Solids

WARNING: We DO NOT ACCEPT samples with enriched 14C (often used as a tracer).  Any contamination of any amount of enriched 14C ("hot") material may cause thousands of dollars in clean-up and other costs. If you submit "hot" samples to this lab, you may be liable.

Quantitative - nchs

Requirements:

  • All material must be dry and powdered.
  • Special cases such as small feathers or 1cm lengths of hair for example are not possible to powder.
  • Store in air-tight vials or bottles. Glass is usually better (less static), but plastic is ok too.
  • Glass fibre filters may be stored and shipped wrapped flat in aluminum foil.
  • If the material is too coarse or non-homogenised, an extra charge per sample for grinding with the ball mill or mortar and pestle will be applied (see price list).
  • Typically 4-5 mg of organic matter is used, 10-100mg of sediments. Our large capacity elemental analyser can combust up to 500 mg.
  • Tungstic oxide (WO3) is added to sediments as a combustion aid.
  • Best to group samples with similar properties and matrix.

Methodology:

Solids are weighed into tin capsules, with WO3 (for difficult samples with iron, calcium, potassium or sodium oxides).  Elemental standards are prepared with every batch of samples for normalization of the data.

The prepared capsules are loaded into the carousel of the autosampler.The sample falls down into the top of a column of solid chemicals at 1150°C and is flash combusted at 1800°C with the addition of oxygen. Ultra-pure helium is used to carry the resulting gases through the column of chemicals to obtain N2 , CO2 , H2O, and SO2 , then through a series of adsorption traps to separate the gases:  "purge and trap". A thermo conductivity detector (TCD) measures the gases as they are released.

The analytical precision (2 sigma) is +/- 0.1%.

References:

  • Pella, E., (1990) Elemental organic analysis, parts 1-2. American Laboratory, Feb. & Aug.
  • Instruction Manuals for the elementar Isotope Cube
Quantitative - O

Requirements:

  • Most material should be ground to a dry powder. Some types of material such as small feathers or cut strands of hair may not need to be ground; check with the lab.
  • If the material is too coarse, an extra charge per sample for grinding with the ball mill or mortar and pestle will be applied (see price list).
  • Typically 1-2 mg of material is used.

Methodology:

Dry, powdered samples are weighed into silver capsules and placed into a zero blank autosampler which is place under vacuum for a few minutes. The samples are analysed with a Thermo Scientific TC/EA unit. Benzoic Acid standards are prepared with every batch of samples for individual run calibration.

The analytical precision is +/- 0.3%

References:

  • Instruction Manual for the Thermo TC/EA
  • Instruction manual for Flash Ht Plus.
Carbonate Isotopes

Requirements:

  • Sample grain size should be less than very fine sand. If the material is too coarse, an extra charge per sample for grinding with a mortar and pestle will be applied (see price list).
  • Sample vials must be air tight.
  • One submission sheet for one type of mineral only.
  • Purity of mineral for each sample must be indicated in comments column. Indicate %S or %C(organic) if more than about 1%.
  • If possible, keep the size of vial appropriate to amount of material submitted. We use about 0.5-0.7 mg of calcite equivalent per analysis; please send a few milligrams if possible.

Methodology:

A spare Exetainer vial is filled with about 10mL of specially prepared anhydrous phosphoric acid (method adapted from: Coplen et al., 1983), capped, heated and evacuated on a vacuum line for at least 1 hour to degas the acid. Meanwhile about 0.5-0.7mg of sample or standard is measured into clean Exetainers. A calibrated internal standard is also loaded with each batch to be run as an unknown.

Once the samples and standards have been weighed, the vials are loaded 8 at a time without caps into an extra rack turned on its side (i.e. Exetainers are kept almost horizontal). A 1mL disposable syringe is used to carefully drop 0.1mL of acid just past the threaded top of each Exetainer. Vials are kept horizontal while being recapped (after every 8). Once all the vials have acid added and caps on, each column of 8 vials is flushed and filled with UHP helium off-line for 4 minutes at a rate of 60-70 mL/min.

