动物牙釉结构碳酸盐碳、氧同位素测试方法的比较

不同学者用磷酸平衡法分析古哺乳动物牙齿化石碳酸羟基磷灰石中结构碳酸盐的碳、氧稳定同位素组成时，预处理方法和实验条件也不尽相同。实测结果表明，预处理条件与磷酸法制备CO2的反应温度和反应时间均可能对分析结果产生影响，需在综合运用机械和化学手段除净外表附着碳酸盐的前提下，将样品充分研磨，并彻底分解其中的有机组分和非结构碳酸盐，再制备CO2。70℃的恒温水浴可以使化学反应和同位素分馏均在短时间内结束，且较为完全、彻底，测得的同位素数据重现性好；而25℃时反应进行较缓，氧同位素测试结果有时可能不理想

Analytical Approaches of Carbonate δ13 C and δ18 O Values in Enamel Hydroxylapatite from Mammals

The carbon and oxygen isotope compositions of enamel carbonate hydroxylapatite from mammalian fossils are used to reconstruct paleoenvironment. δ^13C values are indicators for diets and δ^18O values are indicators for water sources of mammals. Commonly, carbonate hydroxylapatites are reacted with pure phosphoric acid at 25 - 90℃ for 10 minutes to 3 days to liberate CO2 gas for analysis. In this study, 23 experiments were performed at diverse reaction temperatures, reaction times or pretreatments. Enamel, dentin and chalk from fossils and enamel from modern equids were collected and 23 δ^13C and δ^18O values were compared. HAC-H2O2-HAC or HC1-H2O2-HAC is more effective than HCl-H2O2-NaHSO4 or HCl-H2O2-Na2B4O7to purify carbonate hydroxylapatites, and high temperature such as 70℃ is more advisable than low temperature, especially for δ^13℃ values