Species determination of selenium in marine plankton body fluid

The vertical distributions of Se(IV) and organic selenium in open sea are similar to those of nutrients. It was therefore considered that Se(IV) and organic selenium in sea water were supplied from the decomposition of marine biological material. In this study, marine planktons were used as biological material. Some pretreatment procedures were investigated for the chemical speciation of selenium in marine plankton samples. Selenium was determined by 2, 3-diaminonaphthalene (DAN) fluorometry. The interference of coexistent fluorescent materials for the fluorescence spectrum of 4, 5-piazselenol (Se-DAN complex) was effectively removed by back-extraction with concentrated nitric acid, followed by a wet-ashing method, and dilution with distilled water to 80 times the initial sample solution. The contents of selenium species in plankton body fluid changed with time. The sample pretreatment must therefore be carried out immediately after plankton thawing.