Prepared vials are then tipped upright and immediately placed in the heated block of the GasBench (either 25.0°C or 50.0°C), and left to react for 24 hours. Regular analysis of CO2 headspace follows.

The analytical precision is +/- 0.15 permil.

References:

  • Coplen, T.B., Kendall, C., and Hopple, J., (1983). Comparison of stable isotope reference samples, Nature, vol. 302, pp. 236-238.
  • Revez, K. et al., (2001). Measurement of delta13C and delta18O Isotopic Ratios of CaCO3 using a Thermoquest Finnigan GasBench II Delta Plus XL Continuous Flow Isotope Ratio Mass Spectrometer with Application to Devils Hole Core DH-11 Calcite. USGS Open-File Report 01-257.
  • Instruction Manuals for the GasBench and the Thermo Finnigan DeltaPlusXP IRMS.
Hydrogen Isotopes

Requirements:

  • Most material should be ground to a dry powder. Some types of material such as small feathers or cut strands of hair may not need to be ground; check with the lab.
  • If the material is too coarse or not homogeneous, an extra charge per sample for grinding with the ball mill or mortar and pestle will be applied (see price list).
  • Organic and inorganic material must be submitted in separate submission files; they have different media codes (one media code per file).
  • Purity of mineral or %H for each sample must be indicated in submission file. If the %H is unknown, an elemental analysis run (separate submission) must be done first.
  • About 0.1mg of H equivalent is required, please send more material though for repeats or duplicates.

Methodology (non-exchangeable H):

Dry, powdered samples are analyzed with a Thermo DeltaPlus XP continuous-flow isotope-ratio mass spectrometer coupled with a Thermo Scientific thermal conversion elemental analyzer (TC/EA) via a Confo IV, and having a Costech Zero-blank autosampler that can be sealed and pumped out. The δ2H and δ18O measurements are performed individually because operating parameters of the TC/EA are different for each each of the two elements. For δ2H measurements, the method of Qi and Coplen is used: He flow rate = 120 mL/min, reactor temperature = 1450°C, GC temperature = 85°C, and GC length = 1m, 5Å. Powdered minerals are weighed into silver capsules targeting about 100 µg H. Calibrated internal/international standards are prepared with every batch of samples for normalization of the data.

The analytical precision is +/- 0.3 permil.

Methodology (exchangeable H):

Dry samples of either pieces or powder are analyzed with a Thermo DeltaPlus XP continuous-flow isotope-ratio mass spectrometer coupled with a Thermo Scientific thermal conversion elemental analyzer (TC/EA) (via a Confo IV) having a Costech Zero-blank autosampler that can be sealed and pumped out. Two identical sets of samples are weighed into silver capsules but left open in trays. One set is allowed to exchange with water depleted in 2H and another set with water enriched in 2H in order to perform isotope-mass-balance calculations.

After the exchange process is complete, samples are dried under vacuum for 24 hours. For δ2H measurements, the method of Qi and Coplen is used; operating parameters included the following: mass of each human-hair sample = 460 ± 10 μg, which were weighed into 3.5 × 5 mm silver capsules; He flow rate = 120 mL/min; reactor temperature = 1350°C; GC temperature = 80°C; and GC length = 1m, 5Å.

The analytical precision is +/- 0.3 permil.

