HPLC analysis of Azadirachtin and formulation of neem seed extracts | Analyse de l'Azadirachtine par HPLC et developpement d'une formulation d'extraits de eem
1997
Schiffers, B.C. | Dieye, A. | Ntema, P. | Dieye, B. | Ekukole, G. (Faculte universitaire des sciences agronomiques de Gembloux (Belgium). Dept. de chimie analytique et phytopharmacie)
An analytical method for the dosage of azadirachin has been developed. Neem oil is removed from seeds with hexane, and azadirachtin is extracted from the neem seeds with methanol. The extracts are first purified with a liquid/liquid partition, followed by a chromatographic separation on a Florisil column. HPLC analysis requires a C 18 ODS phase. The efficacy of the method is about 97 per cent. Extracts from neem seeds (Azadirachta indica) have been formulated as a emulsifiable concentrate (EC). This formulation contents 0.3 to 1 per cent azadirachtin, 18 per cent neem oil, and will be used as an insecticide on cotton at 11 EC per ha mixed with 9 litre of water (very low volume spraying technique). The nature of the solvent appeared to be crucial for the stability of azadirachtin (according to CIPAC MT 46) and neem oil can improve the stability of the compound. Surfactants have been selected (emulsification tests according to CIPAC MT 36) to give a good emulsion in soft (CIPAC A) and hard (CIPAC D) waters, after 24 hours without agitation. Field results from Senegal confirm that azadirachtin used alone at 11 g a.i. per ha (EC) cannot control completely Helicoverpa armigera and Aphis gossypii, but demonstrate that these can be controlled by mixtures of 5 g azadirachtin + 25 g cypermethrin per ha or 5 g azadirachtin + 300 g chlorpyriphos-ethyl per ha (5 sprays each 14 days). The mixture of neem oil and chlorpyriphos-ethyl has shown a knock-down effect.
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