Chlorophyll a extraction from freshwater algae — a reevaluation

In this study, two extracting methods (sonication and dispersing) and three solvents (90% acetone, N,N′-dimethylformamide and methanol) were compared for their ability to extract chlorophyll a of freshwater phytoplankton. Measurements were performed with both spectrophotometry and high-performance liquid chromatography. Results showed that (i) cell disruption is essential and that (ii) the method of cell disruption and solvent applied differed significantly. Dispersing in acetone surpassed all other combinations. Sonication in N,N′-dimethylformamide was found less effective. N,N′-dimethylformamide and methanol seem to promote the formation of degradation products (chlorophyllide a, allomer, epimer and phaeophytin a) which lead to overestimates of chlorophyll a of about 10% by means of spectrophotometry.