References:

  • Coplen, Tyler B., and Qi, Haiping (2012) USGS42 and USGS43: Human-hair stable hydrogen and oxygen isotopic reference materials and analytical methods for forensic science and implications for published measurement results, Forensic Science International, Volume 214, Issues 1–3, 10 January 2012, Pages 135–141.
  • Instruction Manuals for the Thermo TC/EA and the Thermo Finnigan DeltaPlus XP.
Carbon Isotopes

Requirements:

  • All material must be dry.
  • Most material should be powdered. Special cases such as small feathers or 1cm lengths of hair for example are not possible to powder.
  • Store in air-tight vials or bottles. Glass is usually better (less static), but plastic is ok too.
  • Glass fibre filters may be stored and shipped wrapped flat in aluminum foil.
  • If the material is too coarse or non-homogenised, an extra charge per sample for grinding with the ball mill or mortar and pestle will be applied (see price list).
  • Organic and inorganic material must be submitted in separate submission files; they have different media codes (one media code per file).
  • Quantitative %C for each sample must be indicated in the submission file. If the %C is unknown and cannot be found in a literature search, samples (or a subset) must also be submitted for a preliminary elemental analysis run (separate submission).

Methodology (organic):

NOTE: Carbon (C) and nitrogen (N) are usually analysed together in one run. If both are requested, the target weight is determined by the element with the lower %, almost always nitrogen (N); however, a dual run is not recommended for samples with a C:N ratio larger than 100. In this case, two runs are required.

Organic solids are weighed into tin capsules. Calibrated internal standards are prepared with every batch of samples for normalization of the data. In general, 100 ug of nitrogen (or 300µg of C if running only for C) are required for analysis. The carbon is normally diluted with helium since there is almost always higher %C than %N. If a requested analysis is strictly for the C, with a low %C, the analysis can be done without dilution using a lower sample weight (down to 30 µg of C if necessary).

The isotopic composition of organic carbon (and nitrogen) is determined by the analysis of CO2 (and N2) produced by combustion on an Elementar VarioEL Cube Elemental Analyser followed by "trap and purge" separation and on-line analysis by continuous-flow with a DeltaPlus Advantage isotope ratio mass spectrometer coupled with a ConFlo III interface.

For difficult materials such as soils or filters, up to 250 mg of material can be handled in a single sample with at least double that amount of tungstic oxide (WO3). Inorganic carbon must first be removed before samples can be analysed for organic carbon. There are several ways to accomplish the removal; none is perfect. Do a literature search in your field to see what others have done.

The routine precision of the analyses is 0.20‰.

References:

  • Pella, E., (1990) Elemental organic analysis, parts 1-2. American Laboratory, Feb. & Aug.
  • Instruction Manuals for the elementar VarioEL Cube and the Thermo Finnigan DeltaPlus Advantage.
  • Brodie, Chris R., Leng, Melanie J., Casford, James S.L., Kendrick, Christopher P., Lloyd, Jeremy M., Yongqiang, Zong, Bird, Michael I., Evidence for bias in C and N concentrations and d13C composition of terrestrial and aquatic organic materials due to pre-analysis acid preparation methods, Chemical Geology (2011), doi: 10.1016/j.chemgeo.2011.01.007

Methodology (inorganic - graphite):

The analysis of inorganic carbon isotopes is similar to that for organic carbon (above). The main differences are:

  • Graphite is very difficult to combust; therefore, the samples must be extremely finely powdered.
  • WO3 must be added in great excess (at least 4-5 times the weight of sample) and thoroughly homogenised with the sample material before being closed in a tin capsule.

References:

  • Instruction Manuals for the elementar VarioEL Cube and the Thermo Finnigan DeltaPlus Advantage.
Nitrogen Isotopes

Requirements:

  • All material must be dry.
  • Most material should be powdered. Special cases such as small feathers or 1cm lengths of hair for example are not possible to powder.
  • Store in air-tight vials or bottles. Glass is usually better (less static), but plastic is ok too.
  • Glass fibre filters may be stored and shipped wrapped flat in aluminum foil.
  • If the material is too coarse or non-homogenised, an extra charge per sample for grinding with the ball mill or mortar and pestle will be applied (see price list).
  • Organic and inorganic material must be submitted in separate submission files; they have different media codes (one media code per file).
  • The %C and %N of each sample must be indicated in the submission file. If the %C and %N are unknown and cannot be found in a literature search, an elemental analysis run of all samples (or a subset of these) will need to be done first; separate submission. If requesting only N isotopes, the %C is still required so that we can set the dilution properly.
  • About 0.1 mg of N equivalent is required, please send more.

