Colorimetric determination of benzocaine, lignocaine and procaine hydrochlorides in pure form and in pharmaceutical formulations using p-benzoquinone.

A simple, accurate and sensitive method for the microdetermination of benzocaine, lignocaine and procaine hydrochlorides in pure forms and in pharmaceutical formulations is described. The procedure is based on the reaction of those drugs in an aqueous acidic medium with p-benzoquinone to form charge-transfer complexes. The method has been used for the determination of 5.0-70, 5.0-60 and 5.0-90 microg ml(-1) of benzocaine, lignocaine HCl and procaine HCl, respectively. The complexes have apparent molar absorptivities of 1.70 x 10(3), 2.79 x 10(3) and 2.42 x 10(3) L mol(-1) cm(-1) and Sandell sensitivities of 9.72, 10.34 and 11.25 ng cm(-2), respectively. The proposed procedure of analysis is as accurate as the British Pharmacopoeial method (2003). The method was successfully used for the determination of those drugs in the presence of their degradation products, additives and excipients, which were normally encountered in pharmaceutical formulations.     

Toward new biosilicones: hydrosilylation of fish oil unsaturated fatty acid esters

Hydrosilylation of fatty acid methyl esters (FAMEs) were efficiently catalyzed by Speier's and Wilkinson's catalysts in the case of vinylic acid esters, but less efficiently in the case of ­non‐vinylic ones, which gave non‐regiospecific additions. In the latter case, initiation by radicals led to regiospecific reactions for oleic esters (C10‐silylation). This regiospecificity can be attributed to the higher stability of the C10‐silylated adduct and of the corresponding radical intermediate. Only regioselective addition was observed for linoleic esters (C13‐silylation ≈ 70%, C10 ≈ 20%, C9 ≈ 10%). Molecular modeling was used to examine the stability of the isomeric products and radicals. The new concept of radical initiation sequence has been successfully applied to FAMEs and then was extended to crude fish oil. Copyright © 2001 John Wiley & Sons, Ltd.     

1,1‐Organoboration of silylethynyltin compounds studied by multinuclear magnetic resonance spectroscopy: isomerization at the CC bonds and electron‐deficient Si?H?B bridges

1,1‐Organoboration, using triethyl‐, triallyl‐ and triphenyl‐borane (BEt₃, BAll₃, BPh₃), of dimethysilylethynyl(trimethyl)stannane, Me₃Sn? C?C? Si(H)Me₂ ( 1 ), affords alkenes bearing three different organometallic groups at the C?C bond. For BEt₃ and BPh₃, the first products are the alkenes 4 with boryl and stannyl groups in cis‐positions. These rearrange by consecutive 1,1‐deorganoboration and 1,1‐organoboration into the isomers 5 as the final products, where boryl and silyl groups are in cis‐positions linked by an electron‐deficient Si? H? B bridge. 1,1‐Ethylboration of bis(dimethylsilylethynyl)dimethylstannane, Me₂Sn[C?C? Si(H)Me₂]₂ ( 2 ), leads to the stannacyclopentadiene 6 along with non‐cyclic di(alkenyl)tin compounds 7 and 8 . 1,1‐Ethylboration of ethynyl(trimethylstannylethynyl)methylsilane, Me(H)Si(C?C? SnMe₃)C?C? H ( 3 ), leads selectively to a new silacyclopentadiene 13 as the final product. The reactions were monitored and the products were characterized by multinuclear magnetic resonance spectroscopy (¹H, ¹¹B, ¹³C, ²⁹Si and ¹¹⁹Sn NMR). Copyright © 2005 John Wiley & Sons, Ltd.     

Synthesis,characterization and in vitro cytotoxicity of homobimetallic complexes of palladium(II) with 2‐thiouracil ligands. Crystal structure of [Pd2(TU)(PPh3)3Cl2]

Square planar metallic and homonuclear bimetallic complexes of Pd(II) with 2‐thiouracil (HTU) and organophosphines have been synthesized and characterized by FT‐IR and multinuclear ¹H, ¹³C, ³¹P NMR spectroscopy. The thiouracil ligand TU acts as bidentate, is bound through the thioxo moiety and the endo amino group and forms a bridge between a PdCl(R₃P) and a PdCl(R₃P)₂ moiety [R₃P = Ph₃P (o‐tolyl)₃P, ClPh₂P] in the homonuclear bimetallic complexes. The square planar geometry around Pd(II) has been confirmed for these complexes by a single‐crystal X‐ray diffraction study of compound 1 , [Pd₂(TU)(PPh₃)₃Cl₂]. These compounds were also screened against human tumor cell lines and showed promising in vitro cytotoxicity. Copyright © 2007 John Wiley & Sons, Ltd.     

