Theoretical analysis of non-steady-state, pulse introduction membrane extraction with a sorbent trap interface for gas chromatographic detection

Polymeric membranes have been used for extraction of organic compounds from an aqueous matrix, where the analysis is carried out on-line using a GC, a HPLC, or a mass spectrometer. High extraction selectivity and permeation rate can be achieved by choosing an appropriate membrane and optimum operating conditions. The sample can be introduced either continuously or as a pulse into the membrane. The former approach is based on steady-state permeation, while the latter is not. In this paper, pulse introduction membrane extraction is presented for on-line gas chromatography using a sorbent trap as an interface. A mathematical model that incorporates boundary layer effects has been developed, and the process parameters that affect sensitivity and lag time have been studied. It is observed that there is a trade-off between sensitivity and lag time; larger sample volume and lower flow rate enhance sensitivity but also increase lag time.