Rapid and Sensitive LC−MS–MS Method for the Determination of Sarpogrelate in Human Plasma

A rapid and sensitive liquid chromatographic–tandem mass spectrometric method has been developed and validated for the estimation of sarpogrelate in human plasma. Sarpogrelate was extracted from human plasma by solid-phase extraction. Temocapril was used as the internal standard. Heated electron spray ionization mass spectrometry was performed on a TSQ Quantum Ultra MS system. The LC column was a Hypurity C₁₈ and the mobile phase was 2 mM ammonium formate (pH 3.00 ± 0.05):acetonitrile (30:70 v/v). A flow rate of 0.250 mL min^?1 was used. The quantitative analyses were carried out in the positive ion and full scan mode over the mass range m/z 60–500. The capillary, vaporiser temperatures were 325 and 200 °C respectively. The sheath gas pressure, spray voltage, collision energy and tube lense were 40, 3,500 V, 19 V, 198 V, respectively, and the mass spectra of the drugs were recorded by total ion monitoring. Retention times and characteristic mass fragments were recorded and the chosen diagnostic mass fragments were monitored in the mass chromatography mode. Signal intensities of each of the mass fragments: m/z 477 [M + H]⁺ for temocapril, m/z 430 [M + H]⁺ for sarpogrelate, were used for quantification. The calibration curves (the ratio between the peak areas as signal intensities of the drug analyzed and that of the internal standard (temocapril: m/z 477 [M + H]⁺) vs. the concentration of drug) exhibited linearity over the concentration range 5.00–2,500.00 ng mL^?1 human plasma. The recovery and the accuracy were calculated by comparing the peak areas as the signal intensities of each mass fragment for the drug in spiked samples after solid-phase extraction from human plasma to the peak area as the signal intensity of the mass fragment of internal standard sample. The method involves a rapid solid phase extraction from plasma, simple isocratic chromatography conditions and mass spectrometric detection that enables detection up to picogram levels with a total run time of 3.0 min only. The method was validated over the range of 5.0–2,500.0 ng mL^?1. The absolute recoveries for sarpogrelate (93.72%) and IS (91.42%) achieved from spiked plasma samples were consistent and reproducible.     

Attenuation of second sound in superfluid 3He-A1

The attenuation of second sound (spin-entropy) wave in the superfluid A1 phase has been measured in magnetic fields up to 11 T and to sufficiently high frequency to observe the bulk attenuation proportional to the square of frequency. The measured attenuation coefficient is compared with the existing theories of hydrodynamics and dissipative coefficients. The resulting "excess" attenuation is discussed in terms of the temperature dependent spin diffusion coefficient in the superfluid.     

Mg-Al hydrotalcites as the first heterogeneous basic catalysts for the Kornblum oxidation of benzyl halides to benzaldehydes using DMSO

Mg-Al hydrotalcites (Mg/Al = 2, 3, 5) act as efficient heterogeneous base catalysts for the conversion of benzyl halides to the corresponding benzaldehydes using DMSO as an oxidant.     

Photoionization of Al IV (neon-type) from its ground 2s 22p 6 1 S e and excited 2s 22p 53p 3,1 P 0 3 S e states using the R-matrix method

The R-matrix method is used to calculate the total photoionization cross-sections from the ground 2s ²2p ^{6 1} S ^e and the first three excited 2s ²2p ⁵3p ^3,1 S ^e states of Al IV, for photon energies ranging from the first ionization threshold to just above the second threshold of the residual ion Al V. The two lowest LS terms of Al V − 2s ²2p ^{5 2} P ⁰, 2s2p ^{6 2} S ^e, 2s2p ^{6 2} S ^e, represented by sophisticated configuration interaction wavefunctions, are included in the R-matrix calculation. The resulting cross-sections are affected by Rydberg series of resonances converging to the 2s2p ^{6 2} S ^e excited threshold.     

An analytical study of nonlinear double-diffusive convection in a porous medium under temperature/gravity modulation

The article deals with nonlinear thermal instability problem of double-diffusive convection in a porous medium subjected to temperature/gravity modulation. Three types of imposed time-periodic boundary temperature (ITBT) are considered. The effect of imposed time-periodic gravity modulation (ITGM) is also studied in this problem. In the case of ITBT, the temperature gradient between the walls of the fluid layer consists of a steady part and a time-dependent periodic part. The temperature of both walls is modulated in this case. In the problem involving ITGM, the gravity field has two parts: a constant part and an externally imposed time-periodic part. Using power series expansion in terms of the amplitude of modulation, which is assumed to be small, the problem has been studied using the Ginzburg–Landau amplitude equation. The individual effects of temperature and gravity modulation on heat and mass transports have been investigated in terms of Nusselt number and Sherwood number, respectively. Further the effects of various parameters on heat and mass transports have been analyzed and depicted graphically.     

