A simple, rapid and economical method was developed and validated for the determination of metamitron using UV detector with RP-HPLC. Study of metamitron in soil was carried out. The compound was extracted from soil by methanol and clean-up was done on C-18 SPE column. Recovery ranged from 90.75 % to 94.05 % within 0.1-2.0 μg g(-1) and RSD 1.80 %. Retention time was 3.8 min and limit of detection and limit of quantification were 0.001 and 0.008 μg g(-1). The results indicated that the reported method could meet the requirement for the analysis of metamitron in trace amounts.

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Dissipation of fentrazamide in soil under aerobic conditions was studied. Fentrazamide was extracted with 0.1 N HCl: acetone (1:1 v/v) followed by partition and cleanup. Separation was done on ODS-II column with mobile phase acetonitrile: water (70:30 v/v). Recovery varied from 74.51 % to 90.10 % percent in soil. Dissipation followed first order kinetics with monophasic pattern. Half life in soil was 9.02 days. Calibration curves were linear over the range of 0.05-1.00 μg mL(-1) and RSD was 1.82 %. LOD and LOQ were 0.002 and 0.005 μg g(-1) for soil. No residues in soil and crop were observed at harvest.

Dissipation of fentrazamide in soil and water under flooded (anaerobic) conditions was studied. Fentrazamide was applied to soil at 100 g ha(-1). Soil was extracted with 0.1 N HCl : acetone (1 : 1 v/v) followed by partition and cleanup with silica SPE. Separation was achieved in an ODS-II column with a mobile phase of acetonitrile : water (70 : 30 v/v) and detection at 214 nm. Recovery of fentrazamide varied from 75.2-90.4% and 89.9-97.8% in soil and water, respectively. Fentrazamide dissipated rapidly and fentrazamide residues were not detected after 100 and 35 days of application in soil and water, respectively. Half life in soil and water was 9.06 and 3.66 days, respectively. Dissipation followed monophasic first order kinetics pattern. No fentrazamide was detected in soil, rice grain and rice straw at harvest of crop. Calibration curves for quantification were linear and relative standard deviation (RSD) was 1.78%. LOD for instrument was 0.002 μg mL(-1) and LOQ for methods were 0.005 μg g(-1) for soil and water.

This paper aims at developing and validating a convenient, rapid, and sensitive method for estimation of metamitron from soil samples.Determination andquantification was carried out by Gas Chromatography on microcapillary column with an Electron Capture Detector source. The compound was extracted from soil using methanol and cleanup by C-18 SPE. After optimization, the method was validated by evaluating the analytical curves, linearity, limits of detection, and quantification, precision (repeatability and intermediate precision), and accuracy (recovery). Recovery values ranged from 89 to 93.5% within 0.05- 2.0 µg L−1 with average RSD 1.80%. The precision (repeatability) ranged from 1.7034 to 1.9144% and intermediate precision from 1.5685 to 2.1323%. Retention time was 6.3 minutes, and minimum detectable and quantifiable limits were 0.02 ng mL−1 and 0.05 ng g−1, respectively. Good linearity (R 2 = 0.998) of the calibration curves was obtained over the range from 0.05 to 2.0 µg L−1. Results indicated that the developed method is rapid and easy to perform, making it applicable for analysis in large pesticide monitoring programmes.