Determination of ternary mixtures of penicillin G, benzathine and procaine by liquid chromatography and factorial design study

In the present work, a rapid and sensitive method for simultaneous determination of penicillin G (PG), benzathine (BE) and procaine (PR) in drug and serum media is introduced. The polar hydro-organic (55/45) mobile phases containing an aqueous solution adjusted to pH = 3.7 and an organic solvent (MeOH) including triethylamine (TEA) and trifluroacetic acid (TFA) are used. The flow rate of 1 ml min⁻¹, a C₈ column (150 mm × 46 mm) with 5 μm i.d. and wavelength at 215 nm are selected for optimal separation condition. The limit of detection (LOD), linear concentration range and relative standard deviation (R.S.D.) of this method for the PG are 1.1 μg ml⁻¹, 10-2400 μg ml⁻¹ and 1.7% and for the BE are 1.2 μg ml⁻¹, 12-2100 μg ml⁻¹ and 1.8% and for the PR are 1.5 μg ml⁻¹, 20-2000 μg ml⁻¹ and 2%, respectively. The factorial design is used for the determination of main and interaction effects of pH, flow rate and concentration of MeOH, TEA and TFA in the separation at two levels. Also, the analysis of variance (ANOVA) table is obtained. The results show that TFA and TEA have higher effect than concentration of MeOH, pH and flow rate factors.     

Synthesis and Pyrolytical Solid-Phase Structural Transformations of New Oxorhenium(V) Complexes with 2-Benzoxazolethione

2-Benzoxazolethione reacts with the parent oxorhenium(V) complex, H₂[ReOCl₅], to yield either mononuclear or dinuclear complexes depending on the metal: ligand molar ratio and the concentration of hydrochloric acid containing the parent rhenium complex. The mononuclear complexs [ReOLCl(OH₂)₃]Cl₂, [ReOL₂(OH₂)₃]Cl₃ and [ReOLCl₃(OH₂)]; and dinuclear complexes [Re₂O₃(μ-L)₂Cl₄]·2H₂O and [Re₂O₂(μ-L)L₂Cl₆]-2H₂O were obtained. Both types of complexes have octahedral configurations. The mononuclear complexes prepared in 6N HCl or in 9N HCl undergo irreversible one-step solid-phase thermochromism transformation, thus, the colour of complexes changed from green to brown, black or bluish-green, upon heating. For the complexes obtained in 6N HCl, this step corresponds to structural changes due to the formation of other types of dinuclear complexes, while the mononuclear complex obtained in 9N HCl changes to another mononuclear complex with different coordination sites. On the other hand, the colour of the dinuclear complexes prepared in 2N HCl changed from brown to black, upon heating, in one step solid-phase thermochromism transformation corresponding to a change in the mode of coordination sites of the organic ligand. All thermal products obtained have octahedral configurations. The ligand behaves in these complexes either as a neutral, mono-, bidentate or monoanionic bidentate towards the oxorhenium ions. All complexes and the corresponding thermal products were isolated and their structures were elucidated by elemental analyses, conductance, IR and electronic absorption spectra, magnetic moments, ¹H NMR and TG-DTA measurements as well as by mass spectroscopy.     

Analytic Solutions for Asymmetric Model of a Rod in a Lattice Fluid

We consider the problem of determining analytically some exact solutions of the concentration u(x, y, t) of particles moving by diffusion and advection or drift. It is assumed that the advection is nonlinear. The driven diffusive flow is impeded by an impenetrable obstacle (rod) of length L. The exact solutions for u are evaluated for small and big values of vL/D, where v is the drift velocity and D is the diffusion coefficient. The results show that in some regions in the (x, y) plane the concentration first increases (or decreases) monotonically and then is nearly constant after some critical length L. The location at which u is nearly constant depends on the nature of the driving field v/D. This problem has relevance for the size segregation of particulate matter which results from the relative motion of different-size particles induced by shaking. Methods of symmetry reduction are used in solving the nonlinear advection-diffusion equation in (2+1) dimensions.     

New exact solutions of heat conduction in metals

We consider the way in which a solution to a class of nonlinear partial differential equationsS(u)u _t=(K(u)u_x)_x approaches the similarity form. The problem we solve is chosen for two main reasons: first the equation above is of widespread use in modeling physical situations and second it provides a tractable but significant example of a free boundary problem.     

A catalytic multicomponent protocol to dihydropyridine-3-carboxylate from terminal alkynes,isocyanates, and malonates

Monatshefte für Chemie - Chemical Monthly - A domino catalytic reaction between terminal alkynes, isocyanates, and malonates has been developed. Copper acetylides attack on isocyanates to form...     

Resolution of enantiomers of [α-hydroxy-(o-chlorophenyl)methyl]phosphinic acid via diastereomeric salt formation with enantiopure 1-phenylethylamines

The resolution of racemic α-hydroxy-H-phosphinic acid with enantiopure 1-phenylethylamines via diastereomeric salt formation was investigated. X-Ray crystallographic analysis of the salt revealed that (R)-1-phenylethylamine to be efficient resolving agent for obtaining a single enantiomer of [α-hydroxy-(o-chlorophenyl)methyl]phosphinic acid. Resolving racemic α-hydroxy-H-phosphinic acid with (S)-2-phenylethylamine also gave access to (S)-α-hydroxyalkylphosphinic acid in good yield.     

Impedometric monitoring of the behavior of the supported liquid membrane in electromembrane extraction systems: An insight into the origin of optimized experimental parameters

Electromembrane extraction (EME) was carried out using a novel instrumentation capable of impedometric monitoring of the system during the extraction. This instrumentation involves a classical two-electrode assembly fed by two time-resolved potential functions, the first for the extraction of analyte and the second for obtaining the impedance information. The impedometric analysis of the system was achieved by Laplace transformation of the current recorded during the extraction. It has been shown that the obtained impedance information can be converted to very useful knowledge about time dependence of double layer capacitance, kinetics of analyte depletion, total permeability of the SLM and the effect of experimental parameters on system behavior. It has also been shown that the impedance analysis is a powerful tool for the estimation of optimum experimental parameters without determination of analyte in the acceptor phase.     

Some Analytical Solutions for Groundwater Flow and Transport Equation

This paper presents the use of symmetry reduction method resulting in new exact solutions for the groundwater flow and transport equation. It is assumed that the radionuclides are transported by advection-diffusion in a single fracture and diffusion in the surrounding rock-matrix. The application of one-parameter group reduces the number of independent variables, and consequently the governing PDE of (1+2)-dimension reduces to set of ODEs which are solved analytically. This enables us to present some new exact time-dependent solutions of the advection-diffusion equation.     

An efficient MAI cancellation technique in Optical CDMA

Optical code division multiple access (OCDMA) is a promising operational system for future backhaul optical networks especially for switching and optical signal multiplexing. However, OCDMA operation is restricted by multiple access interference (MAI) due to the asynchronous nature of transmission. In this study, we discuss an efficient MAI technique for OCDMA systems that depends not only on using hybrid frequency shift keying (FSK) modulation but also on employing the double padded modified prime code (DPMPC) as a signature sequence. MAI cancellation is performed by subtracting a reference signal from the received signal of the desired user. The simulation results show that the performance of the FSK-OCDMA technique is superior to the performance of the PPM-OCDMA technique. Furthermore, the obtained results illustrate that the FSK-OCDMA technique is able to accommodate a large number of simultaneous active users with low error-rate.