||30 ml||2σ = 0.8 ‰ VSMOW|
|δ18O||30 ml||2σ = 0.2 ‰ VSMOW|
|δ17O (LGR Only)||30 ml||2σ = 0.2 ‰ VSMOW|
Sample Requirements for Tritium
|Tritium (direct)||30 ml||2σ = 6.0 TU|
|Tritium (enriched)||600 ml||2σ = 0.8 TU|
|Tritium (ULL)||2 L||2σ = 0.1 TU|
The Environmental Isotope Lab (EIL) requests 30 ml in plastic bottles be submitted for δ18O and/or δ2H (30 ml is sufficient for both). Bottles should be filled to the top with no head space and be air tight to prevent evaporation. No preservation is required. Hold time is unlimited if there is no evaporation. Field conductivity and pH should be included in the Excel Sample List (copy in shipping container).
- Conductivity >30,000 µS/cm, TDS >500mg/L, pH <5 or >9, coloured and/or smell (VOCs):
The EIL requests 30 ml in HDPE plastic bottles (never solvent or alcohol washed). Keep refrigerated until shipment to reduce chances of evaporation. Field conductivity and pH should be included in the Excel Sample List (copy in shipping container). These samples may require an additional azeotropic distillation pretreatment.
Conductivity <30,000 µS/cm, TDS <500mg/L, pH 5 to 9, and not coloured and/or smell (VOCs):
The EIL requests 30 ml in HDPE plastic bottles (never solvent or alcohol washed) or for a discount be filtered (0.45 micron) into 12x32 septum vials for the LGR-OA-ICOS Laser System. Filter vials such as 0.45 micron Whatman Mini-Uniprep, Thomson SINGLE StEP or Relia Syringeless Chamber Filters (they hold 0.4-0.5 ml) may be used or individually filtered with a syringe through a 0.45 micron syringe filter into standard 12x32 septum vials filled to 1.5 ml so as not to over-pressure as this will result in abnormally high injected volumes. Keep refrigerated until shipment to reduce chances of evaporation.
The isotopic ratios of low TDS water samples are measured using a Los Gatos Research (LGR), Liquid Water Isotope Analyser (LWIA), model T-LWIA-45-EP instrument with published precisions of δ2H = ± 0.3 ‰ and δ18O = ± 0.1 ‰.
Quality Assurance / Quality Control (QA/QC)
Quality control is maintained by running a suite of water standards (from the instrument company calibrated to the international reference materials VSMOW (Vienna Standard Mean Ocean Water) and VSLAP (Vienna Standard Light Antarctic Precipitation) from the International Atomic Energy Agency (IAEA)) throughout of the batch. Duplicates are run at a minimum of every tenth sample. Each run also includes an in house check standard for QA/QC of each individual sample batch.
Intercomparison Programs Participation:
- IAEA WICO 2002
- IAEA TEL-2011
- IAEA WICO 2016
BERMAN, E. S. F., Levin, N. E., Landais, A., Li, S., and Owano, T. Measurement of δ18O, δ17O, and 17O-excess in water by Off-Axis Integrated Cavity Output Spectroscopy and Isotope Ratio Mass Spectrometry. Analytical Chemistry. 2013;85:10392-10398.
DRIMMIE, R. J., Shouakar-Stash, O., Walters, R., and Heemskerk, A. R. Hydrogen isotope ratio of H2O by automatic Elemental Analysis-Continuous Flow-Isotope Ratio Mass Spectrometry. Environmental Isotope Laboratory Technical Procedure 4.1. 2001;1:1-8.
LIS, G., Wassenaar, L. I. and Hendry, M. J., High-Precision Laser Spectroscopy D/H and 18O/16O Measurements of Microliter Natural Water Samples. Analytical Chemistry. 2008;80:287-293.
MORRISON, J., Brockwell, T., Merren, T., Fourel, F., and Phillips, A. M. On-line high-precision stable hydrogen isotopic analyses on nanoliter water samples. Analytical Chemistry. 2001;73:3570-3575.
PENNA, D., Stenni, B., Šanda, M., Wrede, S., Bogaard, T. A., Michelini, M., Fischer, B. M. C., Gobbi, A., Mantese, N., Zuecco, G., Borga, M., Bonazza, M., Sobotková, M., Cejková, B., and Wassenaar, L. I. Evaluation of between-sample memory effects in the analysis of δ2H and δ18O of water samples measured by laser spectroscopes. Hydrology and Earth System Sciences. 2012;16:3925-3933.
- 30 mL for direct analysis
- 600 mL for enriched analysis
- 2 L for ultra enriched analysis
High Density Polyethylene (HDPE) is preferred or other well sealing plastic bottles. All bottles should be filled to the top with no head space and be air tight to prevent evaporation. No preservation is required. Hold time is unlimited if there is no evaporation. Field conductivity and pH should be included.
Enrichment can be performed on intermediate volumes with the concomitant lower enrichment. We recommend that the minimum be 75 ml for E3H for ~5x enrichment (cost remains the same) and for ULL up to 500 ml ~25x ($300), or up to 750 ml ~ 35x ($400).
Liquid scintillation counting (LSC) is the technique used by EIL for quantification of tritium.
Direct quantification has a detection limit of 6.0 ± 6.0 TU at 2 sigma. For higher precision and lower limit of detection, samples are enriched 15 times by electrolysis and then counted. The detection limit for enriched samples is 0.8 ± 0.8 TU at 2 sigma (at low levels). EIL uses a scintillation cocktail which has a high carrying capacity for water with high efficiency and low background. For even higher precision, samples may also be enriched (ultra-low levels) 45-50 times by electrolyzing multiple additions of sample followed by counting. The detection limit of ultra-low level enriched samples is 0.1 ± 0.1 TU at 2 sigma (at low levels).
Quality Assurance / Quality Control (QA/QC)
Each batch of samples includes 3 backgrounds (water from a well near Newmarket, Ontario with no detectable tritium and Radiocarbon age dated to >6000 BP), a long term monitor (lab deionized water) and a standard traceable to NIST-4926-E which has been calibrated with NIST-SRM-4361B-21. Repeat analyses are included within each batch, from a previous batch with another repeat for a subsequent batch. All samples are pre-treated (ion exchange ≤15,000 µS/cm or azeotropic distillation >15,000 µS/cm) so conductivity is <100 µS/cm and preferable < 50 µS/cm.
Tritium Inter-comparison programs:
- IARMA ETRIT-PT-2018
- IAEA TRIC 2018
- IARMA ETRIT-PT-2016
- IARMA ETRIT-PT-2014
- IAEA TRIC 2014
- IAEA TRIC 2012
- IAEA TRIC 2008
- IAEA TRIC 2004
- IAEA TRIC 2000
- ASPO and Laxemar 1999
TAYLOR, C. B. Tritium enrichment of environmental waters by electrolysis: development of cathodes exhibiting high isotopic separation and precise measurement of tritium enrichment factors. International Atomic Energy Agency. 1977;42:32-42.