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The new kinetically-based spectrophotometric method for the determination of microquantities of ampicillin is proposed in the present paper. Ampicillin degradation in strong alkaline medium was applied for the method development. The reaction rate was monitored at 265 nm. A differential variation of the tangent method was used to process the kinetic data. The method is valid over the 3.49-55.84 µg/mL ampicillin concentration interval with relative standard deviation (RSD) range 7.79-3.20%. The calculated detection limit was determined at 2.58 µg/mL based on the 3.3S0 criterion. The interference effects of some metal ions, anions, amino acids and other molecules were investigated in order to assess the method selectivity. The method was successfully applied to determining the content of ampicillin in commercial pharmaceutical preparations and human urine. The obtained results were in good correlation with the HPLC method results. The newly developed method is simple, inexpensive and efficient for the analysis of a large number of samples at room temperature in a short time.

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This paper presents results of analyses of metal ions effects on hop strobili antioxidant characteristics. Determination of total phenols (TP), total flavonoids (TF) and fifteen phenolic compounds, as well as the antioxidant activity (DPPH, ABTS and FRAP) of hop extracts from eight samples was conducted using UV/Vis spectrophotometry and HPLC method. Contents of 24 elements in mineralized hop samples were determined by ICP-OES. Very strong negative relationship between TP, TF, antioxidant capacity results and Pb, Co, Cr, Sb and Na was determined applying principal component and cluster analyses. Namely, the higher concentrations of these metals were associated with lower contents of TP and TF and lower values of antioxidant tests. Impact of metal ions on phenolic and flavonoids content and antioxidant activity of hop strobili has not been previously published.