Improving quantification of particulate phosphorus

Abstract

AbstractTotal particulate phosphorus (TPP) is often determined using the high‐temperature dry combustion (HTDC) method followed by hydrolysis of the ash and then molybdenum colorimetry. Here, we show that a higher than traditionally used combustion temperature, 800°C vs. 450–550°C, improves phosphorus recovery from several phosphorus standard compounds, marine phytoplankton cultures, and particulate samples from the field. The ashing auxiliary MgSO4 further improves P recovery by improving decomposition, reducing volatilization during combustion, and increasing the efficiency of hydrolysis. A 0.2 M HCl hydrolysis, under 90°C for 30 min yields a higher P recovery compared with hydrolysis at room temperature or 60°C. In aggregate, these improvements to the method double the P recovery from phospholipids to 97%. TPP recovery from laboratory phytoplankton cultures and field samples increased an average of 11%, primarily due to the improvements in P recovery from phospholipids, polyphosphate, and nucleic acids. We refer to this new method as the eXtra high temperature dry combustion (X‐HTDC) Ash/Hydrol method and recommend its application for measuring particulate phosphorus from organic compounds in aquatic systems.