Aqueous Samples

Sample Submission

Provide sufficient water to produce a minimum of 3 mg of Cl^- or Br^- as well as major ion geochemistry (SO₄^2- is most important). High density polyethylene (HDPE) bottles are preferred. No preservation or field sample preparation is required. Holding time is infinite.

Tips for sampling, labelling and shipping

Equipment

The analysis of aqueous samples for δ³⁷Cl isotope measurements is determined through gas chromatography continuous flow isotope ratio mass spectrometry (GC-CF-IRMS) utilizing an Agilent 7890B gas chromatograph (Agilent Technologies Inc., Santa Clara, CA, USA) equipped with a CTC Analytics PAL Headspace Autosampler (CTC Analytics AG, Zwingen, Switzerland) and a Micromass IsoPrime continuous flow mass spectrometer (Manchester, UK). A minimum of four different analyses from a minimum of two independent 20 mL reaction vials are used to ensure repeatability and to rule out contamination or fractionation due to leakage. Sample precision is calculated using the standard deviation of a minimum of four acceptable results. The maximum allowable precision is 0.1‰.

The analysis of aqueous samples for δ⁸¹Br isotope measurements is determined through gas chromatography isotope ratio mass spectrometry (GC-CF-IRMS) utilizing an Agilent 7890B gas chromatograph (Agilent Technologies Inc., Santa Clara, CA, USA) equipped with a CTC Analytics PAL Headspace Autosampler (CTC Analytics AG, Zwingen, Switzerland) and a 253 continuous flow mass spectrometer (Thermo Fisher Scientific, Bremen, Germany). A minimum of four different analyses from a minimum of two independent 20 mL reaction vials are used to ensure repeatability and to rule out contamination or fractionation due to leakage. Sample precision is calculated using the standard deviation of a minimum of four acceptable results. The maximum allowable precision is 0.1‰.

Quality Assurance / Quality Control (QA/QC)

For δ³⁷Cl the standards used include standard mean ocean chloride (SMOC) and two different in-house standards, one enriched and the other depleted relative to SMOC. For δ⁸¹Br analysis the standards used include standard mean ocean bromide (SMOB) and two different in-house standards, one enriched and the other depleted relative to SMOB. In a given run standards make up approximately 50% of the samples analyzed in order to effectively characterize linearity and time drift corrections.

A minimum of four different analyses from a minimum of two independent 20 mL reaction vials are used to ensure repeatability and to rule out contamination or fractionation due to leakage. Sample precision is calculated using the standard deviation of a minimum of four acceptable results. The maximum allowable precision is 0.1‰.

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

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.

Sample Submission

Nitrate, Nitrite and Chloride concentrations are required (provide clear units of measurement, i.e. NO₃-N or NO₃). Highly discoloured samples i.e. septic sites, refuse leachate, etc. (high DOC) may be problematic for analysis. Because concentration is so critical in obtaining the required quantity of N₂O, you must guarantee that the provided nitrate concentration is correct. If it is not and insufficient N₂O is generated, you will be charged full price for this analysis and additionally we would need to have a new concentration analysis performed ($25) followed by another full cost analysis.

We request 30 ml of 0.2 or 0.45 micron filtered frozen sample (no other preservative, be sure to leave room for expansion upon freezing and cap tightly) in plastic bottles. Nitrite (NO₂^-) concentrations are to be provided and not exceed 2% of the NO₃^- concentration. This is because during sample preparation the NO₃^- in solution is reduced to NO₂^- before eventual conversion to N₂O. If there is a high abundance of initial NO₂^-, it may compromised and invalidate the final results. Such samples will be flagged and not analyzed.

Although our routine limit is 0.50 mg/L, we have produced results for samples as low as ~0.17 mg/L NO₃-N but with potentially lower precision. In all cases we use a volume of sample based on the chemistry provided to obtain 2.0 µg of nitrate for processing but using higher volumes risks greater concentrations of all other aqueous constituents and may not result in no isotope values. We request 50ml of samples with lower concentrations.

The caveat is, as above, if your concentration is wrong and we process your sample you will be charged the full price of $100 with no results.

Minimum concentration: 0.50 mg/L NO₃-N
Minimum sample size: 30 ml
Chloride concentration: 20,000 mg/L practical limit (seawater)
Concentrations Required: NO₃, NO₂, Cl
Container: plastic (glass vials tend to break)
Filtration: <0.45 µm
Preservation: keep frozen

Filtered samples should be collected in HDPE bottles then frozen as soon as possible. During transit from field site to the lab, samples are to be kept chilled in a cooler with freezer blocks/bags (not loose ice or dry ice). If freezing is not possible, store samples @ ~4°C in a refrigerator.

Freezing and filtering of the sample is to limit biological activity that may potentially cause nitrification or denitrification. This may skew the nitrate isotopic values from the insitu sample.

