Spectrophotometric method of controlled pheophytinization for the determination of both chlorophylls and pheophytins in plant extracts

Conventional spectrophotometric methods of chlorophyll (Chl) measurement with double-wavelength readings of absorbances corresponding to the peak values of both Chl a and Chl b are usable only is pheophytins (Pheo) are absent in the pigment extract. We present here a kinetic method of controlled phenophytinization of the Chl present in acetone/water ( 90 10 , v v ) exctracts that allows the measurement of both Chl a and b, as well as of the initial Pheo preexisting in the plant material at the moment of the extraction. This method gives better accuracy in Chl b determination than conventional methods, particularly when Chl a Chl b ratios are greater than 5. Examples are given illustrating the usefulness of this method.