Liquid Chromatography–Tandem Mass Spectrometry Method for the Screening of Eight Paralytic Shellfish Poisoning Toxins, Domoic Acid, 13-Desmethyl Spirolide C, Palytoxin and Okadaic Acid in Seawater

Simultaneous determination of trace marine lipophilic and hydrophilic phycotoxins in various environmental and biota matrices

An efficient and sensitivity approach, which combines solid-phase extraction or ultrasonic extraction for pretreatment, followed by ultra-performance liquid chromatography-tandem mass spectrometry, has been established to simultaneously determine eight lipophilic phycotoxins and one hydrophilic phycotoxin in seawater, sediment and biota samples. The recoveries and matrix effects of target analytes were in the range of 61.6-117.3 %, 55.7-121.3 %, 57.5-139.9 % and 82.6 %-95.0 %, 85.8-106.8 %, 80.7 %-103.3 % in seawater, sediment, and biota samples, respectively. This established method revealed that seven, six and six phycotoxins were respectively detected in the Beibu Gulf, with concentrations ranging from 0.14 ng/L (okadaic acid, OA) to 26.83 ng/L (domoic acid, DA) in seawater, 0.04 ng/g (gymnodimine-A, GYM-A) to 2.75 ng/g (DA) in sediment and 0.01 ng/g (GYM-A) to 2.64 ng/g (domoic acid) in biota samples. These results suggest that the presented method is applicable for the simultaneous determination of trace marine lipophilic and hydrophilic phycotoxins in real samples.

Marine toxins in seafood: Recent updates on sample pretreatment and determination techniques

Marine toxins can lead to varying degrees of human poisoning, often resulting in fatal symptoms and causing significant economic losses in seafood-producing regions. To gain a deeper comprehension of the role of marine toxins in seafood and their impact on the environment, it is imperative to develop rapid, cost-effective, environmentally friendly, and efficient methods for sample pretreatment and determination to mitigate adverse impacts of marine toxins. This review presents a comprehensive overview of advancements made in sample pretreatment and determination techniques for marine toxins since 2017. The advantages and disadvantages of various technologies were critically examined. Additionally, the current challenges and future development strategies for the analysis of marine toxins are provided.

Oriented-aptamer encoded magnetic nanosensor with laser-induced fluorescence for ultrasensitive test of okadaic acid

Okadaic acid (OA) biotoxin acts a well-established inhibitor of protein phosphatase even a tumor promoter of human being, arouse great attention in safety monitoring. However, the powerful and convenient nanosensing technologies for addressing the demands such as rapidity, high sensitivity, and stability in the in-field test of OA shellfish toxin is still scarce. Herein, a high-performance magnetic biometric nanosensor (MBNS) integrating oriented aptamers and ultrasensitive laser-induced fluorescence (LIF) was firstly proposed for the in-field detection of trace OA in seafoods. High-density aptamers hybridized with FAM-labeled cDNA were tethered to the surface of AuNPs on magnetic MIL-101@Fe3O4, and then finely regulated by mercaptohexyl alcohol (MCH) to be orderly assembled, as was successfully utilized to engineer an active biological nanosensor for highly specific recognition of OA. Aptamers anchored on magnetic Fe3O4@MOF@AuNPs activate a biometric microreactor of OA, in which the superior LIF properties, conformation regulation of aptamer, and the specific recognition using aptamer genes were adopted. The magnetic nanosensor with an excellent specificity and super sensitivity for OA analysis was achieved within 20 min. Moreover, the content of captured OA could facilely be recorded by measuring the fluorescence intensity, and the limit of detection (LOD) and limit of quantitation of OA (LOQ) reached 0.015 and 0.050 ng/mL respectively, which was far better than most aptamer-based biometric sensing methods. The feasibility for accurate test of trace OA toxin in the fortified shellfish samples was validated with the recovery yields of 88.2-107.5% and RSD of 0.5-7.6%, respectively. The result demonstrated that the oriented-aptamer encoded MNS had significant practical values in rapid and ultrasensitive detection of OA biotoxin and the related safety applications.

