PIGMENT CONTAMINANTS IN POLYCARBONATE FILTERS

Membrane filters are often used to size fractionate phytoplankton when measuring biomass-specific production. Polycarbonate filters are repu ted to have the lowest extractables for membranes used for environment al analysis, however, we show that Nuclepore(R) polycarbonate filters contain a dye that co-extracts with algal pigments into methanol. The contaminating dye has characteristics similiar to those of pigments ex tracted from mixed populations of naturally occurring phytoplankton wh en measured spectrophotometrically. The dye can, however, be separated from the chlorophylls using high performance liquid chromatography. I n addition, the dye does not fluoresce and hence does not interfere wi th fluorometric analysis of chlorophyll a. The purpose of this note is to alert investigators to the presence of the contaminating pigment i n Nuclepore(R) polycarbonate filters which can be mistaken for algal p igments. Other brands, such as Poretics(R), do not contain the contami nant and could be used as an alternative.