A High Accuracy and Simple Analytical Method for Microcystins Using ¹⁵N－labeled Microcystins

Abstract

Microcystins, cyclic heptapeptide hepatotoxins, are the most frequently detected from freshwater cyanobacteria around the world. WHO recommended a guideline value of microcystin-LR that the dosage should be below 1 µg ・ L -1 in drinking water. To monitor microcystins concentration in water, LC-MS/MS has been used. However, ionization efficiencies of internal standards are different from those of microcystins. As the results, the accuracy of microcystin determination is not enough for the monitoring.To improve the accuracy, we developed a simple and precise method using stable isotope ( 15 N)-labeled microcystin. As procedures, a frozen water-sample (0.5 mL) was thawed and added 15 N-labeled microcystin with 0.5 mL of MeOH. After ultra-sonication for 10 min of the treated sample, the sample solution was filtered using 0.22 µm membrane filter. The filtrate was injected to LC-MS/MS and quantified. The limit of quantification was around 0.1 µg ・ L -1 depended on the instrument sensitivity. Using this method, high accurate quantified results of microcystins in water sample were obtained.Keywords: Microcystin, LC-MS/MS, surrogate, 15 N-labeled microcystin, analysis Abbreviation:15 N-method, high accuracy and simple analytical method using 15 N-labeled microcystins.

Annamia dubia sp. nov. with a description of a new family, Geminocystaceae fam. nov. (Cyanobacteria)

“…Microcystins were analyzed as described (Sano et al 2016). Briefly, the fresh culture (0.2 ml) was mixed with 200 µl of methanol (MeOH) and sonicated in an ultrasonic bath for 10 min.…”

An Analytical Method for Simultaneous Measurement of Various Cyanotoxins Using Stable Isotope-Labeled Surrogates and a Microbial Flora Analysis to Assign Each Cyanotoxin to its Source

“…Later, we developed 15 N-labeled microcystins and an analytical method using those as surrogates. The method enables to correct the suppression of ionization during the analysis of individual microcystins, such as MC-LR, and sought to further simplify this method [12,13]. We have also proposed cleanup methods for CYN [14].…”