Detection, occurrence, influencing factors and environmental risks of paralytic shellfish toxins in seawater in a typical mariculture bay

Paralytic shellfish toxins (PSTs) producing algae are widely distributed in the global coastal aquatic environment, posing a threat to coastal ecosystem health and mariculture safety. However, the levels and potential environmental risks of PSTs frequently detected in shellfish remain largely unexplored in seawater of mariculture zones. In this study, a new method for trace detection of 13 common PSTs (<1.0 ng/L) in seawater was established based on off-line solid phase extraction (SPE) and on-line SPE-liquid chromatography-tandem mass spectrometry (on-line SPE-LC-MS/MS), and a systematic investigation of PSTs in seawater of the Laizhou Bay, a typical aquaculture bay in China, was conducted to understand their pollution status, environmental impact factors and ecological risks for the first time. Eleven PSTs were detected in the seawater of Laizhou Bay with total concentrations ranging from 0.75 to 349.47 ng/L (mean, 176.27 ng/L), which indicates the rich diversity of PSTs in the mariculture bay and demonstrates the reliability of the proposed analytical method. C1, C2, GTX2, GTX3, dcGTX2, and dcGTX3 were found to be the predominant PSTs, which refreshed the knowledge of PST contamination in the coastal aquatic environment. PST levels in seawater exhibited the highest levels in the southeastern mouth of Laizhou Bay and decreased toward the inner bay. Correlation analyses showed that climatic factors, nutrient status and hydrological conditions had significant effects on the distribution of PST in mariculture bay. Preliminary environmental risk assessments revealed that aquatic organisms throughout the waters of Laizhou Bay are at risk of chronic PST toxicity. These findings imply that the risk of PST in seawater of mariculture bay has previously been grossly underestimated, and that the coastal aquatic environment in North China and even the world may be at more serious risk of PST pollution, which should be taken seriously.

Trace determination of multiple hydrophilic cyanotoxins in freshwater by off- and on-line solid phase extraction coupled to liquid chromatography-tandem mass spectrometry

Hydrophilic cyanotoxins (HCTs), such as paralytic shellfish toxins (PSTs), anatoxin-a (ATX-a), and cylindrospermopsin (CYN) are highly toxic and toxin-producing algae are widely distributed worldwide. However, HCTs, especially PSTs, are rarely reported in freshwater due to analytical limitations. This may result in an underestimation of the ecological risks and health risks. This study developed a new method to detect ATX-a, CYN, and thirteen common PSTs in freshwater simultaneously by using off-line solid phase extraction (SPE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). The limits of detection (LODs) of all targets were lower than 0.05 μg/L, which could meet the regulatory requirements for monitoring of HCTs in drinking water in different countries and regions. To improve the detection sensitivities for trace PSTs, a method based on off-line SPE and on-line SPE-LC-MS/MS was established with LOD around 0.001 μg/L. GTX1&4, GTX2&3, and GTX5 were detected in freshwater in China for the first time, highlighting that overall communities are facing potential risks of exposure to various PSTs in China. High concentrations of ATX-a and CYN were also detected in freshwater from Northern China. The proposed method helps to understand the pollution status of HCT in water bodies, especially during the non-algal bloom period.

Core-shell structured magnetic covalent-organic frameworks for rapid extraction and preconcentration of okadaic acid in seawater and shellfish followed with LC-MS/MS quantification

Core-shell structured magnetic covalent-organic frameworks (Fe₃O₄@TaTp) were facilely synthesized based on one-step functionalization at room temperature and applied for magnetic solid-phase extraction of okadaic acid from seawater and shellfish prior to LC-MS/MS detection. Parameters, including adsorbent amount, extraction time, desorption solution, and desorption time which could affect the extraction efficiency, were respectively investigated. The developed methods demonstrated good linearity (R² > 0.99), acceptable accuracy and good precision (<15%), and low limit of detection (0.5 pg·mL^-1 for seawater and 0.04 µg·kg^-1 for shellfish). The amount of the material used (1 mg for seawater and 5 mg for shellfish) and the time required (4 min for seawater and 15 min for shellfish) for extracting analyte from 5 mL of seawater and 2 g of shellfish are both greatly shortened compared with the previous reports. In addition, we successfully applied this method to real sample analysis.

