Cipac collaborative study to test a colorimetric method for determination of the stability of dilute emulsions

A colorimetric method for the determination of the stability of dilute emulsions (down to 1 ml litre−1) of emulsifiable concentrates (EC) has been subjected to a collaborative study with 27 participating laboratories, on behalf of the Collaborative International Pesticides Analytical Council (CIPAC). A dye is added to the emulsifiable concentrate and an aliquot is poured into standard water to obtain an aqueous emulsion. After a specified time, the absorbance of an aliquot of the dyed emulsion is measured and compared to the absorbance measured after initial formation of the emulsion. Collaborators were furnised with four emulsifiable concentrate formulations and the dye, and requested to make three replicate determinations on each dyed sample in CIPAC standard waters A and D. The repeatability and reproducibility figures obtained in these trials indicate that the method permits a good estimation of the stability of dilute emulsions when it is followed exactly.