Compound-Specific Radiocarbon Analysis by Elemental Analyzer-Accelerator Mass Spectrometry: Precision and Limitations

Area of Science:

• Paleoscience
• Geochemistry
• Analytical Chemistry

Background:

• Radiocarbon dating is crucial for paleoclimate and paleoceanography.
• Microscale analysis of individual compounds requires high precision.
• Existing methods need evaluation for small sample sizes (10-50 μg C).

Purpose of the Study:

• To evaluate instrumental and methodological capabilities for microscale radiocarbon analysis.
• To determine precision, accuracy, and reproducibility of measurements on isolated compounds.
• To establish minimum sample sizes for high-precision radiocarbon dating of specific organic molecules.

Main Methods:

• Utilized an elemental-analyzer-accelerator-mass-spectrometry (EA-AMS) setup.
• Analyzed 14C-free and modern reference materials.
• Processed and analyzed fatty acids, alkenones, and amino acids from sediment samples.
• Developed and applied a MATLAB code for blank assessment and parameter evaluation.

Main Results:

• Identified minimum sample sizes for high-precision radiocarbon data (<5% error) and reproducibility (F14C ≈ 0.1) as 50 μg C for alkenones and 30 μg C for fatty acids.
• Achieved 2% precision for alkenones (≥15 μg C) and fatty acids (≥10 μg C) when F14C > 0.5.
• Validated a computational approach for blank assessment in small radiocarbon samples.

Conclusions:

• Current isolation methods necessitate specific minimum sample sizes for reliable microscale radiocarbon dating.
• The developed MATLAB code provides a reliable method for blank assessment in small radiocarbon samples.
• This research advances the application of radiocarbon dating for detailed paleoclimate and paleoceanography studies.