TM25-01 Verification of segmented flow analyzer for the analysis of phosphorus and nitrogen by alkaline-persulfate digestion

This technical memorandum provides method verification data for determination of nitrogen and phosphorus by alkaline-persulfate digestion using source method Water Resources Investigation Report 03-4174 (Patton and Kryskalla, 2003). The instrumentation for analysis of phosphorus and nitrogen has been updated, but no changes in coding (method code, or lab codes) are necessary. Results from a paired sample study are provided to allow data users the ability to compare results from the new instrument and historical results. Comparison data indicate that stakeholders will experience little to no change in analytical results for acidified and unacidified nitrogen and phosphorus on the new analytical platform; however, the change in instrumentation will necessitate a change in the detection limit for phosphorus measured by alkaline persulfate digestion. The new instrument for determination of nitrogen and phosphorus by alkaline-persulfate digestion was implemented February 10, 2025.