Enhanced removal of perfluorooctanoic acid with sequential photocatalysis and fungal treatment.

In this paper, we report the degradation of perfluorooctanoic acid (PFOA), which is a persistent contaminant in the environment that can severely impact human health, by exposing it to a photocatalyst, bismuth oxyiodide (BiOI), containing both Bi4O5I2 and Bi5O7I phases and a fungal biocatalyst (Cunninghamella elegans). Individually, the photocatalyst (after 3 h) and biocatalyst (after 48 h) degraded 35-40% of 100 ppm PFOA with 20-30% defluorination. There was a marked improvement in the degree of degradation (90%) and defluorination (60%) when PFOA was first photocatalytically treated, then exposed to the fungus. GC- and LC-MS analysis identified the products formed by the different treatments. Photocatalytic degradation of PFOA yielded short-chain perfluorocarboxylic acids, whereas fungal degradation yielded mainly 5:3 fluorotelomer carboxylic acid, which is a known inhibitor of cytochrome P450-catalysed degradation of PFAS in C. elegans. The combined treatment likely resulted in greater degradation because photocatalysis reduced the PFOA concentration without generating the inhibitory 5:3 fluorotelomer carboxylic acid, enabling the fungus to remove most of the remaining substrate. In addition, new fluorometabolites were identified that shed light on the initial catabolic steps involved in PFOA biodegradation.

Trace-level detection of atrazine using immuno-chemiluminescence: dipstick and automated flow injection analyses formats.

A sensitive chemiluminescence (CL)-based immunoassay technique based on both dipstick and flow injection analytical formats is reported for the detection of atrazine. In the dipstick-based immunoassay technique, antibody (anti-atrazine) was first immobilized on the nitrocellulose membranes. The dipstick was then treated with atrazine and atrazine-horseradish peroxidase conjugate (atra-HRP) to facilitate the competitive binding. The dipstick was further treated with urea-hydrogen peroxide (U-H202) and luminol to generate photons. The number of photons generated was inversely proportional to the atrazine concentration. In the flow injection analysis (FIA) format, the antibody was immobilized on protein-A sepharose matrix and packed in a glass capillary column, which functioned as an immunoreactor. Competitive binding of antigen and antibody occurred. The CL signals generated during the biochemical reactions were correlated with atrazine concentrations in the analytical samples. By using dipstick technique, it was possible to detect atrazine concentration down to 0.1 ng/mL; with the FIA format, the detection of atrazine was down to 0.01 ng/mL.