Simple method for the determination of rosiglitazone in human plasma using a commercially available internal standard

To the best of our knowledge, bioanalytical methods to determine rosiglitazone in human plasma reported in literature use internal standards that are not commercially available. Our purpose was to develop a simple method for the determination of rosiglitazone in plasma employing a commercially available internal standard (IS). After the addition of celecoxib (IS), plasma (0.25 mL) samples were extracted into ethyl acetate. The residue after evaporation of the organic layer was dissolved in 750 microL of mobile phase and 50 microL was injected on to HPLC. The separation was achieved using a Hichrom KR 100, 250 x 4.6 mm C(18) with a mobile phase composition potassium dihydrogen phosphate buffer (0.01 m, pH 6.5):acetonitrile:methanol (40:50:10, v/v/v). The flow-rate of the mobile phase was set at 1 mL/min. The column eluate was monitored by fluorescence detector set at an excitation wavelength of 247 nm and emission wavelength of 367 nm. Linear relationships (r(2) > 0.99) were observed between the peak area ratio rosiglitazone to IS vs rosiglitazone concentrations across the concentration range 5-1000 ng/mL. The intra-run precision (%RSD) and accuracy (%Dev) in the measurement of rosiglitazone were <+/-10.69 and <-12.35%, respectively across the QC levels (50-1000 ng/mL). The extraction efficiency was >80% for both rosiglitazone and IS from human plasma. The lower limit of quantitation of the assay was 5 ng/mL. In summary, the methodology for rosiglitazone measurement in plasma was simple, sensitive and employed a commercially available IS.     

Synthesis and structural characterization of Pd(II) thiosemicarbazonato complex: Catalytic evaluation in synthesis of diaryl ketones from aryl aldehydes and arylboronic acids

A simple route to synthesize triphenylphosphinopalladium(II) thiosemicarbazonato complex has been described. Elemental analysis, spectral (IR, NMR) and single crystal X-ray diffraction techniques were employed for the complete characterization of the complex. The latter was found to be effective catalyst for carbon–carbon cross-coupling reaction of aryl- and heteroarylboronic acids with aromatic and heteroaromatic aldehydes to form the corresponding diaryl ketones. The influence of reaction parameters such as solvent, base, reaction temperature and catalyst loading was also investigated.     

Simple and one-pot synthesis of tri and tetracyclic frameworks containing [1,8]naphthyridin-2-one moiety from the Baylis-Hillman adducts

A facile synthesis of tri and tetracyclic frameworks containing [1,8]naphthyridin-2-one skeleton from the Baylis-Hillman alcohols via the Johnson-Claisen rearrangement, followed by the treatment with Fe/AcOH in simple one-pot multi-step process is described.     

Binuclear ruthenium(II) pyridazine complex catalyzed transfer hydrogenation of ketones

A convenient and general method of synthesis of binuclear ruthenium(II) pyridazine complex was reported. The synthesized complex was characterized by analytical and spectral methods. The structure of the complex was confirmed by X-ray diffraction technique and was found to be an efficient catalyst for the transfer hydrogenation of ketones with excellent conversions in the presence of isopropanol/KOH at 82 °C. The effect of solvents, bases, and different catalyst/substrate ratio for the reaction was also investigated.     

Validation and clinical application of an LC‐ESI‐MS/MS method for simultaneous determination of tolmetin and MED5, the metabolites of amtolmetin guacil in human plasma

A highly sensitive, rapid assay method has been developed and validated for the simultaneous estimation of tolmetin (TMT) and MED5 in human plasma with liquid chromatography coupled to tandem mass spectrometry with electrospray ionization in the positive‐ion mode. A simple solid‐phase extraction process was used to extract TMT and MED5 along with mycophenolic acid (internal standard, IS) from human plasma. Chromatographic separation was achieved with 0.2% formic acid–acetonitrile (25:75, v/v) at a flow rate of 0.50 mL/min on an X‐Terra RP₁₈ column with a total run time of 2.5 min. The MS/MS ion transitions monitored were 258.1 → 119.0 for TMT, 315.1 → 119.0 for MED5 and 321.2 → 207.0 for IS. Method validation and clinical sample analysis were performed as per FDA guidelines and the results met the acceptance criteria. The lower limit of quantitation achieved was 20 ng/mL and the linearity was observed from 20 to 2000 ng/mL, for both the anlaytes. The intra‐day and inter‐day precisions were in the range 3.27–4.50 and 5.32–8.18%, respectively for TMT and 4.27–5.68 and 5.32–8.85%, respectively for MED5. This novel method has been applied to a clinical pharmacokinetic study. Copyright © 2010 John Wiley & Sons, Ltd.     

