Dwaipayan Sengupta

Impact of pesticides use in agriculture: their benefits and hazards

Impact of pesticides use in agriculture: their benefits and hazards

Degradation dynamics and dissipation kinetics of an imidazole fungicide (Prochloraz) in aqueous medium of varying pH

Degradation dynamics and dissipation kinetics of an imidazole fungicide (Prochloraz) in aqueous medium of varying pH Laboratory degradation studies were performed in water at pH 4.0, 7.0 and 9.2 using Prochloraz (450 EC) formulation at the concentration of 1.0 (T1) and 2.0 (T2) μg/mL. Water samples collected on 0 (2 h), 3, 7, 15, 30, 45, 60 and 90 days after treatments were processed for residue analysis of Prochloraz by HPLC-UV detector. In 60 days, dissipation was 89.1-90.5% at pH 4.0, 84.1-88.2% at pH 7.0, and 92.4-93.8% at pH 9.2 in both treatments. The results indicate that at pH 7.0 the degradation of Prochloraz was much slower as compared to other two. Between pH 4.0 and 9.2 the degradation of compound is little faster at pH 9.2. The half-life periods observed were 18.35 and 19.17 days at pH 4.0, 22.6 and 25.1 days at pH 7.0 and 15.8 and 16.6 days at pH 9.2 at T1 and T2 doses respectively.

Vertical migration of some herbicides through undisturbed and homogenized soil columns

Vertical migration of some herbicides through undisturbed and homogenized soil columns A laboratory experiment was conducted by using three herbicides, two from dinitroaniline group and one from thiocarbamate group to know their degree of downward movement (leachability) through soil columns and their contribution in ground water contamination. Soil columns were loaded with Pendimethalin, Benthiocarb and Oryzalin at doses of 10.0, 10.0 and 7.7 kg/ha, respectively. After 30 days soil samples were analyzed from each segments (i.e. 0-6, 6-12, 12-18, 18-24 and 24-30 cm) for Benthiocarb and Pendimethalin by GLC equipped with Ni63 electron capture detector (ECD) and for Oryzalin by HPLC coupled with UV-VIS detector. The results obtained in the present study reveal that the residues of the three herbicides under investigation were predominantly confined to the upper soil layer (0-6 cm). Comparatively, low mobility of these herbicides in soils could be due to strong adsorption of these chemical to soil colloids.

An Improved Commercial Method for Determination of Nicotine in Tobacco

A high-pressure thin-layer chromatography (HPTLC) method for quantitative analysis of nicotine in Nicotiana sp. was developed using a methanol extract of leaves and stems and TLC plates (silica gel 60 GF254) with spot visualization under ultraviolet (UV) light. Scanning at 235 nm in the absorption-reflection mode produced linear calibration curves in the range of 2 to 25 μg, with a correlation coefficient of 0.991. The average recovery rate was 95% (CV % 1.35). From the present study, the lower limit of detection was 0.08 μg spot−1 for the nicotine. The validity of the method was confirmed by comparing the UV spectra of the tobacco plant samples with standards within the same Rf window.