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See detailDevelopment and validation of a quantitative method for the selective determination of tin species in tin octoate by differential pulse polarography
Hubert, Cédric ULg; Ziemons, Eric ULg; Rozet, Eric ULg et al

in Talanta (2010), 80(3), 1413-1420

Tin octoate is used as a catalyst in the synthesis of polydimethylsiloxane (PDMS), a room temperature vulcanizing (RTV) silicone rubber. This rubber is largely used in the medical field due to its great ... [more ▼]

Tin octoate is used as a catalyst in the synthesis of polydimethylsiloxane (PDMS), a room temperature vulcanizing (RTV) silicone rubber. This rubber is largely used in the medical field due to its great biocompatibility. In this framework, a high-speed and costless analytical method for the determination of stannic ions, Sn(IV), in the presence of stannous ions, Sn(II), has been developed. The separation of these two ions was carried out using differential pulse polarography (DPP). For this purpose, the tin species contents in the catalyst is quantitatively extracted under inert condition to avoid any changes in the ratio Sn(IV)/Sn(II). Polarography showed well-shaped oxidation and reduction peaks respectively at −650 and −860 mV for stannous ions. The peak of the stannic ion was well separated and appeared at −1210 mV. Many parameters such as extraction process, extraction time, pH, chelating agents and polarographic conditions were optimized. We have also demonstrated that no oxidation of the stannous ions occurred during the sample preparation. The dosing range considered in this study extends between 10 and 40 μg/mL, corresponding to 6.8% and 27.2% of the degradation product (Sn(IV)) in the catalyst, regarding to the sampling. Finally this method was successfully validated using the total error concept. [less ▲]

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See detailSupports visuels réalisés dans le cadre des travaux pratiques de Chimie Analytique (Partie II)
Ziemons, Eric ULg; Lejeune, Robert ULg; Hubert, Philippe ULg

Learning material (2008)

Plusieurs vidéos (étalonnage des pipettes, argentimétrie: méthode de Fajans et argentimétrie: méthode de Mohr) illustrent les manipulations des travaux pratiques de 2ème Baccalauréat en Sciences ... [more ▼]

Plusieurs vidéos (étalonnage des pipettes, argentimétrie: méthode de Fajans et argentimétrie: méthode de Mohr) illustrent les manipulations des travaux pratiques de 2ème Baccalauréat en Sciences pharmaceutiques. [less ▲]

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See detailOptimisation of SFE method on-line coupled to FT-IR spectroscopy for the real-time monitoring of the extraction of tagitinin C in T-diversifolia
Ziemons, Eric ULg; Mbakop, N. W.; Rozet, Eric ULg et al

in Journal of Supercritical Fluids (2007), 40(3), 368-375

The monitoring in real time of dynamic extractions of tagitinin C from Tithonia diversifolia leaves was carried out with a home made high-pressure fiber optic cell which coupled a supercritical fluid ... [more ▼]

The monitoring in real time of dynamic extractions of tagitinin C from Tithonia diversifolia leaves was carried out with a home made high-pressure fiber optic cell which coupled a supercritical fluid extractor with carbon dioxide as the extraction medium and a FT-IR spectrometer equipped with a mercury cadmium telluride detector (MCT). The shape of extraction curves obtained during the monitoring was used to decide when to stop the supercritical fluid extraction (SFE). No significant density dependence of the molar absorption coefficient or wavenumber of the C=O stretching vibration (v(C=O)) of tagitinin C at 1668 cm(-1) was noticed. The physical characteristics of SCCO2 governing the extraction yield of the active component from leaves were optimized by means of a central composite design (CCD). The studied variables were temperature (40, 60 and 80 degrees C) and pressure (8.0, 14.0 and 20.0 MPa) of the supercritical fluid. The composition profile of T diversifolia extracts obtained by SFE was investigated in the range from 3400 to 2600 cm-1 according to the pressure and temperature conditions of SCCO2. The qualitative approach of the extracts composition was accomplished through the CH stretching vibrations of components. [less ▲]

