Dissolution profiles of perindopril and indapamide in their fixed-dose formulations by a new HPLC method and different mathematical approaches

A new HPLC method was introduced and validated for simultaneous determination of perindopril and indapamide. Validation procedure included specificity, sensitivity, robustness, stability, linearity, precision and accuracy. The method was used for the dissolution test of perindopril and indapamide in three fixed-dose formulations. The dissolution procedure was optimized using different media, different pH of the buffer, surfactants, paddle speed and temperature. Similarity of dissolution profiles was estimated using different model-independent and model-dependent methods and, additionally, by principal component analysis (PCA). Also, some kinetic models were checkedwith dissolved amounts of drugs as a function of time

Revisiting a perovskite-like copper-formate framework NH4[Cu(HCOO)3]: order-disorder transition influenced by Jahn-Teller distortion and above room-temperature switching of the nonlinear optical response between two SHG-active states

Metal-formate frameworks comprising ammonium cations as guests are proven to be a fertile ground to study various phenomena associated with the temperature-induced changes in structural, dielectric, optical, and magnetic properties. In this contribution, we revisit NH4[Cu(HCOO)3], a member of metal formates that distinguishes itself in terms of its phase transition behavior and associated properties. New data on structural dynamics of all phases of NH4[Cu(HCOO)3] have been obtained with the use of variable-temperature Raman measurements. Smooth changes of band positions observed near 220 K attest to the postulated continuous nature of low-temperature phase transition, whereas apparent discontinuities at 355 K confirm the first-order type of transition between orthorhombic (II) and hexagonal (I) phases. Low-temperature Raman data were confronted with diffraction results, pointing to a significant effect of Jahn-Teller distortion on the vibrational properties the CuO6 subnetwork. In the high-temperature range, a significant broadening of bands is observed, confirming that phase I is highly disordered, with the strongest changes of full width at half maximum (FWHM) parameters being observed for bands corresponding to NH4+ cations. Dielectric investigations revealed the symmetric shape of the observed process indicating the Debye-like relaxation. Thus, the dielectric relaxation was characterized in terms of the dipolar relaxation model using the Cole–Cole relaxation function, leading to an Ea value of approximately 0.76 eV. Finally, temperature-resolved second harmonic generation (SHG) measurements unequivocally corroborate the noncentrosymmetric setting of phases II and I, as well as allowed us to realize temperature-induced switching of second-order nonlinear optical (NLO) responses. We demonstrate that NH4[Cu(HCOO)3] serves as a host to uncommon kind of quadratic NLO switching, which takes advantage of two SHG-active states: SHG-high state below Tc, and SHG-low state above Tc. The demonstrated SHG-high – SHG-low temperature-driven bistability stands out from the vast majority of molecular and coordination polymer NLO switches that employ binary SHG-on and SHG-off switching schemes

Dissolution profiles of perindopril and indapamide in their fixed-dose formulations by a new HPLC method and different mathematical approaches

A new HPLC method was introduced and validated for simultaneous determination of perindopril and indapamide. Validation procedure included specificity, sensitivity, robustness, stability, linearity, precision and accuracy. The method was used for the dissolution test of perindopril and indapamide in three fixed-dose formulations. The dissolution procedure was optimized using different media, different pH of the buffer, surfactants, paddle speed and temperature. Similarity of dissolution profiles was estimated using different model-independent and model-dependent methods and, additionally, by principal component analysis (PCA). Also, some kinetic models were checked for dissolved amounts of drugs as a function of time

Quantification of Exciton Fine Structure Splitting in a Two-Dimensional Perovskite Compound

International audienceApplications of two-dimensional (2D) perovskites have significantly outpaced the understanding of many fundamental aspects of their photophysics. The optical response of 2D lead halide perovskites is dominated by strongly bound excitonic states. However, a comprehensive experimental verification of the exciton fine structure splitting and associated transition symmetries remains elusive. Here we employ low temperature magneto-optical spectroscopy to reveal the exciton fine structure of (PEA)2PbI4 (here PEA is phenylethylammonium) single crystals. We observe two orthogonally polarized bright in-plane free exciton (FX) states, both accompanied by a manifold of phonon-dressed states that preserve the polarization of the corresponding FX state. Introducing a magnetic field perpendicular to the 2D plane, we resolve the lowest energy dark exciton state, which although theoretically predicted, has systematically escaped experimental observation (in Faraday configuration) until now. These results corroborate standard multiband, effective-mass theories for the exciton fine structure in 2D perovskites and provide valuable quantification of the fine structure splitting in (PEA)2PbI4

Quantification of Exciton Fine Structure Splitting in a Two-Dimensional Perovskite Compound

Applications of two-dimensional (2D) perovskites have significantly outpacedthe understanding of many fundamental aspects of their photophysics. The optical response of2D lead halide perovskites is dominated by strongly bound excitonic states. However, acomprehensive experimental verification of the excitonfine structure splitting and associatedtransition symmetries remains elusive. Here we employ low temperature magneto-opticalspectroscopy to reveal the excitonfine structure of (PEA)2PbI4(here PEA is phenyl-ethylammonium) single crystals. We observe two orthogonally polarized bright in-plane freeexciton (FX) states, both accompanied by a manifold of phonon-dressed states that preservethe polarization of the corresponding FX state. Introducing a magneticfield perpendicular tothe 2D plane, we resolve the lowest energy dark exciton state, which although theoreticallypredicted, has systematically escaped experimental observation (in Faraday configuration)until now. These results corroborate standard multiband, effective-mass theories for theexcitonfine structure in 2D perovskites and provide valuable quantification of the finestructure splitting in (PEA)2PbI