Breakthrough characteristics of volatile organic compounds in the -10 to + 170 degrees C temperature range on Tenax TA determined by microtrap technology.

In this work the breakthrough volumes (BTVs) of volatile organic compounds (VOCs) on Tenax TA were determined in the -10 to 170 degrees C temperature range by using microtrap (MT) technology. The MT technology allowed experimental investigation of the temperature dependence of BTVs. Along with the BTV data, we also discuss the thermodynamics of the temperature dependence of the BTV through a two-parameter equation In (BTV) = A1/T + C1 where T is temperature (K), A1 = -deltaH/R where deltaH is enthalpy of sorption and C1 is constant. This equation fitted well the experimental results with R2 values between 0.9737 (acetone) and 0.9995 (dimethyl disulfide), with n between 6 and 11. However, for n-pentane, n-hexane and 1-hexene it proved that a three parameter equation In (BTV) = A2/ T + BTB + C2 fitted better to the experimental results, with A2 = -deltaHT0/R, B = deltaCp/R, TB = 1n(T/T0) + (T0 - T)/T, C2 a constant, deltaHT0 the adsorption enthalpy at reference temperature T0 and deltaCp the difference in the molar heat capacity of compound under investigation between the sorbed and the free gas phase state. The statistical analysis showed for example for n-pentane now R2 = 0.9969 instead of R2 = 0.9746, and Fisher statistics F = 487 instead of F = 153, with a significance level P = 0.018 for the third parameter. The results show that microtrap technology well serves as a technology to get information on temperature dependence of BTVs in an extended range. Simultaneously, it turns out that MT technology, extending the operational temperature range, is well served by a careful investigation of the temperature dependence models of BTVs.