Abstract Preventing the inclusion of oxygen bearing compounds from the organic fraction of skeletal tissues is often considered key to obtaining faithful δ18O measurements of the mineral fraction, which are widely used across the archaeological, forensic and geochemical sciences. Here we re-explore the contentious issue of organic removal pretreatments by establishing how different silver phosphate preparation methods perform in producing pure silver phosphates with a faithful biogenic isotopic signal. We then compare this baseline performance to a pretreatment based approach. Our results show that anion exchange purification combined with slow precipitation of silver phosphate consistently produces silver phosphates of high purity without prior pretreatment. Rapid precipitation protocols without additional purification, while effective and time-efficient for low organic samples such as enamel, suffer from the inclusion of substantial amount of organic matter in silver phosphates from bone or dentine samples. However, despite substantial organic contamination in such samples, δ18O values do not necessarily show substantial shifts. Further study is needed to clarify the reason for this, but for now the use of an anion exchange based protocol represents the most cautious approach to processing bone and dentine samples and we recommend its use for such samples. Confirming previous work we find H2O2 pretreatment to be only partially effective at removing higher amounts of organic matter. Both H2O2 and NaOCl pretreatments show unpredictable side effects on δ18O values of both bones and inorganic samples. We additionally find no indication that the presence of organic material hinders the dissolution of bioapatite samples.

中文翻译：

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阴离子交换树脂和缓慢沉淀排除了在磷酸银制备中对生物磷灰石氧同位素分析进行​​预处理的需要

摘要 防止骨骼组织的有机部分中包含含氧化合物通常被认为是获得矿物部分的 δ18O 测量值的关键，这些测量值广泛用于考古、法医学和地球化学科学。在这里，我们通过建立不同的磷酸银制备方法在生产具有可靠生物同位素信号的纯磷酸银方面的表现，重新探索有机去除预处理的有争议的问题。然后，我们将此基线性能与基于预处理的方法进行比较。我们的结果表明，阴离子交换纯化与磷酸银的缓慢沉淀相结合，无需事先预处理即可始终如一地产生高纯度的磷酸银。无需额外纯化的快速沉淀方案，虽然对牙釉质等低有机样品有效且省时，但骨或牙本质样品的磷酸银中含有大量有机物质。然而，尽管这些样品中存在大量有机污染，δ18O 值并不一定显示出实质性的变化。需要进一步研究来澄清其原因，但目前使用基于阴离子交换的协议是处理骨骼和牙本质样品的最谨慎方法，我们建议将其用于此类样品。确认之前的工作，我们发现 H2O2 预处理在去除大量有机物方面仅部分有效。H2O2 和 NaOCl 预处理对骨骼和无机样品的 δ18O 值都显示出不可预测的副作用。