Browsing by Author "Stoykova I."

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    Determination of N-methyl carbamates in a liver sample using an optical biosensor
    (2019-01-01) Yaneva S.; Stoykova I.; Danalev D.; Yotova L.
    N-Methyl carbamates are insecticides that inhibit acetylcholinesterase (AChE) causing same symptomatology in acute and chronic exposures. Traces of them could be found in animal tissues, milk, honey, eggs, etc. because of some foods treatment during growth. There is an increasing interest in fast screening methods for detection of different pollutant groups in the foods. Biosensors are a promising alternative of the existing chromatographic methods such as HPLC, GC, etc. They are fast, easy to use and provide fully acceptable values for the monitoring methods like sensitivity, LOD, LOQ, etc. In order to construct an optical biosensor, AChE is immobilized as a target enzyme for N-methyl carbamates on the surface of new membranes synthesized by a sol-gel technology. The designed biosensensor is tested for determination of methomyl, aldicarb, carbofuran, propoxur in liver samples. An appropriate method for sample preparation is also developed. Further, the new method is validated in accordance with document SANTE/11945/2015 covering the required criteria for N-Methyl carbamates determination. The biosensor could detect levels lower than 10 μg/kg which is the maximum residue limit (MRL) for pesticides in foods. Km of 2,2x10-3 M is calculated for acetylcholine using a 4 month life-time of a biosensor.
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    Determination of organophosphorus pesticides in liver samples using an optical biosensor
    (2019-01-01) Yaneva S.; Stoykova I.; Danalev D.; Yotova L.
    Biosensors are a promising alternative of the existing chromatographic methods as GC, HPLC, etc. They are fast, easy to use and provide fully acceptable values of monitoring like sensitivity, LOD, LOQ, etc. In order to construct an optical biosensor, AChE is immobilized as a target enzyme for organophosphorus pesticides (OPPs) onto new membranes synthesized by a sol-gel technology. The designed biosensensor is tested for determination of chlorpyrifos-methyl, parathion, pirimiphos-methyl and diazinon in liver samples. An appropriate method for sample preparation is also developed. The new method is validated in accordance with document SANTE/11945/2015 covering the required criteria for pesticides determination. The biosensor developed can detect levels lower than 30μg/ kg. The latter is the maximum residue limit (MRL) for pesticides in food. Km of 2,2x10-3M for acetylcholine and 4 months life-time of the biosensor are obtained.