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Abstract

Polyunsaturated aldehydes (PUAs) are a group of microalgal metabolites that have attracted a lot of attention
due to their biological activity. Determination of PUAs has become an important routine procedure in
plankton and biofilm investigations, especially those that deal with chemically mediated interactions. Here
we introduce a fast and direct derivatization free method that allows quantifying PUAs in the nanomolar
range, sufficient to undertake the analysis from cultures and field samples. The sample preparation requires
one simple filtration step and the initiation of PUA formation by cell disruption. After centrifugation the
samples are ready for measurement without any further handling. Within one chromatographic run this
method additionally allows us to monitor the formation of the polar oxylipins arising from the cleavage of
precursor fatty acids. The robust method is based on analyte separation and detection using ultra high performance
liquid chromatography-atmospheric pressure chemical ionization mass spectrometry (UHPLC-APCI
MS) and enables high throughput investigations by employing an analysis time of only 5 min. Our protocol
thus provides an alternative and extension to existing PUA determinations based on gas chromatographymass
spectrometry (GC-MS) with shorter run times and without any chemical derivatization. It also enables
researchers with widely available LC-MS analytical platforms to monitor PUAs. Additionally, non-volatile
oxylipins such as x-oxo-acids and related compounds can be elucidated and monitored.