LC-MS based strategies for the comprehensive analysis of marine toxins in environmental and food matrices.

Microalgae are vitally important to marine ecosystems and most of the microalgal species are not harmful. However, an important number of species produces potent, heat-stable toxins. Concomitantly to harmful algal blooms (HAB), these toxins can be transferred to humans mainly through the food web but also through other exposure routes, such as aerosol and/or skin contact, or even cause mortality of aquatic organisms. These events result in adverse effects and sanitary problems, as well as in significant economic losses related to aquaculture, fishery and tourism sectors. Efficient analytical strategies are thus required to detect toxins in the environment and in food supply to the final aim of protecting human health and guaranteeing seafood safety and quality. Selection of the appropriate instrumental technique may be challenging because marine toxins are a heterogeneous group of structurally complex compounds, usually contained at sub-mg levels in complex matrices in the form of a wide array of different congeners. In addition, certified reference material of individual toxins is in some cases unavailable, which hampers full validation of analytical methods. The combination of liquid chromatography with mass spectrometry (LC-MS) is pointed by official organizations, such as the European Food Safety Authority (EFSA), as the most promising instrumental technique for the monitoring of marine toxins in the environment and in seafood. Several MS-based approaches employing either tandem MS or high resolution MSn have been developed so far for the detection of both the regulated and the emerging toxins, validated, and eventually used as an effective alternative to animal based methods in official monitoring of marine toxins in seafood. They allowed to disclose the presence of known and unknown toxins in the Mediterranean area and even to structurally characterize new congeners based on the interpretation of their fragmentation patterns. An overview of the different experimental strategies used to discover marine toxins, determine toxin profile and content of algal and mussel samples, and elucidate the structure of new low-, mid- and high-MW congeners will be presented. Although LC tandem MS proved useful to face most of the HAB-related outbreaks occurred so far due its high sensitivity, selectivity and reproducibility, in some cases it lacked in providing a comprehensive overview of the toxin profile of a real sample. That's where high resolution MSn played a key role, proving to be the most desirable approach to avoid underestimation of sample toxicity.