Voltammetric and Square-Wave Anodic Stripping Determination of Amlodipine Besylate on Gold Electrode

The oxidative behaviour of amlodipine besylate was studied. The gold electrode and Au/o-MWCNT (oxidized multi-wall carbon nanotubes) were used for determination of amlodipine besylate standard and as a content of Alopres tablet, in 0.05 M NaHCO3 and in phosphate buffer (pH=11) by cyclic voltammetry and square-wave anodic stripping voltammetry. Electrode surfaces were characterized by AFM in the presence of amlodipine and the concentrations of drugs in electrolytes were simultaneously followed by HPLC. The linear dependency of the anodic currents of amlodipine besylate as standard and in Alopres tablet vs. concentration was observed in both electrolytes, but in phosphate buffer for the higher concentrations. The peak currents obtained in all experiments are more than fifty-fold higher comparing to all previously published results concerning the glassy carbon electrode and the carbon paste electrode. The gold electrode is better catalyst for anodic oxidation of amlodipine besylate than glassy carbone. The results obtained with Au/o-MWCNT show lower anodic activity comparing to previously published GC/o-MWCNT. GC/o-MWCNT is better catalyst than Au/o-MWCNT under similar experimental conditions

Uticaj supstituenata na IR, 1H- i 13C-NMR spektralne podatke N-(supstituisanih fenil)-2-cijanoacetamida - korelaciona analiza

Linear free energy relationships (LFER) were applied to the IR, H-1- and C-13-NMR spectral data of N-(substituted phenyl)-2-cyanoacetamides. A variety of substituents were employed for phenyl substitution and fairly good correlations were obtained using the simple Hammett and the Hammett-Taft dual substituent parameter equations. The correlation results of the substituent induced C-13-NMR chemical shifts (SCS) of the Cl, C=O and N-H atom indicated different sensitivity with respect to electronic substituent effects. A better correlation of the SCSc=O with a combination of electrophllic and nucleophilic substituent constants indicated a significant contribution of extended resonance interaction (pi-delocalization) within the pi(1)-unit. The conformations of the investigated compounds were studied using the OFT B3LYP/6-311G** method and, together with the results of C-13-NMR and IR spectroscopic studies, a better insight into the influence of such a structure on the transmission of electronic substituent effects was obtained.Principi linearnih korelacija slobodnih energija (LFER) su primenjeni na IR, 1H- i 13C-NMR spektralne podatke N-(supstituisanih fenil)-2-cijanoacetamida. Pri sintezi N-(supstituisanih fenil)-2-cijanoacetamida izvršen je zadovoljavajući izbor supstituenata u pogledu elektronskih svojstava kako bi se adekvatno sagledao uticaj elektronskih efekata supstituenata na pomeranja u IR, 1H- i 13C-NMR spektralnim podacima. Primenom proste Hametove jednačine dobijene su zadovoljavajuće korelacije. Na osnovu korelacionih rezultata uočen je primaran uticaj elektronskih efekata na SCS (supstituentom indukovana hemijska pomeranja) vrednosti N-H vodonika, C1 i C=O ugljenika ispitivanih jedinjenja. Korelacioni rezultati za C=O ugljenik se značajno popravljaju ako se koristi kombinacija Ϭ+ i Ϭ- konstanti supstituenata, takozvane elektrofilne i nukleofilne konstante supstituenata, što ukazuje na postojanje značajne proširene rezonancione interakcije supstituenata i elektronske gustine karbonilne grupe. Vrednosti konstanti proporcionalnosti pF i pR za sve atome, ukazuju na približno isti doprinos efekta polja i rezonancionog efekta supstituenata. Efekat polja je nešto izraženji na N-H vodoniku, i za sve atome pokazuje značajne razlike u odnosu na njihov položaj u molekulskoj strukturi ispitivanih jedinjenja. Uticaj efekata supstituenata na IR vibracije istezanja N-H (simetrične i antisimetrične), C=O i CN veze je prevashodno elektronske prirode što se može zaključiti na osnovu dobrih korelacija dobijenih primenom Hametove jednačine i Ϭ parametara supstituenata. Osim toga izvršena je optimizacija geometrije ispitivanih jedinjenja primenom DFT B3LYP/ 6-311G**metode, pri čemu je nađeno da je trans-izomer nešto stabilnji, izuzev u slučaju jedinjenja 3. Supstituisana fenil-grupa i amidna grupa, kod trans-izomera, su približno koplanarne, dok se kod cis- izomera uočava značajna devijacija koja je značajno određena elektronskim efektima prisutnog supstituenta. Takođe je ispitivan položaj cis/trans ravnoteže u ugjen-tetrahloridu, i na osnovu rezultata FT/R analize, kada je prisutan H, CH3, OCH3, Br, i COOH supstituent, nađeno je da je cis izomer u velikom višku, a za ostala jedinjenja utvrđeno je postojanje ravnoteže cis- i trans-izomera

