Determination of the hydrogen isotopic composition of bone collagen and correction for hydrogen exchange

The hydrogen isotopic measurement (δD) of the non-exchangeable hydrogens in herbivore bone collagen has potential for paleoclimate research. We have developed the methodology for extracting the hydrogen from collagen for isotopic analysis and for correcting the δD results for hydrogen exchange. Preparations of whole bone powders, demineralized bone, or gelatin extracts from fresh bone samples all give reliable δD results and have isotopic results, yields, and proportions of exchangeable hydrogens consistent with that expected for collagen. Gelatin extraction for removal of contaminants remains a valuable option for the study of fossil bone samples.Vacuum preheating under good vacuum at 150°C for two days for whole bone powders and at 100°C for one day for gelatins is an important step to remove all adsorbed water before samples are oxidized for isotopic analysis. Of the remaining hydrogens released following oxidation, 20.5% in whole bone powders and 23.1% in gelatin extracts exchange with laboratory atmospheric water vapor within 48 hours. The δD results can be corrected for this exchange and for minor effects of sample preparation by using a calibration bone standard to determine the δD value of laboratory water vapor.