Numerical study of penetration and distribution of charged particles in the magnetosphere during southward IMF case

The energetic charged particles penetration in the plasmasphere are carried out using the updated version of 3D Stanford PIC code. We considered slow and fast wind streams to know the penetration of the energetic charged particles (electrons and ions) having different velocities into four regions i.e. cusp, plasmasphere, sunward, and tailward sides. It is observed that the ion penetrations are higher than electrons for solar slow wind streams in the plasmasphere, while it is reverse for the solar fast streams. Also, the results show that the percentage of penetration of the energetic charged particles (both electrons and ions) are the same into the cusp and subsolar point reconnection region. It is different for the higher speed of fast streams; so that the penetrated electrons reached about 10–20 times than penetrated ions. The results show that for the tailward reconnection region, the penetration of ions is 2–3 times higher than the penetration of electrons, but it is the same for the case of higher solar fast speed.     

The influence of sidewall cooling on boundary layer pressure fluctuations for a two-dimensional supersonic nozzle

Broadband root-mean-square (rms) values and frequency spectra for pressure fluctuations in the supersonic boundary layer on a Mach 3 DeLaval nozzle sidewall and in the freestream are reported for both adiabatic and cooled surface conditions. The flat sidewall of the nozzle contained four sections independently cooled by liquid nitrogen. During the experiments, the flat sidewall was operated (1) adiabatically, (2) cooled in an approximately uniform manner to ?40°C, and (3) cooled in a nonuniform manner. For all thermal boundary conditions on the sidewall, a dynamic pitot probe was traversed through the boundary layer and into the freestream to measure the broadband pressure fluctuations from 30 Hz to 100 kHz. The influence of sidewall cooling on the measured pressure fluctuations was dependent on the unit Reynolds number. Compared with the pressure fluctuations measured with an adiabatic sidewall, uniform cooling of the sidewall was found to reduce the rms pressure fluctuations in both the boundary layer and the freestream by approximately 50% at the highest stagnation pressures used (unit Reynolds numbers above 44,000/cm). Uniform cooling of the sidewall increased rms pressure fluctuations for lower stagnation pressures (unit Reynolds numbers below 44,000/cm). A reduction in the pressure fluctuation amplitude within the boundary layer resulted in a corresponding reduction in the pressure fluctuation amplitude in the test section freestream. Tests using a nonuniform temperature distribution on the sidewall indicated that cooling the portion of the sidewall covering the nozzle throat had the most influence on the pressure fluctuations in the boundary layer and in the freestream.     

Coexpression of the Pyrroloquinoline Quinone and Glucose Dehydrogenase Genes from Serratia marcescens CTM 50650 Conferred High Mineral Phosphate-Solubilizing Ability to Escherichia coli

The genes gdh and pqqABCDE encoding glucose dehydrogenase and its pyrroloquinoline quinone cofactor were cloned from the mineral phosphate-solubilizing (MPS) bacterium Serratia marcescens CTM 50650. We investigated, for the first time, the impact of their coexpression in Escherichia coli on MPS ability. The production of recombinant PQQGDH conferred high MPS activity to the engineered E. coli. In fact, the amounts of soluble phosphorus (P) produced from tricalcium phosphate, hydroxyapatite, and Gafsa rock phosphate (GRP) were 574, 426, and 217 mg/L, respectively. In an attempt to increase the soluble P concentration, the E. coli strain coexpressing the gdh and pqqABCDE genes was immobilized in agar, calcium alginate, and k-carrageenan and was then further applied in a repeated batch (six batches) fermentation process to solubilize GRP. Compared to other encapsulated systems, alginate cell beads were noted to yield the highest concentration of soluble P, which attained 300 mg/L/batch. MPS efficiency was maximal in the presence of 5 and 40 g/L of GRP and glucose, respectively.     

Electrothermal atomic absorption spectrometric determination of cadmium in bangladeshi vegetables with a metal tube atomizer and slurry sampling technique

Ultrasonic slurry sampling electrothermal atomic absorption spectrometry with a molybdenum tube atomizer has been applied for the determination of cadmium in vegetable samples in Bangladesh. The suspension-stabilizing medium was 10% glycerol solution. The optimum pyrolysis temperature was 300°C. The detection limit was 13?fg (3S/N). Matrix element interference was studied and it was found that thiourea as a chemical modifier eliminated the interference. The results for the determination of cadmium in vegetable samples by the proposed method were in good agreement with those measured in dissolved acid-digested samples. The method enables rapid calibration, and simple and rapid analysis of cadmium in vegetable samples at low cost.     

Polyanthranilides. I. Synthesis and Characterization of Polyamides from Isatoic Anhydrides

Ring-scission polymerization of simple and bz-nitro and bz-chlorosubstituted isatoic anhydrides is studied in the presence of reagents like aqueous HCl, anthranilamide, N-methyl aniline, o-chloroaniline, and acid amides under various reaction conditions. Only simple isatoic anhydride is found to undergo ring-scission polymerization affording polyanthranilides in the presence of the first four reagents under appropriate conditions. These samples are insoluble in all organic solvents including formic acid. They are characterized by IR spectral study and thermogravimetric and differential thermal analysis.