There are many protocols available for calculating pigment c on tent using the well known and widely used text :the chemistry and biochemistry of plant pigments, by Goodwin, 1965. we have been using this text for years with excellent results.
Extract the fresh material with 80% acetone, then centrifuge the extract for 5min. take the clear extract and measure the absorbance at 645 and 663nm.using spectrophotometer. then calculate the concentration of chlorophyll a,b and total chlorophyll using the following formula: mg /l chlorophyll a=12.7xO.D.663-2.69xO.D.645
mg/l chlorophyll b= 22.9xO.D.645-4.68xO.D.663
mg/l total chlorophyll=20.2xO.D.645+18.2xO.D.663
Then you get rid of the liter by dividing the product on1000,you will be left with mg,then you could express the results as you like, for example mg per 100 mg fresh weight.