Incurred sample reanalysis of cefuroxime in rabbit ocular tissues—A case study

In this paper, we present the incurred sample reanalysis (ISR) data for cefuroxime in various ocular tissues of rabbits. Based on the cefuroxime concentration vs. time profile in various ocular tissues, three chosen time points enabled ISR assessment. Cefuroxime was quantitated in the ocular tissues using a published liquid chromatography–electrospray ionization/tandem mass spectrometry method operated under the multiple reaction-monitoring mode in positive ion mode. Regardless of the ocular tissue, the linearity range was 12.7–2760 ng/ml with a correlation coefficient (r²) of ≥0.996. All of the ISR samples representing various ocular tissues met the acceptance criteria. To the best of our knowledge, this is the first report showing the ISR of ocular tissues in any species.     

Determination of quinapril and quinaprilat in human plasma by ultraperformance liquid chromatography–electrospray ionization mass spectrometry

A novel, specific and sensitive ultraperformance liquid chromatography tandem mass spectrometry (UPLC–MS/MS) method was developed for the simultaneous determination of quinapril and its active metabolite quinaprilat in human plasma. The method involves a simple, one‐step extraction procedure coupled with an Acquity UPLC? BEH C₁₈ column (100 × 2.1 mm, i.d., 1.7 µm) with isocratic elution at a flow‐rate of 0.2 mL/min and lisinopril as the internal standard. Detection was performed on a triple‐quadrupole tandem mass spectrometer in multiple reaction monitoring mode via electrospray ionization. Using 250 µL plasma, the methods were validated over the concentration range 5.010–500.374 ng/mL for quinapril and 10.012–1000 ng/mL for quinaprilat, with a lower limit of quantification of 5.010 ng/mL for quinapril and 10.012 ng/mL for quinaprilat. The intra‐ and inter‐day precision and accuracy were within 10.0%. The recovery was 85.8, 62.6 and 61.3% for quinapril, quinaprilat and lisinopril, respectively. Total run time was 3.0 min only. Copyright © 2008 John Wiley & Sons, Ltd.     

Anomalies of the specific heat near the quantum critical point in Tm<Subscript>0.74</Subscript>Yb<Subscript>0.26</Subscript>B<Subscript>12</Subscript>

The behavior of the specific heat near the quantum critical point x ∼ 0.3 in the Tm_{1 − x} Yb _x B₁₂ system has been studied. Detailed measurements have been performed on high-quality single-crystalline Tm_0.74Yb_0.26B₁₂ samples within a wide temperature range of 1.9–300 K in a magnetic field up to 9 T. The temperature dependence of the magnetic contribution to the specific heat has a logarithmic divergence of the form C/T ∼ lnT at T < 4 K, which can be attributed to the quantum critical behavior regime suppressed by the external magnetic field. The Schottky anomaly of the magnetic contribution to the specific heat in Tm_0.74Yb_0.26B₁₂ has been analyzed.     

Development and Validation an LC Method for the Determination of Bendroflumethiazide in Human Plasma and its Pharmacokinetics

A simple, rapid, sensitive high performance liquid chromatography method with fluorescent detection was developed and validated for the determination of bendroflumethiazide in human plasma. Extraction from the plasma was by liquid-liquid extraction using ethyl acetate. Mosapride citrate was used as the internal standard. The chromatographic separation was performed on reverse phase LiChrosphere C18 column with mobile phase comprising of acetonitrile and phosphate buffer (38:62 v/v). The assay precision ranged from 0.9–12.5 and accuracy between 96.8–108.8%, revealing that the method has good reproducibility over the concentration range of 0.98–100.16 ng mL⁻¹. The validated method has been applied to analyze the bendroflumethiazide concentrations for application in pharmacokinetic, bioavailability or bioequivalence studies.     

Synthesis, properties and structures of eight-coordinate zirconium(IV) and hafnium(IV) halide complexes with phosphorus and arsenic ligands

Eight-coordinate [MX(4)(L-L)(2)] (M = Zr or Hf; X = Cl or Br; L-L = o-C(6)H(4)(PMe(2))(2) or o-C(6)H(4)(AsMe(2))(2)) were made by displacement of Me(2)S from [MX(4)(Me(2)S)(2)] by three equivalents of L-L in CH(2)Cl(2) solution, or from MX(4) and L-L in anhydrous thf solution. The [MI(4)(L-L)(2)] were made directly from reaction of MI(4) with the ligand in CH(2)Cl(2) solution. The very moisture-sensitive complexes were characterised by IR, UV/Vis, and (1)H and (31)P NMR spectroscopy and microanalysis. Crystal structures of [ZrCl(4)[o-C(6)H(4)(AsMe(2))(2)](2)], [ZrBr(4)[-C(6)H(4)(PMe(2))(2)](2)], [ZrI(4)[o-C(6)H(4)(AsMe(2))(2)](2)] and [HfI(4)[o-C(6)H(4)(AsMe(2))(2)](2)] all show distorted dodecahedral structures. Surprisingly, unlike the corresponding Ti(iv) systems, only the eight-coordinate complex was found in each system. In contrast, the ligand o-C(6)H(4)(PPh(2))(2) forms only six-coordinate complexes [MX(4)[-C(6)H(4)(PPh(2))(2)]] which were fully characterised spectroscopically and analytically. Surprisingly the tripodal triarsine, MeC(CH(2)AsMe(2))(3), also produces eight-coordinate [MX(4)[MeC(CH(2)AsMe(2))(3)](2)] in which the triarsines bind as bidentates in a distorted dodecahedral structure. There is no evidence for seven-coordination as found in some thioether systems.     

A Facile Method for Nucleophilic Aromatic Substitution of Cyclic Amine

The expeditious solventless nucleophilic aromatic substitution using microwaves is described. A non-conventional synthetic procedure has been developed where basic alumina has been used as energy transfer medium under Microwave Irradiation (MW1). The results were compared with those obtained by the classical method. This rapid and environmentally benign method avoids the use of excess solvents and toxic bases usually employed in the process make this procedure very attractive for synthesis.     

Specific heat of Ce x La1 − x B6 in the low cerium concentration limit (x ≤ 0.03)

The specific heat of high-quality Ce _x La_{1 ? x} B₆ (x = 0, 0.01, 0.03) single crystals is studied in the temperature range 0.4–300 K. LaB₆ samples with various boron isotope compositions (¹⁰B, ¹¹B, ^nat B) are analyzed to estimate the effect of boron vacancies. The experimental data are used to take into account the electron component correctly under the renormalization of the density of states at T < 8 K, the contribution of the quasi-local vibrational mode of a rare-earth ion with the Einstein temperature Θ_E ≈ 152 K, the Debye contribution from the rigid cage of boron atoms with the Debye temperature Θ_D ≈ 1160 K, and the low-temperature Schottky contribution related to the presence of 1.5?2.3% boron vacancies in the rare-earth hexaborides. The detected low-temperature anomalies in the specific heat are shown to be interpreted in terms of the formation of two-level systems with an energy ΔE = 92–98 K caused by the displacement of rare-earth ions from their centrosymmetric positions. A scenario of heavy fermion formation that is alternative to the Kondo mechanism is proposed for the systems with a magnetic impurity.