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

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±1μg 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 ¹⁴Cyears. 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.