A microconductometric biosensor based on lipase extracted from Candida rugosa for direct and rapid detection of organophosphate pesticides

Organophosphate pesticides (OPs) have been intensively used as insecticides in agriculture; after entering the aquatic environment, they may affect a wide range of organisms. A conductometric enzymatic biosensor based on lipase extracted from Candida rugosa (CRL) has therefore been developed for the direct and rapid quantitative detection of organophosphate pesticides: diazinon, methyl parathion and methyl paraoxon in water. The biosensor signal and response time were obtained under optimum conditions, the enzyme being immobilised in the presence of gold nanoparticles. Under these conditions, the enzymatic biosensor was able to measure concentrations as low as 60 µg/L of diazinon, 26 µg/L of methyl parathion and 25 µg/L of methyl paraoxon very rapidly (response time: 3 min). Moreover, this CRL biosensor was not sensitive to interferences such as carbamates. It presented good storage stability for 21 days when kept at 4°C and it was successfully applied to real samples.     

UV‐visible emission of (O2‐ ‐ F+) centres in KBr

Single crystals of KBr containing the (O^2‐ ‐ F⁺) color centres and elaborated in atmospheric air by the Czochralski method are studied. The measure of the UV‐visible emission spectra at 78 K present several emission bands situated between 340 and 800 nm. The photoluminescence excitation shows that these emissions are attributed to O^‐₂ and (O^2‐ ‐ F⁺) centres. This study show the new emission bands of (O^2‐ ‐ F⁺) centres which are situated in the UV‐visible spectral domain. The comparison between the emission spectra before and after the thermal treatment of samples shows clearly the transformation of O^‐₂ centers at high temperature to (O^2‐ ‐ F⁺) centres. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)