Synthesis of amidic alginate derivatives and their application in microencapsulation of λ-cyhalothrin.

1-Octyl amine was covalently coupled to sodium alginate(NaAlg) in an aqueous-phase reaction via acidamide functions using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC-HCl) as a coupling reagent to provide octyl-grafted amphiphilic alginate-amide derivative(OAAD) for subsequent use in λ-cyhalothrin (LCH) microcapsule application. The structure of OAAD was confirmed by FT-IR and (1)H NMR spectroscopies. The new alginate-amide derivative was used for fabricating microcapsule that can effectively encapsulate LCH by emulsification-gelation technique. The microcapsules were characterized by optical microscopy (OM), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and laser particle size analysis. The encapsulation efficiency and drug release behavior of LCH from the microcapsules were investigated. Results showed that the microcapsules were in spherical form with diameter mostly in the range of 0.5-10 μm and possessed a structure with LCH as core and OAAD as shell. The encapsulation efficiency and the release performance of the microcapsules were influenced by DS of OAAD and amount of CaCl(2). The mechanism of LCH release was found to vary from anomalous to Fickian to quasi-Fickian transport with the DS of OAAD varied from 10.8 to 30.3 and the CaCl(2)/emulsion ratios varied from 0.09 to 0.03%.