An organophosphorous insecticide monocrotophos is increasingly being utilized in agriculture to control insects on a broad range of crops. In this study a new reaction system using spectrophotometric method for quantitative determination of monocrotophos is proposed. The method is based on the bromination of monocrotophos to form dibromomonocrotophos which react with Potassium iodide-Potassium iodate mixture in the presence of leuco malachite green (LMG) to form a water soluble greenish blue colored complex. The change in absorbance as a criterion of the bromination reaction progress was followed spectrophotometrically. To obtain t he maximum sensitivity the effective reaction variables were optimized. The absorbance maximum was observed at 620 nm. Under optimized experimental conditions calibration graph was linear over the range of 10.0-60.0 µg. The molar absorptivity of the colored system is 3.66×104 L mol-1 cm-1 and sandell’s sensitivity is 0.25×10-2 µg cm-2. The calculated detection limit was 0.44 µg mL-1. The interfering effect of various species was also investigated. The present method was successfully applied to the analysis of monocrotophos in different environmental and water samples.
Simple and sensitive spectrophotometric scheme was described for the determination of fenvalerate in environmental samples. The scheme was based on the hydrolysis of 1 N of 5 mL NaOH to form cyanohydrin. The cyanohydrin is reacted with bromine and pyridine to form glutaconic aldehyde, which is then coupled with p-Dimethylaminobenzaldehyde to give yellow dye having maximum absorbance at 440 nm. Beer’s law is obeyed over the concentration range of 0.6- 6.2 µg in a nal solution volume of 25 mL. The molar absorptivity of the colored system is 3.84×104 L mol-1cm-1 and Sandell’s sensitivity is 2.4×10-3 µg cm-2. The reproducibility assessed by carrying out seven days replicate analysis of a solution containing 0.6 µg of fenvalerate in a nal solution volume of 25 mL. The standard deviation and relative standard deviation for the absorbance value were found to be ± 3.4×10-3 and 1.5% respectively. The proposed scheme is sensitive and free from the interference of other toxicants. The analytical parameters were optimized and the scheme was applied to the determination of fenvalerate in environmental samples.
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