DETERMINATION OF TOTAL AND DISSOLVED PHOSPHORUS IN AGRICULTURAL RUNOFF SAMPLES BY INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY

Abstract

Leaching of nutrients to the drainage network is an important factor in polluting surface waters, with Phosphorus (P) often being the element of concern. Because P is strongly bound to sediments, different P fractions, including total, particulate and total dissolved P are now routinely measured. For the traditional determination of total P, a digestion followed by UV–Vis detection procedure was applied. The “true” total P content resulted from the digestion of a raw water sample containing suspended matter. Whereas the digestion performed to the sample after filtration through 0.45 μm membrane filter, gave the total dissolved P. The goal of this study was to measure the different fractions of P by ICP-MS. In the case of total P, no addition of coloring agents was necessary after the digestion process. Dissolved P was measured directly after filtration, without the previous digestion and no manipulation of the sample. Similar results were obtained by UV–Vis and by ICP-MS when measurements of demi water spiked with two different amounts of PO4 −3 were performed. Various agricultural runoff samples were digested with (NH4)2S2O8+H2SO4 30% (v/v) for total P determination. Again, similar results were obtained for both techniques. Three certified water samples from the Canadian National Water Research Institute were analyzed for dissolved P by ICP-MS. Beryllium and Sc were added as internal standards for possible drift corrections. Detection limits of 5 μg L−1 and linearity ranges from 10 μg L−1 to 5 mg L−1 were achieved.