Quantitative determination of pravastatin and its metabolite 3α‐hydroxy pravastatin in plasma and urine of pregnant patients by LC‐MS/MS

This report describes the development and validation of a chromatography/tandem mass spectrometry method for the quantitative determination of pravastatin and its metabolite (3α‐hydroxy pravastatin) in plasma and urine of pregnant patients under treatment with pravastatin, as part of a clinical trial. The method includes a one‐step sample preparation by liquid–liquid extraction. The extraction recovery of the analytes ranged between 93.8 and 99.5% in plasma. The lower limits of quantitation of the analytes in plasma samples were 0.106 ng/mL for pravastatin and 0.105 ng/mL for 3α‐hydroxy pravastatin, while in urine samples they were 19.7 ng/mL for pravastatin and 2.00 ng/mL for 3α‐hydroxy pravastatin. The relative deviation of this method was <10% for intra‐ and interday assays in plasma and urine samples, and the accuracy ranged between 97.2 and 106% in plasma, and between 98.2 and 105% in urine. The method described in this report was successfully utilized for determining the pharmacokinetics of pravastatin in pregnant patients enrolled in a pilot clinical trial for prevention of preeclampsia. Copyright © 2015 John Wiley & Sons, Ltd.     

Simultaneous effect of rotation and natural convection on the flow about a liquid sphere

The problem of mixed convection around a liquid sphere that experiences a rotation about its axis parallel to the free stream is studied numerically using a finite- difference technique. The coupled boundary-layer energy and momentum equations are numerically solved over a wide range of Grashof number that represents the cases of aiding and opposing free convection and for wide range of the spin parameter Ta/Re². The surface of the sphere also rotates as a result of the shear stress exerted from the external flow of air. The effect of both parameters on the velocity components as well as the temperature within the thermal boundary-layer is presented. Results show that increasing the aiding free convection and the spin parameter cause increases in the shear stress and the local heat transfer coefficient.     

Microchip analysis of plant glucosinolates

We describe a new and selective analytical method for the separation and quantitation of plant glucosinolates. The new method, which utilizes microchip CE (micro-CE) with fluorescence detection, circumvents the multistep procedures characteristic of conventional methods. Glucosinolates form charge transfer complexes with the xanthene dyes phloxine-B and eosin-B. The glucosinolates-phloxine-B complex cannot be excited at 470 nm. Thus, the decrease in peak intensity of phloxine-B after complex formation is used to quantitatively measure total glucosinolates in Arabidopsis thaliana seeds. For qualitative analysis, complex formation with eosin-B is used. The sensitivity of eosin-B detection at excitation/emission 470 nm/540 nm was low. However, sensitivity increased following complex formation with sinigrin (> or =3 microg/mL). A batch-learning, self-organizing map was applied to visualize and organize analytical data into 2-D matrix with similar and related data clustered together or near each other. This organized matrix was used to optimize electrophoretic conditions for the analysis. This study suggests potential applications of micro-CE in plant metabolomics analyses without use of labeling fluorophores.     

Fluorescence lifetime properties of near-infrared cyanine dyes in relation to their structures

Structurally diverse near-infrared (NIR) absorbing polymethine dyes were prepared and their fluorescence lifetimes (FLT) were evaluated in relation to their structural features. Comparative FLT analysis based on the modification of methine chain length and heterocyclic system showed that indolium or benzo[e]indolium heptamethine dyes exhibited longer FLT than the benzo[c,d]indolium trimethine dye. Modification of heterocyclic system alone with an intact chain length showed that indolium-based heptamethine dyes showed approximately 30% longer FLT than the benzo[e]indolium-based dyes. In general, the FLT of polymethine dyes increased from polar to non-polar solvents. In addition, correlation study between the theoretical and the experimental FLT for indocyanine green (ICG) suggests that the lack of structural rigidity for these cyanine dyes is primarily responsible for the loss of the excited state energy via non-radiative pathway.     

