title: Solid-phase extraction-fluorimetric high performance liquid chromatographic determination of domoic acid in natural seawater mediated by an amorphous titania sorbent.
abstract: The feasibility of using sol-gel amorphous titania (TiO2) as a solid-phase sorbent for the pre-concentration of domoic acid (DA), a potent amnesic shellfish poisoning (ASP) toxin, directly from seawater was explored. The sol-gel titania material is able to adsorb DA from seawater, via the formation of ester-linkage between the carboxylic moieties of DA and the Ti-OH groups on the sorbent surface, at low pH and desorb it at high pH. The chemisorption process is not significantly interfered by the seawater matrix. The optimum pH values for the adsorption and desorption of DA were found to be pH 4 and 11, respectively. The optimal sorbent loading for the batch-type solid-phase extraction of DA was 0.67 mg-TiO2 ng-DA(-1) and adsorption equilibrium was achieved in 2 h at room temperature. The desorbed DA in 500 microL of 0.1 M alkaline borate buffer can be directly derviatized by 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) in aqueous media for fluorimetric HPLC quantification. Analyte recovery, repeatability and detection limit of this titania SPE-fluorimetric HPLC determination are 89%, 6.2% and 120 pg-DA mL(-1) (n=7, P<0.05), respectively, for a sample volume of 30 mL. This titania SPE technique should also be applicable to the pre-concentration of other polar carboxylate- and phosphonate-containing biomolecules and pharmaceuticals in complex and interfering environmental sample matrices.
authors: Centre for Coastal Pollution and Conservation, Department of Biology & Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong SAR, China.
authors: Ivy O M
authors: IO
authors: Chan
authors: Vic W H
authors: VW
authors: Tsang
authors: K K
authors: KK
authors: Chu
authors: S K
authors: SK
authors: Leung
authors: Michael H W
authors: MH
authors: Lam
authors: T C
authors: TC
authors: Lau
authors: Paul K S
authors: PK
authors: Lam
authors: Rudolf S S
authors: RS
authors: Wu
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods; D007202:Indicators and Reagents; D007608:Kainic Acid / Q000031:analogs & derivatives* / Q000032:analysis / Q000302:isolation & purification; D008387:Marine Toxins / Q000032:analysis* / Q000302:isolation & purification; D044367:Phase Transition; D012623:Seawater / Q000032:analysis*; D013050:Spectrometry, Fluorescence; D014025:Titanium
chemical_list: D007202:Indicators and Reagents; D008387:Marine Toxins; C009495:titanium dioxide; D014025:Titanium; C012301:domoic acid; D007608:Kainic Acid