Shuokui Han

Reducing degradation of azo dye by zero-valent iron in aqueous solution

The reducing degradation kinetics of five azo dyes, Acid orange II, Acid orange IV, Acid orange GG, Acid red 3B and Orange I, by zero-valent iron powder in aqueous solution were studied. It showed that the degradation is a two-step reaction, with the first step being reversible. Solution acidity and iron surface area are the factors greatly influencing the degradation rates, and with increasing of acidity and iron surface area, the degradation rates increase.

Trace analysis of dissolved polychlorinated organic compounds in the water of the Yangtse River (Nanjing, China).

Eighteen organochlorine contaminants from the water samples of the Yangtse River have been qualitatively and quantitatively analyzed. The analysis of polychlorinated organic compounds (PCOCs) extracted by C18 Solid Phase Extract (SPE) was performed using HP6890 gas chromatograph coupled by ECD detector. The analytical results demonstrate that the analytical methods are reliable based on the fact that most of the recoveries for the targeted compounds are 60-90%. Most of the concerned contaminants, i.e. chlorinated pesticides and PCBs were found in the water samples of the Yangtse River, but their concentration was very low, <2.97 ng l(-1), which is far less than 1 microg l(-1)--the standard of drinking water of China. It is apparent that the PCOCs were in high concentration during the dry season, and in low concentration during the rainy season. The situation of PCOCs contamination in the water of the Yangtse River in 1999 was greatly improved in comparison with 10 years ago.

Acute toxicity of substituted phenols to Rana japonica tadpoles and mechanism-based quantitative structure–activity relationship (QSAR) study

Acute 12 h and 24 h lethal toxicity (12 h-LC50 and 24 h-LC50) of 31 substituted phenols to Rana japonica tadpoles was determined. Results indicate that toxicity of phenols to tadpoles varied only slightly with length of exposure and the 12-h test could serve as surrogate of the 24-h test. A mechanism-based quantitative structure-activity relationship (QSAR) method was employed and 1-octanol/water partition coefficient (log K(ow))-dependent models were developed to study different modes of toxic action. Most phenols elicited their response via a polar narcotic mechanism and an excellent logK(ow)-dependent model was obtained. Soft electrophilicity and pro-electrophilicity were observed for some phenols and a good log K(ow)-dependent model was also achieved. Additionally, the significant dissociation of carboxyl on benzoic acid derivatives sharply reduced their toxicity. A statistically robust QSAR model was developed for all studied compounds with the combined application of log K(ow), energy of lowest unoccupied orbital (E(lumo)), heat of formation (HOF) and the first-order path molecular connectivity dices (1chi(p)).

Studies of 3D-quantitative structure–activity relationships on a set of nitroaromatic compounds: CoMFA, advanced CoMFA and CoMSIA

By using comparative molecular field analysis (CoMFA), advanced CoMFA and comparative molecular similarity index analysis (CoMSIA) methods, the 3D relationships between the structures of 35 nitroaromatic compounds and their toxicities have been investigated to yield statistically reliable models of considerable predictive power. In contrast to CoMFA, CoMSIA produces better results for the correlation. Moreover, the obtained CoMSIA contour maps that interpret the correlations in terms of field contributions allow physicochemical properties relevant for binding to be easily mapped back onto molecular structures, and thus elucidate structural features among ligands that are responsible for toxicities. Besides, most of the highlighted regions in CoMSIA and CoMFA contour maps are mirrored by features in the surrounding environment. Thereby, CoMFA and CoMSIA both help to give explanations of the toxic mechanism of tested compounds.