Methodology (organic):

NOTE: Carbon (C) and nitrogen (N) are usually analysed together in one run. If both are requested, the target weight is determined by the element with the lower %, almost always the nitrogen (N).

Organic solids are weighed into tin capsules. Calibrated internal standards are prepared with every batch of samples for normalization of the data. In general, 100 µg of N are required for analysis. The carbon is normally diluted with helium since there is almost always higher %C than %N. It is possible to do samples targeting only 30 µg of N if necessary.

Please check with us before weighing your samples either here in the lab or in your own space. In some cases (C:N ratio >50), the quantities might need to be altered . In extreme cases (C:N ratio >100), it is not possible to run both C and N isotopes on a single sample. Weights must be targeted to the %N only for one run and for %C for a second run.

The isotopic composition of organic nitrogen is determined by the analysis of N2 produced by combustion on an Elementar Vario Cube Elemental Analyser followed by "trap and purge" separation and on-line analysis by continuous-flow with a DeltaPlus Advantage isotope ratio mass spectrometer coupled with a ConFlo III.

For difficult materials such as soils or filters, up to 250 mg of material can be handled in a single capsule with at least double that amount of tungstic oxide (WO3). If inorganic carbon must first be removed from soils or sediments for C analysis, some unaltered material must be kept for the N analysis. Any treatment will alter the N isotope signature.

The routine precision of the analyses is 0.2‰.

References:

  • Pella, E., (1990) Elemental organic analysis, parts 1-2. American Laboratory, Feb. & Aug.
  • Instruction Manuals for the elementar VarioEL Cube and the Thermo Finnigan DeltaPlus Advantage.
  • Brodie, Chris R., Leng, Melanie J., Casford, James S.L., Kendrick, Christopher P., Lloyd, Jeremy M., Yongqiang, Zong, Bird, Michael I., Evidence for bias in C and N concentrations and d13C composition of terrestrial and aquatic organic materials due to pre-analysis acid preparation methods, Chemical Geology (2011), doi: 10.1016/j.chemgeo.2011.01.007

Methodology (inorganic):

The analysis of inorganic nitrogen isotopes is similar to that for organic nitrogen (above).The main differences are:

  • Some material may require the addition of sucrose to help with combustion.
  • Some material may require chemical preparation in silver capsules, then re-encapsulation in tin capsules.

References:

  • Instruction Manuals for the elementar VarioEL Cube and the Thermo Finnigan DeltaPlus Advantage.
Oxygen Isotopes

Requirements:

  • Most material should be ground to a dry powder. Some types of material such as small feathers or cut strands of hair may not need to be ground; check with lab.
  • If the material is too coarse or non-homogenised, an extra charge per sample for grinding with the ball mill or mortar and pestle will be applied (see price list).
  • Organic and inorganic material must be submitted in separate submission files; they have different media codes (one media code per file).
  • Purity of mineral or %O for each sample must be indicated in submission file. If the %O is unknown and cannot be found in a literature search, an elemental analysis run (separate submission) must be done first.
  • About 0.1 mg of O equivalent is required, please send at least double if possible.

Methodology:

Dry, powdered samples are analyzed with a Thermo DeltaPlus XP continuous-flow isotope-ratio mass spectrometer coupled with a Thermo Scientific thermal conversion elemental analyzer (TC/EA) via a Conflo IV having a Costech Zero-blank autosampler that can be sealed and pumped out. The δ2H and δ18O measurements are performed individually because operating parameters of the TC/EA are different for δ2H and δ18O measurements. For δ18O measurements, the method of Qi and Coplen is used; He flow rate = 120 mL/min, reactor temperature = 1450°C, GC temperature = 85°C, and GC length = 1m, 5Å. Powdered minerals are weighed into silver capsules targeting about 100 µg O. Calibrated internal/international standards are prepared with every batch of samples for normalization of the data.