Revealing the Chemical State of Palladium in Operating In2O3 Gas Sensors: Metallic Pd Enhances Sensing Response and Intermetallic InxPdy Compound Blocks It

The sensing response of metal oxides activated with noble metal nanoparticles is significantly influenced by changes to the chemical state of corresponding elements under operating conditions. Here, a PdO/rh-In₂O₃ consisting of PdO nanoparticles loaded onto rhombohedral In₂O₃ was studied as a gas sensor for H₂ gas (100–40000 ppm in an oxygen-free atmosphere) in the temperature range of 25–450 °C. The phase composition and chemical state of elements were examined by resistance measurements combined with synchrotron-based in situ X-ray diffraction and ex situ X-ray photoelectron spectroscopy. As found, PdO/rh-In₂O₃ undergoes a series of structural and chemical transformations during operation: from PdO to Pd/PdH_x and finally to the intermetallic In_xPd_y phase. The maximal sensing response (R_N2/R_H2) of ∼5 ⋅ 10⁷ towards 40000 ppm (4 vol %) H₂ at 70 °C is correlated with the formation of PdH_0.706/Pd. The In_xPd_y intermetallic compounds formed around 250 °C significantly decrease the sensing response.     

Molecular dynamics and conduction mechanism of poly(vinyl chloride-co-vinyl acetate-co-2-hydroxypropyl acrylate) terpolymer containing ionic liquid

Dielectric spectroscopy (DS) measurements were performed to probe the segmental dynamics and ion mobility of poly(vinyl chloride-co-vinyl acetate-co-2-hydroxypropyl acrylate) terpolymer dopped with different amounts of tetrabutylammonium tetrafluoroborate ([TBA] [BF₄]) ionic liquid (IL). Differential scanning calorimetry (DSC) was also employed to trace the change in the glass transition temperature (T_g) at different loads of IL. The DSC measurements revealed a remarkable reduction in the PVVH T_g from 344 to 310 K just by adding 20 wt% of IL. The DS measurements revealed three relaxation processes named α, β₁, and β₂. The α-process is related to the segmental motion of PVVH while the β₁ and β₂ are due to the restricted local dynamics of side chains. The segmental relaxation times (α-relaxation) speed up with increasing the concentration of IL due to the plasticization effect of IL on polymer chains. The temperature dependence of α-relaxation follows the Vogel-Fulcher-Tammann (VFT) relation with dynamic glass transition between 323 and 294 K in agreement with the DSC measurements. The β₁ and β₂-relaxations have an Arrhenius temperature dependence. The temperature dependence of ionic conductivity obeys the VFT behavior indicating the coupling between the segmental motion of PVVH chains and ion transport. Polaronic tunneling is the predominant conduction mechanism in PVVH and its composites. The specific capacitance increases with increasing both the temperature and IL concentration.     

High-performance thin-layer chromatographic determination of trigonelline content in various extracts and different varieties of some commercial coffees available in the Saudi Arabian market

JPC – Journal of Planar Chromatography – Modern TLC - The proposed research study was undertaken to establish a simple, rapid and sensitive high-performance thin-layer chromatography...     

Two new indoloquinoline alkaloids from cryptolepis sanguinolenta: Cryptosanguinolentine and cryptotackieine

The roots of the indigenous West African shrub Cryptolepis sanguinolenta have proved to be a rich source of indoloquinoline alkaloids. To date, all of the alkaloids isolated have been analogs of indolo[3, 2-b]quinoline. We now wish to report examples of two new indoloquinoline alkaloids which differ in the fusion of the indole and quinoline rings. The first, cryptosanguinolentine, is an angular indolo[3, 2-c]quinoline. The second, cryptotackieine, is a linear indolo[2, 3-b]quinoline system. Both of these families of alkaloids are without precedent from C. sanguinolenta. The structures of both were established through the extensive use of inverse-detected micro nmr methods.     

Zinc(II)-selective ratiometric fluorescent sensors based on inhibition of excited-state intramolecular proton transfer

To develop a zinc(II)-selective emission ratiometric probe suitable for biological applications, we explored the cation-induced inhibition of excited-state intramolecular proton transfer (ESIPT) with a series of 2-(2'-benzenesulfonamidophenyl)benzimidazole derivatives. In the absence of Zn(II) at neutral pH, the fluorophores undergo ESIPT to yield a highly Stokes' shifted emission from the proton-transfer tautomer. Coordination of Zn(II) inhibits the ESIPT process and yields a significant hypsochromic shift of the fluorescence emission maximum. Whereas the paramagnetic metal cations Cu(II), Fe(II), Ni(II), Co(II), and Mn(II) result in fluorescence quenching, the emission response is not altered by millimolar concentrations of Ca(II) or Mg(II), rendering the sensors selective for Zn(II) among all biologically important metal cations. Due to the modular architecture of the fluorophore, the Zn(II) binding affinity can be readily tuned by implementing simple structural modifications. The synthesized probes are suitable to gauge free Zn(II) concentrations in the micromolar to picomolar range under physiological conditions.