Photodegradation of Oryzalin in aqueous isopropanol and acetonitrile.

The phototransformation of Oryzalin was studied under UV light (λmax ≥ 290 nm) and sunlight (λmax ≥ 250 nm) in aqueous isopropanol and acetonitrile solution in absence and presence of TiO2 as sensitizer. The rate of photodegradation of Oryzalin in different solvent system followed first-order kinetics, and calculated half-lives were found to be in the range of 23.52-53.75 h for UV light and 41.23-61.43 h for sunlight. From this study, total 12 photoproducts were identified and characterized on the basis of column chromatography and Q-Tof micromass spectral data. The plausible mechanism of phototransformation involved was hydrolysis, breaking of sulfonic bond, and loss of amino and sulfonic acid group.

Studies on the fate of ready-mix formulation of endosulfan and cypermethrin in tea.

Ready-mix formulation consists of two insecticides-endosulfan (35%) and cypermethrin (5%). To understand the dissipation pattern of the insecticides on made tea from the north-east region of India, it was applied twice in 10 day interval @ 1,000 mL/ha (350 g a.i. endosulfan + 50 g a.i. cypermethrin) and 2,000 mL/ha (700 g a.i. endosulfan + 100 g a.i. cypermethrin) along with untreated control. The made tea samples were collected at 0, 1, 3 and 7 days interval after last application. The dissipation rate of endosulfan and cypermethrin followed first order kinetics. The calculated half-life values were found in the range between 1.7 to 2.1 days for endosulfan and 1.0 to 1.1 days for cypermethrin.

Studies on the residue of hydrogen cyanamide in grape berries.

Multilocational field trials were conducted in grapevines at four different locations by applying hydrogen cyanamide 50% SL during 2006-2007. In order to determine the residue of hydrogen cyanamide in grape, hydrogen cyanamide 50% SL was applied to the freshly pruned grapevines at the rate of 1.20% a.i./L, 2.40% a.i./L, 4.80% a.i./L along with untreated control. No residue was detected in grape berries at the time of harvest irrespective of any locations.

Persistence of napropamide in/on tea under North-East Indian climatic condition.

Napropamide is an amide group of herbicide, used as pre-emergence herbicide controlling in broad leaved weeds of tea, ground nut, citrus, etc. Napropamide 45 SC (Devrinol) was applied on tea bushes twice @ 1.125 and 2.250 g a.i./ha along with untreated control. After following the standard extraction process, the residue of napropamide in made tea and soil cropped with tea was analyzed by HPLC. Napropamide was rapidly dissipated in soil following the first-order kinetics with half-lives in the range of 12.54-27.87 days. The residue in made tea found to be below detectable limit on 7th day samples.

Laboratory simulated dissipation of metsulfuron methyl and chlorimuron ethyl in soils and their residual fate in rice, wheat and soybean at harvest.

Two sulfonylurea herbicides, metsulfuron methyl (Ally 20 WP) and chlorimuron ethyl (Classic 25 WP) were evaluated for their dissipation behaviour in alluvial, coastal saline and laterite soils under laboratory incubated condition at 60% water holding capacity of soils and 30 degrees C temperature was maintained. In field study herbicides were applied twice for the control of grasses, annual and perennials broad leaves weeds and sedges in rice, wheat and soybean to find out the residual fate of both the herbicides on different matrices of respective crops after harvest. Extraction and clean up methodologies for the herbicides were standardized and subsequently analyzed by HPLC. The study revealed that the half-lives of metsulfuron methyl and chlorimuron ethyl ranged from 10.75 to 13.94 d irrespective of soils and doses applied. Field trials with rice, wheat and soybean also revealed that these two herbicides could safely be recommended for application as no residues were detected in the harvest samples.