In this report we outline a method to isolate phosphate as pure Ag3PO4 for waters with high C:P ratios for 18O analysis. This report details a method that can be used to minimise residual organic contamination of the final Ag3PO4, therefore significantly reducing uncertainties in the final interpretation of 18O results.
This includes the use of column resins in series to (i) remove the majority of dissolved organic carbon and (ii) isolate/pre-concentrate PO4. This is followed by the use of a modified McLaughlin et al (2004) method for PO4 precipitation, with an additional final hydrogen peroxide clean-up step to remove residual organic matter following precipitation of Ag3PO4. The reagents required for this method are first listed, and then a step-by-step account of the process is outlined. Importantly, it contains adequate detail to be used by other researchers in this field or modified to suit their particular research objectives
