Volume 3, Issue 2 (February 2006)

    Use of Carbodiimides as Stabilizing Agents to Deliver Water—Labile Active Ingredients in Liquid Systems Including Aqueous Medium—Amitraz as a Case Study

    (Received 31 August 2004; accepted 7 August 2005)

    Published Online: 2005

    CODEN: JAIOAD

      Format Pages Price  
    PDF Version 7 $25   ADD TO CART


    Abstract

    Several active ingredients such as sulfonylureas and diimidines (Amitraz) are unstable in water. They undergo hydrolysis producing metabolites that are no longer biologically active. The rate of hydrolysis is a function of several factors, such as the solvent system, access to water, pH, temperature, ionic strength, and the types of emulsifiers used in the liquid matrices. Some of the active ingredients undergo rapid hydrolysis even with the residual water present in the emulsifier system in an organic emulsifiable concentrate formulation. It is therefore difficult to formulate such active ingredients in liquid delivery systems. Use of carbodiimides like Stabaxol I® (bis-2,6-diisopropylphenylcarbodiimide) as a water scavenger to stabilize oil-based formulations for Amitraz is well documented and is commercially practiced. We have found that unique combinations of carbodiimides with specific solvent-emulsifier-polymer blends in a buffered system can produce stable microemulsions of Amitraz in water. Such aqueous formulations with 200–500 ppm Amitraz in >99 % water, were stable with 95 % retention on accelerated storage at 50°C for two weeks. This data translates to greater than two years stability at room temperature. Such formulations may be extended to deliver sulfonylureas. We also observed that the concentrate and the matrix containing Stabaxol I® and emulsifiers can produce gels on storage, adversely affecting physical stability. We have identified several additives and alternatives to prevent gel formation enabling long-term storage stability of the matrix and the concentrate. Examples with supporting data will be provided. A rationale and proposed mechanism for the enhanced stability and potential biological activity will be discussed.


    Author Information:

    Narayanan, KS
    Science Fellow/Director, Ph.D., International Specialty Products, Wayne, NJ

    Jon, DI
    Senior Research Chemist, Ph.D., International Specialty Products, Wayne, NJ

    Beestman, G
    Beestman Formulations Consulting, Madison, WI


    Stock #: JAI12912

    ISSN: 1546-962X

    DOI: 10.1520/JAI12912

    ASTM International is a member of CrossRef.

    Author
    Title Use of Carbodiimides as Stabilizing Agents to Deliver Water—Labile Active Ingredients in Liquid Systems Including Aqueous Medium—Amitraz as a Case Study
    Symposium Pesticide Formulations and Delivery Systems: Advances in Crop Protection Technologies: 25th Volume, 2004-10-07
    Committee E35