Purification techniques for oxygen isotope analysis of inorganic phosphate across environmental matrices: A...

Phosphorus (P) is an essential element for all living organisms, playing a critical role in various biological processes. Tracing the origin and cycling of P is vital to understand its fate and transformation as it relates to broader Earth system processes. Unlike other major elements with multiple stable isotopes, P only has one stable isotope (³¹P), making direct isotopic analysis unfeasible. However, phosphate oxygen isotopes (δ¹⁸O_P) are a powerful tool to study P across various environments. Measuring phosphate oxygen isotopes requires the collection, purification, and isolation of inorganic phosphate (PO₄). Here, we provide a cross-discipline evaluation of the range of pre-processing techniques and best practices required to obtain pure PO₄ from diverse environmental matrices for δ¹⁸O_P analysis. This critical evaluation is intended to increase efficiency and accessibility for new and existing practitioners by serving as a centralized source of information for the most common matrices analyzed for δ¹⁸O_P, such as bioapatite, water, soil, sediment, plants, and rocks. New opportunities and methodological approaches are also identified to overcome current challenges and improve future applications of δ¹⁸O_P, thereby informing our understanding of the behavior, fate, and distribution of P in the environment.