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PFT is continuously fed into the stream of drilling fluid using an Alltech 301 high-performance liquid chromatography (HPLC) pump located within a black cabinet in the Mud Pump room ( Figure 1). Although the majority of the PFMD is not volatilized in the vial, it is consistently volatilized at a steady temperature in both the standard vials and the sample vials, so a consistent concentration of PFMD will be measured by the GC-♞CD. It is therefore recommended that the samples be heated at 85☌, at which temperature, the PFMD can be expected to have a partial pressure of approximately 6% of atmosphere (0.06 bar). Even temperatures close to 100☌ will liberate significant water vapor, which can be problematic for the gas chromatography conditions. It is impossible to heat the vial to the boiling point of the PFMD, however, because it will boil the water in the samples and exceed the pressure capacity of the vial. The purity of a batch may be found by navigating to Oakwood Chemical's website, searching for "decalin", selecting perfluoromethyldecalin, going to the CofA tab and entering the LOT # located on the bottle label.Ī Note about the Relative Volatility of PFMCH and PFMDĪt 70☌, 100% of the PFMCH can be expected to be in the volatile phase, whereas the Antoine-derived curve for PFMD predicts that the partial pressure of PFMD in the 20 mL vial would be approximately 3% of atmosphere (0.03 bar). The predominant contaminants tend to be perfluorodecalin and perfluoro-tert-cyclohexane.
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The purity of PFMD purchased from Oakwood Chemical is approximately 80-90%. The low solubility in water for either compound facilitates gas-phase partitioning and quantitative headspace analysis. The evaporation of PFMD is less significant. The vapor pressure of PFMCH is fairly high so it evaporates readily and quickly at standard room pressure and temperature. Both perfluoromethyldecalin (PFMD) and perfluoromethylcyclohexane (PFMCH) are miscible in each other.