Department of Archaeology, Memorial University, St. John's, Newfoundland, A1C 5S7, Canada.
Rapid Commun Mass Spectrom. 2013 Feb 15;27(3):375-90. doi: 10.1002/rcm.6463.
The integrity of the biological phosphate oxygen isotope (δ(18)O(p) ) signal is thought to be contingent upon the complete removal of competing sources of oxygen such as associated organic matter. A range of pretreatment methods to purify phosphate material from competing sources of oxygen has been reported, with contradictory evidence on the usefulness and efficiency of one or another. Yet, a systematic comparison of these techniques for bioapatite phosphate has not been conducted.
Chemical and thermal pretreatment techniques were tested for their effectiveness at removing organic matter and the likelihood that they modify original δ(18)O values. The test was performed in inorganic (synthetic apatite and a phosphorite rock) and organic (bone and tooth tissues) phosphate materials for which we had an expectation of the actual original δ(18)O(p) value. Analysis of nitrogen content (wt.%), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy were employed.
We detected variable efficiency at removing organic matter between pretreatment methods with no correlation to any specific structural change. The δ(18)O(p) results showed considerable variation between samples pretreated with the different methods and the untreated samples, with a compositional range of up to 4.5 ‰ in the bone samples. Variations of the δ(18)O(p) values within error were found for tooth enamel, phosphorite rock and inorganic apatite.
We recommend a cautious approach when interpreting and comparing δ(18)O(p) data from bone samples treated with different pretreatment protocols. In general, the untreated samples seem to show δ(18)O(p) values closer to the expected ones. According to our results, pretreatment is completely unnecessary in highly mineralized tissues.
生物磷酸盐氧同位素（δ¹⁸Op）信号的完整性被认为取决于完全去除竞争氧源，如相关有机质。已经报道了一系列从竞争氧源中纯化磷酸盐材料的预处理方法，但关于一种或另一种方法的有用性和效率存在相互矛盾的证据。然而，尚未对这些用于生物磷灰石磷酸盐的技术进行系统比较。
测试了化学和热预处理技术去除有机质的效果以及它们改变原始δ¹⁸O 值的可能性。该测试在无机（合成磷灰石和磷块岩）和有机（骨骼和牙齿组织）磷材料中进行，我们对这些材料的实际原始δ¹⁸Op 值有预期。分析了氮含量（wt.%）、扫描电子显微镜（SEM）和傅里叶变换红外（FTIR）光谱。
我们检测到预处理方法之间去除有机质的效率存在差异，但与任何特定的结构变化均无相关性。δ¹⁸Op 结果显示，用不同方法预处理的样品与未处理的样品之间存在相当大的差异，骨骼样品的组成范围高达 4.5‰。牙釉质、磷块岩和无机磷灰石内的δ¹⁸Op 值存在误差范围内的变化。
当解释和比较用不同预处理方案处理的骨骼样品的δ¹⁸Op 数据时，我们建议采取谨慎的方法。一般来说，未处理的样品似乎显示出更接近预期的δ¹⁸Op 值。根据我们的结果，在高度矿化的组织中，预处理是完全不必要的。
