Analysis of Orphenadrine Citrate in Various Chiral Stationary Phases: A Comparative Study

Background: Polysaccharide based chiral stationary phases (CSPs) were used to perform enantiomeric separation of Orphenadrine Citrate by Ultra-Fast Liquid Chromatography (UFLC) technique. Trials were conducted using the polar mode, reverse phase mode and normal phase mode. Amylose and Cellulose-based CSPs were used for the same. Materials and Methods: Eight Amylose-based CSPs and four Cellulose-based CSPs were used in the reverse phase mode. Five Amylose-based CSPs and two Cellulose-based CSPs were used in polar mode. The only Cellulose-based CSP used in the normal phase mode could effectively separate Orphenadrine Citrate enantiomers with a good resolution. Results and Discussion: Successful enantioseparation was obtained using Chiralcel OD-H containing Cellulose tris (3, 5- dimethylphenylcarbamate) as a chiral selector and n-hexane: Ethanol: Diethylamine (95: 05: 0.1, v/v/v) as the mobile phase. The developed method was validated in accordance with ICH guidelines (Q2R1). Conclusion: The proposed objectives were successfully accomplished as the developed method could effectively resolve Orphenadrine Citrate enantiomers.

A survey of the structural models proposed for PbZr1−x Ti x O3 using mode analysis

The numerous structures that have been reported for the different phases of the lead zirconate titanate system, PbZr1−x Ti x O3 (PZT), are analysed by means of a systematic symmetry-mode analysis. The distortion corresponding to the order parameter has been separated out and expressed in all phases in a comparable form. The fact that the physical origin of the PZT phases is an unstable threefold degenerate polar mode, plus in some cases an unstable octahedral tilting mode, produces structural correlations between the different phases. These correlations had remained unnoticed until now but are directly observable in a mode parameterization. They can be used both to characterize the evolution of the order parameters through the phase diagram and as a stringent test of the reported structural models. It is further shown that the activity of a single polar mode yields a specific feature in the mode decomposition of the monoclinic phases. This single-mode signature can be observed in the majority of the monoclinic structures proposed, making the others questionable. In fact, this internal constraint is satisfied by PZT to such a high degree that it drastically reduces the number of effective structural degrees of freedom. It is conjectured that this type of structural constraint beyond space-group symmetry can be a rather general property of low-symmetry distorted structures. As shown here, its existence can be detected and assessed by a symmetry-mode analysis, if considered in relation to the single underlying multidimensional order parameter.

On the oscillation spectra of ultra compact stars

Quasi-normal modes of ultra compact stars with uniform energy density have been calculated. For less compact stars, there is only one very slowly damped polar mode (corresponding to the Kelvin f-mode) for each spherical harmonic index l . Further long-lived modes become possible for a sufficiently compact star (roughly when M/R ≥ 1/3). We compare the characteristic frequencies of these resonant polar modes to the axial modes first found by Chandrasekhar & Ferrari ( Proc. R. Soc. Lond . A 434, 449 (1991)). We find that the two spectra approach each other as the star is made more compact. The oscillation frequencies of the corresponding polar and axial modes agree to within a percent for stars more compact than M/R = 0.42. At the same time, the damping times are slightly different. The results illustrate that there is no real difference between the origin of these axial and polar modes: They are essentially spacetime modes.

On the non-radial oscillations of slowly rotating stars induced by the Lense-Thirring effect

In a star that is rotating so slowly that the distortion of its figure may be ignored, the axial modes of non-radial oscillation exhibiting resonance can be excited by the polar modes of perturbation by the coupling derived from the dragging of the inertial frame by the rotation of the star (i. e. by the Lense-Thirring effect). The coupling of these two modes of opposite parity is subject to the standard selection rule, ∆ l = ±1. Also, the excitation of ( l + 1)-axial mode by the l -polar mode is favoured relative to the excitation of the ( l - 1)-axial mode, in conformity with the ‘propensity’ rule. As an illustrative example, the excitation of the sextupole axial modes of oscillation by the quadrupole polar perturbations is considered in some detail; and it is shown that both the real and the imaginary parts of the characteristic frequency of the quasi­-normal modes decrease dramatically with the amplitude of the coupling. The relatively very long damping times of these rotationally induced oscillations may be a decisive factor in their eventual detection in neutron stars following the glitches.