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.

Warming Affects Growth Rates and Microcystin Production in Tropical Bloom-Forming Microcystis Strains

“…The hot methanol (MeOH) extraction in our study uses 75% MeOH, which is far above the recommended >40% to avoid adsorption to laboratory tools when working with MC-containing solutions [ 47 ]. Lack of or acceptable loss was also confirmed by recovery determinations using spiked cyanobacterial matrix for the MC variants [ 48 ].…”

Removal of the algal toxin microcystin‐LR in permeable coastal sediments: Physical and numerical models

“…However, our tank was exposed to light no more than several hours each day, with light intensity measured from 0.8 lux (lights off) to 407 lux (lights on) (Light Meter Model 407026, Extech Instruments). Sorption to glass tank walls likely contributes negligible MC‐LR loss at circumneutral pH, as Altaner et al () has demonstrated with glass labware. Some sorption to pipette tips could have occurred in both trials but would have affected each trial similarly.…”

“…We took multiple precautions to minimize the bias in our trials due to these effects. First, we used a glass tank and water was kept at circumneutral pH during both trials to prevent adsorption to tank walls, following recommendations by Altaner (). Second, the tank was located under bench space within a laboratory that was kept as dark as possible throughout the experiment.…”

“…MC-LR is known to sorb to plastics and glass (Metcalf et al 2000;Hyenstrand et al 2001a;Altaner et al 2017), as well as photodegrade (W€ ormer et al 2010). We took multiple precautions to minimize the bias in our trials due to these effects.…”

“…Harmful algal blooms (HABs) are increasing in intensity, frequency, and duration throughout the world, likely due to increasing water temperatures, runoff, and nutrient availability (Moore et al 2008;Michalak et al 2013). HAB presence negatively impacts human health, socioeconomic interests, and the aquatic environment (Anderson et al 2012). A recent survey of United States lakes indicated cyanobacteria presence in 98% and dominance in 76% of samples (U.S. Environmental Protection Agency 2009).…”