A simple and efficient method for the solid-phase extraction of dissolved organic matter (SPE-DOM) from seawater

A simple protocol is presented for the solid-phase extraction of dissolved organic matter (SPE-DOM) from seawater using commercially prepacked cartridges. The method does not require major instrumentation and can be performed in the field. Modified styrene divinyl benzene polymer type sorbents ( Varian PPL and ENV) and sorbents of a silica structure bonded with different hydrocarbon chains ( Varian C8, C18, C18OH, and C18EWP) were considered. Except for C18OH, which heavily contaminated the samples, none of the sorbents leached significant amounts of dissolved organic carbon ( DOC) or nitrogen ( DON). Samples from the North Brazil shelf with strong mixing gradients of terrigenous and marine DOM were used to compare the various sorbents. PPL was the most efficient - on average, 62% of DOC was recovered as salt-free extracts. C18 was found to be most efficient among the silica-based sorbents, but it showed only two- thirds of the extraction efficiency of PPL. As indicated by [ H-1] NMR, C/ N, and delta C-13 analyses, PPL extracted a more representative proportion of DOM than C18. Therefore, PPL was used for comparative studies in the Gulf of Mexico and Antarctica. From brackish marsh and river waters, 65% and 62% of total DOC, respectively, could be extracted. For purely marine DOM in Antarctica and the deep sea, the extraction efficiency was lower ( 43% on average). The efficiency of the new method to isolate marine DOM is better than or similar to highly laborious methods. A further advantage is the complete desalination of the sample. The isolation of a major DOM fraction, which is salt- free, offers many possibilities to further characterize DOM by advanced analytical techniques.