Total Phosphorus (P)

One of the more unique offerings of the S-LAB is the analysis of solid-phase phosphorus (P) in sediment, suspended particulate, and organic materials. The fact that P is an essential and potentially limiting nutrient for all organisms makes the lack of routine P analyses problematic for truly comprehensive studies of environmental biogeochemistry and ecology. The S-LAB conducts analysis of solid-phase P via the high-temperature ashing (HTA) method of Aspila et al. (1976). This method quantifies total P (TP) by ashing samples at high temperature in a muffle furnace in the presence of an oxidizing reagent, which converts combined organic P to inorganic phosphate (IP), and extracting the ashed residue in dilute acid. After separating the supernatant via centrifugation, it can be analyzed for phosphate via the AA3 autoanalyzer. Dilute acid extraction of unashed sample yields a measure of inorganic P, and organic P (OP) is calculated by difference (OP = TP - IP).

In addition to quantifying P in sediments, the HTA method can be used to quantify total dissolved P (TDP) in filtered waters by applying the method of Monaghan and Ruttenberg (1999), which is modeled after that of Solorzano and Sharp (1980). Dissolved organic P (DOP) is calculated as the difference between TDP and phosphate. The HTA method for TDP provides superior recovery over the more commonly used UV oxidation and persulfate methods in practice.


Asplia, K. I., H. Agemian, and A. S. Y. Chau. 1976. A semiautomatic method for the determination of inorganic, organic, and total phosphate in sediments. Analyst 101: 187197.

Monaghan, E.J., and Ruttenberg, K.C. 1999. Dissolved organic phosphorus in the coastal ocean: Reassessment of available methods and seasonal phosphorus profiles from the Eel River Shelf. Limnol. Oceanogr. 44)7). 1702-1714.

Solórzano, L., and J. H. Sharp. 1980. Determination of total dissolved phosphorus and particulate phosphorus in natural waters. Limnol. Oceanogr. 25: 754758.