Application of the Transpiration Method To Determine the Vapor Pressure and Related Physico-Chemical Data of Low Volatile, Thermolabile, and Toxic Organo(thio)phosphates.

The present work represents the most recent study on the physico-chemical properties of the organophosphate compound class being directly related to the Chemical Weapons Convention (CWC). This compound class is of great importance in the ongoing conflict in Syria. Here, the vapor pressure of the deadly organo(thio)phosphate Amiton and seven of its derivatives was investigated. These medium to low volatile analytes pose a potential threat toward human life by inhalation or direct contact with the skin at very low doses. Therefore, the vapor pressures in ambient temperature regimes were measured by utilizing the transpiration method to determine the saturation vapor pressure psat and the enthalpy of vaporization ΔlgHm° at 298.15 K. We also successfully applied the transpiration method for the examination of thermolabile compounds. In particular, five of the molecules can undergo a thiono-thiolo rearrangement at elevated temperatures within a couple of hours and thus could possibly alter in the course of the experiment. In addition we demonstrate that the concentration under diffusion conditions, cdif, is a useful parameter for the choice of suitable gas phase detection equipment for Amiton and its derivatives, because it can be directly compared with the limit of detection LOD [ng L-1] of the device used. Finally, we proved the transpiration method to be applicable for the investigation of toxic and also high boiling and even thermolabile chemicals in general.