A pulse perturbation technique was applied to the Bray–Liebhafsky (BL) oscillatory reaction system in a stable nonequilibrium stationary state close to the bifurcation point, to determine micro-quantitatively 6-O-acetylmorphine (6-O-AM). The proposed method, in optimized reaction conditions ([KIO3]0 = 5.9×10−2 M, [H2SO4]0 = 5.5×10−2 M, and [H2O2]0 = 2.0×10−1 M, jo=2.95×10−2 min−1, and T=42.9 °C), relied on the linear relationship between maximal potential shift, ΔEm, caused by perturbation, and the logarithm of the amount of 6-O-acetylmorphine. The method had a rather good sample throughput of 40 samples h−1 with the sensitivity determined to be 0.9 μg mL−1 and the precision RSD = 1.8%. The proposed method was successfully applied to the quantitative determination of 6-O-AM in a real seized street drug sample. The obtained result agrees with those obtained by HPLC. There was no interference from structurally related and associated compounds, such as papaverin, noscapin, and heroin.

A simple and reliable kinetic method for the determination of hesperidin (Hesp) is developed. It is based on potentiometric monitoring of the concentration perturbations of the matrix reaction system which is in a stable non-equilibrium stationary state close to the bifurcation point. The Bray-Liebhafsky oscillatory reaction is used as the matrix system. The response of the matrix to perturbations by different concentrations of Hesp is followed by using a Pt electrode. A linear relationship between maximal potential shift and the logarithm of Hesp concentrations is obtained between 7.5 and 599.4 microg mL-1. The limit of detection is 0.65 microg mL-1. The described procedure has been successfully applied to the determination of Hesp from different sources (capsules, industrial and hand-squeezed orange juice, and white wine).

Composition and stability constant of the Pd(II)-quercetin complex were determined by suitable spectrophotometric methods and pH-metric measurements in 507 Ethanol. It was found that the Pd 2 ion and quercetin form a 1:1 complex in which Pd 2 is linked to quercetin through the carbonyl and the 3-hydroxyl group. The stability constant log 1 ranged from 6.05 at pH 5X00 to 4.96 at pH 6X50X The conditions for the spectrophotometric determination of quercetin by means of complex formation were investigated. Beer's law was obeyed up to 5X00 Â 10 À5 M quercetin.

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It has been established, by the application of suitable spectrophotometric methods and pH-metric measurements, that titanyl oxalate anion and 3-hydroxyflavone (3HF) form a [TiO(C2O4)2(C15H9O3)2]4-complex. The investigation of the composition and the concentration stability constant of the complex were carried out in a 50 % aqueous ethanol solution at room temperature (20?C), in the pH range from 1.9 to 9.0. The concentration stability constant of the complex, log b2, ranged from 16.65 at pH 5.0 to 13.96 at pH 7.0. The conditions for the spectrophotometric determination of 3HF by means of the complex formation were investigated in the concnetration range from 2.5?10-5 to 3.0?10-4 mol dm-3 3HF.