Urszula Kucharska

Aflatoxins in nuts assayed by immunological methods.

Abstract Different kinds of raw and processed nuts available in the local retail market were investigated for aflatoxin content. Total aflatoxins and aflatoxin B1 content were determined by immunoaffinity chromatography with fluorescence detection after reaction with bromine solution and by immunoenzymatic test kits. Of 29 investigated samples, 38% were contaminated. The total aflatoxin content in contaminated samples was between 1.20 μg/kg for peanuts and 5.50 μg/kg for walnuts. The concentration of aflatoxin B1 found in contaminated samples was between 0.35 μg/kg for cashew nuts and 4.04 μg/kg for walnuts. The mean recovery of total aflatoxins was 95% for the Ridascreen test and 92% for immunoaffinity chromatography with fluorescence detection. For aflatoxin B1 the mean recovery was 84%.

Determination of chloramphenicol (CAP) in food products by differential pulse polarography

ABSTRACT The electrochemical determination of chloramphenicol (CAP) in food using mini- and micro- mercury drop electrodes and differential pulse polarography (DPP) has been elaborated. A phosphate buffer with pH 6.6 was used as the basic electrolyte. The analysis was based on a peak at the potential Ep = −0.320 V which showed a clearly linear dependence of the peak current on the concentration of chloramphenicol in the sample under investigation. Prior to the determination of chloramphenicol in actual samples it was necessary to extract this antibiotic with organic solvents such as methanol, ethanol and ethyl acetate. In order to separate CAP in its basic form, various modifications of sample preparation procedures were made for the analysis with the use of selected hydrolytic enzymes. The determined quantities of CAP in the samples of meat, milk, eggs and their products ranged in the ng/g d.w. range. For purposes of comparison and verification of the electrochemical results of CAP determination, chloram...

Complexing influence of cobalt and nickel ions on the electrochemical reduction of pterin and related compounds at a mercury drop

The effect of Co(2+) and Ni(2+) ions on the electrochemical reduction of pterin and its derivatives, pteroic and pteroylmonoglutamic acids, has been studied. The measurements were carried out in aqueous solutions at fixed pH (7.5 +/- 0.2), temperature (298 +/- 0.2 K) and ionic strength (mu = 1.00; NaClO(4)) using polarographic techniques. By employing cyclic voltammetry and differential pulse polarography displacements were determined of the half-wave potentials E (1 2 ) of ligands of the reducible organic compounds at a dropping mercury electrode. The recorded polarograms and inherent potential differences were then utilized to calculate conditional stability constants of the complexes. The Casassas-Eek method was employed for the interpretation of the potential differences of the free and complexed ligands. The log beta(1) values of the stability constants revealed moderate stability of the complexes. The donor atoms of the ligands in the coordination compounds have also been identified.