Hollow fiber based supported liquid membrane: a novel analytical system for trace metal analysis

A new versatile tool for speciation of trace metals, in particular Cu, Pb and Cd based on a hollow fiber supported liquid membrane (HFSLM) consisting of 1,10-didecyl diaza 18-crown-6, fatty acid and a mixture of toluene and phenylhexane (1 + 1) has been studied for application in natural water conditions. Two types of single hollow fiber modules i.e. non flow and flow systems for free metal ion separation and preconcentration were used. The effect of target elements, sample volume, target metal concentration, and flow rates of sample solution in the case of the flow system on the preconcentration factor for a given receiver solution volume (ca 50–60 μl) placed in the lumen of the membrane) have been studied. High preconcentration factors in the range 100–3000 for Cu, Pb and Cd, for preconcentration times in the range 5–120 min were found using sample and receiver solution volumes of 250 ml and 60 μl, respectively. Preconcentration factors were found to be independent of the initial concentration of target elements in the sample and dependent on initial sample volume. Long term stabilities of these membranes showed that they are stable for at least seven days of continuous use. The results of these studies suggest that by combining SLM with sensitive analytical detectors e.g., voltammetric ones, detection limits of below 10−10 mol l−1 can be achieved.