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See detailDirect determination of tagitinin C in Tithonia diversifolia leaves by on-line coupling of supercritical carbon dioxide extraction to FT-IR spectroscopy by means of optical fibres
Ziemons, Eric ULg; Barillaro, Valéry; Rozet, Eric ULg et al

in Talanta (2007), 71(2), 911-917

Supercritical fluid extraction (SFE) with carbon dioxide as extraction medium was on-line coupled to a FT-IR spectrometer equipped with a Mercury Cadmium Telluride (MCT) detector using a tailor-made high ... [more ▼]

Supercritical fluid extraction (SFE) with carbon dioxide as extraction medium was on-line coupled to a FT-IR spectrometer equipped with a Mercury Cadmium Telluride (MCT) detector using a tailor-made high-pressure fibre optic flow cell. This method was optimised and developed for the monitoring in real time and the quantification of dynamic extractions of tagitinin C from Tithonia.diversifolia leaves. In order to demonstrate the method ability to allow the direct quantification of tagitinin C in the extract medium the standard addition method was used. The area integration Of Curves obtained by plotting the absorbance of the highly specific C=O stretching vibration at 1668 cm(-1) versus time (i.e. extractograms) was used as instrumental response. The SFE/FT-IR process was successfully validated using the accuracy profile as decision tool. On this basis, a linear regression model was chosen for the calibration curve. The relative standard deviation for repeatability and intermediate precision were between 0.8 and 3.1 %, respectively. Moreover, the method was found to be accurate as the two-sided 95% beta-expectation tolerance interval did not exceed the acceptance limits of 85 and 115% on the analytical range investigated (500-2500 mu g of added amount of tagitinin Q. The proposed method allowed the non-destructive extraction of tagitinin C and its on-line quantitative determination in less than 25 min thus facilitating the subsequent experiments or the pharmacological studies performed on this compound. [less ▲]

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See detailStudy of the physicochemical properties in aqueous medium and molecular modeling of tagitinin C/cyclodextrin complexes
Ziemons, Eric ULg; Dive, Georges ULg; Debrus, Benjamin ULg et al

in Journal of Pharmaceutical & Biomedical Analysis (2007), 43(3), 910-919

The inclusion complexes of tagitinin C with beta-, 2,6-di-O-methyl-beta- and gamma-cyclodextrin (CyD) was investigated in aqueous medium. The stoichiometric ratios and stability constants (K(f)) which ... [more ▼]

The inclusion complexes of tagitinin C with beta-, 2,6-di-O-methyl-beta- and gamma-cyclodextrin (CyD) was investigated in aqueous medium. The stoichiometric ratios and stability constants (K(f)) which describe the extent of formation of the complexes have been determined by UV spectroscopy and direct current tast polarography (DC(tast)), respectively. For each complex, a 1:1 molar ratio was formed in solution and the trend of stability constants was K(f) (2,6-di-O-methyl-beta-CyD)>K(f) (gamma-CyD)>K(f) (beta-CyD). The effect of molecular encapsulation on the photochemical conversion of tagitinin C was evaluated. No significant protection efficacy was noticed with beta- and gamma-CyD for the complexed drug with the respect to the free one. On the other hand, the photochemical conversion rate was slowed in presence of 2,6-di-O-methyl-beta-CyD. Data from (1)H NMR and ROESY experiments provided a clear evidence of formation of inclusion complexes. The lactone, the ester and the unsaturated ketone parts of tagitinin C inserted into the wide rim of the CyDs torus. These experimental results were confirmed by the molecular modeling using semiempirical Austin Model 1 (AM1) method. [less ▲]

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See detailSupports visuels réalisés dans le cadre des travaux pratiques de Chimie Analytique (Partie I)
Ziemons, Eric ULg; Houbart, Virginie ULg; Lejeune, Robert ULg et al

Learning material (2007)

Plusieurs vidéos (utilisation de la burette, calibration de la balance analytique, nettoyage de la balance analytique, gravimétrie, rinçage des pipettes, prélèvement à l'aide d'une pipette à 1 trait ... [more ▼]

