Ultratrace Analysis of Dopamine Using a Combination of Imprinted Polymer-Brush-Coated SPME and Imprinted Polymer Sensor Techniques

A combination approach in solid-phase microextraction, based on a molecularly imprinted polymer-brush coating on an optical fiber coupled with a complementary molecularly imprinted polymer sensor, has been adopted for isolation, preconcentration, and analysis of dopamine at ultratrace levels in highly dilute aqueous samples. This combination enabled enhanced (up to 8.5-fold) preconcentration of the analyte, which is appropriate for achieving a stringent detection limit in clinical diagnosis of several neurodegenerative diseases. The detection limit of dopamine in biological samples was 0.018 ng mL^?1 with a relative standard deviation less than 2.1% and without any non-specific contributions.     

Some aspects of stabilization and degradation of nigerian natural rubber. I. Photostabilization of natural rubber with bound di-tert-butyl-4-hydroxybenzyl thioglycollate (dbhbt)

3,5-Di-tert-butyl-4-hydroxybenzyl thioglycollate (DBHBT) has been reacted with Nigerian Natural rubber latex at 65 ± 1°C using 4,4-azobiscyanovaleric (AZBN) acid-ferrous sulfate redox system to obtain a binding efficiency of 13%. The bound DBHBT was investigated as a UV stabilizer in unprocessed and unvulcanized rubber using spectroscopic method. With respect to the C? O index, the masterbatch diluted to 56% gave the optimum activity and higher concentrations showed significant pro-oxidant activity. The C? C bonds in particular, showed greater stability which is a function of DBHBT concentration. The methylenic and the allylic hydrogen atoms, the most susceptible, and probably the sites of the primary attack, were not protected by DBHBT.     

Simultaneous analysis of furosemide and bumetanide in horse plasma using high performance liquid chromatography

A high performance liquid chromatographic method is described for the simultaneous determination of furosemide and bumetanide in horse plasma. The C8 (3 microns) reversed phase column (4.8 x 150 mm) provided clear separation of furosemide and bumetanide with other components present in the horse plasma. The detection limit for both the drugs was 10 ng/mL. Both drugs were stable in plasma (at natural or acidic pH) for up to 24 h. The method is sufficiently sensitive to detect furosemide levels in plasma obtained from horses receiving a therapeutic dose of furosemide.     

Synthesis and electrochemical studies of charge-transfer complexes of thiazolidine-2,4-dione with σ and π acceptors

In the present work, we report the synthesis and characterization of novel charge-transfer complexes of thiazolidine-2,4-dione (TZD) with sigma acceptor (iodine) and pi acceptors (chloranil, dichlorodicyanoquinone, picric acid and duraquinone). We also evaluated their thermal and electrochemical properties and we conclude that these complexes are frequency dependent. Charge-transfer complex between thiazolidine-2,4-dione and iodine give best conductivity. In conclusion, complex with sigma acceptors are more conducting than with pi acceptors.     

Preparation,X-ray crystallography,and thermolysis of phenylenediammonium dibromide salts

Phenylenediammonium dibromide (PDADBr) salts have been prepared and characterized by X-ray crystallography. The thermal decomposition of PDADBr has been studied by thermogravimetry (TG) and differential thermal analysis (DTA). Kinetic parameters have been evaluated using model fitting and isoconversional methods. The thermolytic pathways have also been suggested which involve proton transfer as a primary step to regenerate parent amine and HBr. Interaction between amine and HBr at higher temperature yields gaseous products.     

Time-resolved spectra of coumarin 30-rhodamine 6G dye mixture

The effect of acceptor concentration on the energy transfer from Coumarin 30 (donor) to Rhodamine 6G (acceptor) has been studied. The nature of energy transfer reaction has been studied through lifetime measurements by recording the time-resolved fluorescence decay curves. The energy transfer parameters calculated were used to confirm the occurrence of energy transfer on the basis of the emission-reabsorption effect.     

Thiol derivatives of arylnaphthylmethane as novel anti-osteoporotic agents

(Mercaptophenyl)naphthylmethane derivatives were synthesized as novel estrogen receptor binding ligands. [4-(Methylsulfonyl)phenyl](naphth-1-yl)ketone shows a very promising activity towards osteoporosis. Correspondence: Sangita, Medicinal and Process Chemistry Division, Central Drug Research Institute, Lucknow 226001, India.     

Molecular complexity from aromatics: synthesis of highly functionalized spiro δ-lactones

A novel, general, and efficient method has been developed for the synthesis of highly functionalized spiro δ-lactones from aromatic precursors. Our methodology involves a tandem oxidative dearomatization-rearrangement of tertiary furyl carbinols and ring-closing metathesis as key features. This method allows an access to the spirolactones attached to carbocycles of various sizes.     

Screening effect of impurities in metals: a possible explanation of the process of cold nuclear fusion

Summary The screening length of the deuterium ion by surrounding electrons in a palladium metal lattice, as estimated using two approaches—viz. the Thomas-Fermi screening theory and the Debye screening theory for plasmas in metal—is found to be less than the interatomic separation of ordinary hydrogen molecules. This has important implications for the possibility of cold nuclear fusion at room temperature, since slight fluctuations in equilibrium conditions may drive the deuterons to fuse together. The relative magnitudes of screening length for the cold nuclear fusion regime and classical hot nuclear regimes (inertial and magnetic confinement) reveal that in the former a comparatively smaller amount of energy is needed to overcome the repulsive Coulomb barrier between two deuterium ions.