FIA-fluorimetric determination of adrenaline in pharmaceutical formulations by oxidation with molecular oxygen

The fluorimetric determination of adrenaline is carried out in a continuous-flow assembly and by means of the molecular dissolved oxygen. The sample solution merges with an NaOH stream, then the resulting mixture is heated at 73 °C and led to the flow-cell of the fluorimeter. The flow-assembly is very simple and the procedure is quick (107 samples h^–1) reproducible (R.S.D. 0.6%), selective and suitable to be applied to determination of adrenaline in formulations. Calibrations graph are linear over the ranges 0.05–15 and 20–40 mgl^–1.     

Crystal,Molecular, and Electronic Structure of 1-Acetyl-indoline and Derivatives

The crystal and molecular structures of the following molecules have been determined: 1-acetyl-indoline, 1-acetyl-5-nitro-indoline, l-acetyl-5-nitro-7-bromo-indoline, 1-acetyl-5-bromo-7-nitroindoline, and l-acetyl-5-bromo-7-nitro-indol. Molecular orbital calculations are performed for these compounds and two related species.     

Preconcentration of cadmium, cobalt, copper, nickel and zinc by solvent extraction into methyl isobutyl ketone with 1,5-bis [1-(2-pyridyl) ethylidene] thiocarbonohydrazide and 1,5-bis [phenyl-(2-pyridyl) methylene] thiocarbonohydrazide

The synthesis, physicochemical properties and interactions of two new thiocarbohydrazones, namely 1,5-bis[1-(2-pyridyl) ethylidene] thiocarbonohydrazide (APTH) and 1,5-bis[phenyl-(2-pyridyl) methylene] thiocarbonohydrazide (BPTH) have been studied as well as the use of both compounds as extracting reagents. These thiocarbohydrazones form yellow complexes with bivalent metal ions, and these are extractable into methyl isobutyl ketone. Conditions for quantitative extraction of Cd(II), Co(II), Cu(II), Ni(II) and Zn(II) are established from a critical study of the effect of pH, shaking time, reagent concentration in the organic phase, ionic strength and volume ratio of aqueous to organic phase.     

Effect of the carbon burn-off on the performance of activated carbon as a support for hydrogenation catalysts

The hydrogenation activity of Pt supported on activated carbon would depend on both the Pt dispersity (which can be modified by a partial carbon burn-off in air) and the impurities concentration.     

INTERMEDIATES IN THE ROOM TEMPERATURE FLASH PHOTOLYSIS AND LOW TEMPERATURE PHOTOLYSIS OF PURINE SOLUTIONS

The flash photolysis of purine in acetonitrile and in water at different pH was studied. The transients produced on flash excitation of degassed aqueous solutions have been identified as the triplet excited state, the hydrated electron, a purine radical cation and radical anion on the basis of quenching experiments and comparison to transients observed in low temperature photolysis.     

Why copper is intrinsically more selective than silver in alkene epoxidation: ethylene oxidation on Cu(111) versus Ag(111)

The heterogeneously catalyzed epoxidation of alkenes is experimentally challenging, theoretically interesting, and technologically important. Although large-scale ethylene epoxidation is universally carried out with Ag catalysts, recent laboratory studies on single crystal surfaces show that Cu is intrinsically much more selective than Ag in the epoxidation of a variety of terminal alkenes. The reasons for this striking difference between Ag and Cu have been investigated by means of density functional theory. It is found that the fundamental cause is the inversion in the ordering of activation barriers for the competing pathways to epoxide formation versus acetaldehyde formation (the latter being the first step on the route to combustion). On Cu, epoxide formation is less activated than aldehyde formation; the opposite is true on Ag. This behavior is associated with a late transition state to epoxidation on Cu (i.e., product-like) compared to an early (reactant-like) transition state to epoxidation on Ag.     

Di-2-pyridyl ketone 2-furoylhydrazone as a reagent for the fluorimetric determination of low concentrations of aluminium

The synthesis and properties of di-2-pyridyl ketone 2-furoylhydrazone as an analytical reagent are described. A rapid procedure for the fluorimetric determination of aluminium at the 10-100 ng ml level, at pH 6.1-6.5 (lambda(exc) 395 nm, lambda(em) 465 nm) has been established. Interferences have been evaluated, and the procedure has been applied satisfactorily to determination of aluminium in sea-water.     

Supramolecular phthalocyanine dimers based on the secondary dialkylammonium cation/dibenzo-24-crown-8 recognition motif

[formula: see text] New unsymmetrically substituted DB24C8-phthalocyanines, which are able to form complexes with suitable dialkylammonium cations, have been prepared. These complexes most probably have a pseudorotaxane geometry.     

(Z)-3-p-tolylsulfinylacrylonitrile as a chiral dienophile: diels-alder reactions with furan and acyclic dienes

The behavior of (Z)-3-p-tolylsulfinylacrylonitrile (1) as a chiral dienophile has been evaluated from its reactions with furan and acyclic dienes. Electrostatic interactions of the cyano group with the sulfinyl one restrict the conformational mobility around the C-S bond, thus controlling the pi-facial selectivity, which is almost complete in all cases, the approach of the diene from the less-hindered face of the dienophile (that bearing the lone electron pair) in the predominant rotamer being the favored one. The regioselectivity is also completely controlled by the cyano group. Additionally, the reactivity of compound 1 as well as its endo-selectivity are both higher than those observed for the corresponding (Z)-3-sulfinylacrylates, thus proving the potential of sulfinylnitriles as chiral dienophiles.     

Nanoscale organization of a phthalocyanine-fullerene system: remarkable stabilization of charges in photoactive 1-D nanotubules

Induction of self-organization between zinc phthalocyanine (ZnPc) and C60 moieties in a novel amphiphilic ZnPc-C60 salt results in uniformly nanostructured 1-D nanotubules. Their photoreactivity, in terms of ultrafast charge separation (i.e., approximately 1012 s-1) and ultraslow charge recombination (i.e., approximately 103 s-1), is remarkable. In addition, the observed ZnPc*+-C60*- lifetime of 1.4 ms implies, relative to that of the monomeric ZnPc-C60 ( approximately 3 ns), an impressive stabilization of 6 orders of magnitude.