Simultaneous Pre-Concentration and HPLC-MS/MS Quantification of Phycotoxins and Cyanotoxins in Inland and Coastal Waters

The purpose of this study was to set up a sensitive method for the simultaneous determination of phycotoxins and cyanotoxins-Emerging pollutants with different structures and harmful properties (hepatotoxicity, neurotoxicity and cytotoxicity)-In environmental waters. Due to the low concentrations detected in these samples, a pre-concentration step is required and here it was performed in a single step with a commercial cartridge (Strata™-X), achieving enrichment factors up to 200 and satisfactory recovery (R = 70-118%) in different aqueous matrices. After solid-phase extraction (SPE), toxins were separated and quantified by High Performance Liquid Chromatography- Heated ElectroSpray Ionisation Tandem Mass Spectrometry (HPLC-HESI-MS/MS) in Multiple Reaction Monitoring (MRM) mode. An analytical evaluation of the proposed method was done based on the analytical figures of merit, such as precision and trueness, linearity, selectivity, and sensitivity, and it turned out to be a robust tool for the quantification of ng L^-1 levels, phycotoxins and cyanotoxins in both freshwater and saltwater samples.

Monitoring and warning of lipophilic marine algal toxins in mariculture zone based on toxin profiles of phytoplankton

Some toxigenic dinoflagellates can produce lipophilic marine algal toxins (LMATs), which are potent threats to marine breeding industries. In this study, a new method based on the profiling analysis of six LMAT classes in phytoplankton was developed for the monitoring and warning of LMATs in mariculture zones. This method was applied to monitor and evaluate LMATs in the Jiaozhou Bay and the Changjiang estuary in China. Results demonstrated that the occurrence and spatiotemporal variations of LMATs in mariculture zones can be revealed by the toxin profiles of phytoplankton, indicating the method's effectiveness for the comprehensive monitoring of the composition and levels of various LMATs in coastal aquaculture zones. The method was further used as an alarm for potential pollution risk from LMATs in mariculture zones at an early stage. The "alert" thresholds of LMAT pollution in the mariculture zones were preliminarily proposed based on the statistical data analysis of LMATs in phytoplankton in three typical mariculture areas in China. This study is the first to conduct simultaneous monitoring and warning of multi-class LMATs based on toxin profiles of phytoplankton, thereby providing new insight into the monitoring and early warning of natural poisonous pollutants in coastal aquaculture zones around the world.

l-Cysteine-modified magnetic microspheres for extraction and quantification of saxitoxin in rat plasma with liquid chromatography and tandem mass spectrometry

Saxitoxin, which is one of the most typical paralytic shellfish poisoning toxins, ranks the highest intoxication rate of marine biological poisoning cases globally. Efficient clean-up and extraction of saxitoxin from complex biological matrices are imperative for the analysis and concentration monitoring of the toxin when correlative poisoning cases happen. Herein, l-cysteine-modified magnetic microspheres based on metal-organic coordination were synthesized by a facile approach and applied for magnetic solid-phase extraction of saxitoxin from rat plasma samples before liquid chromatography-tandem mass spectrometry detection. Parameters, including adsorbent amount, extraction time, desorption solution, and desorption time that could affect the extraction efficiency, were respectively investigated. The developed method demonstrated good linearity in the range of 5-300 ng/mL (R²  = 0.9985) with a limit of quantification of 5 ng/mL and a limit of detection of 0.5 ng/mL, acceptable accuracy. and precision of within-run and between-run.

Validated HPLC-MS/MS Method To Quantify Low Levels of Domoic Acid in Plasma and Urine after Subacute Exposure

Domoic acid (DA) is a marine neurotoxin produced by several species of Pseudo-nitzschia. DA causes severe neurological toxicity in humans and animals. To address the current analytical need to quantify low levels of DA in human and animal body fluids, a sensitive and selective high performance liquid chromatography-tandem mass spectrometry method was developed to measure DA in plasma and urine. This method was fully validated to accurately and precisely quantify DA between 0.31 and 16 ng/mL in plasma and between 7.8 and 1000 ng/mL in urine. Our group introduced the use of a novel internal standard, tetrahydrodomoic acid to control for matrix effects and other sources of variability. This validated method will be useful to assess DA concentrations in biological samples of human or animal origin after suspected DA exposure from contaminated food. It will also be applicable to sentinel programs and research studies to analyze body fluids with low levels of DA.