Lipophilic metal complexes are potentially toxic or bioavailable. These complexes may be present in natural waters but, due to lack of sensitive methods for their detection, their contribution to biouptake is poorly understood. Hence, an analytical technique, based on permeation liquid membrane (or supported liquid membrane) (PLM or SLM) has been investigated for the determination of lipophilic metal complexes. For this purpose, key parameters, such as the nature of solvent, diffusion coefficient in the membrane, D(m), partition coefficient between the solution and the membrane, K(p), and permeability coefficient, P, governing the transport of Cu(II)-8-hydroxyquinolinate (CuQ(2)(0)) through a flat sheet PLM comprising toluene/phenylhexane have been evaluated. CuQ(2)(0) was chosen as model lipophilic complex. Copper-8-hydroxyquinolinate is used as a pesticide and may be present in natural waters. The effects of pH, in the range 6-8, and the membrane thickness on the CuQ(2)(0) transport were also studied. The results showed that the neutral species is transported efficiently across the membrane containing toluene/phenylhexane mixture. Values of D(m) = 3.0 x 10(-7) cm(2)s(-1) and P=1.45 x 10(-3) cm s(-1) were found; P is independent of pH in the studied pH range. The partition coefficient. K(p), of CuQ(2)(0) in phenylhexane/toluene mixture was also determined using the classical liquid/liquid extraction method for comparison. The application of PLM method was tested for the trace level determination of lipophilic complexes using hollow fibre permeation liquid membrane to preconcentrate the analyte. High preconcentration factor for CuQ(2)(0) was achieved using the designed HFPLM device. Finally, the applicability of this method to CuQ(2)(0) was tested in a real water sample by spiking it with 8-hydroxyquinoline (10 mu mol L(-1)). The results showed a quantitative recovery. The theoretically estimated LOD is few pmol L(-1).