Vapor Pressure and Surface Tension Measurements of Seven Mosquito Repellents.
Final rept. Sep 78-1 Jan 79,
LETTERMAN ARMY INST OF RESEARCH PRESIDIO OF SAN FRANCISCO CA
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An investigation was initiated to determine whether or not a relationship exist, first, between the relative vapor pressure of a repellent and its loss from the skin by evaporation and, second, between the surface tension of a mosquito repellent and its intrinsic repellency. The relative vapor pressure of five of these compounds was measured by a head space sampling gas chromatographic procedure. The surface tension of seven mosquito repellents was measured by a pendant drop or de Nouy method. The median effective dose ED50 of the seven compounds was determined against Aedes aegypti mosquitoes. A comparison was made between repellent ED50 values and the more difficult to measure minimum effective evaporation rate MEER or intrinsic repellency of 4 of the compounds. Repellent ED50 increased as MEER increased which supports the concept that ED50 is a measure of intrinsic repellency. A comparison was made between previously reported values for repellent evaporative loss from skin and relative vapor pressure increased. No apparent linear relationship exists between surface tension and ED50 values.
- Pesticides Pollution and Control