Use of Poretics(R) 0.7 mu m pore size glass fiber filters for determination of particulate organic carbon and nitrogen in seawater and freshwater

Poretics(R) glass fiber filters of 0.7 mu m nominal pore size (GF-75) were evaluated for determination of particulate organic carbon and nitrogen in seawater and freshwater. Carbon and nitrogen blanks determined by CHN analysis of precombusted 25 mm filters were, respectively, 0.8 +/- 0.3 and 0.02 +/- 0.01 mu mol for Poretics(R) GF-75 filters, compared to 1.7 +/- 0.7 and 0.19 +/- 0.12 mu mol for Whatman(R) GF/F filters. These results suggest that GF-75 filters are characterized by lower blanks and better analytical precision for determination of carbon and nitrogen than GF/F filters. Comparable POC and PON concentrations were obtained using GF-75 and GF/F filters on paired analyses of samples from the Gulf of Maine, Narragansett Bay, and a freshwater creek. Depth profiles of POC and PON determined using GF-75 filters are presented for the Gulf of Maine and the Canada Basin, Arctic Ocean. Results reported in this study demonstrate that the Poretics(R) GF-75 filter is a suitable, cost effective, alternative to the widely used Whatman(R) GF/F filter. (C) 1997 Elsevier Science B.V.