METHOD FOR DETERMINING THE TOTAL CONTENT OF PHENOLIC COMPOUNDS IN PLANT EXTRACTS WITH FOLIN-DENIS REAGENT AND FOLIN-CHOCALTEU REAGENT: MODIFICATION AND COMPARISON

A modification of the method for determining the total content of phenolic compounds in plant tissue extracts with the Folin-Denis reagent and the Folin-Ciocalteu reagent has been carried out, allowing to establish the correspondence of the results obtained when using them. The method using the Folin-Denis reagent is adapted for conducting determinations in microvolumes. For the method using the Folin-Ciocalteu reagent, the concentration of the latter (0.4 N, a 5-fold dilution of the standard reagent) and the composition of the reaction mixture were selected, using which the optical densities of the reduction products of the Folin-Denis and Folin-Ciocalteu reagents containing polyphenols in ethanol extracts from wheat, buckwheat and calus tissue of tea were almost the same. The absorption spectra of the reduction products of these reagents by gallic acid, rutin, (-)-epicatechin, as well as ethanol extracts from wheat, buckwheat, and tea calus tissue, were located in the same region (680–770 nm) and had similar characteristics. Calibration graphs of the dependence of the optical density of solutions on the concentration of standard substances (gallic acid, (-)-epicatechin, rutin), constructed using the Folin-Denis and Folin-Ciocalteu reagents, had a linear character within the concentration range of 10–100 μg/ml and practically coincided. The results of determining the content of phenolic compounds in ethanol extracts of plants, differing in their ability to accumulate, showed very similar and statistically significant values when using these two reagents.

The Rr Form of the Kedem–Katchalsky–Peusner Model Equations for Description of the Membrane Transport in Concentration Polarization Conditions

The paper presents the Rr matrix form of Kedem–Katchalsky–Peusner equations for membrane transport of the non-homogeneous ternary non-electrolyte solutions. Peusner’s coefficients Rijr and det [Rr] (i, j ∈ {1, 2, 3}, r = A, B) occurring in these equations, were calculated for Nephrophan biomembrane, glucose in aqueous ethanol solutions and two different settings of the solutions relative to the horizontally oriented membrane for concentration polarization conditions or homogeneity of solutions. Kedem–Katchalsky coefficients, measured for homogeneous and non-homogeneous solutions, were used for the calculations. The calculated Peusner’s coefficients for homogeneous solutions depend linearly, and for non-homogeneous solutions non-linearly on the concentrations of solutes. The concentration dependences of the coefficients Rijr and det [Rr] indicate a characteristic glucose concentration of 9.24 mol/m3 (at a fixed ethanol concentration) in which the obtained curves for Configurations A and B intersect. At this point, the density of solutions in the upper and lower membrane chamber are the same. Peusner’s coefficients were used to assess the effect of concentration polarization and free convection on membrane transport (the ξij coefficient), determine the degree of coupling (the rijr coefficient) and coupling parameter (the QRr coefficient) and energy conversion efficiency (the (eijr)r coefficient).

Study on the dependence of fluorescence intensity on optical density of solutions: the use of fluorescence observation field for inner filter effect corrections

Absorbance value that corresponds to maximum fluorescence intensity (Aflmax) depends on fluorescence observation field.

DEPENDENCE OF DENSITY OF JOINT AQUEOUS SOLUTIONS OF AMMONIA, AMMONIUM CHLORIDE, AMMINES OF ZINC AND COPPER ON THEIR COMPOSITION

The dependence of the pressure of joint aqueous solutions of ammonia, ammonium chloride, ammines of zinc and copper on their component concentrations was studied by pycnometric method. The equation wich allow calculating the density of solutions mentioned above using known molar concentrations of components was obtained. The error of calculation on equation is not more than 3%. The data obtained can be used at the design of pilot devices for the extraction of zinc and copper by ammonia-ammonium solutions from industrial waste.