Purification of hydroxyproline for small-scale radiocarbon dating verified using archaeological bone collagen

Abstract We developed a novel technique for the accurate radiocarbon dating of single amino acids from archaeological human and animal remains. Despite the extensive use of bulk collagen for radiocarbon dating of archaeological bones, obtaining accurate dates can be difficult in some cases due to unremovable C contamination in collagen. To obtain a reliable, uncontaminated age, we developed a purification method for analysing hydroxyproline, a major amino acid in bone collagen. This method uses two purification processes: liquid–liquid extraction and recrystallization after high-performance liquid chromatography. This purification method substantially reduced the contamination by exogenous C in the isolated amino acids. The reliability of the method was demonstrated by radiocarbon dating an archaeological bone with a known date of death. This method enables compound-specific radiocarbon dating of amino acids with < 100 μg of C, reducing collagen and bone sample consumption relative to previous approaches. This method is expected to enable the extensive application of radiocarbon dating to degraded archaeological bones that were previously unusable. In addition, our technique of isolation and purification of amino acids is useful for the isolation of compounds for the radiocarbon analysis from diverse organic tissue beyond collagen and other organic molecules in marine sediments targeted by studies in the field of Earth and planetary science.