A wet-oxidation method for determination of particulate organic nitrogen on glass fiber and 0.2 μm membrane filters

A persulfate wet-oxidation method is presented for determining particulate organic nitrogen (PON) on 0.2 μm membrane filters. We evaluated the suitability of 6 types of membrane filters on the basis of filter blanks, chemical interference and adsorption characteristics. Concurrent comparisons were made using the bicinchoninic acid (BCA) protein assay. The 0.2 μm TF-200 teflon filters had low background N, no chemical interference with either assay, low N adsorption and a higher trapping efficiency than glass fiber filters (Whatman GF/F). A 20–90% increase in PON estimates for water off the coast of Oregon was found using 0.2 μm TF-200 filters compared with GF/F filters. Our results indicate that submicron PON may be a significant component of total N in seawater.