Plusieurs vidéos (utilisation de la burette, calibration de la balance analytique, nettoyage de la balance analytique, gravimétrie, rinçage des pipettes, prélèvement à l'aide d'une pipette à 1 trait, prélèvement à l'aide d'une pipette à 2 traits et transfert quantitatif) illustrent le B.A.-BA des manipulations des travaux pratiques de 2ème Baccalauréat en Sciences pharmaceutiques. [less ▲]

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See detailSupercritical carbon dioxide extraction of tagitinin C from Tithonia diversifolia
Ziemons, Eric ULg; Goffin, Eric ULg; Lejeune, Robert ULg et al

in Journal of Supercritical Fluids (2005), 33(1), 53-59

Different parameters as temperature, pressure, solvent mass and sample granulometry governing the extraction yield of tagitinin C from the aerial parts of Tithonia diversifolia were optimised. An ... [more ▼]

Different parameters as temperature, pressure, solvent mass and sample granulometry governing the extraction yield of tagitinin C from the aerial parts of Tithonia diversifolia were optimised. An experimental design was carried out to map the effects of pressure (at 20.3, 30.4 and 40.5 MPa) and temperature (at 40, 60 and 80degreesC) on the extraction yield of the active component and to determine the optimal conditions for the extraction of tagitinin C from T diversifolia. The best conditions are met for a pressure of 35.0 MPa and a temperature of 68degreesC. The effect of the particle size was studied under low pressure (13.7 MPa) and temperature (40degreesC) conditions, which failed to extract quantitatively the tagitinin C from leaves sieved to 250 mum size. The reduction of the particle size increased the extraction yield which became comparable to that of the optimised SFE for the particle in the range of 0-63 mum. From the analysis of extraction kinetic curves of 200 mg of plant with supercritical carbon dioxide (range of 5-30 g), it appears that 15 g of this supercritical fluid is never limiting. The optimised supercritical fluid extraction (SFE) was compared favourably to Soxhlet extraction with dichloromethane (S) and to maceration followed by lixiviation with diethyl ether (ML), which gave similar extraction yields but higher extract content of tagitinin C were found using SFE (15.6 and 30.7% w/w tagitinin C in S and ML extracts, respectively, versus 52.8% in SFE extract). [less ▲]

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See detailFT-IR measurement of tagitinin C after solvent extraction from Tithonia diversifolia
Ziemons, Eric ULg; Goffin, Eric ULg; Lejeune, Robert ULg et al

in Talanta (2004), 62(2), 383-387

Tagitinin C, an antiplasmodial compound, identified as one major compound of the subtropical medicinal plant, Tithonia diversifolia, was, determined by FT-IR spectroscopy method. The crude ether extracts ... [more ▼]

Tagitinin C, an antiplasmodial compound, identified as one major compound of the subtropical medicinal plant, Tithonia diversifolia, was, determined by FT-IR spectroscopy method. The crude ether extracts from aerial parts of the plant were evaporated to dryness and re-dissolved in tetrachloroethylene (C2Cl4) before analysis. The magnitude of the absorbance of the very specific C=O stretching vibration (v(c=o)) at 1664.8 cm(-1) was exploited in order to quantify tagitinin C. The determination coefficient (r(2)) of the calibration scale was 0.9994, the detection limit was lower than 3 mug ml(-1) and the quantification limit was lower than 10 mug ml(-1). Recovery values from 100.5 to 101.7% were found for spiked concentration levels from 19.91 to 89.95 mug ml(-1). The main characteristics of the curves obtained from the calibration standards and from the standard addition technique were not statistically different (Student t-test) suggesting that matrix effects were negligible. The results obtained for the determination of tagitinin C in the crude ether extract from aerial parts of T diversifolia by LC and FT-IR spectroscopic method agreed well: 0.76 +/- 0.02 and 0.773 +/- 0.009, of tagifinin C in dried plant respectively. (C) 2003 Elsevier B.V. All rights reserved. [less ▲]

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