The electrochemical investigation of inclusion complexes of nifedipine and amlodipine with ß-cyclodextrin and (2-hydroxypropyl)-ß-cyclodextrin

The electrochemical behavior of inclusion complexes of nifedipine (Nif) and amlodipine (Aml), a long-acting calcium channel blockers dihydropyridine (DHP) class, with ß-cyclodextrin (ßCD) and (2-hydroxypropyl)-ß-cyclodextrin (HPßCD), is examined using cyclic and square wave voltammetry in 0.05 M NaHCO3 and phosphate buffer (pH=11) on a gold electrode. The voltammograms show a single irreversible anodic wave with the current controlled by adsorption. It was found that phosphate buffer favorites the electrochemical activity of both complexes of Nif with the linear dependency of the oxidative currents on their concentrations. In phosphate buffer, only HPßCD-Aml complex showed linear dependency of the oxidative currents on the concentration. In 0.05 M NaHCO3 as electrolyte only HPßCD-Nif exhibited apparent activity. The initial potential of the anodic reaction as well as the value of the potential for anodic currents maximum of all the examined complexes in both electrolytes were shifted to the positive direction compared to their standards. In addition, the value of anodic currents decreased

Supplementary data for article: Matijević, B. M.; Vaštag, T. T.; Apostolov, S. L.; Milčić, M. K.; Marinković, A. D.; Petrović, S. D. N-(Substituted Phenyl)-2-Chloroacetamides: LSER and LFER Study, 2015. https://doi.org/10.1016/j.arabjc.2015.09.008

Supplementary material for: [https://doi.org/10.1016/j.arabjc.2015.09.008]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/293

Combustion Parameters Calibration and Intake Manifold Redesign for Formula Student YAMAHA YZF-R6 Engine

In order to improve the performance of previous season 599cc Yamaha YZFR6 Formula Student air-flow restricted racing engine, an intensive research in developing a trustworthy engine mathematical model, using 1D thermodynamic Ricardo WAVE® simulation environment was carried out. The Internal Combustion Engine Department has provided simulation software and equipment for in-laboratory engine testing. Data acquired during last season control parameter optimization process (ignition and fuelling main maps) on the engine test bench was used to calibrate the combustion model. Research was based on engine effective parameters, because the crank-angle-resolved cylinder pressure measurement was not carried out. Engine work cycle simulation results analysis and combustion parameters decision-making process were processed using MATLAB® in-house developed code. The engine model with recalibrated combustion parameters was used for assessment of characteristic geometrical dimensions for the new intake manifold. Using this approach for intake manifold design we were able to simulate various design concepts in an effective and fast manner

Light Vehicles Test Procedures on an Automated Engine Test Bed

The vehicle test procedure provides a strict guidance regarding the conditions of dynamometer tests and road load, gear shifting, total car weight, fuel quality, ambient temperature, and tire selection and pressure. Designed as a tool for testing vehicles fuel consumption and emission these tests are usually conducted on expensive and infrastructuraly demanding road dynamometers. This paper presents a method for conducting tests like NEDC or WLTC on an automated engine test bed equipped with high dynamic dynamometer in a manner which provides very similar testing environment. Particularly from the educational point of view, this approach, combining simple mathematical modelling, automated engine test bed and software testing and measurement environment like AVL Cameo, provides numerous possibilities in demonstrating engine operation in a virtual but, by performance, fully realized vehicle

Swelling behavior of synthesized poly(1-vinyl-2-pyrrolidone-co-vinyl acetate) hydrogels

