The Spectral Determination of Chlorophylls a and b, as well as Total Carotenoids, Using Various Solvents with Spectrophotometers of Different Resolution

Specific absorption (α) coefficients for individual carotenoids and chlorophylls a and b, as well as the E1%1cm values for combined carotenoids, have been (re)estimated using 6 solvents (80 % acetone, chloroform, diethyl ether, dimethyl formamide, dimethyl sulphoxide, and methanol) using 2 different types of spectrophotometer (0.1—0.5 nm and 1—4 nm band pass resolution). From these values, 2 sets of equations to calculate concentrations of chlorophyll a (Ca), chlorophyll b (Cb) and total carotenoids (Cx+c) in γg mL-1 for the different instrument types were freshly derived or confirmed from earlier publications. These were then tested with 3 different types of spectrophotometers (the two variable types plus 2 nm fixed resolution diode array) using equal aliquots of a mixed extract in the 6 different solvents. These showed that the concentrations and ratios derived by the 2 sets of equations were comparable when used with their own type of spectrophotometer but less so if the inappropriate equations were used. Measurements taken with the diode array spectrophotometer, however, did not give accurate concentrations or ratios of chlorophylls and carotenoids.