DETERMINATION OF THE HYDROGEN ISOTOPIC COMPOSITION OF BONE COLLAGEN AND CORRECTION FOR HYDROGEN EXCHANGE

Abstract

The hydrogen isotopic measurement (∆D) of the non-exchangeable hydrogens in herbivore bone collagen has potential for paleoclimate research. The authors have developed the methodology for extracting the hydrogen from collagen for isotopic analysis and correcting the [delta]D results for hydrogen exchange. Preparations of whole bone powders, demineralized bone, or gelatin extracts from fresh bone samples all give reliable ∆D 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 ∆D results can be corrected for this exchange and for minor effects of sample preparation by using a calibration bone standard to determine the ∆D value of laboratory water vapor.