Study of heat transport by stationary magneto-convection in a Newtonian liquid under temperature or gravity modulation using Ginzburg–Landau model

The present paper deals with a weak non-linear stability problem of magneto-convection in an electrically conducting Newtonian fluid, confined between two horizontal surfaces, under a constant vertical magnetic field, and subjected to an imposed time-periodic boundary temperature (ITBT) or gravity modulation (ITGM). In the case of ITBT, the temperature gradient between the walls of the fluid layer consists of a steady part and a time-dependent oscillatory part. The temperature of both walls is modulated in this case. In the problem involving ITGM, the gravity field has two parts: a constant part and an externally imposed time periodic part, which can be realized by oscillating the fluid layer. The disturbance is expanded in terms of power series of amplitude of convection, which is assumed to be small. Using Ginzburg–Landau equation, the effect of modulations on heat transport is analyzed. Effect of various parameters on the heat transport is also discussed.     

Unsteady natural convection in a liquid-saturated porous enclosure with local thermal non-equilibrium effect

Stability analysis of free convection in a liquid-saturated sparsely-packed porous medium with local-thermal-non-equilibrium (LTNE) effect is presented. For the vertical boundaries free–free, adiabatic and rigid–rigid, adiabatic are considered while for horizontal boundaries it is the stress-free, isothermal and rigid–rigid, isothermal boundary combinations we consider. From the linear theory, it is apparent that there is advanced onset of convection in a shallow enclosure followed by that in square and tall enclosures. Asymptotic analysis of the thermal Rayleigh number for small and large values of the inter-phase heat transfer coefficient is reported. Results of Darcy–Bénard convection (DBC) and Rayleigh–Bénard convection can be obtained as limiting cases of the study. LTNE effect is prominent in the case of Brinkman–Bénard convection compared to that in DBC. Using a multi-scale method and by performing a non-linear stability analysis the Ginzburg–Landau equation is derived from the five-mode Lorenz modal. Heat transport is estimated at the lower plate of the channel. The effect of the Brinkman number, the porous parameter and the inter-phase heat transfer coefficient is to favour delayed onset of convection and thereby enhanced heat transport while the porosity-modified ratio of thermal conductivities shows the opposite effect.

     

Effect of gravity modulation on linear,weakly-nonlinear and local-nonlinear stability analyses of stationary double-diffusive convection in a dielectric liquid

Meccanica - The paper deals with the study of effect of gravity modulation on double-diffusive convection in a dielectric liquid for the cases of rigid-rigid and free-free boundaries. Using a...     

Steady finite-amplitude Rayleigh–Bénard convection of ethylene glycol–copper nanoliquid in a high-porosity medium made of 30% glass fiber-reinforced polycarbonate

Journal of Thermal Analysis and Calorimetry - In the paper, we make linear and nonlinear stability analyses of Rayleigh–Bénard convection in a Newtonian nanoliquid-saturated...     

Development of stability-indicating assay method and liquid chromatography-quadrupole-time-of-flight mass spectrometry-based structural characterization of the forced degradation products of alpelisib

The US Food and Drug Administration and the European Medicines Agency approved alpelisib in 2019 for the treatment of metastatic breast cancer. A thorough literature review revealed that a stability-indicating analytical method (SIAM) is not available for the quantification of alpelisib and its degradation products (DPs). In this study, per the comprehensive stress study recommended by the International Council for Harmonisation (ICH), alpelisib was exposed to hydrolysis, oxidation, photolysis, and thermal stress. Degradation of the drug was observed under hydrolysis, oxidative, and photolysis conditions, whereas the drug was stable under thermal stress condition. We developed a SIAM for the separation of alpelisib and its major DPs that were formed under different stress conditions. The validation of the developed method was performed per ICH Q2(R1) guidelines. Five DPs were identified and characterized. Structure elucidation of all DPs was performed with the modern characterization tool of liquid chromatography-quadrupole time-of-flight mass spectrometer (LC-Q-TOF-MS/MS). The degradation pathway of the drug and its mechanisms were outlined, and in silico toxicity prediction was performed using the ProTox-II tool.