To keep the samples cool during shipping, include additional freezer blocks or plastic bottles filled with water and frozen to increase the mass in an insulated picnic cooler. They will keep cool for 4-8 days depending on ambient temperature.

Tips for sampling, labelling and shipping

Equipment

NO₃^- is converted to NO₂^- using a cadmium catalyst then chemically converted to N2O which is then analysed on an Isoprime Trace Gas continuous flow mass spectrometer (GV Instruments Ltd., Manchester, UK).

Quality Assurance / Quality Control (QA/QC)

Duplicate Analysis:

Each sample is prepared in duplicate and analyzed as independent samples. A sample is repeated if the duplicate is not within specification OR the peak signal measured is not within the targeted EA calibration range; which happens if the sample N concentrations provided are incorrect.

Calibration:

Three calibrated standards, USGS 34, USGS 35 and in house EGC 17 are used for normalization. Also included in each batch are three check standards at the start middle and end. Two are in house EGC 1 and a single IAEA NO-3. During a sample run, linearity checks are included using a suite of 100 ppm N₂O in Helium of known isotopic composition to produce a range of peak heights that encompass the expected sample peaks range.

References

BROOKS, P.D., Stark, J.M., McInteer, B.B., and Preston, T. Diffusion method to prepare soil extracts for automated nitrogen-15 analysis. Soil Science Society of America Journal. 1989;53:1707.

MCILVIN, M. R., and Altabet, M. A. Chemical conversion of nitrate and nitrite to nitrous oxide for nitrogen and oxygen isotopic analysis in freshwater and seawater. Analytical Chemistry. 2005;77:5589-5595.

SNIDER, D.M., Schiff, S.L., and Spoelstra, J. ¹⁵N/¹⁴N and ¹⁸O/¹⁶O stable isotope ratios of nitrous oxide produced during denitrification in temperate forest soils. Geochimica et Cosmochimica Acta. 2009;73:877-888.

SPOELSTRA, J., Kralt, B.J., and Elgood, R. J. A chemical method for the conversion of nitrate to nitrous oxide for isotopic analysis. Environment Canada National Water Research Institute, Report Number 14. 2014;14:88.

Sample Submission

The sulphate concentration is required to know how much sample will be needed for extraction and to determine the method of extraction. Chloride concentrations are required where the sulphate concentration is low and the sample must be passed through a sorbant resin column to concentrate the sulphate as the chloride competes with the sulphate for on the resin. Sulphate is eluted from the resin with a chloride solution so if the chloride concentration is above 1000 mg/L the sample will self-elute and nothing will be collected. Otherwise, samples are acidified with 10% HCl to remove any bicarbonate. Sulphate is then precipitated from solution using barium chloride (BaCl₂) to form barium sulphate (BaSO₄). Sample pH is then neutralized with DI rinses and dried in an oven before analysis on the EA-IsoPrime.

Minimum concentration: 2ppm (mg/L) as SO₄²⁺
Minimum sample size: 5 mg BaSO₄ or 2.5 L of H2O @ 2ppm as SO₄²⁺ or 1 L @ 5ppm or 100 ml @ 50ppm
Maximum Chloride concentration: 1000 mg/L
Concentrations Required: SO₄²⁺, Cl, NO3
Container: plastic or glass
Filtration: 0.45µm
Preservation: keep refrigerated (~4°C) until shipped (preferred) or HCl to a pH of 4

Tips for sampling, labelling and shipping

Equipment

The analysis of solid materials for δ³⁴S isotope measurements is determined through combustion conversion of sample material to gas through an 4010 Elemental Analyzer (Costech Instruments, Italy) coupled to a precisION (Elementar Americas, USA) continuous flow isotope ratio mass spectrometer (CFIRMS). The analysis of solid materials for δ¹⁸O measurements is determined through high temperature (1450°C) pyrolysis combustion conversion of sample material to CO gas. This is accomplished using an Elementar Vario Pyro Cube elemental analyzer coupled to an Isoprime (GV Instruments) continuous flow isotope ratio mass spectrometer (CFIRMS).

See: EA-IRMS for more information.

Quality Assurance / Quality Control (QA/QC)

δ¹⁸O is corrected to BaSO₄ IAEA-SO5 (+12.13‰), IAEA-SO-6 (-11.35‰) and NBS-127 (+8.59‰) to a precision of ± 0.3‰.

δ³⁴S is corrected to BaSO₄ IAEA-SO5 (+0.49‰), IAEA-SO-6 (-34.05‰) and NBS-127 (+21.1‰) to a precision of ± 0.3‰.

