- Acknowledgements: The authors gratefully acknowledge the financial support of the Spanish Ministry of Science, Innovation and Universities (Project Ref.: RTI2018-097043-B-I00). Maryam Hemmati thank Semnan University as well as Ministry of Science, Research, and Technology of Iran for endowment of the predoctoral fellowship. FJL is grateful for personal funding through the Special Research Program of the University of Granada. The authors gratefully acknowledge also Luciano Vílchez for the provision of the saline water samples analyzed in this study and John Ray for English revision.
- Authors: M. Hemmati, C. Tejada-Casado, F.J. Lara, A.M. García-Campaña, M. Rajabi, M. del Olmo-Iruela.
- Reference: Journal of Chromatography A 1608 (2019) 460409.
In this study two different analytical approaches have been developed to determine the presence of several cyanotoxins in saline water samples from a continental salt marsh. A salting-out assisted liquid-liquid extraction (SALLE) has been used in combination with ultra-high performance liquid chromatography-tandem mass spectrometry and UV-diode array detection (UHPLC-MS/MS and UHPLC-DAD). The target analytes are eight microcystins named MC-RR, MC-YR, MC-LR, MC-WR, MC-LA, MC-LY, MC-LW, MC-LF and nodularin (NOD), covering a wide range of polarities. The separation was achieved using a Zorbax Eclipse Plus RRHD C18 column (50 × 2.1 mm, 1.8 μm) in less than 7.5 and 5.5 min for UV and MS/MS detection, respectively. The mobile phase used consisted of water (solvent A) and acetonitrile (MeCN) (solvent B), both containing 0.01% of formic acid for DAD and 0.4% of formic acid for MS/MS detection, at a flow rate of 0.4 mL min−1. The temperature of the column was set at 25 °C and 20 μL of sample were injected. The main parameters affecting the SALLE procedure were studied and the following optimum values were obtained: neutral pH, 2 mL of acetonitrile as extraction solvent and 1.2 g of ammonium sulfate as salting-out agent for 4 mL of water sample. The validation protocols for both methods were accomplished with real water samples obtaining LODs ranging from 1.0 to 3.4 μg L−1 and 0.02 to 0.11 μg L−1 for DAD and MS/MS respectively. Although the SALLE-UHPLC-DAD methodology is easier and cheaper than UHPLC-MS/MS significantly better detection limits were achieved with tandem mass spectrometry as well as allowing for unambiguous identification. Extraction recoveries were higher than 77.0% (except for MC-RR and NOD which were 53.2% and 54.3, respectively) with satisfactory inter-day and intra-day precisions (RSD below 13.3%).
