THE USE OF LIQUID CHROMATOGRAPHY‐MASS SPECTROMETRY TO MONITOR THE ALLOMERIZATION REACTIONS OF CHLOROPHYLL a and PHEOPHYTIN a:m IDENTIFICATION OF THE ALLOMERS OF PHEOPHYTIN a

Abstract

Abstract— This paper reports a new method for monitoring the allomerization reactions of chlorophyll a and pheo‐phytin a. Complex mixtures are generated from illuminating pure compounds and monitored using both diode array high‐performance liquid chromatography (DAD‐HPLC) and liquid chromatography‐mass spectrometry (LC‐MS). LC‐MS allows molecular weight and fragment ion analysis of significant HPLC peaks. Five products of the degradation of chlorophyll a can be simultaneously detected in a mixture, namely the monohydroxy allomer, the methoxylactone allomer, pheophytin a and the two corresponding allomers of the pheophytin. It is demonstrated that more than one pathway must be involved in the in vitro photodegradation of chlorophyll a as shown by the simultaneous existence of several intermediates.