Integrated analytical pervaporation-gas-phase absorptiometry: theoretical aspects and applications

A new pervaporator is designed in which analytical pervaporation is integrated with gas-phase absorptiometry in order to monitor the mass transfer through a hydrophobic membrane in a continuous mode. From the recording obtained, the theoretical principles which govern the steps involved in pervaporation (namely, evaporation of the volatile species into the air-gap over the liquid sample surface, diffusion through the membrane and acceptance of the diffused species in a gas phase, then recovery of the baseline by removal of the remaining analyte in the opposite direction to pervaporation) were established and expressed by the corresponding equations. Finally, a method for the determination of ammonia in the gas phase was developed in order to demonstrate the usefulness of the integrated approach and then applied to the determination of ammonia nitrogen in fertilisers.