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We have developed a stable microemulsion (Microbio® from Cesalpinia Chemicals SpA,Italy) containing a citric ester of alkylpolyglucoside, fatty acid esters fromtransesterification of a vegetable oil and an ethoxylated fatty alcohol, which proved to be ahigly effective adjuvant with different herbicide actives.
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MICROBIO: A NOVEL MICROEMULSION AS AN EFFICIENT TANK-MIX ADJUVANT FOR HERBICIDE TREATMENTS
Alberto Colombo, Gianfranco Paganini and Peter Bohus
Cesalpinia Chemicals SpA (Lamberti Group), Agro Chemistry Laboratory
via Piave 18; 21041 Albizzate (VA) – Italy
Corresponding author: [email protected] Fatty acid esters from transesterification of vegetable oils, alkylpolyglucosides and ethoxylated fatty alcohols have individually been widely used as tank-mix or built-in adjuvants for herbicides. Recently, a new class of anionic esters of alkylpolyglucoside have been described as novel tank-mix adjuvants (1,2), which appear to have good potential as adjuvants in agro-chemistry. Microemulsion is a highly effective physical form of agrochemical delivery system, which combines stability of complex formulations, performance and easy handling. We have developed a stable microemulsion (Microbio® from Cesalpinia Chemicals SpA, Italy) containing a citric ester of alkylpolyglucoside, fatty acid esters from transesterification of a vegetable oil and an ethoxylated fatty alcohol, which proved to be a higly effective adjuvant with different herbicide actives. It was developed by optimizing physico-chemical properties in order to improve stability, synergism amongst components and compatibility with various pesticide formulations. Surface tension and sinking time of the microemulsion system are lower than a corresponding emulsifiable vegetable oil, suggesting better wetting properties. Spreading of aqueous solutions, evaluated from dynamic contact angle determinations in comparison to a solution of ethoxylated fatty alcohol, indicates that the higher the concentration of Microbio, the lower the contact angle measured. Particle size distribution falls within the microemulsion range (3), while the flow curve of Microbio shows a Newtonian behaviour, whereby viscosity is independent of shear rate. Thermodynamic parameters derived from rheological studies suggest an intrinsic stability of Microbio, as reported in literature for a similar system (4). Biological efficacy in weed control of various tank-mix combinations of the adjuvant with different active ingredients was studied using standard, commercial herbicide formulations, and compared to a well known commercial adjuvant (Hasten®, from Victorian Chemicals, Australia). Three herbicide-weed combinations of Microbio as tank mix adjuvant were examined: one water soluble herbicide (Bentazone Na salt, alias Basagran® from BASF) applied on Black nightshade; two water insoluble actives (Nicosulfuron and Quizalofop-P-ethyl, alias Milagro® from Syngenta and Targa Prestige® from Bayer, respectively) applied on Wild oat. These herbicide actives were applied at sub-optimal dosages, while the concentration of our new adjuvant or Hasten was constant at 0.25% (v/v) in water. At all hebicide dosages tested, Microbio showed either an equal or better efficacy than Hasten. The innovative aspects of this new adjuvant microemulsion will be discussed.
REFERENCES
1. Bohus, P., Colombo, A.; 2004. Proceedings of 7th International Symposium on
Adjuvants for Agrochemicals, Cape Town, SA pp 301 – 306 2. European Patents n° EP 510564 3. Tadros, T. F.; 2005. Applied Surfactants; Wiley-VCH; Weinheim pp 309 – 311 4. Acharya, A., Ghosal, S.K., Moulik, S.P., Subramanian, N. et al.; 2005. Chem. Pharm.
Bull. vol 53(12) pp 1530 –1535. Acknowledgements We wish to thank Dr. Hans de Ruiter for very helpful suggestions and collaboration.
