Atmospheric pressure chemical ionisation liquid chromatography/mass spectrometry of type II chlorophyll-a transformation products: Diagnostic fragmentation patterns

Atmospheric pressure chemical ionisation liquid chromatography/multistage mass spectrometry (APCI LC/MSn) is an ideal tool for the analysis of complex mixtures of natural compounds produced in the aquatic environment. In contrast to extensive reports of open chain (type II) chlorophyll (chl) transformation products (also known as chl catabolites) in terrestrial plants, there have been no reports relating to aquatic equivalents. This study examines the fragmentation pathways of type II chl transformation products from APCI LC/MSn analysis in order to determine whether it is a suitable analytical method for detecting and distinguishing among such compounds if they are present in samples from the aquatic environment. An extract from the medium of a laboratory culture of the alga Chlorella protothecoides was analysed and found to contain a number of structurally similar compounds assigned as being either red chlorophyll catabolites (RCCs) or fluorescent chlorophyll catabolites (FCCs). The five structures examined were found to exhibit one of three distinct fragmentation patterns, a result that highlights the potential of APCI LC/MSn for distinguishing among different type II chl transformation products.