Date of Award
Doctor of Philosophy
Dr. Kevin J. James
The most frequently found cyanobacterial toxins in blooms from fresh and brackish waters are the cyclic peptide microcystins (MCs) and nodularin family. These toxins cause fatal poisonings of agricultural livestock, wild animals, birds and fish on a worldwide basis. The involvement of these toxins in human health problems has also been inferred in several countries and their presence in drinking water sources is of interest to the drinking water industry.
One of the biggest problems in the analysis of MCs is the lack of commercially available standards to be used for the identification and characterisation of these cyanobacterial toxins. One way to overcome this problem could be the use of LC-MSn methods. On this context, making use of mass spectrometry techniques, quadrupole ion trap and hybrid quadrupole time-of flight, the fragmentation pathway of the six commercially available MCs and nodularin was described by assigning the different ions found in the MSn spectra. The objective of this study is to allow an easier characterisation and identification of those non-commercially available MCs. Furthermore, several new product ions were found and identified for each of these microcystins and nodularin and some different structures were suggested for those product ions already published.
Traditionally prior to the analysis of MCs, and other freshwater algal toxins, rigorous sample preparation has been required. Most commonly solid phase extraction (SPE) protocols have been used. These SPE methods are tedious, often specific to particular manufacturer sorbents, offer variable rates of recovery for MCs, and there can be a lot of operator know-how involved in the successful day-to-day operation of methods. An alternative method that can provide a sample suitable for high performance liquid chromatography mass spectrometric (LC/MS) analysis in a matter of minutes was developed. During these studies a multiple reaction monitoring (MRM) methodology was developed for a suite of MCs on a triple quadrupole mass spectrometer for the analysis of MCs in freshwater samples.
Ortea, Paloma Muniz, "Elucidation of the Mass Spectral Fragmentation Pathways of Cyclic Hepatopeptides Microcystins" (2005). Theses [online].
Available at: https://sword.cit.ie/allthe/670