Interaction of β-Cyclodextrin with Unsaturated and Saturated Straight Chain Fatty Acid Anions Studied by Phenolphthalein Displacement

The interaction of -cyclodextrin (-CD) with palmitoleate, linolenate, caprinate and caprylate was studied by the displacement of phenolphthalein (PHP) from the -CD cavity. Absorbance values of -CD–PHP solutions at 550 nm in 0.020 mol L-1 Na2CO3 buffer, pH 10.5, at 21.0 ± 0.5 °C, increased as the fatty acid anion was added. The concentration range of fatty acid anion used was 0.390–32.1 × 10-4 mol L-1 in the study of palmitoleate and linolenate, 1.92–80.0 × 10-4 mol L-1 in the study of caprinate and 0.770–32.0 × 10-3mol L-1 in the study of caprylate. Concentrations of -CD and PHP were 1.00 × 10-3 mol L-1 and 1.00–3.00 × 10-4 mol L-1 respectively. Data were fitted by nonlinear regression to a two step complexation model. Complex formation constants thus determined for the 1 : 1 and 1 : 2, fatty acid anion : -CD complex were: (1.2 ± 0.2) × 104 and (2.9 ± 0.2) × 102 mol-1 L for palmitoleate, (9.3 ± 0.9) × 103 and (1.1 ± 0.1) × 102 mol-1 L for linolenate, (4.1 ± 0.2) × 103 and 81 ± 8 mol-1 L for caprinate, and (5.2 ± 0.7) × 102 and 27 ± 5 mol-1 L for caprylate respectively. The PHP–-CD complex was also evaluated as a spectrophotometric sensor for the determination of olive oil acidity.     

Reentrant Structural and Optical Properties and Large Positive Thermal Expansion in Perovskite Formamidinium Lead Iodide

The structure of the hybrid perovskite HC(NH₂)₂PbI₃ (formamidinium lead iodide) reflects competing interactions associated with molecular motion, hydrogen bonding tendencies, thermally activated soft octahedral rotations, and the propensity for the Pb²⁺ lone pair to express its stereochemistry. High‐resolution synchrotron X‐ray powder diffraction reveals a continuous transition from the cubic α‐phase (Pm m, #221) to a tetragonal β‐phase (P4/mbm, #127) at around 285 K, followed by a first‐order transition to a tetragonal γ‐phase (retaining P4/mbm, #127) at 140 K. An unusual reentrant pseudosymmetry in the β‐to‐γ phase transition is seen that is also reflected in the photoluminescence. Around room temperature, the coefficient of volumetric thermal expansion is among the largest for any extended crystalline solid.     

New synthesis of vaulted biaryl ligands via the Snieckus phenol synthesis

[reaction: see text] In an effort to develop a synthesis of the VAPOL ligand that avoids the use of a chromium carbene complex, a route was examined that involved the annulation of a naphthalene carboxamide via the method of Snieckus. The latter derivatives could be converted in a two-step sequence to 2-phenyl-4-phenanthrols in 60-72% overall yields. The utility of this method for the synthesis of VAPOL derivatives is demonstrated in the synthesis of (S)-7,7'-dimethyl-VAPOL.     

Liquid chromatographic tandem mass spectrometric determination of trandolapril in human plasma

A liquid chromatographic tandem mass spectrometric method for the determination of trandolapril in human plasma has been developed and fully validated. The article describes, in detail, the bioanalytical procedure and summarizes the validation results obtained. The samples were extracted using HLB Oasis solid-phase extraction cartridges. The chromatographic separation was performed on X-Terra C8 MS column (150 mm × 4.6 mm i.d., 5 μm particle size) using a mobile phase consisting of acetic acid 20 mM and triethylamine 4.3 mM/acetonitrile (40:60 (v/v)), pumped isocratically at 0.35 ml/min.

The analytes were detected using a micromass quattro micro triple quadrupole mass spectrometer with positive electrospray ionization in multiple reaction-monitoring (MRM) mode. Tandem mass spectrometric detection enabled the quantitation of trandolapril down to 2.0 ng/ml. Calibration graphs were linear (r better than 0.996, n = 9) in the concentration ranges 2.0–750 ng/ml and the intra- and inter-day R.S.D. values were less than 3.83 and 3.86% for trandolapril.     

