Test de toxicidad sobre la especie Atriplex lampa, su aplicación para la evaluación de riesgo asociado a derrames de petróleo en suelos de la Patagonia / The application of toxicity test on the specie Atriplex lampa in the risk assessment of oil spills in Patagonian soils

Se estudiaron suelos contaminados con hidrocarburos del petróleo, en cercanías de la ciudad de Comodoro Rivadavia (Chubut, Argentina). Además de cuantificar el contenido de hidrocarburos totales en suelo (TPH), se realizaron bioensayos, utilizando especies vegetales como organismos de prueba. Los índices utilizados fueron: el porcentaje de germinación (G), la elongación de la radícula (R) y del hipocotilo (H) en Lactuca sativa L y dos especies autóctonas de la región patagónica, Atriplex lampa y Prosopis denudans. Se consideró, además, el efecto de la salinidad sobre los bioensayos, en base a la medición de la conductividad eléctrica del suelo (CE). Los resultados obtenidos del análisis por componentes principales, muestran que la primera componente explica el 58,3 % de la variabilidad total con un gradiente de toxicidad al cual contribuyen, principalmente, el porcentaje de germinación de Lactuca sativa L (GL) y Atriplex lampa (GA), en este orden de significancia. La segunda componente explica el 16,9 % y la misma está caracterizada por TPH y CE. Además, no se ha encontrado una correlación simple y directa entre TPH y toxicidad, lo cual sugiere que TPH, en conjunción con ensayos ecotóxicos, parece ser una herramienta más adecuada para definir el punto final de una remediación. La especie autóctona Atriplex lampa mostró tener una sensibilidad similar a la especie Lactuca sativa L por lo que podría considerarse su utilidad como una especie fitoindicadora en las evaluaciones de riesgo ambiental (AU)

Oil spills near of the Comodoro Rivadavia city (Chubut, Argentina) were studied. Total petroleum hydrocarbon (TPH) is used to characterize the samples and bioassays were carried out using plants as test organisms. The percentage germination (G), the root elongation (R) and the hypocotyls elongation (H) in Lactuca sativa L and two native species to Patagonian region, Atriplex lampa and Prosopis denudans were used as toxicological indexes. It was considered the effect of salinity on the bioassays, based on the measurement of the electrical conductivity of soil (EC). Application of principal component analysis to experimental data showed that the first component accounted for more than 58.3 % of variance. The 1st PC is largely influenced by the germination percentage of Lactuca sativa L (GL) and Atriplex lampa (GA), in that order of significance. The second component accounted 16.9 % of variance. The 2nd PC is largely influenced by TPH and EC. A simple and direct correlation between TPH and toxicity was not found suggesting that TPH in conjunction with ecotoxicity test would be more successfully tool to define the end point of a remediation. The native specie Atriplex lampa showed to have a similar sensibility to the Lactuca sativa L suggesting that it could be used as a phytoindicator in assessement of environmental risk (AU)

Determination of TBT in water and sediment samples along the Argentine Atlantic coast.

Cases of imposex have been reported for some organisms living in areas of the Argentine Atlantic coast. Since this is one of the known effects of the anti-fouling agent tributyltin (TBT), quantitative determinations of organotins in samples of water and sediments collected from sites along the Argentine coast were carried out. Severe cases of imposex were first reported for two gastropod species living in the Mar del Plata area, and determinations of TBT in samples collected from this site gave extremely high values and showed a close correlation between the degree of imposex and TBT concentration. Recent investigations in the area have shown a significant decrease. Surveys were also conducted in sites that exhibit highly irregular coastal profiles to examine the relevance of physical environments. Alarming concentrations of TBT were determined in most of the sites where heavy boat traffic and/or marine activities occur, demonstrating the urgent need for regulations to avoid further input of TBT. Reports from other sites in South America reveal that this should be a subject of regional concern in order to avoid severe damage to the biodiversity of regional marine organisms.

Natural attenuation of oil spills in Patagonian soils. Characterization by 1H NMR spectroscopy.

The natural attenuation of oil spill contaminated soils, with different exposure times, in Patagonian environment was evaluated by the use of several parameters to quantify the degree of changes in the composition. Column (CC) and gas chromatography (GC); UV-visible and 1H NMR techniques were used to determine compositional and structural indexes. The results show that the nC18/Phytane GC index, that was 1.5 for crude oil, decreased with exposure time to values between 0.97-0.17 in the residues. The percentages for the four aliphatic (H1-H4) and the aromatic (H(A)), proton types, determined by 1H NMR, were: 12.9-34.4 (H1), 43.3-60.2 (H2), 4.24-24.2 (H), 1.33-17.9 (H4), and 0.44-4.81 (HA), in crude oil and residues, respectively. Furthermore, the characterization of significant 1H NMR signals indicated the presence of carboxylic acid hydrogens in the polar fraction of the crude oil and of residues of two years age. The Principal Components Analysis (PCA) of the parameters determined by CC, GC and NMR showed that the first three principal components (1st, 2nd, and 3 rd PC), accounted for more than 84% of variance. The 1st PC is largely influenced by H, H,, H, H, and the nC,,/Phytane GC parameter, in the order given. The evaluation of the different parameters by PCA suggests that 1H NMR is more useful than GC to evaluate the degree of the chemical transformations of oil spills in soils

Organic co-solvent effect on the estimation of the equilibrium aqueous concentrations of oil residuals in Patagonian soil.

