title: Adsorption of Ten Microcystin Congeners to Common Laboratory-Ware Is Solvent and Surface Dependent.
abstract: Cyanobacteria can produce heptapetides called microcystins (MC) which are harmful to humans due to their ability to inhibit cellular protein phosphatases. Quantitation of these toxins can be hampered by their adsorption to common laboratory-ware during sample processing and analysis. Because of their structural diversity (>100 congeners) and different physico-chemical properties, they vary in their adsorption to surfaces. In this study, the adsorption of ten different MC congeners (encompassing non-arginated to doubly-arginated congeners) to common laboratory-ware was assessed using different solvent combinations. Sample handling steps were mimicked with glass and polypropylene pipettes and vials with increasing methanol concentrations at two pH levels, before analysis by liquid chromatography-tandem mass spectrometry. We demonstrated that MC adsorb to polypropylene surfaces irrespective of pH. After eight successive pipet actions using polypropylene tips ca. 20% of the MC were lost to the surface material, which increased to 25%-40% when solutions were acidified. The observed loss was alleviated by changing the methanol (MeOH) concentration in the final solvent. The required MeOH concentration varied depending on which congener was present. Microcystins only adsorbed to glass pipettes (loss up to 30% after eight pipet actions) when in acidified aqueous solutions. The latter appeared largely dependent on the presence of ionizable groups, such as arginine residues.
authors.affiliation: Human and Environmental Toxicology, University of Konstanz, P.O. Box 662, 78457 Konstanz, Germany. Stefan.altaner@uni-konstanz.de.
authors.forename: Stefan
authors.initials: S
authors.lastname: Altaner
authors.affiliation: Cawthron Institute, Private Bag 2, Nelson 7010, New Zealand. jonathan.puddick@cawthron.org.nz.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Puddick
authors.affiliation: Environmental Research Institute, University of Waikato, Private Bag 3105, Hamilton 3240, New Zealand. susie.wood@cawthron.org.nz.
authors.forename: Susanna A
authors.initials: SA
authors.lastname: Wood
authors.affiliation: Human and Environmental Toxicology, University of Konstanz, P.O. Box 662, 78457 Konstanz, Germany. Stefan.altaner@uni-konstanz.de.
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Dietrich
mesh_terms: D000327:Adsorption; D004864:Equipment and Supplies; D005898:Glass / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007753:Laboratories; D000432:Methanol / Q000737:chemistry; D052998:Microcystins / Q000737:chemistry*; D011126:Polypropylenes / Q000737:chemistry; D012997:Solvents / Q000737:chemistry; D013499:Surface Properties; D014867:Water / Q000737:chemistry
chemical_list: D052998:Microcystins; D011126:Polypropylenes; D012997:Solvents; D014867:Water; D000432:Methanol
keywords: acidification; cyanobacteria; cyanotoxin; glass; liquid chromatography-tandem mass spectrometry; polypropylene; sample handling; sample loss