Colorimetric method for determination of the nematicide, cadusafos in aqueous medium at different temperature and ph levels [electronic resource]

Includes references.

A colorimetric method has been developed to determine residues of cadusatos in water. This method is based on the oxidation of sulphur atom in cadusafos or its breakdown product by using concentrated HNO₃ to the corresponding sulphone. Then the oxidation product can readily react with the p-aminobenzene sulfonic acid and 4-aminoantipyrine chromogenic reagents to form a colored compound in alkaline medium with maximum absorption at 580 nm. The relationship between absorbance and concentration of cadusafos is linear and obeys Beer's law in the range of 0.04-1.0 µg/6.65ml solution. The method is sensitive and can be applied to the determination of levels as low as 0.02 µg/ml cadusafos in water. The effect of pH and temperature on cadusafos stability in aqueous solution is also studied. The results indicated that the amount of cadusafos hydrolyzed was temperature dependent rather than pH dependent. The disappearance of cadusatos appeared to follow first order kinetics with different rates. The highest hydrolysis rate was found at 40°c followed by 20°C and the lowest was at 5°c (k = 0.19- 0.20 day⁻¹, 0.15-0.16 day⁻¹ and 0.095- 0.1 day⁻¹, respectively). Rapid hydrolysis rate was obtained at pH 5 and 40°c with short half life (to.5 = 3.31 days) whereas the rate of hydrolysis was slower at pH 6.5 and 5oc (to.5 = 7.27 days).

Summary in Arabic.

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