Photocatalysis of S-metolachlor in aqueous suspension of magnetic cerium-doped mTiO2 core-shell under simulated solar light.

Magnetic cerium-doped mesoporous titanium dioxide was synthesized by combining sol-gel method and calcination using tetrabutanate and ammonium cerium nitrate as precursors and Pluronic P123 as a template coating on iron oxide covered with carbon in ethanol. The magnetic Ce-doped catalyst showed only anatase structure with a slight increase in lattice parameters compared to the undoped catalyst. The Ce LIII-edge X-ray absorption near-edge spectroscopy (XANES) spectra showed Ce3+, and the cerium substitution doping into titanium dioxide was proposed. Degradation of S-metolachlor in aqueous magnetic photocatalyst suspension followed (pseudo) first-order kinetics in the presence of 0.5 g L-1 of γ-Fe2O3@C@0.16 mol% Ce-mTiO2 with a half-life of 55.18 ± 1.63 min. Fifteen degradation products were identified, and their transformation routes of the photocatalytic degradation were then proposed. Complementary toxicity assessment of the treated S-metolachlor solution was undertaken with Environment Canada's algal microplate assay measuring growth inhibition (72-h IC50) in the freshwater chlorophyte Pseudokirchneriella subcapitata. This test method revealed a significant decrease in toxicity (1.7-fold reduction after 180 min of irradiation treatment), thereby confirming that the by-products formed following photocatalysis would be less harmful from an environmental point of view. Photocatalytic degradation of S-metolachlor thus appears to hold promise as a cost-effective treatment technology to diminish the presence of this herbicide in aquatic systems.

Photocatalytic degradation of triazophos in aqueous titanium dioxide suspension: identification of intermediates and degradation pathways.

The photocatalytic degradation of triazophos in aqueous TiO2 suspension has been studied in a photoreactor operating with simulated solar radiation. The decrease in triazophos concentration followed first-order kinetics with a half-life of 4.76+/-0.42 h at a TiO2 suspension concentration of 10 mg/L. Seventeen degradation products were identified using HPLC-UV, HPLC/MS/MS, GC/MS/MS and IC, and by comparing retention times and spectra with commercially available authentic standards. On the basis of the observed transformation products, two routes were proposed, one based on the initial oxidative cleavage of PS bond to PO bond, and the other on initial cleavage of the ester P-O bonds. Photocatalysis holds promise for the solar treatment of pesticide-contaminated waters.

Confirmatory determination of organochlorine pesticides in surface waters using LC/APCI/tandem mass spectrometry open diamond.

A confirmatory method for the determination of organochlorine pesticides (OCPs) and their metabolites (endrin, alpha-endosulfan, beta-endosulfan, endosulfan sulfate, heptachlor, heptachlor epoxide, 2,4'-DDD, 4,4'-DDD, 2,4'-DDE 4,4'-DDE, 2,4'-DDT, and 4,4'-DDT) in surface waters using liquid chromatography /APCI/tandem mass spectrometry has been developed. Chromatographic separation was carried out on a ChromSpher 5 Pesticide column using a gradient elution with mobile phase 1mM ammonium acetate-acetonitrile. Endrin, alpha-endosulfan, beta-endosulfan , endosulfan sulfate, heptachlor and heptachlor epoxide were determined in the negative ionization mode, while the rest compounds in positive ionization mode. For the identification of the analytes, two multireaction monitoring transitions were selected per compounds except for the heptachlor which selected ion monitoring was used. The linearity of the optimized method ranges after SPE concentration, from 0.009 to 30.60 microgL(-1) with correlation coefficients greater than 0.99. The method recovery values varied from 72 to 119 % for the different fortification levels . The developed method was successfully applied to determine OCPs and their metabolites in surface water samples collected near paddy fields in growing season of rice, at year 2005 in Pathumthani province, Thailand. Endosulfan sulfate was detected in five out of seven samples and three of them could be quantitated in the range of 0.31 to 0.50 microgL(-1).

D:A friedo-oleanane lactones from the stems of Mallotus repandus.

Three new D:A-friedo-oleanane lactones, viz., 3-oxo-D:A-friedo-oleanan-27,16alpha-lactone (1), 3alpha-benzoyloxy-D:A-friedo-oleanan-27,16alpha-lactone (2), and 3beta-hydroxy-D:A-friedo-oleanan-27,16alpha-lactone (3) were isolated from the stems of Mallotus repandus. Extensive use of NMR spectroscopic techniques led to full assignment of all 1H and 13C chemical shifts. The structure for 2 was confirmed by X-ray diffraction analysis.

Labdane and pimarane diterpenes from Croton joufra.

From the chloroform extract of the leaves of Croton joufra, the diterpenes 2alpha,3alpha-dihydroxy-labda-8(17),12(13),14(15)-triene and 3beta-hydroxy-19-O-acetyl-pimara-8(9),15-dien-7-one, were isolated. Their structures were established by spectroscopic methods. One of the compounds showed weak lethality in the brine shrimp assay.

Constituents and bioactivity of the tubers of Euphorbia sessiliflora.

The diterpene ent-12-hydroxy-12[R]-abieta-8(14),13(15)-dien-16,12-olide was isolated from the tubers of Euphorbia sessiliflora Roxb., together with four known ent-abietadienolides, four known cycloartane triterpenes and ellagic acid-beta-D-glucopyranoside. Two of these metabolates displayed moderate antibacterial activities.