Publications

Abstract The standard (p degrees = 0.1 MPa) massic energies of combustion Delta(c)u degrees at T = 298.15 K were measured by static bomb combustion calorimetry for 5-amino-6-nitroquinoline and 4-aminoquinaldine, from which the standard molar enthalpies of formation of both compounds, in the crystalline state, were derived. The standard molar enthalpies of sublimation Delta(cr)(g)H(m)degrees of the same compounds were derived from the Knudsen effusion measurements of the vapour pressures as a function of the temperature. [GRAPHICS] The derived standard molar enthalpies of formation in the gaseous state are shown to fit a group addictivity scheme. (C) 1998 Academic Press.

Abstract Six leaf litter extracts (LLE) (eucalyptus (Eucaliptus globulus), fern (Pteridium aquilinium), oak (Quercus robur), chestnut (Castanea sativa), laurel (Laurus nobilis), and ulex (Ulex europoeus) canopies) were isolated following an extraction procedure similar to that used for fulvic acids (FA) and were characterized by elemental analysis and UV-Vis, FT-IR, and synchronous molecular fluorescence (SyF) spectroscopies. Moreover, information about their interaction with the Cu(II) ion in aqueous solution (100 mg/L of LLE in 0.1 M KNO(3) at pH = 6) was obtained from the measurement of SyF spectra at increasing concentrations of Cu(II). These spectral sets were treated by a self-modeling mixture analysis method (SIMPLISMA) to obtain improved quenching profiles to be used in the estimation by the method of Ryan and Weber of the conditional stability constants (K(c)), concentration of binding sites, and percentage of fluorescent binding sites accessible for complexation. For comparison purposes, two samples of FA extracted from two horizons of an oak forest soil (0-5 cm and 5-15 cm) were also studied. The spectroscopic data obtained for LLE and FA were different. The results suggest that LLE are characterized by relatively high concentrations of individualized simple molecules and include reactive structures (alkene and protein residues). The ratio of aliphatic/aromatic structures was higher in LLE than for FA. Both LLE and soil FA form stable complexes with Cu(II), but the logarithm of the conditional stability constant of the 1:1 complexes is larger for LLE (about 5) than for the soil FA (about 4.5).

Abstract The interaction of Fe(III) with two samples of fulvic acids (FAs) extracted from a pinewood soil (FA2: horizon 0-10 cm; FA3: horizon 10-25 cm) was monitored by synchronous fluorescence (SyF) spectroscopy at four pH values (3, 4, 5, and 6). Spectral data were preprocessed by SIMPLISMA, a self-modeling curve-resolution method, and from the calculated quenching profiles, equilibrium parameters for the interaction of Fe(III) and FAs were obtained (conditional stability constants [K(c)s] and ligand site concentrations). The calculated log K(c)s were (I = 0.1 M KNO3; standard deviation in parentheses) FA2, pH = 3, 4.9 (2) pH = 4, 4.7 (2), pH = 5, 5.1 (4), and pH = 6, 5.1 (1); FA3, pH = 3, 5.48 (1); pH = 4, 4.96 (7), pH = 5, 4.89 (1), and pH = 6, 5.1 (2), where I is the ionic strength. These results show that FA forms quite stable soluble complexes with Fe(III) in the acid pll range.

Abstract The acid-base properties of two samples of anthropogenic fulvic acids (FA) extracted from the untreated sewage sludge (rsFA) of a municipal wastewater treatment plant and from the compost (csFA) obtained in the aerobical digestion of this sludge were studied. Potentiometric titrimetry, infrared spectroscopy and synchronous molecular fluorescence (SyF) spectroscopy were used to obtain experimental information about the acid-base properties of the samples. Moreover, the SyF spectral data which were collected as function of the pH were analysed by a self-modelling curve resolution technique, evolving factor analysis with a gradient concentration window (EFA-GCW), to calculate the number of acid-base systems, their SyF spectra and the corresponding distribution diagrams, from which the pK(a) values were estimated. Two acid-base systems with pK(a) values about 6.2 and 8.9 were detected for rsFA and three systems with pK(a) values about 3.8, 6.6 and 9.4 for csFA. The amounts of acid groups directly titrated in water were (standard deviations in brackets) about 6.8(1) for rsFA and 6.73(3) for csFA. This information for rsFA and csFA was compared with similar information for natural soil FA samples extracted from a pinewood soil. Beyond different structural composition, this comparison showed that the anthropogenic samples have a higher amount of acid structures, but the structures of natural samples have stronger acid properties.

