Effects of decalcification on bulk and compound‐specific nitrogen and carbon isotope analyses of dentin

• Published in: Rapid Communications in Mass Spectrometry
• Main Authors: Brault, Emily K., Koch, Paul L., Gier, Elizabeth, Ruiz‐Cooley, R. I., Zupcic, Jessica, Gilbert, Kwasi N., McCarthy, Matthew D.
• Other Authors: National Science Foundation
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2014
• Subjects: Sperm whale
• Online Access: http://dx.doi.org/10.1002/rcm.7073; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Frcm.7073; https://onlinelibrary.wiley.com/doi/full/10.1002/rcm.7073

RATIONALE For bulk carbon and nitrogen isotope analysis of dentin, samples are typically decalcified. Since the non‐protein carbon in dentin is low, whole sample analysis may produce reliable data. Compound‐specific isotope analysis (CSIA) of bone and tooth dentin protein is a powerful tool for reconstructing the flow of carbon and nitrogen in modern and past food webs. Decalcification has also been used to prepare bone and dentin samples for CSIA, but the effects of this process on bulk dentin, amino acid composition, and their specific isotope values are not known. METHODS The bulk isotope values of raw and decalcified dentin from a sperm whale tooth were measured to determine the effects of decalcification and the accuracy of untreated dentin results. CSIA was also performed on decalcified and raw dentin to examine differences in the amino acid isotope values and molar composition between these two approaches. RESULTS Analysis of raw dentin yields precise and accurate bulk isotope measurements for this animal. The isotopic values of decalcified samples and raw dentin for individual amino acids were similar, but the average of the isotope value offsets between the two sample types was significant. The presence of inorganic material complicated raw sample processing for individual amino acid isotope values, and may have contributed to the isotopic differences between decalcified and raw samples. CONCLUSIONS Decalcification is not needed to measure bulk isotope values in dentin from this modern odontocete, probably because the lipid and carbonate concentrations are low and the carbon isotope values of dentin protein and carbonate are similar. This method should not be applied in some cases (e.g., with fossil dentin and modern bone). Decalcification should still be used prior to CSIA since significant matrix issues occur with raw dentin processing and decalcification does not alter the amino acid molar composition or isotopic values of dentin. Copyright © 2014 John Wiley & Sons, Ltd.