Determination of Henrys law constants for low volatile mixed halogenated anisoles using solid-phase microextraction

Trihalogenated anisoles (THAs) that have been identified at low concentration levels (ng L^-1) in drinking water are suspected of causing odor episodes, which are a frequent source of complaint by consumers. Henryʹs law constant (KH) is an important parameter in controlling the diffusion of organic compounds from the water to the vapor-phase, so its evaluation is of significance in the study of odor events. In this paper, the KH of a wide range of trihalogenated anisoles - in its dimensionless form KʹH - were calculated at two temperatures, 45 and 22 °C using equilibration partitioning in a closed system and headspace microextraction (EPICS-SPME). Two methodological approaches, Ramachandran and Dewulf, were used for the assessment of the Henryʹs law constant. Nevertheless, to apply these methods to THAs, a relatively narrow headspace/water volume ratio range (80/1-8/1) is required. At these conditions, a linearity (r^2) using Ramachandranʹs theoretical relationship from 0.9276 to 0.9989 was obtained and the variability (R.S.D.%) when Dewulfʹs theoretical relationship was employed was lower than 20% (n = 5).