Analytical techniques for monitoring harmful cyanobacteria in lakes

Abstract

The toxins of cyanobacteria include potent neurotoxins and hepatotoxins. Deaths after exposure by ingestion of cyanobacterial cells and toxins from freshwater sources have been reported. The hepatotoxins are cyclic peptides, which comprise microcystins (MC) and nodularin (NOD), and they cause poisonings with an established syndrome of human and animal illnesses. The identification and determination of these hepatotoxic peptides are challenges for analytical chemists. Methods based on solid phase extraction and size exclusion chromatography are available for the clean up of raw extracts. Both principles are also used for the enrichment of MC from low contaminated sample material. The separation of MC is achieved by high‐pressure liquid chromatography methods with ultraviolet (UV) detection or mass spectrometric detection. The unambiguous identification of MC not available as standards is possible by mass spectrometry (MS) or, under optimal conditions, by UV spectrometry using diode array detection. To date, 60 different MC and four NOD have been described, but new compounds are frequently identified. Therefore, powerful tools for the elucidation of the structure of unknown MC are an important need. In addition to classical methods for structure elucidation (e.g. nuclear magnetic resonance spectrometry), microwave‐assisted hydrolysis of cyclic peptides followed by enantio‐selective determination of the amino acid profiles can be used. More recently, MS with collision‐activated dissociation has become an important tool for obtaining structure information. The present paper discusses the advantages and disadvantages of the various analytical techniques used for monitoring of cyanobacteria in lakes, optimized or developed at the Institute of Nutrition, Jena, Germany. A pathway for handling MC‐containing samples with regard to different analytical tasks (i.e. the identification and elucidation of structure followed by qualitative and quantitative determination) is proposed.

Relevance of Intra- and Extracellular Cyanotoxins for Drinking Water TreatmentPaper presented in parts as a lecture at the annual meeting of the Water Chemical Society — a Division of the German Chemical Society (Wasserchemische Gesellschaft — Fachgruppe in der Gesellschaft Deutscher Chemiker), Bad Wildungen, May 2001.

“…The dominant cyanotoxin produced by this population of Planktothrix rubescens was identified by tandem-MS as a demethylated variant of microcystin-RR (m/z 1023) reported previously as [DAsp 3 ]-MC-RR or [Dha 7 ]-MC-RR[33]. 5 mg/L) containing cyanobacteria of the genera Planktothrix rubescens up to biovolumina of 10 mm³/L.…”

Nutrient concentrations in Nyanza Gulf, Lake Victoria, Kenya: light limits algal demand and abundance

“…According to Hecky (2000), P enrichment of Lake Victoria waters will rapidly lead to nuisance algal blooms through positive feedback effects of increased P availability and denitrification favored by declining oxygen concentration. The increased dominance of cyanobacteria in the gulf will negatively impact on the water quality as this group of algae is known to have species that produce phycotoxins which can both cause fish kills and compromise the drinking water quality (Bugenyi & Magumba, 1996;Hummert et al, 2001;Kling et al, 2001;Krienitz et al, 2001), and it is possible that toxins also played a role in the death of fish during the blooms reported by Ochumba (1990). In the last four decades dissolved silica has become depleted in Lake Victoria (Hecky & Bugenyi, 1992;Hecky, 1993;Vershuren et al, 1998).…”

Development and validation of a liquid chromatography–tandem mass spectrometry assay for the simultaneous quantitation of microcystin-RR and its metabolites in fish liver

“…In LC-ESI-ITMS analysis the most intense ions of analytes are doubly charged ([M+H] 2+ at m/z 673.61, 580.56 and 520.05), which is typical for MCs containing two Arg residues [25,26], as well as its metabolites formed via addition of GSH and Cys. The [M+2H] 2+ at m/z 673.6 and 580.6 were then used as precursor ion for a production MS/MS scan.…”