| Popis: |
We have developed a new, simple, quick, precise and inexpensive method to estimate vapor pressure by the use of gas chromatography. This new method differs significantly from previous gas chromatography methods because it uses a temperature gradient rather than a series of isocratic experiments extrapolated back to room temperature using the Clausius-Clapeyron equation. In addition, it uses a typical methyl silicone capillary column rather than a short (1 m) non-polar capillary. To improve reproducibility of results between different instruments, a cocktail containing two standards with well-established vapor pressures is injected along with the sample compound(s). The vapor pressure at 25°C of the compound(s) in the liquid state is determined by simply finding the retention times of the compound(s) and those of the two standards. Corrections can be made for crystalline compounds. This method can be used for the measurement of the vapor pressures of organic compounds ranging from 10 2 to 10 −7 Pa at 25°C (1 mmHg to 10 −9 mmHg). |
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