Zenovia Moldovan

Rapid determination of total polyphenolic content in tea samples based on caffeic acid voltammetric behaviour on a disposable graphite electrode

The present paper describes the voltammetric behaviour and the quantitative determination of caffeic acid (CA) on a disposable pencil graphite electrode (PGE). The anodic peak current of CA recorded by differential pulse voltammetry (DPV) varies linearly with CA concentration in the range 1×10(-7)-3×10(-3) M. The detection and quantification limits were 8.83×10(-8) M and 2.94×10(-7) M caffeic acid, respectively. The mean recoveries of CA from Turkish green, white and black teas were 98.30%, 99.57% and 91.46%. For these three tea types the corresponding total polyphenolic contents (TPCs) evaluated by DPV on PGE were 35.81, 34.59 and 31.21 mg caffeic acid equivalent/g tea, respectively. These TPC values were in good accordance with those obtained by the Folin-Ciocalteu method. The developed DPV on PGE method constitutes a simple and inexpensive tool for the rapid assessment of TPC of tea samples.

Kinetic Spectrophotometric Determination of Nitrite with Tropaeolin 00-Bromate System

A simple accurate kinetic spectrophotometric method was developed for the determination of nitrite based on its catalytic effect on the redox reaction between tropaeolin 00 and bromate in acid medium. Nitrite was determined by measuring the decrease in the absorbance of tropaeolin 00 at 530 nm by a fixed time method, after 30 s from the initiation of the reaction. The calibration graph was linear in the range 6–500 ng mL−1 of nitrite and the detection limit was 2 ng mL−1. The proposed method is selective and is useful for the determination of nitrite in drinking water samples.

Cheap pencil graphite electrodes for rapid voltammetric determination of chlorogenic acid in dietary supplements

A disposable, cheap and easily available pencil graphite electrode (PGE) was used to develop, for the first time, a rapid voltammetric method for chlorogenic acid (CGA) determination. Cyclic voltammograms emphasised a quasi-reversible, diffusion controlled and pH dependent electrode process. Differential pulse voltammetry (DPV) applied to the anodic peak was used for the quantitative determination of CGA. The linear range, the limit of detection and the limit of quantification were 1 × 10−7 to 5 × 10−4 mol L−1 CGA, 7.14 × 10−8 mol L−1 CGA and 2.1 × 10−7 mol L−1 CGA, respectively, being similar to or even better than those reported in the literature. The developed DPV on PGE method was applied with good results to the quantitative determination of CGA in commercially available green coffee extract based dietary supplements. The results compared well with those obtained by the Folin–Ciocalteu method, a fact proved by the statistical analysis.

A Spectrophotometric Method for Diosmin Determination

A rapid and sensitive spectrophotometric method for the determination of diosmin (D) has been developed. The method is based on the reaction of D with 4-aminoantipyrine (AAP) in the presence of hexacyanoferrate (III) (HCF) in an alkaline medium and subsequent formation of a purple coloured product havingmax at 524.5 nm. The conditions affecting the reaction (reagents concentration, pH, order of addition of reagents, stability in time) were optimized. Under the optimum conditions, Beers law was obeyed in the range of 0.3 - 35 μg mL -1 D with a correlation coefficient of 0.9993. The assay limits of detection and quantitation were 0.1 and 0.3 μg mL -1 , respectively. The proposed method was successfully applied to the analysis of the drug tablets formulation. The results were compared favorably with those obtained by other reported methods.

Study on Fluorimetric Properties of 1,2-Dihydro-2,2,4-trimethylquinoline

The title compound, 1,2-dihydro-2,2,4-trimethylquinoline (TMQ), is a quinoline family member and is among others used to prevent the oxidative degradation of polymers. TMQ has been characterized by its fluorescence emission. In this work the effects of solvent, acidity, continuous irradiation and the influence of some interferents upon the fluorescence intensity of TMQ were investigated. Under the selected conditions (in propan-1-ol solution at λexcitation/λemission = 334 nm/412 nm), the fluorescence intensity is proportional to the concentration of TMQ over the range 0.05–5 μg ml−1 with a correlation coefficient of 0.9963. The proposed method was applied to the determination of TMQ in synthetic mixtures of polymer additives and specific rubber samples.

