Determination of chlorophyll in plant samples by liquid chromatography using zinc-phthalocyanine as an internal standard

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 C₁₈ reverse-phase column and fluorescence detection.