Persistence of spiromesifen in soil: influence of moisture, light, pH and organic amendment.

Persistence of spiromesifen in soil as affected by varying moisture, light, compost amendment, soil sterilization and pH in aqueous medium were studied. Degradation of spiromesifen in soil followed the first-order reaction kinetics. Effect of different moisture regimes indicated that spiromesifen dissipated faster in submerged soil (t 1/2 14.3-16.7 days) followed by field capacity (t 1/2 18.7-20.0 days), and dry soil (t 1/2 21.9-22.9 days). Dissipation was faster in sterilized submerged (t 1/2 17.7 days) than in sterilized dry (t 1/2 35.8 days). Photo spiromesifen metabolite was not detected under different moisture regimes. After 30 days, enol spiromesifen metabolite was detected under submerged condition and was below detectable limit (<0.001 µg g(-1)) after 90 days. Soil amendment compost (2.5 %) at field capacity enhanced dissipation of the insecticide, and half-life value was 14.3 against 22.4 days without compost amendment. Under different pH condition, residues persisted in water with half-life values 5.7 to 12.5 days. Dissipation in water was faster at pH 9.0 (t 1/2 5.7 days), followed by pH 4.0 (t 1/2 9.7 days) and pH 7.2 (t 1/2 12.5 days). Exposure of spiromesifen to different light conditions indicated that it was more prone to degradation under UV light (t 1/2 3-4 days) than sunlight exposure (t 1/2 5.2-8.1 days). Under sunlight exposure, photo spiromesifen metabolite was detected after 10 and 15 days as compared to 3 and 5 days under UV light exposure.

Mobility of spiromesifen in packed soil columns under laboratory conditions.

On percolating water equivalent to 1,156 mm of rainfall, spiromesifen formulation did not leach out of 25-cm long columns, and 62.7 % of this was recovered in 5-10-cm soil depth. In columns treated with the analytical grade, 52.40 % of the recovered spiromesifen was confined to 0-5-cm soil depth, with 0.04 % in leachate fraction, suggesting high adsorption in soil. Results revealed that percolating 400 mL of water, residues of enol metabolite of spiromesifen was detected up to 20-25-cm soil layer, with 23.50 % residues of spiromesifen in this layer and 1.73 % in the leachate fraction indicating that metabolite is more mobile as compared to the parent compound. Results suggested a significant reduction in leaching losses of enol metabolite in amended soil columns with 5 % nano clay, farmyard manure (FYM), and vermicompost. No enol spiromesifen was recovered in the leachate in columns amended with nano clay, vermicompost, and FYM; however, 85.30, 70.5, and 65.40 %, respectively, was recovered from 0-5 cm-soil depth of column after percolating water equivalent to 1,156 mm of rainfall. Spiromesifen formulation is less mobile in sandy loam soil than analytical grade spiromesifen. The metabolite, enol spiromesifen, is relatively more mobile than the parent compound and may leach into groundwater. The study suggested that amendments were very effective in reducing the downward mobility of enol metabolite in soil column. Further, it resulted in greater retention of enol metabolite in the amendment application zone.

Synthesis of borax cross-linked Jhingan gum hydrogel for remediation of Remazol Brilliant Blue R (RBBR) dye from water: Adsorption isotherm, kinetic, thermodynamic and biodegradation studies.

This paper reports synthesis of hydrogel from an unexplored Jhingan gum via microwave assisted technique for efficient remediation of toxic RBBR dye from aqueous solution. The synthesized hydrogel was confirmed through various analytical techniques. Adsorption mechanism was studied comprehensively and correlation coefficient (R2) values of Langmuir (0.8492-0.9147), Freundlich (0.9802-0.9932), Temkin (0.7744-0.9048), Sips (0.9832-0.9987) recommended that adsorption process fitted best with Freundlich and Sips models. Additionally, the sorption energy E, calculated using the Dubinin-Radushkevich isotherm, has a value of 0.971-0.989 kJmol-1, which confirmed that the type of adsorption was physisorption. Kinetic study revealed that adsorption was well described by pseudo-second-order kinetics. Feasibility of adsorption process determined thermodynamically suggested an endothermic process accompanied with decrease in randomness and non-spontaneous nature. The synthesized hydrogel exhibited an excellent regeneration capacity. The biodegradation study revealed that the hydrogel degraded 89.5% in 180 days with a half-life of 53.3 days.

In vitro release kinetics of graft matrices from Lannea coromandelica (Houtt) gum for treatment of colonic diseases by 5-ASA.

Polyacrylamide graft Jhingan gum (Jh-g-PAMs) was synthesized adopting microwave assisted graft co-polymerization technique. The synthesized graft copolymer was characterized by various analytical techniques such as Elemental analysis, FTIR, TGA, XRD and NMR. Following standard protocol, drug matrix tablets using 5-Aminosalicylic Acid (5-ASA) were prepared and swelling and erosion studies were carried out in different pH dissolution media. The result revealed that maximum swelling and erosion took place in pH 7.4 while the lowest was recorded in pH 1.2. The 'in vitro' drug release studies revealed that grades with higher grafting % exhibited more sustained release. The highest sustained release was observed in Jh-g-PAM 3 (%G 1231) in pH 1.2 while the least was observed in native gum in pH 7.4. Furthermore, the kinetic studies revealed that 'n' values in all dissolution media lies within 0.5-1.0 which suggested non-Fickian diffusion mode of release. From the above results, it can be said that controlled release of 5-ASA using graft material was successful and hence it can be explored for treatment of colon related diseases.