A novel tertiary prep-HPLC method for the isolation of single amino acids for AMS-radiocarbon measurement

- A method for radiocarbon measurement of HPLC-isolated amino acids was developed.
- The 14C content and amount of method contaminant carbon was determined.
- The method allows for high sample throughput and small measurement uncertainties.
- The method can be applied to improve quality of ancient bone radiocarbon measurements.

AMS-radiocarbon measurements of amino acids can potentially provide more reliable radiocarbon dates than bulk collagen analysis. Nonetheless, the applicability of such an approach is often limited by the low-throughput of existing isolation methods and difficulties in determining the contamination introduced during the separation process.A novel tertiary prep-HPLC amino acid isolation method was developed that relies on the combustion of eluted material without requiring any additional chemical steps. Amino acid separation was carried out using a gradient mix of pure water and phosphoric acid with an acetonitrile step in-between runs to remove hydrophobic molecules from the separation column. The amount of contaminant carbon and its 14C content were determined from two-point measurements of collagen samples of known 14C content.The amount of foreign carbon due to the isolation process was estimated at 4 ± 1 μg and its 14C content was 0.43 ± 0.01 F14C. Radiocarbon values corrected for carbon contamination have only a minor increase in uncertainties. For Holocene samples, this corresponds to an added uncertainty typically smaller than 10 14C years.The developed method can be added to routine AMS measurements without implying significant operational changes and offers a level of measurement uncertainty that is suitable for many archaeological, ecological, environmental, and biological applications.