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Institut für Lebensmittelchemie

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Browsing Institut für Lebensmittelchemie by Person "Akkad, Rami"

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    Determination of organophosphorus and carbamate insecticides in food samples by high-performance thin-layer chromatography multi-enzyme inhibition assay
    (2011) Akkad, Rami; Schwack, Wolfgang
    In terms of effect-directed analysis, esterase inhibitor assays allow a rapid and selective detection of insecticidal organophosphates and carbamates in food and environmental samples. With consideration to the toxicological mechanism of action of these insecticides, cholinesterases of different origin were used in different test formats, as microtiterplate assays, in test strip formats, as biosensors or coupled to thin-layer chromatography (bio-autography). Instead of cholinesterases, Ingrid Walz (PhD thesis, University of Hohenheim, 2008) introduced rabbit liver esterase (RLE), Bacillus subtilis (BS2)-esterase and cutinase (CUT) from Fusarium solani pisi for a multi-enzyme microtiterplate assay. In particular, RLE and BS2 proved to be much more sensitive than chloinesterases for the detection of inhibitors, while CUT displayed oneself by special tolerance for matrix components from fruits. This multi-enzyme assay was successfully transferred onto high-performance thin-layer chromatography (HPTLC). With the insecticide examples of carbofuran, malaoxon and paraoxon as weak, medium and strong inhibitors, HPTLC-enzyme inhibition (HPTLC-EI) assay conditions were optimized concerning enzyme concentrations, incubation times and substrate reactions. In the presence of the substrate α-naphthyl acetate/Fast Blue Salt B leads to colourless inhibitor zones are obtained on a purple background, which can be sensitively quantified by scanning at 533 nm. The limits of detection for paraoxon were determined to 1.3, 1.2, and 540 pg/zone for RLE, BS2, and CUT, respectively. Malaoxon was detectable up to 7.9, 7.4 and 760 ng/zone, while the limits of detection for carbofuran were at 33, 54 and 1420 ng/zone.