Rapid determination of desorption efficiency, and analysis of solvent mixtures for occupational exposure studies

Summary An analytical procedure has been developed for simultaneous determination of solvent mixture vapors to enable evaluation of occupational exposure. To determine the desorption efficiency the volatile components of the solvent mixtures were generated from a glass tube filled with glass wool. This device is easy to prepare and use. These vapors were then collected in activated charcoal tubes and analyzed by capillary gas chromatography. The method was tested with a mixture of 22 solvents, including aliphatic and aromatic hydrocarbons, alcohols, ethers, esters, and ketones, all at low concentrations. All the components were detected. When a 99∶1 mixture of carbon disulfide-dimethylformamide was used for desorption the efficiency was>75% for most of the solvents.     

Enhancement of Oral Bioavailability of Rofecoxib Using β-Cyclodextrin

The purpose of the present work was to investigate the effect ofcomplexation of rofecoxib with -cyclodextrin on its dissolutioncharacteristics and bioavailability. Inclusion complexes of rofecoxibwith -cyclodextrin were made by freeze-drying technique. Phasesolubility studies were conducted as suggested by Higuchi and Connors.The samples were characterized by performing dissolution studies, X-rayDiffraction studies and Differential Scanning Calorimetry. The complexeswere compressed into tablets and compared in-vitro with various marketedformulations. A single dose study on healthy human volunteers was performedin comparison with a marketed formulation of rofecoxib (without-cyclodextrin) to investigate the relative bioavailability.Phase solubility studies confirmed the formation of a 1 : 1complex in solution of rofecoxib with -cyclodextrin. Tablets ofsolid inclusion complexes of rofecoxib with -cyclodextrin preparedby freeze drying technique showed enhanced dissolution rate in distilledwater in comparison with all the marketed formulations analyzed. This isattributed to the increased solubility and wettability along with decreasedcrystallinity caused by complex formation, which is confirmed, by XRD and DSCstudies. The bioequivalence studies performed showed statistically significantenhancement in bioavailability as compared to the marketed formulation.Apparently, tablets containing complexes of rofecoxib with -cyclodextrinshows faster onset of action due to improved solubility, enhanced dissolutionand faster absorption of the molecule. The results of this investigation withrofecoxib in -cyclodextrin lend ample credence to its better oralbioavailability on complexation.     

Calorimetric study of cesium hexafluoroarsenate CsAsF<Subscript>6</Subscript> at elevated temperatures

Summary Cobalt(II), nickel(II) and copper(II) complexes of some aroylhydrazone Schiff’s bases derived from isoniazide (hydrazide of isonicotinic acid) with p-hydroxybenzaldehyde; 2,4-dihydroxybenzaldehyde or 2-hydroxy-1-naphthaldehyde are prepared and characterized. The study reveals that the ligands coordinate in the keto form. That transformed to the enol through the loss of HCl upon heating the solid complexes. The copper(II) complexes are thermochromic in the solid-state while the cobalt(II) complex, 3 of 2,4-dihydroxybenzaldehyde moiety is solvatochromic in hot DMF. The chromisms obtained were discussed in terms of change in the ligand field strength and/or coordination geometry.     

Conformational studies of soluble and immobilized frog epidermis tyrosinase by fluorescence

Fluorescence spectra and soluble quenching of intrinsic protein fluorescence were used as indexes of conformational changes suffered by frog epidermis tyrosinase. The activation process and the immobilization of the enzyme involving either free amino groups or its carbohydrate moiety were studied. The conformational changes resulting from denaturation of each one of the protein derivatives, as well as the effect of active center copper extraction, were followed by fluorescence studies. The results showed that: (a) both activation and immobilization were accompanied by conformational changes of the protein leading to more unfolded states; (b) neither enzyme nor immobilized enzyme were fully unfolded upon denaturation although enzymic activity was lost; (c) the enzyme immobilized through its carbohydrate moiety was more unfolded upon denaturation than the enzyme immobilized through amino groups, thus pointing to a higher conformational stabilization in the last situation; and (d), that tryptophyl residues moved to a localization near the active site upon activation.     

