Development of a novel RP‐HPLC method for the efficient separation of aripiprazole and its nine impurities

The development of an RP‐HPLC method for the separation of aripiprazole and its nine impurities was performed with the use of partial least squares regression, response surface plot methodology, and chromatographic response function. The HPLC retention times and computed molecular parameters of the aripiprazole and its nine impurities were further used for the quantitative structure–retention relationship (QSRR) study. The QSRR model, R²: 0.899, Q²: 0.832, root mean square error of estimation: 4.761, root mean square error of prediction: 6.614, was developed. Very good agreement between the predicted and observed retention times (t_R) for three additional aripiprazole impurities (TC1–TC3) indicated the high prediction potential of the QSRR model for t_R evaluation of other aripiprazole impurities and metabolites. The developed HPLC method is the first reported method for the efficient separation of aripiprazole and its nine impurities, which could be used for the analysis of an additional three aripiprazole impurities (TC1–TC3).     

Potential inequality

We prove a general inequality for kernels satisfying the maximum principle. This is then used to derive a sufficient condition for the kernel to define a continuous map of Lebesgue spaces. Exactly this condition happens to be necessary and sufficient for the validity of Hardy’s inequality with weights in one dimension. Some applications indicating the unifying nature of the potential inequality are given. A part of this paper was presented at the 865th AMS meeting, March 1991, Tampa, Florida.     

Calcium trifluoromethanesulfonate-catalysed aminolysis of epoxides

Aminolysis of epoxides catalysed by calcium trifluoromethanesulfonate under mild reaction conditions is described. The novel method is very efficient in the synthesis of wide variety of β-amino alcohols with high regio- and stereoselectivity.     

Nanostructured lipid carriers for triamcinolone acetonide delivery to the posterior segment of the eye

Triamcinolone acetonide (TA) is a corticosteroid drug currently administered by intravitreal injection for a broad spectrum of inflammatory, edematous and angiogenic ocular diseases. To increase the drug's bioavailability by ocular instillation, TA was encapsulated in nanostructured lipid carriers (NLC), previously optimized by our group using a factorial design approach. In the present paper, nanometric (∼200 nm), unimodal and negatively charged NLC loaded with the fluorescent lipid marker Nile red (NR-NLC) and drug (TA-NLC) were produced by high pressure homogenization. Based on the selected formulations, in vivo tests were carried out by eye-drop instillation of NR-NLC in mice, revealing the systems’ ability of delivering lipophilic actives to the posterior segment of the eye via the corneal and non-corneal pathways. Short and long-term stability of TA-NLC was assessed by high performance stability analysis using the Turbiscan^®. The results showed a backscattering of less than 1.5% and during a period of 6 months, anticipated the low tendency of these particles for aggregation during shelf life when stored at room temperature.     

Focusing surface plasmon polariton wave packets in space and time

The spatiotemporal focusing of surface plasmon polariton (SPP) wave packets (WPs) by planar plasmonic‐lens coupling structures is described using combined femtosecond interferometric time‐resolved photoemission electron microscopy (ITR‐PEEM) imaging and model simulations. The focusing properties of lens structures inscribed lithographically into Ag films depend on the angle of incidence of the excitation field. Severe aberrations are introduced by the phase delay in the interaction of obliquely incident plane waves with the commonly employed circular arc‐shaped lens structures. It is shown that the aberration can be corrected by accounting for propagation delays caused by the incidence angle‐dependent retardation of the optical field‐lens structure interaction. The focusing of SPP‐WPs in both space and time is demonstrated with aberration corrected lens structures.     

Quantitative Structure-Retention Relationship Modeling of the Retention Behavior of Guanidine and Imidazoline Derivatives in Reversed-Phase Thin-Layer Chromatography

JPC – Journal of Planar Chromatography – Modern TLC - The quantitative structure-retention relationship (QSRR) study has been performed in order to investigate the retention behavior of...     

Adaptive numerical modeling using the hierarchical Fup basis functions and control volume isogeometric analysis

A novel adaptive algorithm that is based on new hierarchical Fup (HF) basis functions and a control volume formulation is presented. Because of its similarity to the concept of isogeometric analysis (IGA), we refer to it as control volume isogeometric analysis (CV-IGA). Among other interesting properties, the IGA introduced k-refinement as advanced version of hp-refinement, where every basis function of the nth order from one resolution level are replaced by a linear combination of more basis functions of the n+1th order at the next resolution level. However, k-refinement can be performed only on whole domain, while local adaptive k-refinement is not possible with classical B-spline basis functions. HF basis functions (infinitely differentiable splines) satisfy partition of unity, and they are linearly independent and locally refinable. Their main feature is execution of the adaptive local hp-refinement because any basis function of the nth order from one resolution level can be replaced by a linear combination of more basis functions of the n+1th order at the next resolution level providing spectral convergence order. The comparison between uniform vs hierarchical adaptive solutions is demonstrated, and it is shown that our adaptive algorithm returns the desired accuracy while strongly improving the efficiency and controlling the numerical error. In addition to the adaptive methodology, a stabilization procedure is applied for advection-dominated problems whose numerical solutions “suffer” from spurious oscillations. Stabilization is added only on lower resolution levels, while higher resolution levels ensure an accurate solution and produce a higher convergence order. Since the focus of this article is on developing HF basis functions and adaptive CV-IGA, verification is performed on the stationary one-dimensional boundary value problems.     

Conductometric studies on the stability of copper complexes with different oligosaccharides

Bioactive copper complexes with pullulan or dextran oligosaccharides are the subject of intensive research mainly because of their possible application in veterinary and human medicine. The thermal stability and stability under oxidative conditions of the Cu(II) complexes with reduced low-molar pullulan or dextran were investigated in this paper, using a conductometric method. The influence of ligand constitutions on the stability of the complexes was examined on the basis of ligand property. Forced degradation studies were performed on bulk sample of complexes by using heat (25, 40 and 60°C) and an oxidation agent (0.1, 0.5, 1.0 and 10.0% v/v hydrogen peroxide). It can be concluded, according to the results obtained (by examining conductivity during the forced degradation studies), that Cu(II) complexes show a large pharmaceutical stability for both tests.      

Spatial supercontinuum generation in nonlinear photonic lattices

We show that two Bloch modes launched into a nonlinear photonic lattice evolve into a comb or a supercontinuum of spatial frequencies, exhibiting a sensitive dependence on the difference between the quasi-momenta of the two initially excited modes. This phenomenon results from four-wave mixing combined with exchanges of momentum between the optical field and the lattice.     

Luminescence thermometry using Gd<Subscript>2</Subscript>Zr<Subscript>2</Subscript>O<Subscript>7</Subscript>:Eu<Superscript>3+</Superscript>

In this paper we study the possibility of using the synthesized nanopowder samples of Gd₂Zr₂O₇:Eu³⁺ for temperature measurements by analyzing the temperature effects on its photoluminescence. The nanopowder was prepared by solution combustion synthesis method. The photoluminescence spectra used for analysis of Gd₂Zr₂O₇:Eu³⁺ nano phosphor optical emission temperature dependence were acquired using continuous laser diode excitation at 405 nm. The temperature dependencies of line emission intensities of transitions from ⁵D₀ and ⁵D₁ energy levels to the ground state were analyzed. Based on this analysis we use the two lines intensity ratio method for temperature sensing. Our results show that the synthesized material can be efficiently used as thermographic phosphor up to 650 K.