Use of Poretics® 0.7 μm pore size glass fiber filters for determination of particulate organic carbon and nitrogen in seawater and freshwater

Poretics® glass fiber filters of 0.7 μm 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 μmol for Poretics® GF-75 filters, compared to 1.7 ± 0.7 and 0.19 ± 0.12 μmol for Whatman® 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® GF-75 filter is a suitable, cost effective, alternative to the widely used Whatman® GF/F filter.