Stable Isotope Analysis
CSU-IsoLab possesses three isotope ratio mass spectrometers (IRMS), several interfaces and preparation systems that enable isotope analyses of different elements (C, N, O, H) in solid, liquid and gas at atmospheric and trace concentrations. The facility management maintains the instruments, develops methods and provides training. Within the lab, an area is designed for teaching, research seminars and small workshops, which can be used by CSU faculty.
Analytical capabilities and equipment:
- Solid sample 13C and 15N analysis
- 13C analysis of CO2 in concentrated samples
- 18O analysis of water
- Trace gas isotope analysis
- Compound-specific stable isotope analyses
Solid sample 13C and 15N analysis by Carlo Erba NA 1500 (Milano, IT) elemental analyzer coupled to a VG Isochrom continuous flow IRMS (Isoprime Inc., Manchester, UK). An integrated thermal conductivity detector (TCD) also allows the determination of carbon and nitrogen concentrations simultaneously with an isotopic determination. Each analysis (13C or 15N) requires one sample.
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Observed precision |
0.2‰ |
0.3‰ |
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Minimum sample size* |
1 umol C |
2 umol N |
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Run time/sample |
6 min |
6 min |
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*Click here to download our sample size calculator |
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13C analysis of CO2 in concentrated samples (e.g. from incubations) by micro-gas Injector coupled to a VG Optima IRMS (Isoprime Inc., Manchester, UK). Requires manual injection.
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Observed precision |
0.4‰ |
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Minimum sample size |
2000 ppm CO2 |
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Run time/sample |
3 min |
18O analysis of water by CO2 equilibration (equilibration block) and micro-gas Injector with auto-sampler coupled to a VG Optima IRMS (Isoprime Inc., Manchester, UK). The lab also has a vacuum line for extracting water from soils and plant tissues.
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Observed precision* |
0.3‰ |
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Nominal sample size |
0.2 mL |
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Capacity (max. samples/day) |
40 |
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*Smaller samples may be analyzed with some loss of precision. Click here to see the graph of precision vs. sample size. |
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Trace gas isotope analysis (i.e. CO2, N2O and CH4) by Thermo PreCon coupled to a Delta V IRMS (Thermo Scientific). The PreCon is a fully automated trace gas pre-concentrator for the isotope characterization of N2O, CH4 and CO2 at natural concentrations. Following manual gas injection, the PreCon carries out sample concentration, purification, cryofocusing, and injection onto a gas chromatograph prior to IRMS analysis. Currently configured for 13C analysis of CO2 at atmospheric concentrations.
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Observed precision* |
0.2‰ |
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Sample size range |
0.007 - 0.021 umol CO2 |
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Run time/sample |
15 min |
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*Standard deviation of 34 injections over 3 running days |
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Compound-specific stable isotope analyses by a Thermo GC-c/py-IRMS system composed of a Trace GC Ultra gas chromatograph with TriPlus autosampler, GC IsoLink Unit, coupled to a Delta V Advantage IRMS through a ConFlo IV universal interface (Thermo Scientific). The instrument allows for the determination of 13C and 15N on CO2 and N2 generated by combustion (1030°C) and 18O and 2H on CO and H2 generated by pyrolysis (1450°C) on individual compounds separated by GC. The instrument is currently configured for 13C analysis in fatty acid methyl esters (FAMEs). FAMEs dissolved in hexane are injected in splitless mode and separated on a BPX-5 column (60m x 0.25mm ID x 0.25um film thickness). δ13C values can be corrected using internal FAME working standards added to the sample if δ13C values for these standards are known. Alternatively, we will calibrate against our CO2 reference gas.
EcoCore only allows experienced users to operate the GC-c/py-IRMS. EcoCore currently only offers 13C analysis of FAMEs as a service to external clients. We only accept FAME samples dissolved in hexane in standard GC vials (volume: 2 mL OD x length: 12 x 32 mm). For small samples, inserts can be used. We will provide the client with an Excel report listing peak retention times, peak areas and δ13C values for all detectable peaks. We will indicate where some peak overlap occurred, as this will affect their isotope ratio. Individual chromatograms can be provided upon request. EcoCore does not currently offer any further data analysis to external clients.
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Observed precision* |
0.4‰ |
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Sample size range |
5-150ng C (per FAME) |
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Run time/sample |
approx. 1 h |
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*Based on 16 replicate injections of a C19:0 standard. Precision is greatly affected by peak separation. |
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