[UV spectrophotometry used for quantitative determination of oleanolic acid].

In order to adapt the UV spectrophotometry method to oleanolic acid dosing, absorption spectra within the range from 230 to 350 nm have been determined for both OA systems in glacial acetic acid (lambda max = 256 nm) and OA systems in ethyl alcohol (lambda max = 277 nm). The time stability of oleanolic acid in the presence of the two solvents has also been investigated in this study. Besides, the composition of etalon series and graphical representation of experimental results (n = 6) have been performed.

[The polarimetric determination of pentavalent vanadium by using quinine chlorohydrate as reagent].

The researches of the authors on the quinine chlorohydrate QH+Cl- and sodium metavanadate (Vv) reaction have led to the elaboration of two methods--a conductometric one and a gravimetric one--of dozing the QH+Cl- and, in general, of any quinine soluble salt with NaVO3. The methods, that have applications in the domain of drugs and is based on the formation of a white precipitate, in which the molar ratio QH+:Vv = 1:1. Since some authors have used quinine as a reagent in order to determine polarimetrically some ions (Ag+ and Cu2+), by taking into consideration the optic activity of quinine, we have aimed at using the formation reaction of QHVO3 for quantitatively determine the Vv with quinine chlorohydrate, by measuring the rotation angle of polarized light alpha both for the excess of QHCl reagent and for the solution obtained by dissolving the QHVO3 precipitate formed within the reaction.

[VIS spectrophotometry used for quantitative determination of iodide in food products of animal origin].

The spectrophotometric method used in dozing the iodides in the water, has been studied in order to use it in determining the iodides in a series of food products. This method is based on the catalyzed reduction of the iodide of Ce4+ by the arsenious acid. In order to determine the iodide in several food products of animal origin (eggs, milk and meat), the sample is first treated with a concentrated KOH solution and is maintained on a water bath until is obtained a residue; this is then subjected to calcination at temperatures of 500-600 degrees C until a perfectly white ash is obtained.