Effect of ultrafilter pretreatment, acid strength and decalcification duration on archaeological bone collagen yield

Recent attempts to date batches of poorly preserved archaeological bone prompted a re-evaluation of existing protocols for bone sample preparation and ultrafilter cleaning methods at the Keck-Carbon Cycle Accelerator Mass Spectrometer (KCCAMS) facility. The emphasis of the study was to optimize decalcification time and ultrafiltration retention efficiency to improve overall collagen yields, especially for poorly preserved bone. Decalcification time and acid strength tests were done on four in-house bone standards of varying states of preservation. Through systematic testing, we found that 200 mg bone chip samples decalcified in 4 mL of 1.0 N HCl over 16 h showed increases of collagen yield across all samples relative to our existing protocol. Ultrafilters precleaned with weak acid (0.01 N HCl) showed greater retention efficiencies than those cleaned by sonication in ultrapure Milli-Q (MQ) water. Collagen produced from each sample were analyzed via AMS dating to check the quality of the collagen.