Poly(1-vinyl-2-pyrrolidone-co-vinyl acetate) has great application in cosmetics, primarily in personal care products. It is used in drug delivery, and in a variety of biomedical applications. Also, significant is the application as an adsorbent of various pesticides. The aim of this paper is to examine structural characterization and the swelling behavior of synthesized poly(1-vinyl-2-pyrrolidone-co-vinyl acetate) copolymer hydrogels with 10 mol% of vinyl acetate and with 1.0; 1.5; 2.0; 2.5 and 3.0 mol% of cross-linker ethylene glycol dimethacrylate (EGDM). The characterization of the synthesized hydrogels was performed using FTIR spectroscopy. The swelling study was monitored gravimetrically until equilibrium was reached in solutions of different pH values (3.0, 6.0, 9.0) at a temperature of 25°C. The sensitivity of poly(1-vinyl-2-pyrrolidone-co-vinyl acetate) hydrogels to changes in external temperature was examined by monitoring the change in the equilibrium degree of swelling with increasing fluid temperature from 25ºC to 80ºC in a pH solution of 6.0. FTIR spectra of xerogels confirm the performed synthesis. Swelling of hydrogels poly(1-vinyl-2-pyrrolidone-co-vinyl acetate) was favored at a lower temperature (25°C), in a solution whose pH=6.0, when the sample with 1.0 mol% EGDM reaches the highest degree of swelling (αe=87.23) compared to the achieved capacity at a temperature of 80ºC (αe=20.74). The most intense phase transition was observed in the temperature range of 40-45°C. Based on the obtained results, the synthesized copolymers can be classified into negative thermosensitive hydrogels that have a lower critical dissolution temperature (LCST). pH sensitivity analysis led to the conclusion that the highest value of the equilibrium degree of swelling (αe=168.97) was observed in the hydrogel sample with 1.5 mol% EGDM in the solution whose pH=9 at 25°C. An increase in the molar content of cross-linkers in the hydrogels composition shows a decrease in swelling capacity at all pH values and temperaturesVIII International Conference on Radiation in Various Fields of Research : RAD 2020 : book of abstracts; Virtual Conferenc

CORRELATION ANALYSIS OF IR, 1 H- AND 13 C-NMR SPECTRAL DATA OF N-ALKYL AND N-CYCLOALKYL CYANOACETAMIDES

Linear free energy relationships (LFER) were applied to the IR, 1H- and 13C--NMR spectral data in N-alkyl and N-cycloalkyl cyanoacetamides. N-alkyl and N-cycloalkyl cyanocetamides were synthesized from corresponding amine and ethyl cyanoacetate. A number of substituents were employed for alkyl substitution, and fairly good correlations were obtained, using simple Hammett equation. In N-alkyl and N-cycloalkyl cyanoacetamides substituent cause SCS of N-H hydrogen primarily by steric interaction, polar subtituent effect influences SCS shift of C=O carbon, while steric effect of N-alkyl substituent causes IR stretching frequencies of N-H, C=O and CN group. The conformations of investigated compounds have been studied by the use of semiempirical PM6 method, and together with LFER analysis, give a better insight into the influence of such a structure on the transmission of electronic substituent effects. Negative ρ values for several correlations (reverse substituent effect) were found

Electrochemical Characterization of Oxaprozin on Bare Gold Electrode and Electrode Modified with Bovine Serum Albumin

As the very first electrochemical investigation of oxaprozin, nonsteroidal anti-inflammatory drug, using cyclic voltammetry on gold electrode in 0.05 mol dm(-3) NaHCO3, the synthesized drug, its analytical standard and its content in Duraprox (R) tablets were characterized with one oxidation reaction and the three reduction reactions. All they exhibited the linear concentration dependency of anodic currents at 0.83V for the analytical standard and 0.85V for Duraprox (R) tablets in the range of concentrations 8.44 - 32.78x10(-6) mol dm(-3). The strong adsorption of bovine serum albumin (BSA) on gold electrode in 0.1 mol dm(-3) phosphate buffer solution (pH 7.4) is shown and concentration dependency of anodic currents of oxaprozin standard on BSA/Au is studied. Following the Langmuir adsorption thermodynamic equation, the binding constants of oxaprozin on BSA/Au electrode was calculated with the results 1.23x10(5) dm(3) mol(-1)

A Simulation Study of Fuel Economy Improvement Potentials of a Transit Bus

The AMESim model of motor vehicle driving simulation has been applied on a transit bus to investigate the potentials for fuel economy improvement. With the purpose to calibrate the simulation model and to evaluate the real driving cycle, a data acquisition using vehicle CAN bus has been performed on a transit bus in real driving conditions. This was the basis for constructing a high-fidelity AMESim simulation model of the vehicle for subsequent hybrid systems simulations. It was observed that a great fraction of the total fuel mass was consumed when the bus was stationary. Initial simulation study shows that fuel consumption reduction in excess of 12% could be achieved by implementing a relatively simple start/stop micro-hybrid system. Also, braking energy reaches cca. 60% of the energy released by the engine, representing a potential basis for the application of regenerative braking hybrid system