Determination of the equilibrium aqueous concentration and the distribution coefficients, K, in soil samples containing oil residuals of different age, was carried out using an organic co-solvent (methanol). It was found that the solvophobic theory could be applied for the interpretation of results. The behavior of the residuals turned out to be dependent on the co-solvent fraction and the age of the oil spill. The values of K vary between 900 (l kg(-1)) and 2,900 (l kg(-1)) showing a general and marked increase for residues of increasing age. The determined parameters are useful for the modeling of environmental impact on polluted soils.

Spectrofluorimetric assay for the photodegradation products of alprazolam.

A new spectrofluorimetric assay for the photodegradation products of the ansiolytic drug alprazolam is described. Alprazolam was found to be highly photolabile and special care should be taken to avoid light exposure during alprazolam storage and handling. The photostability of alprazolam was evaluated at pH 2.0, 3.6 and 5.0. The drug was exposed to UVA-UVB radiations, the photodegradation of alprazolam was followed by high-performance liquid chromatographic (HPLC) and the developed spectrofluorimetric assay allowed determination of the photodegradation products at very low concentrations (> or = 10(-5) M). The photoinstability was found to increase with the pH value decreasing, consequently acidic media should be avoided during the drug-development process.

Tandem addition beta-lithiation-alkylation sequence on alpha,beta-unsaturated aldehydes.

A tandem reaction between (E)-cinnamaldehyde, 1a, and phenyllithium affording beta-substituted dihydrochalcones was recently reported. NMR spectroscopic studies on the reaction mixture, as well as isotopic exchange reactions and trapping of two intermediates, provide clues on the several mechanistic steps of this new reaction. Extended studies revealed that beta-alkyl-substituted alpha,beta-unsaturated aldehydes and aliphatic lithium reagents did not afford good yields of the tandem reaction products, while aromatic lithium reagents gave good results. The aggregation features of the aryllithium reagents and the extended charged delocalization effects are considered to promote beta-selectivity. This approach provides a convenient route for the synthesis of a wide variety of beta-alkyl-substituted dihydrochalcones.

Acid hydrolysis of diazepam. Kinetic study of the reactions of 2-(N-methylamino)-5-chlorobenzophenone, with HCl in MeOH-H2O.

In the acid hydrolysis of diazepam (1), several unusual products, apart from 2-(N-methylamino)-5-chlorobenzophenone (2) and glycine, were isolated. On the assumption that some of those products could arise from further degradation of 2, the reaction of this compound with 0.5-2 M HCl was studied, in 1:1 MeOH-H2O, at 60 and 80 degrees C. Several unexpected products were isolated from the reaction of 2 with HCl, namely, 2-amino-5-chlorobenzophenone (3), 2-(N,N-dimethylamino)-5-chlorobenzophenone (4), 2-(N-methylamino)-3,5-dichlorobenzophenone (5), 2-amino-3,5-dichlorobenzophenone (6), 2,4-dichloro-10-methyl-9,10- acridinone (7), and 2,4-dichloro-9,10-acridinone (8). The methyl transfers, the chlorination, and the cyclization reactions that give rise to products 3-8 are unexpected under the present reaction conditions. The rate of reaction of 2, as well as the rate of formation of compounds 3-6, was measured at several HCl concentrations.

Isolation and structure elucidation of novel products of the acidic degradation of diazepam.

The acidic degradation of diazepam in methanolic aqueous solution has been investigated. Apart from the known degradation products, 2-(N-methylamino)-5-chlorobenzophenone and glycine, produced by the hydrolytic cleavage of the benzodiazepinone ring, five novel products were isolated and fully characterized by their spectroscopic features and independent synthesis. Substituted 2-amino-3,5-dichlorobenzophenones and 2,4-dichloroacridinones were found, the formation of which in the reaction media is mechanistically intriguing. The role of these unexpected products in accelerated studies of diazepam stability is discussed.

Specific colorimetric determination of niacinamide in dosage forms.

A chemical method for determining the amount of niacinamide in multicomponent preparations was developed. Neither niacin resulting from the degradation of niacinamide nor vitamin A, thiamine hydrochloride, riboflavin, ascorbic acid, ergocalciferol, or calcium pantothenate interferes. The method is based on the reaction of niacinamide with 1-chloro-2,4-dinitrobenzene, followed by the spectrophotometric measurement of the colored solution obtained after treatment with sodium hydroxide. The proposed method is at least as accurate as the methods currently in use. A structure is proposed for the colored product, and its route of formation is outlined.