There are many methods to measure chlorophyll a on 2-3 ml of cultures (see MacIntyre and Cullen 2005, below for examples); for rapid monitoring of cultures we use the following.

Using a fluorometer with a non-acidification filter set (c.f. Welsmeyer 1994), pipet 100 microliter of culture directly into ~2ml of acetone:DMSO mix (e.g. MacIntyre and Cullen 2005 ). Extract for 15 minutes at room temperature before measurement (though be careful some algae may require more). We vortex before the measurement.

Note: The acetone:DMSO volume required will largely depend on the geometry of the fluorometer/measuring vial, so different volumes must be tested on each system (e.g. by increasing the volume until the measurement remains stable with increasing volumes). The ratio of culture to the acetone:DMSO mix should not be increased much from the above as it may lead to high variability.

References

Welschmeyer, N A. "Fluorometric Analysis of Chlorophyll a in the Presence of Chlorophyll B and Pheopigments." Limnology and Oceanography (1994)

MacIntyre, H L, and J J Cullen. "Using Cultures to Investigate the Physiological Ecology of Microalgae." In Algal Culturing Techniques. Edited by R M Anderson. Academic Press, 2005