Anion-exchange resin modified with pyrocatechol violet as a functional resin for retention of Sn(IV)

Abstract A selective chelating resin was prepared by loading pyrocatechol violet (PV) on a conventional anion-exchange resin, Dowex 2x4. PV loaded Dowex 2x4 was mixed with Sn(IV) solution and the pH was adjusted to 4 with acetate buffer. After equilibration for 6–7 h on a mechanical shaker, the mixture was set aside for 12 h, the resin was filtered off and Sn(IV) was desorbed with 1 M HNO3 (25 ml). The Sn(IV) was determined in the acidic solution by direct current plasma atomic emission spectrometry at 283.999 nm. The loaded resin was also used for the separation of Sn(IV) from several metal ions.

A SENSITIVE SPECTROPHOTOMETRIC METHOD FOR DETERMINATION OF DIOSMIN USING SODIUM NITROPRUSSIDE AS A CHROMOGENIC REAGENT

A simple and sensitive method for the spectrophotometric determination of diosmin has been developed, and optimum reaction conditions along with other analytical parameters have been evaluated. Diosmin, as a phenolic compound, reacts with sodium nitroprusside and hydroxylamine hydrochloride in a basic medium to give a green-colored product. At analytical wavelength of 763 nm, Beers law is obeyed over the concentration range 2–140 μg mL−1 of diosmin with a correlation coefficient of 0.9997. The molar absorptivity is 9671 L mol−1 cm−1. The limits of detection (LOD) and quantification (LOQ) are 0.05 and 0.2. μg mL−1, respectively. The method has been successfully applied to the determination of diosmin in a commercial pharmaceutical preparation. The results were compared favorably with those obtained by the 4-aminoantipyrine method.

SPECTROPHOTOMETRIC METHOD FOR RANITIDINE DETERMINATION IN DRUGS USING RHODAMINE B

A new spectrophotometric method has been developed for the determination of ranitidine hydrochloride (R.HCl) in bulk drug and in tablet formulation. The proposed method involves the addition of a measured excess of bromate–bromide reagent in hydrochloric acid medium to R.HCl, followed by determination of residual bromine by reacting with a fixed amount of Rhodamine B (RB) and measuring the absorbance at λ max =557 nm. Beer’s law was found in the range of 0.3-3.2 μg ml-1 of R.HCl, with a good correlation coefficient (r=0.9997). The limits of detection and quantification were calculated to be 0.08 μg ml -1 and 0.24mg ml-1, respectively. The different experimental parameters affecting the development and stability of the proposed method were carefully studied and optimized. The validity of the proposed method tested by analyzing the pure and pharmaceutical formulations and compared well with those obtained by the official method, demonstrated good accuracy and precision.

Characteristics of natural leather finished with some ecofriendly mixtures of polymeric aqueous dispersions

Abstract A series of mixtures of acrylic copolymer aqueous dispersions or acrylic copolymers and polyurethane water dispersions were used as environmentally friendly base coatings and an acrylic self-crosslinkable copolymer dispersion containing epoxy resin as top coating for natural leather. Samples finished with the proposed additives were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and physical-mechanical tests. FT-IR spectra show that the proposed ecofriendly dispersion used as top coating not only covers the surface of leather, but it is chemically bound with the base coat, assuring a resistant coverage. SEM images show smooth and uniform surfaces. Physical-mechanical characteristics are superior to those imposed by standards in force, demonstrating that the proposed dispersion is able to substitute successfully the top coating nitrocellulose aqueous emulsions (noted EMAL) commonly used as finishing agents, in which the nitrocellulose is dispersed as solution.

Indirect Determination of Ranitidine Hydrochloride Using a Chloride Ion Selective Electrode

Abstract A simple, rapid, and reliable potentiometric method is described for determination of ranitidine hydrochloride in pharmaceutical formulations. Experiments were performed to determine the suitability of using a chloride-ion selective electrode for the indirect estimation of ranitidine hydrochloride. The precision and accuracy of the potentiometric method were determined. We found that they not differ significantly. The advantage of the proposed method is the fact that it can be applied without filtration of the drug sample before analysis.