Polyesters,polyurethanes and epoxy resins derived from 2,2′-(1,4-phenylenedivinylene)bis-8-hydroxyquinaldine and 6-(4-hydroxystyryl)-3-hydroxypyridine

New polyesters and polyurethanes as well as diepoxides bearing styrylpyridine segments were prepared utilizing 2,2′-(1,4-phenylenedivinylene)bis-8-hydroxyquinaldine (PBHQ) and 6-(4-hydroxystyryl)-3-hydroxypyridine (HSHP) as starting materials. The polyesters were prepared by reacting PBHQ or HSHP with terephthaloyl dichloride in the presence of an acid acceptor utilizing the solution polycondensation method. The polyurethanes were prepared from the reactions of PBHQ and HSHP with tolylene diisocyanate and methylenebis(4-phenylisocyanate). In addition, model diesters and diurethanes were synthesized by reacting PBHQ and HSHP with benzoyl chloride and phenyl isocyanate, respectively. Model compounds and polymers were characterized by FT-IR and ¹H-NMR spectroscopy as well as by DTA and TGA. Diepoxides were also prepared from the reactions of PBHQ and HSHP with epichlorohydrin which were polymerized in the presence of 4,4′-diaminodiphenylsulfone. The polyesters were the most thermostable polymers obtained. After curing at 240°C for 20 h, they were stable in N₂ up to 345–370°C and afforded anaerobic char yields of 65–75% at 800°C. © 1993 John Wiley & Sons, Inc.     

A validated liquid chromatographic tandem mass spectrometric method for the determination of mirtazapine and demethylmirtazapine in human plasma: application to a pharmacokinetic study

A new liquid chromatographic tandem mass spectrometric method for the determination of mirtazapine and demethylmirtazapine in human plasma has been developed and fully validated. The article describes in detail the bioanalytical procedure and summarizes the validation results obtained. The samples were extracted using liquid-liquid extraction with a mixture of 1-chlorobutane/isopropanol/ethyl acetate (88:2:10, (v/v/v)). The chromatographic separation was performed on a reversed-phase XTerrra MS C₈ column ( i.d.; 3.5 μm particle size) using a mobile phase consisting of 0.010 M ammonium formate (pH 7.8) and acetonitrile (35:65, (v/v)), pumped at a flow rate of 0.80 ml min⁻¹. The analytes were detected using a Finnigan LCQ advantage ion-trap mass spectrometer with positive electrospray ionization in selected reaction monitoring (SRM) mode. Tandem mass spectrometric detection enabled the quantitation of both compounds down to 0.10 ng ml⁻¹. Calibration graphs were linear (r better than 0.990, n=11), in concentration ranges 0.10 to 200 ng ml⁻¹ for mirtazapine demethylmirtazapine. The intra- and inter-day R.S.D. values were less than 14.8 and 16.6% for mirtazapine and demethylmirtazapine, respectively. The method was successfully applied to a kinetic study in order to assess the main pharmacokinetic parameters of mirtazapine and demethylmirtazapine.     

Dense colloid transport in a bifurcating fracture

In this work, the transport of dense colloids through a water-saturated, bifurcating fracture is investigated using a constant spatial step particle tracking technique. The size of the constituents of a colloid plume is an important factor affecting the partitioning of dense colloids at the bifurcation. While neutrally buoyant colloids partition between daughter fractures in proportion to flow rates, dense colloids will preferentially exit fractures that are gravitationally downgradient, notwithstanding that the majority of the interstitial fluid may flow through the upper fracture. Comparison of the partitioning ratio between daughter fractures with the ratios of characteristic settling, diffusion, and advection time reveal that these parameters control how colloids behave at fracture bifurcations.     

Synthesis,Spectroscopic Characterization,Magnetic Properties,and Electronic Structure of New Copper(II) μ-isophthalato Dimers

Synthesis and Properties of 1,2,3-Thiazaboroles, 3-Sulfoimido- and 3-Pseudohalido-1,2,3-dithiaboroles The reactions of 3,4,5-trimethyl- and 4,5-diethyl-3-methyl-1,2,3-dithiaborole with di-t.-butylsulfurdiimide leads to the 1,2,3-thiazaboroles 2 . 3-Bromo-1,2,3-dithiaboroles react with trimethylsilyl-N-sulfinylamine, -isocyanate, and -cyanide by formation of 3-sulfoimido- ( 3 ), 3-isocyanato- ( 4 ), and 3-cyano- ( 5 ) -1,2,3-dithiaboroles. 3-Isothiocyanato-1,2,3-dithiaboroles ( 6 ) are formed by addition of elemental sulfur to 5 . ¹H-, ¹¹B-, ¹³C-, ¹⁴N-, ¹⁵N-NMR-, mass-, and IR spectra are reported and discussed.     

Preconcentration at a carbon-paste electrode and determination by adsorptive-stripping voltammetry of rutin and other flavonoids

The non-Faradaic preconcentration behaviour of nine flavonoids (six flavones: fisetin, galangin, morin, quercetin, rhamnetin, rutin, and three flavanones: hesperidin, hesperitin, naringin) at a carbon-paste (nujol/graphite) electrode and the factors affecting it (pH, accumulation potential, presence of various surfactants) for their subsequent differential pulse voltammetric determination are examined. All flavones tested are readily accumulated on the carbon paste electrode resulting in a considerable signal enhancement making determinations feasible down to 10⁻⁸ − 10⁻⁷ M after preconcentration for 1–4 min. Flavanones are not preconcentrated so their lower determination limits are of the order of 10^-6 M. A simple voltammetric procedure for the determination of rutin in a multivitamin preparation is presented.