title: Rapid quantitative analysis of microcystins in raw surface waters with MALDI MS utilizing easily synthesized internal standards.
abstract: The freshwater cyanotoxins, microcystins (MCs), pose a global public health threat as potent hepatotoxins in cyanobacterial blooms; their persistence in drinking and recreational water has been associated with potential chronic effects in addition to acute intoxications. Rapid and accurate detection of the over 80 structural congeners is challenged by the rigorous and time consuming clean up required to overcome interference found in raw water samples. MALDI-MS has shown promise for rapid quantification of individual congeners in raw water samples, with very low operative cost, but so far limited sensitivity and lack of available and versatile internal standards (ISs) has limited its use. Two easily synthesized S-hydroxyethyl-Cys(7)-MC-LR and -RR ISs were used to generate linear standard curves in a reflectron MALDI instrument, reproducible across several orders of magnitude for MC-LR, -RR and -YR. Minimum quantification limits in direct water samples with no clean up or concentration step involved were consistently below 7 μg/L, with recoveries from spiked samples between 80 and 119%. This method improves sensitivity by 30 fold over previous reports of quantitative MALDI-TOF applications to MCs and provides a salient option for rapid throughput analysis for multiple MC congeners in untreated raw surface water blooms as a means to identify source public health threats and target intervention strategies within a watershed. As demonstrated by analysis of a set of samples from Uruguay, utilizing the reaction of different MC congeners with alternate sulfhydryl compounds, the m/z of the IS can be customized to avoid overlap with interfering compounds in local surface water samples.
authors.affiliation: Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
authors.forename: Amber F
authors.initials: AF
authors.lastname: Roegner
authors.affiliation: Cátedra de Bioquímica, Facultad de Química, Universidad de la República, Montevideo, Uruguay; Cátedra Inmunología, Facultad de Química, Universidad de la República, Instituto de Higiene, Montevideo, Uruguay.
authors.forename: Macarena Pírez
authors.initials: MP
authors.lastname: Schirmer
authors.affiliation: Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
authors.forename: Birgit
authors.initials: B
authors.lastname: Puschner
authors.affiliation: Cátedra de Bioquímica, Facultad de Química, Universidad de la República, Montevideo, Uruguay.
authors.forename: Beatriz
authors.initials: B
authors.lastname: Brena
authors.affiliation: Cátedra Inmunología, Facultad de Química, Universidad de la República, Instituto de Higiene, Montevideo, Uruguay. Electronic address: ggonzal@fq.edu.uy.
authors.forename: Gualberto
authors.initials: G
authors.lastname: Gonzalez-Sapienza
mesh_terms: D005618:Fresh Water / Q000737:chemistry*; D057097:Harmful Algal Bloom; D052998:Microcystins / Q000032:analysis* / Q000737:chemistry; D015394:Molecular Structure; D012015:Reference Standards; D012680:Sensitivity and Specificity; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D014583:Uruguay; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D052998:Microcystins; D014874:Water Pollutants, Chemical
keywords: Cyanobacterial blooms; Cyanotoxins; Internal standards; Microcystins; Quantitative MALDI-TOF