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Sample Types & Considerations

Carbon and Nitrogen stable isotopes (δ13C and δ15N) are measured by Elemental Analysis – Isotope Ratio Mass Spectrometry (EA-IRMS) using a Sercon HS20-22 continuous flow isotope ratio mass spectrometer and accompanying Sercon PyroEarth elemental analyser, both newly installed in January 2023.

Analyses on bone collagen are routinely undertaken on samples submitted for carbon dating provided there is adequate material remaining following 14C processing.

The EA-IRMS is also used to produce a %Nitrogen content value on raw bone samples at the initial stages of bone processing. This value helps to decide if pre-treatment is viable by indicating how likely the sample is to yield sufficient collagen suitable for 14C dating.

Analyses on other sample types (e.g. flesh, hair, feathers, blood, food residues, charcoal, plants, insects) can be carried out by prior arrangement. Currently we are unable to provide stable isotope analysis as a routine stand-alone service. However, collaboration or specific projects can be discussed with Centre Director, Dr M Blaauw (maarten.blaauw@qub.ac.uk).

Specific questions regarding Isotope Ratio Mass Spectrometry can be directed to the IRMS Technician, Dr Naomi Pratt (n.pratt@qub.ac.uk).

Protocol and Standards

Two blank (empty) capsules are measured at the start of the sequence and any C or N contribution from the tin is automatically deducted from the results.

Samples are measured in duplicate with a drift correction standard of certified isotopic composition bracketing every 10-12 samples. Reference materials with known isotopic compositions are measured to create a two-point regression line, which is used to calibrate the sample data to the VPDB (carbon) and AIR (nitrogen) scales. These calibration reference materials encompass the result range normally observed for the material and are each measured three times during the analytical session.

Reference materials of a similar isotopic composition to the sample material being analysed are used to monitor measurement uncertainty.

Reference materials of known isotopic composition currently in use in the laboratory

For NITROGEN isotopes
For CARBON isotopes
IAEA-N-2 Ammonium Sulphate  δ15N +20.41 ± 0.12 IAEA-CH-7 Polyethylene  δ13C -32.15 ± 0.05
IA-R068 Soy Protein δ15N +0.99 ± 0.07 IAEA-R006 Cane Sugar  δ13C -11.64 ± 0.03
IA-R069 Tuna Protein  δ15N +11.60 ± 0.09 IA-R068 Soy Protein  δ13C -25.22 ± 0.02
Caffeine OAS  δ15N -3.29 ± 0.07 IA-R069 Tuna Protein  δ13C -18.88 ± 0.05
Coldwater Fish Gelatin OAS  δ15N +14.71 ± 0.14 Caffeine OAS  δ13C -32.63 ± 0.06
Bovine Gelatin OAS  δ15N +7.54 ± 0.12  Coldwater Fish Gelatin OAS δ13C -16.63 ± 0.1
  Bovine Gelatin OAS  δ13C -11.11 ± 0.09

Note: IAEA=International Atomic Energy Agency; IA=Iso-Analytical; OAS=Organic Analytical Standard by Elemental Microanalysis

An in-house mammoth bone standard (UB 33333) is repeatedly measured both for C14 and stable isotopes for quality control purposes.

As the weight of the sample is known, the %C and %N can also be determined if a specific weight of a standard of known %C and %N is also combusted and measured. The reference materials currently in use to calibrate %element values are Atropine (70.55% C, 4.85% N), Cystine (30% C, 11.64% N) and Nicotinamide (59% C, 22.81% N). The values are then used to calculate C:N ratios which are one of the primary indicators of the degree of preservation of bone collagen and/or contamination by soil organic substances. Bovine Gelatin (16.1 %N, 43.73 %C) and Coldwater Fish Gelatin (16.63 %N, 42.93% C) are used as quality control standards to understand the uncertainty of the %element values.

The long term average standard uncertainty is 0.29‰ for δ15N and 0.36‰ δ13C. This is based on 8 sessions of ~80 measurements. The standard uncertainty for each analytical session is estimated by combining random and systematic errors using the methodology described in Szpak et al (2017).

Other Stable Isotopes

14CHRONO Centre is also linked to the Stable Isotope Facility in the School of Natural and Built Environment, which offers stable isotope analysis of liquid, solid and gas samples for the following elements: carbon, hydrogen, oxygen, sulfur and nitrogen. The facility is one of the most comprehensive, centralised facilities for stable isotope analysis in the island of Ireland and UK.

Contact: Dr Neil Ogle

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email: n.ogle@qub.ac.uk
phone: +44 28 9097 4908

The facility has:
  • Thermo Delta V (IRMS) for 34S/32S (δ34S) ,18O/16O (δ18O) and 2H/1H (δ2H) Solids & GC-PAL Autosampler for (δ18O) and (δ2H) fluids
  • Analytical Precision 2003 with Acid Digester for the 13C/12C (δ13C) and δ18O analysis of carbonates.
  • Thermo Finnigan Delta Plus Advantage IRMS & Trace DSQ coupled Trace GC for compound specific isotope analysis (δ13C).
  • Isoprime Mass Spectrometer with EA for measurement of 13C/12C and 15N/14N in organic matter.