FLOW-INJECTION AMPEROMETRIC DETECTION OF HYDRAZINE BY ELECTROCATALYTIC OXIDATION AT A PRUSSIAN BLUE FILM-MODIFIED ELECTRODE

A Prussian Blue-modified glassy carbon electrode prepared by simple adsorption exhibited excellent electrocatalytic activity in the oxidation of hydrazine in acidic media. A film of the perfluorosulphonic acid polymer Nafion coated on top of the Prussian Blue-modified glassy carbon electrode can improve the mechanical stability of the Prussian Blue layer in the flow stream. Hydrazine was detected by flow-injection analysis at the modified electrode with high sensitivity. The limit of detection was 0.6 ng.

Rapid detection of virulent protease secreted by Vibrio anguillarum by dot enzyme-linked immunosorbent assay

Dot enzyme-linked immunosorbent assay (dot-ELISA), indirect ELISA and Western blot were performed to detect the virulent protease secreted by Vibrio anguillarum which was isolated from the diseased left-eyed flounder, Paralichthys olivaceous. Sensitivity results showed that dot-ELISA is a more sensitive, rapid and simple technique for the protease detection. The minimal detectable amount of protease is about 7 pg in the dot-ELISA test, while 7.8 ng in the indirect ELISA and 6.25 ng in the Western blot respectively. Protease could be detected 2 h after incubation of V. anguillarum in the 2216E liquid medium but enzyme activity was very low at that period. From 6 to 12 h, the amount and enzyme activity of protease increased markedly and reached maximum at stationary phase. Analysis of serum samples periodically collected from the infected flounders showed that after 2 h of infection by V. anguillarum, the pathogenic bacteria could be detected in the blood of the infected flounders but no protease was found. It was 5 similar to 6 h after infection that the protease was detected in blood and then the amount increased as infection advanced. Quantitative detection of protease either incubation in the medium or from the blood of infected flounders could be accomplished in virtue of positive controls of quantificational protease standards ("marker") so that the alterations of protease secretion both in vitro and in vivo could be understood generally. In addition, the indirect ELISA and dot-ELISA were also performed to detect V. anguillarum cells. Results indicated that the sensitivity of indirect ELISA to bacteria cells is higher than that of the dot-ELISA, and that the minimal detectable amount is approximately 10(4) cell/mL in the indirect ELISA, while 10(5) cell/mL in the dot-ELISA.

Protein phosphatase inhibition assay for detection of diarrhetic shellfish poison in oyster

A method based on protein phosphatase enzyme activity inhibition for the detection of diarrhetic shellfish poison (DSP) was used to analyze the DSP toxicity in three oyster samples. Based on the standard dose-effect curve developed with a series of okadaic acid (OA) standard solutions, the DSP toxicity of the three oyster samples collected were screened, and the results showed that there were no OA and dinophysis toxins ( DTXs) in the samples without hydrolization. However, the OA toxicity could be detected in two of the hydrolyzed samples, and the OA toxicity of the two samples were 1.81 and 1.21 mu g OA eq./kg oyster, respectively.