Insect sex pheromones: Determination of half-lives from formulations by collection of emitted vapor.

A new method for determining half-lives for the evaporation of sex pheromones from formulations has been developed. A previously unexploited mathematical relationship makes possible the determination of half-lives of over 1000 days by collecting evaporated pheromone for 1-4 hr and measuring the amount collected and the amount left in the formulation. Purified nitrogen flows over the test material and the evaporated pheromone is qualitatively collected on an adsorbent of 80-100 mesh silica gel silanized with octadecyltrichlorosilane. Quantitation is by gas chromatography. Quantitative mass balance was achieved and half-lives determined by this new method are in agreement with half-lives previously determined by measuring the amount of pheromone left in septa after a sequence of time intervals. Previously undetermined half-lives for acetates and alcohols are reported.