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) c onsisting of 1,10-didecyl diaza 18-crown-6, fatty acid and a mixture o f toluene and phenylhexane (1+1) has been studied for application in n atural water conditions. Two types of single hollow fiber modules i.e. non flow and flow systems for free metal ion separation and preconcen tration were used. The effect of target elements, sample volume, targe t metal concentration, and flow rates of sample solution in the case o f the flow system on the preconcentration factor for a given receiver solution volume (ca 50-60 mu l) placed in the lumen of the membrane) h ave been studied. High preconcentration factors in the range 100-3000 for Cu, Pb and Cd, for preconcentration times in the range 5-120 min w ere found using sample and receiver solution volumes of 250 mi and 60 mu l, respectively. Preconcentration factors were found to be independ ent of the initial concentration of target elements in the sample and dependent on initial sample volume. Long term stabilities of these mem branes showed that they are stable for at least seven days of continuo us use. The results of these studies suggest that by combining SLM wit h sensitive analytical detectors e.g., voltammetric ones, detection li mits of below 10(-10) mol l(-1) can be achieved.