EA-IRMS: Tracking human and animal dietary habits using isotope fingerprints recorded in bone collagen

Importance of the topic

Stable isotope analysis of carbon nitrogen and sulfur in bone collagen provides direct insight into dietary protein sources and geographic origins of both past and present populations. It is crucial for reconstructing ancient food webs in archaeology, tracking human and animal migrations, and supporting forensic and ecological investigations.

Study objectives and overview

This application demonstrates a streamlined method to obtain δ13C δ15N and δ34S values simultaneously from approximately 1 mg of bone collagen using a single EA IsoLink IRMS workflow. The goal is to overcome challenges associated with low sulfur content and to reveal dietary and environmental trends in human and animal samples.

Methodology and instrumentation

• Sample preparation: about 1 mg of dried homogenized bone collagen weighed into tin capsules
• Thermo Scientific EA IsoLink IRMS System with MAS Plus Autosampler featuring a combustion reactor at 1020 °C packed with tungstic anhydride oxidizer and copper reducer
• Separation of N₂ CO₂ and SO₂ by temperature-ramped gas chromatography and transfer to DELTA V IRMS via ConFlo IV interface
• Calibration against USGS 40 USGS 42 IAEA S1 IAEA S2 and IAEA S3 standards
• Analysis time under 10 minutes and helium consumption below 1.4 liters per sample

Key results and discussion

The method delivers high-precision isotope values (mostly ≤ 0.1 ‰) and distinct dietary signatures:

• Cattle samples: δ13C from –20 to –16 ‰ and δ34S between 2 and 12 ‰ reflecting terrestrial C3/C4 plant protein
• Human samples: δ15N above 8 ‰ and δ34S around 3–5 ‰ indicating marine protein consumption
• Mammoth samples: δ13C near –21.7 ‰ and δ34S ranging from –25 to +4 ‰ pointing to diverse habitats and diets

A δ15N versus δ34S scatter plot demonstrates clear separation of species and dietary regimes.

Advantages and practical applications

• Simultaneous measurement of N C S isotopes in a single run reduces sample requirements and preparation time
• Lower operational costs and higher throughput by avoiding instrument reconfiguration
• Applications in archaeological paleodietary studies forensic casework wildlife ecology and provenance research

Future trends and potential applications

• Combining multi-isotope data with radiocarbon dating for improved chronological models
• Development of micro-sampling and non-destructive techniques for precious specimens
• Expansion of geographic isotope databases to refine provenance analyses
• Use of advanced data analytics and machine learning for complex isotope pattern interpretation

Conclusion

The Thermo Scientific EA IsoLink IRMS System enables efficient high-precision δ13C δ15N and δ34S analysis from minimal bone collagen, supporting robust dietary reconstruction and provenance investigations while reducing cost and analysis time.

References

1. Nehlich O Oelze V M Jay M Conrad M Stauble H Teegen W R Richards M P Sulfur isotope ratios of multi-period archaeological skeletal remains from central Germany a dietary study Anthropologie LII 1 15-33 2014