Abstract Os sistemas coloidais mistos são objecto de intensa investigação no domínio da química-física actual. A nível molecular apresentam grande diversidade de estruturas auto-agregadas e de forças de interacção; exibem também propriedades macroscópicas versáteis, de vasta aplicabilidade práctica. Nesta tese, o comportamento e a micro-estrutura de fase de sistemas aquosos mistos surfactante-surfactante e polímero-surfactante são investigados, contendo ambos cosolutos de cargas opostas. Abordam-se tópicos centrais tais como separação de fase associativa em sistemas mistos, formação de vesículos termodinamicamente estáveis e interacções polímero-vesículo. É conhecido o forte sinergismo nas propriedades de solução e interfaciais de misturas de surfactantes de carga oposta em água (misturas cat-an-iónicas). Por outro lado, o comportamento e a estrutura de fase destes sistemas, em regime diluído e concentrado, tem sido alvo de estudos menos sistemáticos. A formação espontânea de vesículos estáveis para baixa concentração de surfactante - vesículos termodinamicamente estáveis - em misturas cataniónicas tem suscitado enorme interesse em anos recentes, dadas as suas implicações teóricas e potencialidades técnicas. O sistema anfifílico estudado neste trabalho é composto por um surfactante catiónico de dupla cadeia e um surfactante aniónico de cadeia única, assumindo como tal características de sistema-modelo. Interacções electrostáticas e efeitos de empacotamento geométrico contribuem em graus de complexidade variável para as estruturas micro-heterogéneas observadas. O diagrama de fases pseudo-ternário do sistema é inicialmente investigado para a gama total de concentração de surfactante, incluindo a identificação de regiões multifásicas, por técnicas de microscopia de luz polarizada e de desdobramento quadrupolar do deutério. Na zona diluída, duas regiões monofásicas de vesículos estáveis, contendo excesso de um ou de outro surfactante, são delineadas e caracterizadas. O uso complementar de microscopia de transmissão electrónica associada a criogenia (cryo-TEM) e microscopia de luz associada a técnicas de vídeo (VEM) fornece a visualização de uma vasta gama de tamanhos e de estruturas agregadas. Métodos de RMN de auto-difusão molecular para caracterização quantitativa são usados em paralelo, obtendo-se resultados não-clássicos para a auto-difusão da água em soluções polidispersas de vesículos. Posteriormente, os efeitos micro-estruturais e de comportamento de fase resultantes da adição de macromoléculas a uma solução de vesículos cataniónicos de carga oposta são investigados. Dois polielectrólitos catiónicos derivados da hidroxi-etil-celulose, um homopolímero e um heteropolímero com cadeias alquílicas laterais são usados. As macromoléculas interagem fortemente com a bicamada vesicular, dando origem à formação de estruturas vesiculares facetadas e estruturas discoidais; para concentracções elevadas de polímero, observa-se a formação de um novo tipo de gel vesículo-polímero.

Abstract The quenching of the fluorescence of three anthropogenic fulvic acids (FA) provoked by Cu(II) (pH 6.0), Fe(III) (pH 4.0) and UO(2)(2+) (pH 3.5), was analyzed by a non-linear method and by Stern-Volmer plots. The FA samples were extracted from composted sewage sludges (csFA), composted municipal wastes (mwFA) and composted livestock wastes (IsFA). Synchronous-scan fluorescence (SyF) spectra were collected as a function of metal ion concentration. Spectral data were treated by a self-modeling mixture analysis method (SIMPLISMA) to detect the SyF spectral band with the strongest quenching and to calculate the corresponding quenching profile. The analysis of these profiles by a non-linear method allowed the estimation of conditional stability constants (K) and of the percentage of non-complexing fluorophores. The same quantitative information was obtained by the modified Stern-Volmer equation taking into account the existence of fluorophores that do nor participate in the complexation. Good agreement was found between the results of the two procedures. The log K calculated by the non-linear method were (standard deviation in parenthesis): csFA, Cu(II), 4.22 (5); Fe(III), 5.0 (1); UO(2)(2+), 5.2 (2); mwFA, Cu(II), 4.21 (3); Fe(III), 5.6 (2); UO(2)(2+), 4.7 (3); 1sFA, Cu(II), 4.51 (8); Fe(III), 5.5 (2); UO(2)(2+), 3.6 (2). (C) 1998 Elsevier Science B.V.

