Cristian Tigae

Separation and identification of piperine and chavicine in black pepper by TLC and GC-MS

Conventional extraction of piperine and its derivatives by stirring the black pepper powder with solvents (ethyl alcohol, chloroform, petroleum ether, diethyl ether, etc.) for 16 to 24 h, or in a Soxhlet device for 16 h, can be replaced by extraction with supercritical fluids (CO 2 , CO + ethanol mixtures) [5, 6], or can be aided by use of microwave irradiation [7]. Separation and identification of the compounds present in pepper (essential oils, alkaloids, etc.) has been achieved by gas chromatography combined with mass spectrometry [8] and by thin-layer chromatography [9, 10]. C. Marutoiu, M.I. Moise, Lucian Blaga University of Sibiu, Faculty of Agricultural Sciences, Food Industry, and Environmental Protection, 7–9, Ion Ratiu Street, 550012 Sibiu, Romania; I. Gogoasa, Banat’s University of Agricultural Sciences and Veterinary Medicine, Faculty of Food Technology, 119 Calera Aradului, 300645 Timisoara, Romania; I. Oprean, O.F. Marutoiu, Babes-Bolyai University, Faculty of Chemistry and Chemical Engineering, 11, Arany Janos Street, 400028 Cluj-Napoca, Romania; C. Tigae, University of Craiova, Faculty of Chemistry, Craiova, Romania; and M. Rada, University of Medicine and Pharmacy Victor Babes, Faculty of Medicine, 2, Eftimie Murgu Place, Timisoara, Romania. Separation and Identification of Piperine and Chavicine in Black Pepper by TLC and GC–MS

Catalytic Activity of Thallium on Electrochemical Degradation of Metronidazole from Aqueous Solutions

The platinum/thallium electrode was prepared by thallium electrodeposition on platinum substrate in order to use it for the increase of the electrochemical degradation rate of some drugs, such as, in our study, metronidazole (MNZ). The platinum/thallium electrode was characterized by chronoamperometry, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. 2D progressive nucleation mechanism of thallium layer development was found by chronoamperometry. The value of charge transfer resistance of 537.2 Ω cm2 and the double-layer capacitance value of 2.9 mF cm−2 were deduced by EIS. The scanning electron microscopy showed a relatively fine-grained structure and the uniform distribution of the thallium granules. The electrochemical degradation of metronidazole has been performed using galvanostatic technique associated with UV-Vis spectrophotometry. The degradation degree of metronidazole reached a higher level on platinum/thallium electrode than that on platinum plate, indicating its improved performance and electrocatalytic activity of thallium coating. Moreover, the electrochemical degradation mechanism of this drug was proposed, the best way to fit the experimental data being the kinetics model of the first-order reactions.

Preparation and characterization of some ethyl-phenyl modified stationary phases

Diatomaceous earth from Filia and silica gel RH were chemically modified with trimethoxyethylphenylsilane. The as-obtained compounds have been characterized using covering density, Fourier transform infrared (FTIR) spectroscopy, thermal analysis, and thin layer chromatography. Coverage degree (a) of chemically modified silica gel and of diatomaceous earth are in agreement with literature data. FTIR data have shown the chemical modifications of these two stationary phases. TG—DTA—DTG investigation of chemically modified stationary phases indicates that the exothermic effects can be assigned to the removal of phenyl moiety and also to the water removal from the residual silanols. The analysis of the chromatographic data demonstrates that the separations on ethyl-phenylmodified adsorbents are similar with the ones performed on C8 Merck plates.

Quality Control of Commercial Mustard by Thin-Layer Chromatography

Horseradish samples (Cochlearis armoracia L.) and mustard samples (Sinapis alba L.) were extracted with 70:30 (v/v) methanol—water in accordance with ISO method 91671. Samples of commercial mustard with and without horseradish were submitted to the same extraction procedure. Separation of the active compounds from these samples were performed on silica gel 60 plates with preconcentration zone and on silica gel F254 high-performance thinlayer chromatography plates, with iso-propanol—25% ammonia, 90 + 10 (v/v), containing different volumes of distilled water (1, 2, 3, or 5 parts), as mobile phases. After development the compounds were visualized in UV light at λ = 254 nm or by exposure to iodine vapor.