References

MORRISON, J., Fallick, T., Donelly, T., Leossen, M., St. Jean, G. and Drimmie, R. J. δ³⁴S measurements of standards from several laboratories by continuous flow isotope ratio mass spectrometry (CF-IRMS). Micromass UK Ltd. Technical Note 309. 1996.

MORRISON, J. Inorganic oxygen isotope analysis by EA-Pyrolysis-IRMS. In: 4th Canadian Continuous Flow Isotope Ratio Mass Spectrometry Conference; 24-27 August, 1997; Waterloo, Canada.

Sample Submission

DIC:

Fill a plastic bottle (HDPE preferred) or glass septum cap bottle with water filtered at <0.45 µm (ideally 0.2 µm) for the analysis. Filtration and refrigeration is recommended and preservation can also extend storage times.

Preservation: Zinc chloride (ZnCl₂) can be used to prevent biological activity (0.1 mL of 50% w/v per 10 mL) ensuring that pH is not significantly altered.

DO NOT Acidify DIC samples!

Chemistry Required:

• Alkalinity (clear unit of measurement and ion):
• Minimum 0.5 ppm (mg/L) in 10 ml
• Conductivity must be indicated

Include a copy of the Excel Sample List in the shipping container.

Tips for sampling, labelling and shipping

DOC:

Fill a plastic bottle (HDPE preferred) or glass septum cap bottle with water filtered at <0.45 µm. Filtration and refrigeration is recommended and preservation can also extend storage times.

Preservation: Zinc chloride (ZnCl₂) is recommended and can be used to prevent biological activity (0.1 mL of 50% w/v per 10 mL).

Chemistry Required:

• DOC concentration
• Minimum 2 ppm (mg/L) in 20 ml
• Conductivity must be indicated

Include a copy of the Excel Sample List in the shipping container.

Tips for sampling, labelling and shipping

Equipment

DIC: An aliquot of sample equivalent to 0.2 mg carbonate (concentration supplied by client) is removed through the septum of the sample bottle and injected into a helium flushed 12 mL Labco Exetainer vial. A small volume of 85% phosphoric acid (H₃PO₄) are then injected followed by shaking of the vials to get complete reaction of the inorganic carbon to convert to CO₂ in the headspace. The vials are then placed in a CTC PAL autosampler and analyzed via a Thermo Scientific Gasbench coupled to a Thermo Scientific Delta V Plus isotope ratio mass spectrometer.

DOC: The water sample is treated with Ortho-phosphoric acid and Potassium Persulfate in a 12 mL Labco Exetainer vial. The phosphoric acid addition will convert inorganic carbonates present in the sample to CO₂ which is removed by bubbling with a helium gas stream for about 10 minutes. The sample is then sealed in the vial and heated to 100°C. During heating the Persulfate oxidizes any dissolved organic carbon in the sample to CO₂. The CO₂ in the headspace of the sample vial is analyzed. The vials are then placed in a Gilson 222XL auto-sampler incorporated in the MicroGas-IsoPrime Mass Spectrometer.

Quality Assurance / Quality Control (QA/QC)

DIC/DOC

Minimum 20% duplicate analysis. The result obtained should be within the specification of ≤0.3‰.

Each run incorporates a set of calibrated standards prepared according to IT principle (identical treatment). The results obtained for the standards run are statistically evaluated and must be with the specification of ≤0.2‰. Standards range from +100‰ (IAEA 303A) to -13‰ (EIL-30 - TAP Water). Delta values obtained by dual inlet MS calibrated with IAEA carbonate standards.

References

MCCREA J.M. On the isotopic chemistry of carbonates and a paleo-temperature scale. Journal of Chemical Physics. 1950;18:849

ST JEAN, G. Automated quantitative and isotopic (¹³C) analysis of dissolved inorganic carbon and organic carbon in continuous-flow using a total organic carbon analyser. Rapid Communication in Mass Spectrometry. 2003;17:418-428.

STAINTON, M. P., Capel, M. J. and Armstrong, F. A. The chemical Analysis of Fresh Water. Fisheries and Environment Canada, Fisheries and Marine Service Miscellaneous Special Publication. 1977;25(2).

US ENVIRONMENTAL PROTECTION AGENCY. EPA Standard Operating Procedure for Dissolved Organic Carbon. 2002. EPA LG211(3).

Sample Submission

The EIL is a natural abundance laboratory and cannot accept any samples that have been/may be artificially labelled with ¹⁴C due to contamination concerns.

Three milligrams (3 mg) of carbon are required for standard analysis. The DIC is stripped from up to 1 L of water in the laboratory. Additional charges are incurred for HCO₃^- <15 mg/L (minimum 5 mg/L requiring 2 L) due to multiple extractions.