A novel demonstration of photoacoustic Raman spectroscopy with combined stimulated Raman pumping in H2 molecule

We present the experimental demonstration of a novel, efficient, and vibrational selective technique to prepare population in vibrational level v″ = 1 using the stimulated Raman pumping. Photoacoustic Raman signal has been studied in non-radiative transitions in the molecule H₂ (v″ = 0) and (v″ = 1). The population fraction in the v″ = 1 level can be estimated by using combined photoacoustic Raman spectroscopy with stimulated Raman pumping for the first time.     

Rocks,Shocks and Asteroids,and Some Interesting Research Directions in Mechanics

Mechanics lies at the heart of many of the underpinnings of modern technological civilization: materials, infrastructure, transportation, health and security. The mechanics of dynamic failure processes also has a major bearing on the potential catastrophes that threaten civilization, including airbursts and major asteroid impacts. Recent events (such as the Chelyabinsk meteoroid) have demonstrated the need to understand major impact and fragmentation events. Many of the fundamental problems of current interest in national security also involve impact and fragmentation, typically studied through large-scale computational simulations. In the Murray lecture, these issues were addressed by describing fundamental high-strain-rate experiments, high-speed visualization, theoretical and computational modeling of failure processes, and simulations of asteroid damage and disruption. This paper focuses on experimental results on meteorites and a basalt.     

Release studies on niosomes containing fatty alcohols as bilayer stabilizers instead of cholesterol

Monomers of some amphiphiles organize into bilayers to form liposomes and niosomes. Such bilayers are unstable or leaky and hence cholesterol is a common ingredient included to stabilize them. Cholesterol stabilizes bilayers, prevents leakiness, and retards permeation of solutes enclosed in the aqueous core of these vesicles. Other than cholesterol a material with good bilayer-stabilizing properties is yet to be identified. We have substituted cholesterol with fatty alcohols in niosomes containing polyglyceryl-3-di-isostearate (PGDS) and polysorbate-80 (PS-80) to explore their membrane-stabilizing property via permeation studies. Niosomes of polyglyceryl-3-di-isostearate, fatty alcohol/cholesterol, and polysorbate were prepared by ether injection method. Aqueous solution of ketorolac tromethamine (KT) was entrapped in them. The effects of alkyl chain length of fatty alcohols (C(12), C(14), C(16), C(18), and C(16+18)), of acyl chain length of polyoxyethylene sorbitan monoester surfactants, and of the molar ratio of lipid mixture on the release rate of ketorolac from niosomes were assessed by employing modified dissolution-dialysis method. Niosomes with cholesterol or fatty alcohols have exhibited a common release pattern. Niosomes containing fatty alcohol showed a considerably slower release rate of KT than those containing cholesterol. Based on the release rate, fatty alcohols can be ranked as stearyl相似文献   

Limitations in the use of horseradish peroxidase as an enyzme probe in the development of a homogeneous immunoassay for aflatoxin B1

Horseradish peroxidase (HRPO) was used as a probe to quantitate aflatoxin B₁ by a homogeneous immunoassay. The conjugation of AFB₁ to HRPO resulted in 54% loss of enyzme activity. In the presence of AFB₁ specific antibodies, the HRPO-AFB₁ conjugate showed reversal of its lost enzyme activity by 12%. This positive modulatory effect of antibody on the enzyme activity was used as an analytical tool to quantitate AFB₁. The homogeneous assay carried out with free AFB₁ and HRPO-AFB₁ conjugate in the presence of antibodies indicated poor linearity as compared to the heterogeneous assay. It was observed that the number of HRPO-lysine residues involved in AFB₁ conjugation were 6–8. The low level of modulation of enzyme activity by antibody with respect to HRPO-AFB₁ conjugate, could possibly be attributed to the limited number of lysine residues in the HRPO molecule and its proximity to the active site of the enzyme. Thus, HRPO was found to be limiting as an enzyme with respect to the homogeneous enzyme immunoassay for AFB₁ analysis. The antibodies raised were specific for AFB₁, and showed excellent linearity even at high dilution for the detection of AFB₁ by ELISA indicating that antibodies per se were not the limiting factor.