LC-MS/MS Analysis of Cyanotoxins in Bivalve Mollusks—Method Development, Validation and First Evidence of Occurrence of Nodularin in Mussels (Mytilus edulis) and Oysters (Magallana gigas) from the West Coast of Sweden

Abstract

In this paper, an LC-MS/MS method for the simultaneous identification and quantification of cyanotoxins with hydrophilic and lipophilic properties in edible bivalves is presented. The method includes 17 cyanotoxins comprising 13 microcystins (MCs), nodularin (NOD), anatoxin-a (ATX-a), homoanatoxin (h-ATX) and cylindrospermopsin (CYN). A benefit to the presented method is the possibility for the MS detection of MC-LR-[Dha7] and MC-LR-[Asp3] as separately identified and MS-resolved MRM signals, two congeners which were earlier detected together. The performance of the method was evaluated by in-house validation using spiked mussel samples in the quantification range of 3.12–200 µg/kg. The method was found to be linear over the full calibration range for all included cyanotoxins except CYN for which a quadratic regression was used. The method showed limitations for MC-LF (R2 = 0.94), MC-LA (R2 ≤ 0.98) and MC-LW (R2 ≤ 0.98). The recoveries for ATX-a, h-ATX, CYN, NOD, MC-LF and MC-LW were lower than desired (<70%), but stable. Despite the given limitations, the validation results showed that the method was specific and robust for the investigated parameters. The results demonstrate the suitability of the method to be applied as a reliable monitoring tool for the presented group of cyanotoxins, as well as highlight the compromises that need to be included if multi-toxin methods are to be used for the analysis of cyanotoxins with a broader range of chemical properties. Furthermore, the method was used to analyze 13 samples of mussels (Mytilus edulis) and oysters (Magallana gigas) collected in the 2020–2022 summers along the coast of Bohuslän (Sweden). A complementary qualitative analysis for the presence of cyanotoxins in phytoplankton samples collected from marine waters around southern Sweden was performed with the method. Nodularin was identified in all samples and quantified in bivalve samples in the range of 7–397 µg/kg. Toxins produced by cyanobacteria are not included in the European Union regulatory monitoring of bivalves; thus, the results presented in this study can be useful in providing the basis for future work including cyanotoxins within the frame of regulatory monitoring to increase seafood safety.

Cyanotoxin Occurrence and Diversity in 98 Cyanobacterial Blooms From Swedish Lakes and the Baltic Sea

“…The detection of dcSTX at four sampling sites is the first report on its presence in surface waters in Sweden. The study further confirms that nodularin belongs in brackish water samples from the Baltic Sea, although it has recently also been detected in oysters from the west coast of Sweden [35].…”

“…In general, mass spectrometry (MS) based methods have become more commonly applied in the analysis of cyanotoxins in recent years compared to other techniques [29][30][31][32][33], where Ultra-Performance Liquid Chromatography (UPLC-MS/MS) has been most often preferred in the detection with quantification of cyanotoxins in various sample matrices [34][35][36][37].…”

Cyanotoxin Occurrence and Diversity in 98 Cyanobacterial Blooms from Swedish Lakes and the Baltic Sea

“…The detection of saxitoxin analogue decarbamoylsaxitoxin, dcSTX, at four sampling sites in this study is the first report on the presence of dcSTX in surface waters in Sweden. The study further confirms that nodularin belongs in brackish water samples from the Baltic Sea, although it was recently detected in oysters from the west coast of Sweden [35]. Although differences in toxicities of cyanotoxin congeners are known, there are no toxic equivalency factors (TEFs) that uniformly can be applied to adjust for the variation in their activity.…”

“…In general, mass spectrometry (MS)-based methods have become more commonly applied in the analysis of cyanotoxins in recent years compared to other techniques [29][30][31][32][33], where Ultra-Performance Liquid Chromatography (UPLC-MS/MS) has been most often preferred for detection with the quantification of cyanotoxins in various sample matrices [34][35][36][37].…”

Five Years Monitoring the Emergence of Unregulated Toxins in Shellfish in France (EMERGTOX 2018–2022)

“…España Amórtegui et al [ 67 ] investigated LC-MS/MS 17 cyanotoxins (13 MCs, NOD, ATX-a, h-ATX, CYN) in 13 mussel and oyster samples collected during the summers of 2020–2022 along the Bohuslän coast (Sweden). Nodularin was quantified in all shellfish samples analyzed in the range of 7–397 μg/kg.…”