Deltamethrin was obtained as a gift sample from Tagros India Ltd. Mumbai, India. Polyvinylpyrrolidone (PVP K-30), Dibutylphthalate (DBT), and Ethylcellulose (EC, ethoxy content 48-49.5% w/w) were obtained from Himedia Laboratories Pvt. Ltd. Mumbai, India. Chloroform and water (for HPLC) were obtained from Spectrochem Pvt. Ltd. Mumbai, India. Acetonitrile (for HPLC) was purchased from Merck Specialities Pvt. Ltd. Mumbai, India. Dimethylsulfoxide (DMSO) was purchased from Loba Cheime Pvt. Ltd. Mumbai, India. All reagents and solvents used were of analytical grade and used as received without any further purification.