Vapor pressures and thermodynamic properties of phenylpropanoid and phenylbutanoid attractants of male Bactrocera, Dacus, and Zeugodacus fruit flies at ambient temperatures

We report on the vapor pressures at ambient temperatures of seven attractants of Bactrocera, Dacus, and Zeugodacus fruit flies - raspberry ketone, cuelure, raspberry ketone trifluoroacetate, methyl eugenol, methyl isoeugenol, dihydroeugenol, and zingerone - by a vapor saturation method. Dry nitrogen was passed over each compound at well-controlled temperatures. Entrained vapor from the compounds was trapped on Tenax GR tubes and analyzed by thermal desorption−gas chromatography−mass spectrometry. The measured attractant amounts on the traps were converted to vapor pressures. Data were subsequently fitted by the Antoine equation. From the Antoine equation parameters, thermodynamic properties for each compound were calculated at 298 K. The calculated vapor pressures were used to compare the volatility of the fruit fly attractants and to infer implications for field applications. Using ambient temperature readings yields far better estimates of vapor pressure values at temperatures relevant for insect control than do Antoine equation parameters derived from high-temperature readings.