Determination of vapor pressure-temperature relationships of current–use pesticides and transformation products
Sub-cooled liquid vapor pressures (PL 0) of current–use organochlorine and organophosphate pesticides (chlorothalonil, chlorpyrifos methyl, diazinon, fipronil) and selected transformation products (chlorpyrifos oxon, heptachlor epoxide, oxychlordane, 3,5,6-trichloro-2-pyridinol) were determined at multiple temperatures using the gas chromatography retention time technique. Results were utilized to determine vapor pressure-temperature relationships and to calculate enthalpies of vaporization (ΔHvap). While results for chlorothalonil and diazinon were comparable with published values, the measured value for fipronil (1.82 × 10− 6 Pa) is almost an order of magnitude higher than the reported literature value (3.7 × 10− 7 Pa). The availability of vapor pressure temperature relationships for these chemicals will aid in pesticide risk assessment development and improve the effectiveness of mitigation and remediation efforts.