Abstract:© Versita Sp. z o.o. Changes of total content of phenolic substances, alteration in total titratable acidity and differences in tartaric acid content in grapes of four white (Müller-Thurgau -MT, Pinot Blanc -Rulandské bílé in Czech, RB, Sauvignon (Sg), and Muscat Ottonel -Muškát Ottonel in Czech, MO) and two blue (Dornfelder -Df and Blue Frankish -Frankovka in Czech, Fr) grapevine varieties throughout their growth, ripening and maturing (July -November). Potentiometric titration was applied for the determination of total titratable acids in grapes (expressed as tartaric acid equivalents in g L -1 Keywords: Wine grapes • Vitis vinifera • Organic acids • Phenolic substances •). A spectrophotometric method according Rebelein based on the formation of a colored complex of ammonium metavanadate and tartaric acid was used for determination of tartaric acid in green juice made by pressing unripe grapes. A spectrophotometric method based on reduction of phosphomolybdato-tungsten complex in alkaline solution using Folin-Ciocalteau reagent was applied for determination of total content of phenolic substances (TCP).
Acid-base and optical properties of sanguinarine and dihydrosanguinarine were studied in the presence of HCl, HNO 3 , H 2 SO 4 , H 3 PO 4 , CAPSO and acetic acid (HAc) of different concentrations and their mixtures. The equilibrium constants pK R+ of the transition reaction between an iminium cation Q + of sanguinarine and its uncharged QOH (pseudo-base, 6-hydroxy-dihydroderivative) form were calculated. A numerical interpretation of the A-pH curves by a SQUAD-G computer program was used. Remarkable shifts of formation parts of absorbance-pH (A-pH) curves to alkaline medium were observed. The shifts depend on the type and concentration of inert electrolyte (the most remarkable for HNO 3 and HCl ). The corresponding pK R+ values ranged from 7.21 to 8.16 in the same manner (ΔpK R+ = 0.81 and 0.73 for HNO 3 and HCl, respectively). The priority effect of ionic species and ionic strength was confirmed in the presence of NaCl and KCl. The strength of interaction of SA with bioactive compounds (i.e. receptors, transport proteins, nucleic acids etc.) may be affected because of the observed influence of both cations and anions of the inert electrolytes. Warsaw and Springer-Verlag Berlin Heidelberg. © Versita
Time stability, acid-base and UV-VIS spectral properties of dihydrochelerythrine (DHCHE) were studied spectrophotometrically in water:methanol and water:ethanol media. DHCHE is stable in strongly acid milieu (pH < 3) and at the higher amounts (60% v/v) alcohol. Acid-base characteristics and UV-VIS spectral properties of chelerythrine (CHE) were studied in aqueous solutions in the presence of different concentrations of HCl, HNO 3 , H 2 SO 4 , H 3 PO 4 and their mixtures. Remarkable shifts of formation parts of absorbance-pH (A-pH) curves to the alkaline medium were observed depending on the type and concentration of inert electrolyte (most remarkable for HNO 3 and HCl). The corresponding equilibrium constants pK R+ of the transition reaction between charged iminium Q + and uncharged QOH (pseudo-base, 6-hydroxy-dihydro derivative) forms of chelerythine were calculated using a numerical interpretation of A-pH curves by a SQUAD-G computer program which ranged from 8.51-9.31. The highest changes of ∆pK R+ (0.75 and 0.53) were observed for H 3 PO 4 and H 2 SO 4 , respectively. The priority effect of ionic species and ionic strength was confirmed in the presence of additions of NaCl and KCl. The strength of interaction of CHE with biomacromolecular compounds (i.e., peptides, proteins, nucleic acids etc.) may be affected because of the observed influence of both cation and anion of the inert electrolyte on acid-base behavior.
The effect of cationic (hexadecylpyridinium bromide, hexadecyltrimethylammonium bromide, Septonex), anionic (sodium dodecyl sulfate) and nonionic (Brij 35, Triton X-100) surfactants on the deprotonation of the phenolic oxygen in bromophenol red, bromophenol blue and bromocresol green is studied. The conditional dissociation constants Kai* depend on the surfactant concentration and, in the alkylpyridinium surfactant series, on the alkyl chain length at a constant concentration of inert electrolyte, and on the concentration of the inert electrolyte (Cl-, Br-, NO3-, SO42-, H2PO4-, CH3COO-, HCOO-, ClO4-) or of the sulfophthalein dye at a constant concentration of a cationic surfactant. In acid and alkaline solutions, cationic surfactants (tensides, T) and the dyes (H2L) form ionic associates with the stoichiometric composition {T+, LH-} and {T2+, L2-}, respectively, exhibiting absorption maxima at 400-430 nm (ε = 1.3-2.0 m2 mmol-1) and at 570-630 nm (ε = 3.5-4.5 m2 mmol-1), respectively, formation of these associates was confirmed for chloroform extracts by the continuous variations and molar ratios methods.
The optical properties of bromocresol red, bromophenol blue and bromocresol green were studied spectrophotometrically in aqueous systems in the absence and in the presence of submicellar and micellar concentrations of cationic (Septonex, hexadecylpyridinium and hexadecyltrimethylammonium bromides), nonionic (Brij 35, Triton X-100) and anionic (sodium dodecylsulfate) tensides. The positions of the absorption maxima and molar absorptivities of the LH- and L2- acid-base species of the dyes depend on the kind and concentration of tenside, alkylpyridinium chain length, and kind and concentration of inert electrolyte.
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