Abstract The acid-base properties of four leaf litter extracts, LLE (eucalyptus, fern, oak and chestnut coverture), were characterized by synchronous fluorescence (SyF) spectroscopy and compared with those of two fulvic acids (FA) extracted from two different horizons (0-5 and 5-15 cm) of an oak forest soil. The characterization was based on the variation with the pH of the properties of the fluorescent structures present in the samples, which function as probes and provide a macroscopic image of their acid-base properties. These sets of SyF spectra collected as a function of the pH show fingerprinting potential. They were treated by a self-modeling curve resolution procedure, evolving factor analysis with a gradient concentration window (EFA-GCW), to reduce the raw spectral data to the number of components, their spectra, and SyF intensity profiles (pH distribution diagrams). Four acid-base systems were detected for all samples of LLE and FA with pKas ranging from 2.5 to 10.0 (pKas about 3, 5, 7 and 9, except for the fern LLE sample which showed pKas about 5, 7, 9 and 10). A similarity analysis of the spectra of the components, performed by cluster analysis, showed that the most acidic fluorescent structures of the LLE are not similar to those of the soil FA, but the less acidic are.

Abstract An extract of dead vine leaves (vitis viniferal) (VLE) was obtained by the extraction procedure for fulvic acids and its interaction (at a concentration of 25 mg/L in 0.1 M KNO3) with the Cu(II), Ni(II) and Fe(III) ions was studied in the pH range between 3 and 6. This interaction was monitored by synchronous molecular fluorescence, since bands due to the fluorescent ligands undergo quenching upon complex formation. After the chemometric isolation of the quenching profiles from the raw spectra by a self-modeling mixture analysis, SIMPLISMA, they were analyzed by two methods: (i) graphical procedures based on the Stem-Volmer model; and (ii) a non-linear least-squares procedure. For the Cu(II) and Ni(II) ions, the treatment by these two methods provided similar values both for the logarithm of the conditional stability constants (log Kc) and the percentage of fluorescent structures that do not participate in the complexation. The log Kc were (standard deviations in parenthesis): Cu(II) ion, 2.4(3), 3.37(3), 4.4(1) and 4.92(9), respectively, for pH = 3, 4, 5 and 6; Ni(II)ion, 2.9(1), 3.3(2), and 4.09(3), respectively, for pH = 4, 5 and 6. For Fe(III) an interaction with VLE was observed, but no values for Kc could be obtained.

Abstract A method for the rapid screening of five chlorophenols in the ppm concentration range (2-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, 4-chloro-m-cresol, and pentachlorophenol) is described. It is based on the use of first derivative UV spectrophotometry with a reduced calibration set constituted by eleven standard solutions, selected according to a four level fractional factorial experimental design, and in the use of multivariate calibration: techniques (partial least squares and artificial neural networks) as calibration models. This methodology allows the development of calibration models with good prediction ability for the rapid simultaneous analysis of the five chlorophenols.

Abstract The standard molar enthalpies of formation at T = 298.15 K of some crystalline bis(8-hydroxy-2-methylquinolinate) metal complexes were determined from solution-reaction calorimetric measurements. 8-Hydroxy-2-methylquinoline; or 2-methyloxine, is written as Hmeox. The values of Delta(f)H(m)(0) (M(meox)(2), cr)/(kJ.mol(-1)) are: Mg(meox)(2), -609.0 +/- 4.5; Ca(meox)(2), -707.8 +/- 4.5; Sr(meox)(2), -700.0 +/- 4.8; Cu(meox)(2), -176.6 +/- 4.4; Zn(meox)(2) -369.6 +/- 4.5; Cd(meox)(2), -298.0 +/- 4.5; Pb(meox)(2), -239.9 +/- 4.6; Mn(meox)(2), -418.1 +/- 4.3; Co(meox)(2), -257.8 +/- 4.7; Ni(meox)(2), -243.0 +/- 6.6. Where feasible, the standard molar enthalpies of sublimation at T = 298.15 K were determined by an effusion method. The Delta(cr)(g)H(m)(0) (M(meox)(2))/(kJ.mol(-1)) values are: Mg(meox)(2), 224.3 +/- 6.5; Cu(meox)(2), 172.1 +/- 3.4; Zn(meox)(2), 179.4 +/- 5.0; Cd(meox)(2), 203.3 +/- 7.3; Pb(meox)(2), 188.6 +/- 5.9; Mn(meox)(2), 211.2 +/- 7.2; Co(meox)(2), 204.4 +/- 5.9; Ni(meox)(2), 180.9 +/- 3.7. From the standard molar enthalpies of formation in the gaseous state, the mean metal-ligand dissociation enthalpies were derived and compared with values for other complexes of these metals. (C) 1998 Academic Press Limited.