[PDF] Top 20 J. Braz. Chem. Soc. vol.10 número6

... A his tó ria das re vis tas ci en tí fi cas bra si le i ras está re ple ta de al tos e ba i xos. Den tre as inú me ras que fo ram cri a das, pou cas con se gui ram so bre vi ver ao tem po, por uma ra zão mu i to sim ... See full document

... reactions (36) and (10), respectively. Since photolysis light intensities during the experiments were not reported 26 , the ethyl nitrite photodecomposition coefficient was estimated from the experimental ... See full document

... Thus, even wit hout con si de ring the re com men da ti ons of IUPAC 4,5 it should be cle ar that Mo no seg men ted Flow Analy sis (MSFA) is the ap pro pri a te name for a flow ap pro -[r] ... See full document

... to 10% abundance) and have not been useful for comparation with standards library data, turned to 100% abundance, therefore participating in the compari- son with NBS library (around 40,000 ... See full document

... with a molar absorptivity of 1.31 x 10 4 L mol -1 cm -1 and features a detection limit of 26 ng mL -1 at 588 nm. The selectivity of the reagent was improved by the use of (1,2-cyclo- hexylenedinitrilo) tetraacetic ... See full document

... A number of compounds with different polarities were used to evaluate the efficiency of each stationary phase, as determined by the retention factor (k), plate number (N), resolution (Rs) and asymmetry factor (As) at ... See full document

... Nevertheless, the equations derived for RDE could not be applied for very small or very large values for the electrode rotation rate (ω). When ω is smaller than 100 rpm, the hydrodynamic boundary layer becomes large and ... See full document

... the system, the initiator potassium persulfate dissolved in 4.5 cm 3 of water was added to the reaction mixture. The polymerization reaction was carried out at 70 °C for 10 h under constant 300-350 rpm stirring. ... See full document

... con se quen ce the mo du la ti on pe ri od of the qua si pe ri o dic os cil la ti ons ap pro a ches in fi nity as the for cing fre quency is in cre a sed to wards the cri ti cal va lue of ω = 0.8525, Fig. 2. The emer ... See full document

... in the initial part of the voltammogram since only reactions (8-10) are slowly occurring and blocking the surface. When the potential reaches ca. 1.0 V, the oxidation of the Pd surface starts (11) and, ... See full document

... Analytical Chem- istry should be considered as the Chemistry of the experiments and, in this perspective, the research on Ana- lytical Chemistry must provide not only new evidence or new methods of analysis, but ... See full document

... A new isoflavone named harpalycine and quercetin were isolated from the leaves and 3-hy- droxy-4-isopentenyl-8,9-methyle-nedioxypterocarpan and betulinic acid from the roots of Harpa- l[r] ... See full document

... 15 g of dried ground leaves were boiled for 10 min in a 20% (v/v) sulfuric acid aqueous solution (150 mL), then filtered. The filtrate, after being neutralized with a 25% (v/v) ammonium hydroxide aqueous solution, ... See full document

... The association of lignin and tannins and/or the pres- ence of profisetinidins and prorobinetinidins could account for the great resistance of Astronium urundeuva wood regarding chemical[r] ... See full document

... x 10 -4 s -1 , e este valor foi tomado como referência para reação de oxidação não ...x 10 -2 mg -1 L s -1 ) a reação se processa com velocidade específica cinco vezes superior quando comparado a pH 2,6 ( K ... See full document

... unknown equilibrium constants by least-square techniques were minimized. Three titrations were performed with the metal ion and each ligand. All the potentiometric studies were carried out in a Micronal (Brasil) model ... See full document

... concerning the chemical composition of the volatile com- pounds obtained were not completed, owing to the limita- tion in instrumental and analytical methods 3 . The direct thermal cracking of fatty acids (FFAs) and ... See full document

... Neste trabalho foram montados e caracterizados dois dispositivos eletrocrômicos (ou janelas eletrocrômicas) utilizando como materiais opticamente ativos polímeros instrinsecamente con- dutores. Os materiais usados na ... See full document

... stereoisomeric mixtures: an enantiomeric pair (R,R and S,S) and two meso compounds (R,S and S,R), in a 2:1:1 ratio (Scheme 2). These diastereomers were detected by 31 P- NMR, as three signals (0-10 ppm). ... See full document

... concentration range from 6.5 x 10 -4 to 3.2 x 10 -3 mol L -1 , in 0.5 mol L -1 NaCl solution and v = 20 mV s -1 . To keep the pH constant, the buffers acetic acid/acetate (pH 3.5), biphthalate (pH 6.0) and ... See full document