title: Liquid chromatography/negative electrospray ionization ion trap MS(2) mass spectrometry application for the determination of microcystins occurrence in Southern Portugal water reservoirs.
abstract: Microcystins (MCs) are toxins produced by cyanobacteria which are common organisms in the phytoplankton of eutrophic lakes, rivers and freshwater reservoirs. In the present work, a novel method of liquid chromatography-electrospray ion trap tandem mass spectrometry (LC/ESI/Ion trap-MS/MS), operated in the negative ionization mode, was developed for the analysis of these cyanotoxins. The method was applied to determine the amounts of total microcystins-LR, -YR and -RR in two water reservoirs in Southern Portugal, namely Alqueva and Beliche. A total of 30 water samples were analysed along 2011. Solid phase extraction (SPE) was used for sample cleaning-up and analyte enrichment. The extracted toxins were separated on a C18 column with a gradient of acetonitrile/water with 0.1% formic acid. Detection of microcystins was carried out using multiple reaction monitoring (MRM) in the negative polarity mode, as this method gave a higher selectivity. The MC-RR, YR and LR quantification limits were 17.9, 31.7 and 15.8 ng/L, respectively; quite below the limits recommended by WHO guidelines for drinking water (1 μg/L). Total MC highest concentrations were found in the warm months of June, July and September in Alqueva sampling sites, with concentrations of MC LR and RR ranging 17-344 and 25-212 ng/L, respectively, showing comparable results for MC-RR and LR and slightly lower concentration of MC-YR. Detected values for Beliche reservoir were below quantification limits.
authors.affiliation: CIMA, FCT, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal.
authors.forename: M A
authors.initials: MA
authors.lastname: Rodrigues
authors.forename: M P
authors.initials: MP
authors.lastname: Reis
authors.forename: M C
authors.initials: MC
authors.lastname: Mateus
mesh_terms: D002138:Calibration; D002853:Chromatography, Liquid / Q000379:methods*; D000458:Cyanobacteria / Q000737:chemistry; D004784:Environmental Monitoring; D005618:Fresh Water / Q000737:chemistry; D060106:Lakes / Q000737:chemistry; D008387:Marine Toxins; D052998:Microcystins / Q000032:analysis*; D011174:Portugal; D045483:Rivers / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D053719:Tandem Mass Spectrometry / Q000379:methods*; D014871:Water Microbiology; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D008387:Marine Toxins; D052998:Microcystins; D014874:Water Pollutants, Chemical; C057862:cyanoginosin LR
keywords: Freshwater reservoirs; Ion trap spectrometer; LC–MS/MS; Microcystins; Water analysis