Chlorophyll analysis at high precision and accuracy is limited by the lack of suitable, commercially available internal standards for HPLC analysis. Here, the commercially available dye zinc-phthalocyanine is presented as a new internal standard to quantify chlorophylls in vegetable foods and to detect chlorophyll degradation products. The technique was applied to chlorophyll analysis of a selection of vegetable foods. Pigments were extracted with N,N-dimethylformamide from the vegetables and purified by solid phase extraction. Chlorophyll a, a', b, b', corresponding pheophytins, and zinc-phthalocyanine were separated by HPLC using a C 1 8 reverse-phase column and fluorescence detection.