For sampling it is recommended to utilize glass (Wheaton, Kimble Chase) or heavy walled plastic (HDPE) bottles with a tight fitting septum cap if possible. Bottles and caps can be pre-rinsed in 10% HCl and fully dried to prevent contamination. Water should be filtered (>0.45 µm, glass/quartz preferred) and refrigerated as soon as possible after sampling to prevent contamination and microbial activity. Preservation (i.e. ZnCl₂, being careful not to alter pH significantly) can be used but filtration and refrigeration alone can extend the shelf life beyond 6 months.

Chemistry required:

• pH
• Alkalinity (indicate units completely i.e. HCO₃^- mg/L)
• Preservative

Bicarbonate Alkalinity as HCO₃^- mg/L = 1.22 * Bicarbonate Alkalinity as CaCO₃ mg/L

IAEA water sampling tutorial

Tips for sampling, labelling and shipping

Equipment

Sample DIC is converted to pure carbon dioxide which is trapped in 6mm OD Pyrex glass tubes (breakseal). These subsamples are then sent to an Accelerator Mass Spectrometry Lab for radiocarbon determination. A subsample of the evolved CO₂ is analyzed for δ¹³C (for calibration purposes). Three milligrams of carbon are required for standard ¹⁴C+δ¹³C DIC analysis. The DIC is stripped from up to 1 liter of water in the laboratory. Additional charges are incurred for HCO₃^- <15 mg/L (minimum 5 mg/L requiring 2 L) due to multiple extractions. Graphitized samples are measured on a state-of-the-art National Electrostatics Corporation 1.5SDH-1 Pelletron Accelerator (DirectAMS).

Quality Assurance / Quality Control (QA/QC)

The δ¹³C-DIC result obtained should be within the specification of ±0.2‰. At the DirectAMS facility, carbon dioxide is reduced to graphite according to strictly defined protocols. The accelerator produces measurements to 0.3% PMC precision and accuracy. The dual ion-sources of the AMS instrument process graphite samples in 40-sample and 134-sample batches. By convention any result determined to be older than 45,000 YBP or Not Distinguishable from Background (NDFB) are noted as “>45,000” and negative activity as “Modern”.

References

BROCK, F., Higham, T., Ditchfield, P., and Ramsey, C. Current pretreatment methods for AMS radiocarbon dating at the Oxford Radiocarbon Accelerator Unit (ORAU). Radiocarbon. 2010;52(1):103-112.

ZOPPI, U., J. Crye, Q. Song, and A. Arjomand. Performance Evaluation of the New AMS System at Accium Biosciences. Radiocarbon. 2007;49(1):173-182

Sample Submission

Provide sufficient water to produce a minimum of 10 µg of strontium as well as major ion geochemistry. High density polyethylene (HDPE) bottles are preferred. No preservation or field sample preparation is required. Holding time is infinite.

Tips for sampling, labelling and shipping

Equipment

Purified strontium is loaded on 1-2 zone-refined degassed Re filaments and is ionized and analyzed for ⁸⁷Sr/⁸⁶Sr utilizing a Thermo-Finnegan Triton thermal ionization mass spectrometer (TIMS).

Quality Assurance / Quality Control (QA/QC)

• Duplicate Analyses: A minimum of one in five samples is repeated to ensure repeatability. Sample precision is calculated using approximately 200 discrete measurements per sample. The variability of these 200 measurements is used to calculate precision. Acceptable 2σ for measured ⁸⁷Sr/⁸⁶Sr is less than ±0.0003 and 2σx̅ is less than ±0.000015.
• Calibration: NIST-SRM-987 (⁸⁷Sr/⁸⁶Sr = 0.710245 2σx̅ ±0.000015) is used to calibrate results, standard normalization and to correct for Rb interference. Several in-house standards are used to ensure linearity if sample ratios differ significantly from the accepted NIST-SRM-987 value of ⁸⁷Sr/⁸⁶Sr (~0.71).

References

HORWITZ, E.P., Dietz, M.L., and Chiarizia, R. The application of novel extraction chromatographic materials to the characterization of radioactive waste solutions. Journal of Radioanalytical and Nuclear Chemistry. 1992;161(2):575-583.

Sample Submission

PRESERVATION and refrigeration is extremely important when sampling for low level methane analysis. Microbes can consume available aqueous CH₄ and alter the original isotopic signature. Acidification to a pH of 2 with HCl is a common technique for methane preservation.

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 septa are appropriate for methane isotope analyses. After sampling, vials should be refrigerated and microbial activity should be halted using a preservative or acidification. Preservatives should be carefully selected to avoid interaction with aqueous chemical species.

Minimum detection limits are in the range of 1 nmol of carbon and 2 nmol of hydrogen. In a 12 mL vial this is equivalent to ~2 ppm-V of methane. Clients must provide the aqueous methane concentration ahead of analyses.

Tips for sampling, labelling and shipping

Equipment

δ¹³C and δ²H in dissolved methane can me 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.