An improved method for determining phytoplankton chlorophyll a concentration without filtration

The common and routine procedure for the quantification of chlorophyll a (chl a) in aquatic studies has a series of steps. Here, we sought to find optimal conditions for phytoplankton cell harvesting, chl a extraction, and chl a measurement and calculation, to find an effective, cost-saving, safe, and environment-friendly procedure for determining phytoplankton chl a concentration. We replaced the traditional GF/C filters with inorganic polymer flocculants (IPFs) and clay for phytoplankton harvesting, and then various solvents (acetone, ethanol, DMF, and DMSO), IPFs (PAC, PFS, and PAFS) and clay were tested for their suitability for chl a extraction, with or without homogenization at different temperatures for different extraction durations. About 0.3-1.0 g l(-1) of PAC or PFSA combined with 1.0-2.5 g l(-1) clay were found to provide optimal conditions in terms of yield and cost for phytoplankton cell harvesting from water samples. Based on our results, we recommend flocculation and centrifugation instead of glass-fiber membrane filtration for harvesting phytoplankton cells from environmental water samples, 95% ethanol for chl a extraction without homogenization and heating, and spectrophotometry to determine chl a concentration.The common and routine procedure for the quantification of chlorophyll a (chl a) in aquatic studies has a series of steps. Here, we sought to find optimal conditions for phytoplankton cell harvesting, chl a extraction, and chl a measurement and calculation, to find an effective, cost-saving, safe, and environment-friendly procedure for determining phytoplankton chl a concentration. We replaced the traditional GF/C filters with inorganic polymer flocculants (IPFs) and clay for phytoplankton harvesting, and then various solvents (acetone, ethanol, DMF, and DMSO), IPFs (PAC, PFS, and PAFS) and clay were tested for their suitability for chl a extraction, with or without homogenization at different temperatures for different extraction durations. About 0.3-1.0 g l(-1) of PAC or PFSA combined with 1.0-2.5 g l(-1) clay were found to provide optimal conditions in terms of yield and cost for phytoplankton cell harvesting from water samples. Based on our results, we recommend flocculation and centrifugation instead of glass-fiber membrane filtration for harvesting phytoplankton cells from environmental water samples, 95% ethanol for chl a extraction without homogenization and heating, and spectrophotometry to determine chl a concentration