Analysis of anatoxin-a in aqueous samples by solid-phase microextraction coupled to high-performance liquid chromatography with fluorescence detection and on-fiber derivatization

A simple method for analysis of anatoxin-a in aqueous samples was developed using solid-phase microextraction (SPME) and high-performance liquid chromatography (HPLC) with fluorescence detection. Anatoxin-a was derivatized to a fluorogenic agent on the surface of the SPME fiber. In the method an SPME fiber was immersed for 30 min in the aqueous sample. The fluorogenic derivatizing reagent (4-fluoro-7-nitro-2,1,3-benzoxadiazole, 1.0 mg/ml in methanol) was dropped or sprayed onto the fiber containing extracted analytes. The fiber was then heated for 10 min in an empty vial at 70 °C in a waterbath to promote derivatization. The derivatives formed on the fiber were desorbed in a SPME–HPLC interface. The interface was filled with methanol–1 mM hydrochloric acid (7:3, v/v) before inserting of the fiber into the interface. For desorption, the fiber was inserted in the interface for 5 min. For anatoxin-a in an aqueous sample, the calibration curve showed linearity in the range of 50–1500 ng/ml and the limit of detection of anatoxin-a was 20 ng/ml. No interferences were found, and the time for analysis was 55 min for one sample.