Two-dimensional infrared (2D IR) spectroscopy. A new tool for interpreting infrared spectra

Two-dimensional infrared (2D IR) spectroscopy is used to study atactic polystyrene. 2D IR is a technique based on time-resolved detection of IR signals in response to an external perturbation, such as mechanical strain. Since different chemical functional groups respond to the applied perturbation at unique and often different rates, characteristic time-dependent variations of the IR-band intensities are observed. Correlation analysis of the dynamic variation of the IR signals yields a new spectrum defined by two independent wave numbers. Peaks located on a 2D IR spectral plane imply interactions and connectivities among chemical functional groups. By spreading convoluted IR bands over two dimensions, the spectral resolution is also greatly enhanced.     

High speed liquid chromatography with small bore columns

Using a specially designed column system, we have systematically investigated the effect of mobile phase velocity on column efficiency. The performance of small bore columns operated at different linear velocities of mobile phase was examined for three different types of injection system. Using the value of H^∞/u or n^∞/t${}_{\text{r}}^{\text{º}}$ as a criterion of a high speed separation, we calculated values of n/t${}_{\text{r}}^{\text{º}}$ for different solutes according to the equation \documentclass{article}\pagestyle{empty}\begin{document}$ {{\rm n}\mathord{\left/ {\vphantom {{\rm n} {{\rm t}_{\rm r}^ \circ }}}\right. \kern-\nulldelimiterspace} {{\rm t}_{\rm r}^ \circ }} = {{{\rm n}^\infty } \mathord{\left/ {\vphantom {{{\rm n}^\infty } {{\rm t}_{\rm r}^ \circ }}} \right. \kern-\nulldelimiterspace} {{\rm t}_{\rm r}^ \circ }}\left({\frac{{1 + {\rm k'}}}{{{\rm k' + }\beta }}} \right)^2 $\end{document}; the results obtained are in agreement with the experimentally determined values. These systematic investigations culminated in the separation of seven compounds in less than 10 s; the respective chromatogram is shown.     

Antimicrobial and anticancer activities of Schiff base ligand and its transition metal mixed ligand complexes with heterocyclic base

A new Schiff base ligand (HL) was prepared via a condensation reaction of quinoline‐2‐carboxaldhyde with 2‐aminophenol in a molar ratio of 1:1. Its transition metal mixed ligand complexes with 1,10‐phenanthroline (1,10‐phen) as co‐ligand were also synthesized in a 1:1:1 ratio. HL and its mixed ligand complexes were characterized using elemental analysis, infrared, ¹H NMR, mass and UV–visible spectroscopies, molar conductance, magnetic measurements, solid reflectance, thermal analysis, electron spin resonance and X‐ray diffraction. Molar conductance measurements showed that all complexes have an electrolytic nature, except Cd(II) complex. From elemental and spectral data, the formulae [M(L)(1,10‐phen)(H₂O)]Cl_x?nH₂O (where M = Cr(III) (x = n = 2), Mn(II) and Ni(II) (x = 1, n = 2), Fe(III) (x = n = 2), Co(II), Cu(II) and Zn(II) (x = 1, n = 2)) and [Cd(L)(1,10‐phen)Cl]?3H₂O for the metal complexes have been proposed. The geometric structures of complexes were found to be octahedral. Powder X‐ray diffraction reflected the crystalline nature of the complexes; however, the Schiff base is amorphous. HL and its mixed ligand complexes were screened against Gram‐positive bacteria (Streptococcus pneumoniae and Bacillus subtilis) and Gram‐negative bacteria (Pseudomonas aeruginosa and Escherichia coli). Antifungal activity was determined against Aspergillus fumigatus and Candida albicans, the data showing that most complexes had activity less than that of the Schiff base while Mn(II), Fe(III) and Ni(II) complexes showed no significant antifungal activity. The anticancer activity of HL and its metal complexes was also studied against breast and colon cell lines. The metal complexes showed IC₅₀ higher than that of HL, especially the Cu(II) complex which showed the highest IC₅₀ against breast cell line.     

Stroboscopic microscopy—direct imaging of structure development and phase separation during spin‐coating

Spin‐coated polymer blends possess a rich variety of accessible non‐equilibrium morphologies, formed through a process of phase separation and self‐assembly, the complexities of which remain incompletely understood. The technique of stroboscopic microscopy has now been developed to allow direct observations of microscopic and mesoscopic morphological development during spin‐coating and has afforded unequivocal information regarding morphological development. The technique so far has three modes of operation providing information on topographical, compositional, and crystal development. In this review, we look at the technique's development, its applications and comment on the future potential for this technique. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 17–25