Stock ethanol in a second cuvette

A 15 ml centrifuge tube containing a sample of phytoplankton on a filter paper was collected, and the date and collection site of the sample were recorded. 8 ml of analytical grade ethanol was then added to the tube in a fume chamber after which the tube was wrapped in aluminum foil to prevent the disintegrThe chlorophyll extract was transferred into a 1-cm path length cuvette using a disposable pipetteation of chlorophyll by light. The tube was labeled appropriately, shaken vigorously, and placed in a test tube holder in the refrigerator for two hours to permit the extraction of chlorophyll into the ethanol. The sample was shaken intermittently in the course of the two-hour extraction period. The sample was centrifuged for 5 minutes to detach the filter paper from the chlorophyll extract. . Stock ethanol in a second cuvette was used as a blank to calibrate the spectrophotometer at a wavelength of 630 nm. The absorbance of the chlorophyll extract was then measured. A similar procedure was repeated to obtain the absorbance of the sample at wavelengths of 649, 665, and 750 nm.