Abstract:
Topical repellents play a key role in reducing the outdoor transmission of mosquito-borne diseases
by reducing human-vector contact. Excellent repellents are available, but there is always room
for improvement. This article reports on a particularly effective binary repellent blend of ethyl
butylacetylaminopropionate and nonanoic acid. A composition containing 25 mol% of the acid exhibits
negative pseudo-azeotrope behaviour at 50 °C, meaning that the liquid vapour pressure is lower than
that of the parent compounds and evaporation occurs without a change in the liquid composition. In
tests performed using the South African Medical Research Council’s cup-on-arm procedure, this mixture
provided better protection for a longer time than the “gold standard of mosquito repellents”, namely
N,N-diethyl-m-toluamide, commonly known as DEET.
