Abstract
The vapor pressure of trimellitic anhydride (TMA) over the range 60°–160°C was determined. The dynamic technique of gas saturation, or transpiration, was employed to generate TMA vapor at constant temperature. The generated TMA vapor was collected on a small Chromosorb 104 trap that was subsequently desorbed with water-acetonitrile. The resulting trimellitic acid was quantitatively determined by paired-ion, reversed-phase liquid chromatography. The high sensitivity of this approach permitted vapor pressure measurements of TMA at lower temperatures than previously reported. Measured vapor pressure data extrapolated to 25°C gave a value of 1.6×10−5 Pa (1.2×10−7 torr). Based on this data, the equilibrium vapor concentration of TMA at 25°C would be 1.2 micrograms per cubic meter, which is less than 5% of the recommended limit for workplace atmospheres.