Multiple solid-phase microextraction

Theoretical aspects of multiple solid-phase microextraction are described a nd the principle is illustrated with the extraction of lidocaine from aqueo us solutions. With multiple extraction under non-equilibrium conditions con siderably less time is required in order to obtain an extraction yield that is equal to that of one extraction at equilibrium. On the other side, the extraction yield can be increased if multiple extraction is performed with the same total time as is needed for one extraction at equilibrium time. Th e effect of multiple extraction is strongly dependent on the value of the p artition constant and for practical use the length of the desorption time i s important. A good agreement between theoretical and experimental data has been obtained. Chromatograms are presented showing the potential of multip le solid-phase microextraction. (C) 2000 Elsevier Science B.V. All rights r eserved.