Comparison of N,N-Dimethylformamide, Dimethyl Sulfoxide, and Acetone for Extraction of Phytoplankton Chlorophyll

Abstract

The suitability of N,N-dimethylformamide (DMF) for extraction and measurement of chlorophyll in phytoplantkon was evaluated and the extraction efficiencies of DMF, dimethyl sulfoxide (DMSO)-acetone and 90% acetone were compared. Absorbance spectra and specific absorption coefficients of chlorophylls a, b and c in DMF and 90% acetone are similar. Acidification of 100% DMF extracts of pure chlorophyll a and healthy algal cultures produced acid ratios of .apprx. 1.7. Equations derived from the extinction coefficients of chlorophylls in 90% acetone can be applied to DMF extracts. DMF and DMSO-acetone each extract chlorophyll from green and blue-green algae more effectively than does 90% acetone. DMF is a better extractant than is DMSO-acetone for chlorococcalean species, especially when pigment concentrations are high, but the difference, although significant, is slight. The 3 solvents are equally efficient in extracting chlorophyll from samples composed of chrysophytes and flagellated chlorophytes. The lack of grinding when using either DMF or DMSO-acetone is a considerable convenience. The potential for destabilized spectrophotometer readings and contamination of the investigator due to the incomplete mixing of DMSO and acetone is eliminated when pure DMF is used.