Acute toxicity and quantitative structure–activity relationships of α-branched phenylsulfonyl acetates to Daphnia magna

The acute toxicity (48 h-EC50, microM) of 20 alpha-substituted phenylsulfonyl acetates was measured using Daphnia magna with a static method. On the basis of physicochemical parameters (octanol/water partition coefficient logK(ow) and aqueous solubility logS(w)), the theoretical linear solvation energy relationships (TLSER) and Charge model descriptors, QSARs were calculated for the immobilization of D. magna. For the models with the physicochemical parameters logK(ow) and logS(w), the low squared correlation coefficients indicate that hydrophobicity plays a dominant role on the toxicity and hydrophobicity is not the only factor that influences the activity of the compounds. For the TLSER model and the Charge model, the great squared correlation coefficients suggest that the models have good predictive capability. The higher activity of the compounds can be explained with the disruption of van der Waals interactions between lipid and/or protein compounds within the membrane and the possibility of the compounds to form hydrogen bonds with the receptor molecules. The models may more completely illustrate the toxicity mechanisms.

Solubilization of substituted indole compounds by β-cyclodextrin in water

The solubilization of four pairs of substituted indole compounds (SICs) by beta-cyclodextrin (beta-CD) in water was investigated. The results show that 1,2,3,4-tetrahydrocarbazole and N-methyl-1,2,3,4-tetrahydrocarbazole form 1:1 inclusion complexes with beta-CD, while the other six SICs form 1:2 inclusion complexes, respectively. To each pair of SICs with similar structures, the differences between their solubilization in beta-CD/water solutions has been explained by the difference of their contact area within the beta-CD cavity, the difference of their molecule polarity, or the presence of hydrogen bond between SIC molecule and beta-CD molecule.

Determination and estimation of physicochemical properties for phenylsulfonyl acetates

Abstract Shake flask and RP-HPLC methods were used to determine Kow, Koc and Sw of 28 phenylsulfonyl acetates. Linear relationships between these three properties and solvatochromic parameters of all substances have been established. The estimated values fit well with measured data. According to these relationships, Kow, Koc and Sw of 13 other phenylsulfonyl acetates were estimated.

Prediction of partition coefficient and toxicity for phenylthio, phenylsulfinyl and phenylsulfonyl acetates.

The log K ow values of 27 phenylthio, phenylsulfinyl, and phenylsulfonyl acetates were determined by the shake-flask method. Their capacity factors were determined by RP-HPLC with C18 column and methanol-water eluent. Partial molecular connectivity indices were calculated for these compounds and used to describe their log K ow values and toxicities to Photo-bacterium phosphoreum. Results demonstrated that while both the HPLC results and the molecular connectivity indices (MCls) could be used to predict the K ow for all of the compounds, the MCI method was more accurate. The correlation between toxicity and molecular connectivity index was also significant, and the correlation was better than a previous a and E s analysis.

Sorption of phenylthioacetates on natural soil: Application of partition-adsorption mechanism and model

Abstract Sorption of eight phenylthioacetates from water by natural soil is studied at very low to high relative concentrations (ratios of equilibrium solute concentration to solute water solubilities). The Freundlich isotherm is used to fit the experimental data, where nonlinear sorption isotherms are observed. The partition-adsorption mechanism and model is used to explain the nonlinear isotherms, which show that sorption of phenylthioacetates from water by natural soils consists of two contributions: a linear partition in SOM and a nonlinear residual adsorption on soil minerals and onto SOM because of the specific interactions between functional groups of phenylthioacetatesand OH and COOH groups of SOM Partition dominates the sorption process at moderate to high relative concentrations, and both partition and the residual adsorption dominates over partition at low relative concentration.

Determination and estimation of partitioning properties for phenylthio-carboxylates

Abstract A shake-flask method was used to determine the octanol/water partition coefficients (K ow ) and the water solubilities (S w ). A batch method was used to determine the organic carbon-based sorption coefficients (K oc ) on natural soils of 18 phenylthiocarboxylates. Linear relationships among these three properties were first reported, they provided a quantitative equation to predict all the partitioning properties of an unknown phenylthio-carboxylates from any of the measured properties. The LSER method have been extended to establish a series of correlation equations successfully, they were used to predict these partitioning properties more accurately.