Conditioning of renewable silver amalgam film electrode for the characterization of clothianidin and its determination in selected samples by adsorptive square-wave voltammetry.

A new square-wave adsorptive stripping voltammetric (SWAdSV) method was developed for the determination of the neonicotinoid insecticide clothianidin (Clo), based on its reduction at a renewable silver amalgam film electrode (Hg(Ag)FE). The key point of the procedure is the pretreatment of the Hg(Ag)FE by applying the appropriate conditioning potential (-1.70 V vs. Ag/AgCl reference electrode). Under the optimized voltammetric conditions, such pretreatment resulted in the peak for the Clo reduction in Britton-Robinson buffer pH 9.0 at about -0.60 V, which was used for the analytical purpose. The developed SWAdSV procedure made it possible to determine Clo in the concentration range of 6.0×10(-7)-7.0×10(-6) mol L(-1) (LOD=1.8×10(-7) mol L(-1), LOQ=6.0×10(-7) mol L(-1)) and 7.0×10(-6)-4.0×10(-5) mol L(-1) (LOD=1.3×10(-6) mol L(-1), LOQ=4.2×10(-6) mol L(-1)). The repeatability, precision, and the recovery of the method were determined. The effect of common interfering pesticides was also investigated. Standard addition method was successfully applied and validated for the determination of Clo in spiked Warta River water, corn seeds samples, and in corn seeds samples treated with the commercial formulation PONCHO 600 FS.

Interaction of alcoholic extracts of hops with cocaine and paracetamol in mice.

This work describes a study of the interaction in the mouse model of alcoholic extracts of hops of Magnum, Aroma and wild genotypes with drugs that have excitatory effect on the cerebral cortex (cocaine) and analgesic action (paracetamol). Hop drying and preparation of the extracts were carried out according to standard pharmacological procedures for preparing total alcoholic extracts of dry herbs, consisting of one part of dry drug and two parts of 70% alcohol. The mice received four doses i.p. of 0.5% aqueous solutions of the above-mentioned extracts (10 ml/kg) 24, 16, 4 and 0.5 h prior to receiving cocaine (25 mg/kg) or paracetamol (80 mg/kg). The parameter investigated was the change in spontaneous motility of mice after combined treatment with the extracts and cocaine/paracetamol compared to control animals that received the same dose of the drug after treatment with physiological solution. Only the ethanolic extract of Magnum hops increased the spontaneous motility of mice, while none of the extracts showed analgesic action as measured by the hot-plate method. In the interaction with cocaine, the extract of Magnum hops suppressed almost completely the action of cocaine compared to controls. Extracts of the other hops also decreased the cocaine-induced locomotor activity of mice, but to a lesser extent. Hop extracts exhibited a significant pharmacological interaction with paracetamol, with the most pronounced increase in analgesic action being found for the ethanolic extract of Aroma hops and the tert-butanolic extract of wild hops.