摘要
A facile, rapid and sensitive spectrophotometric method was developed for the determination of carbaryl in its formulations, water and grain （rice and wheat） samples with newly synthesised reagent. The proposed method was based on the alkaline hydrolysis of carbaryl pesticide and thus resulted 1-naphthol was coupled with diazotised 4,4＇-methylene-bis-m-nitroaniline in basic medium （pH 9） to give red colored product having λmax 480 nm for diazonium method （DM） or 1-naphthol reacts with 4,4＇-methylene-bis-m-nitroaniline in the presence of oxidising agent potassium dichromate （K2Cr2O7） to give red colored product having λmax 510 nm for oxidation method （OM）. The formation of colored derivatives with the coupling agent is instantaneous and stable for 48 h （DM） and 32 h （OM） respectively. Beer＇s law was obeyed in the concentration range of 0.2--10.0 μg·mL ^-1 for DM and 0.2--0.150 μg·mL^-1 for OM. The proposed methods are sensitive, easy to operate and permitted for the determination of carbaryl with detection limits of 0.028 μg·mL^-1 for DM and 0.024 μg·mL^-1 for OM respectively. The experimental results indicate that the procedure can eliminate the fundamental interferences caused by other pesticides and non-target ions, which made the methods more sensitive and selective. The method was applicable to the determination of carbaryl residue in water and food grain samples up to μg level.
A facile, rapid and sensitive spectrophotometric method was developed for the determination of carbaryl in its formulations, water and grain （rice and wheat） samples with newly synthesised reagent. The proposed method was based on the alkaline hydrolysis of carbaryl pesticide and thus resulted 1-naphthol was coupled with diazotised 4,4＇-methylene-bis-m-nitroaniline in basic medium （pH 9） to give red colored product having λmax 480 nm for diazonium method （DM） or 1-naphthol reacts with 4,4＇-methylene-bis-m-nitroaniline in the presence of oxidising agent potassium dichromate （K2Cr2O7） to give red colored product having λmax 510 nm for oxidation method （OM）. The formation of colored derivatives with the coupling agent is instantaneous and stable for 48 h （DM） and 32 h （OM） respectively. Beer＇s law was obeyed in the concentration range of 0.2--10.0 μg·mL ^-1 for DM and 0.2--0.150 μg·mL^-1 for OM. The proposed methods are sensitive, easy to operate and permitted for the determination of carbaryl with detection limits of 0.028 μg·mL^-1 for DM and 0.024 μg·mL^-1 for OM respectively. The experimental results indicate that the procedure can eliminate the fundamental interferences caused by other pesticides and non-target ions, which made the methods more sensitive and selective. The method was applicable to the determination of carbaryl residue in water and food grain samples up to μg level.
