Aquatic soluble unreactive phosphorus: HPLC studies on concentrated water samples

Soluble unreactive phosphorus (SUP) in concentrated forest stream (Walker Branch, Tenn.) and lake water (Crystal Lake, Ill.) samples was analyzed with an anion-exchange high performance liquid chromatography (HPLC) system containing a phosphorus-specific detector. The detector, which utilized the ascorbic acid-molybdate reaction, consisted of a flow-injection system, a post-column reactor, and a u.v.-vis detector. Before HPLC analysis, samples were concentrated and molecular size fractionated with a series of ultrafiltration and reverse osmosis membranes. The SUP composition was found to be a function of season in both Crystal Lake and Walker Branch, as well as a function of stream length for Walker Branch. Seasonal and spatial SUP variations could be explained using contemporary knowledge of nutrient cycling in streams and lakes. A signal, seen in many of the HPLC traces and which eluted with the solvent front, was characterized but not fully identified using several extraction and degradation methods, as a function of sample concentration.