Preparation And Applications Of Novel Solid Phase Extraction Sorbents For Amnesic Shellfish Poison-Domoic Acid

The marine pollution becomes worse in recent years. The frequently occurred red tides threat the human health due to the marine algal toxins. Domoic acid (DA), an amnesic shellfish toxin mainly produced by Pseudo-nitzschia, has been identified and reported with poisoning cases in many sea areas. High-performance liquid chromatography (HPLC) is the most commonly used detecting methods for DA. However, the matrix of seawater is complex and the concentration of DA in seawater is very low. Samples must be pretreated before instrumental analysis, to separate and concentrate trace DA in seawater and obtain more accurate results. Although tranditional solid-phase extraction (SPE) is commonly used in the separation and concentration of DA, the materials in SPE cartridges can also adsorb impurities, which may interfere the detection of DA. Therefore novel adsorption materials need to be developed to adsorb DA selectively.Molecular simulation and molecular imprinting technique were used in this paper. SPE sorbents, which can specifically and selectively adsorb DA, were prepared, evaluated and applied in separation and detection of DA in seawater and seafood. The main contents and results are as follows:(1) According to molecular structure of DA, the best functional monomer which adsorbing DA best was screened out by molecular simulation software. Binding energies of DA and nine commonly used functional monomers were calculated by the software Hyperchem. 2-(Trifluoromethyl) acrylic acid (TFMAA) was selected as one of the compounds for the preparation of SPE materials because of its lowest binding energy with DA.(2) Two types of novel SPE sorbents, i.e. non imprinted polymer (NIP) and molecular imprinted polymer (MIP), were prepared based on the selected functional monomer-TFMAA by software simulation. With N, N-Dimethylformamide (DMF) as solvent and TFMAA as functional monomer, club-shaped polymers were heat-polymerized under 60℃with ethylene glycol dimethacrylate (EGDMA) as a cross-linker and 2,2-Azobis(isobutyronitrile) (AIBN) as an initiator. This kind of materials needed to be smashed and rubbed, which was time consuming and could break binding sites in polymers. Thus, using acetonitrile as solvent was further inverstigated to prepare power materials. The preparation process of MIP was similar with that of NIP. However, the template molecule 1,3,5-Pentanetricarboxylic Acid (1,3,5-PeTA) was added into the solvent first in the MIP preparation.(3) To achieve the optimal materials, a series of NIP and MIP materials were prepared under different conditions. Scanning electron microscopy, infrared spectroscopy and static adsorption experiments were carried out to evaluate the material performances. The final selected optimal NIP and MIP materials were filled into SPE cartridges, respectively. The SPE-HPLC method was established and optimized for the detection of DA. The good adsorption performances and satisfactory recoveries of SPE cartridges were achieved. The instrumental detection limit was 10μg/L DA and the quantitation limit was 33μg/L DA.(4) Four types of shellfish seafood (Red heart shellfish, Scallops, White jade shellfish and Meretrix meretrix) were collected and tested by by the developed SPE cartridegs. No DA was identified in the collected samples. The standard addition recoveries in seafood ranged from 67.85% to 84.82%. The results demonstrated that the developed method could be used in seafood DA analysis.(5) To improve the concentration factor of DA in seawter, a joint HLB-NIP/MIP cartridge was applied based on the above SPE-HPLC method. In addition, the optimal pH adjustment and volume of water samples were investigated. No DA was identified in the collected seawater samples. The standard addition recovery was over 80%. The results verified the developed method can be applied in seawater DA detection. It can concentrate 500 times of DA in seawater and reach the method detection limit of 20ng/L DA.The achievements of this study provide the technique support for the quick detection of DA. It will benefit to understand the occurrence of DA pollution in China. Moreover, this study attempts to couple the molecular simulation and molecular imprinting techniques. This provides the useful reference for the development of detection methods for the other trace or emerging contaminants in water body.