The analytical precision is +/- 0.3 permil.

References:

  • Coplen, Tyler B., and Qi, Haiping (2012) USGS42 and USGS43: Human-hair stable hydrogen and oxygen isotopic reference materials and analytical methods for forensic science and implications for published measurement results, Forensic Science International, Volume 214, Issues 1–3, 10 January 2012, Pages 135–141.
  • Instruction Manuals for the Thermo TC/EA and the Thermo Finnigan DeltaPlus XP.
Sulphur Isotopes

Requirements for material sent for analysis:

  • Material must be ground to a powder. If the material is too coarse, an extra charge per sample for grinding with a mortar and pestle will be applied (see price list).
  • Sulphide and sulphate minerals must be submitted in separate submission files; they have different media codes (one media code per file). Organic sulphur is also a different media code.
  • Mineral type and purity or %S must be included for each sample in the submission file.
  • Indicate %C (inorganic) or %C (organic) if more than about 5%.
  • About 50 µg of sulfur equivalent is used, please send more for duplicates or replicates.

Methodology (inorganic):

Sulphide and sulphate minerals are weighed into tin capsules with at least double that amount of tungstic oxide (WO3). Calibrated internal standards are prepared with every batch of samples for normalization of the data. The formula "5 ÷ %S" gives the amount of sample material in milligrams (mg) to be weighed (e.g. pyrite contains 50% sulfur: 5 / 50% = 0.1 mg).

When using the Isotope Cube (Elementar, Germany) samples with as little as 0.05% S can be analysed directly.

The prepared capsules are loaded into the carousel of the Isotope Cube autosampler. A sample falls down into the top of a column of solid chemicals at 1150°C, and is flash combusted at 1800°C with the addition of oxygen. Ultra-pure helium is used to carry the resulting gases through the column(s) of oxidizing/reducing chemicals to obtain N2, CO2, H2O, and SO2. Water is cleaned out of the system by sicapent traps. The SO2 is separated for analysis by the chemical adsorption "trap and purge" method. The SO2 gas is carried by helium into the Thermo Finnigan DeltaPlus XP IRMS via a Conflo IV for analysis.

The analytical precision is +/- 0.3 permil.

References:

  • Grassineau, N. V., et al., (2001). Sulfur Isotope Analysis of Sulfide and Sulfate Minerals by Continuous Flow-Isotope Ratio Mass Spectrometry. Analytical Chemistry, vol. 73, no. 2, pp. 220-225.
  • Instruction Manuals for the Elementar Isotope Cube, and the Thermo Finnigan DeltaPlus XP.

Methodology (organic):

Organic solids are weighed into tin capsules. At least double the amount of tungstic oxide (WO3) is added to the capsule. Calibrated internal standards are prepared with every batch of samples for normalization of the data. In general, 50 µg of S are required for analysis. Elemental analysis must be performed first if the quantity of sulphur in a sample is unknown; separate submission.

If the amount of carbon is very high relative to the amount of sulphur (eg. wood), a special configuration of the elemental analyser is needed. Advance notice to the lab is required.

The prepared capsules are loaded into the carousel of the Isotope Cube autosampler. A sample falls down into the top of a column of solid chemicals at 1150°C, and is flash combusted at 1800°C with the addition of oxygen. Ultra-pure helium is used to carry the resulting gases through the column(s) of oxidizing/reducing chemicals to obtain N2, CO2, H2O, and SO2. Water is cleaned out of the system by sicapent traps. The SO2 is separated for analysis by the chemical adsorption "trap and purge" method. The SO2 gas is carried by helium into the Thermo Finnigan DeltaPlus XP IRMS via a Conflo IV for analysis.

The routine precision of the analyses is 0.4‰.

References:

  • Pella, E., (1990) Elemental organic analysis, parts 1-2. American Laboratory, Feb. & Aug.
  • Instruction Manuals for the Elementar Isotope Cube and the Thermo Finnigan DeltaPlus XP.
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