It is difficult to measure the total amount of chlorophyll derivatives due to their variety. We applied a new method for comprehensive determination of all derivatives by ethylmethylmaleimide (EMMi) derived from chlorin which is a ring structure of chloropigments. Relationships between the amount of applied chloropigments and the yield of EMMi through the chromic acid oxidation were examined for three species of chloropigments. The yield of EMMi from chloropigments was almost constant regardless of the amount or pigment species, indicating the applicability of this method for comprehensive deterimination of chlorophyll derivatives.