[Verification and Improvement of an Official Method for Determining Chlorophyll Decomposition Products Including Pheophorbide].

The official method described in Direction Notification Kanshoku No. 99 （May 8, 1981） for the determination of chlorophyll decomposition products including pheophorbide was verified and improved in order to overcome several problems. Firstly, extraction with a mortar required improvement because of the difficulty of maintaining equal power for a long time. Secondly, the saturated sodium sulfate reagent caused a red-shift of the absorption maximum wavelength from the measured wavelength given in the official method; consequently, the absorption was decreased and a new absorption peak was detected around 729 nm. As a result, chlorophyll decomposition products including pheophorbide were underestimated. Lastly, it was impossible to make up the volume of the diethyl ether layer accurately to 20 mL before measuring the absorption. These points were improved in the modified method, and a validation test was performed. The mean recovery was 82.7％ and the within-laboratory reproducibility was 5.8％.