Speciation of trace metals in waters: Direct selective separation and preconcentration of free metal ion by supported liquid membrane

The potentiality of species-selective supported liquid membrane device (SLM ) for trace metal measurements under natural water conditions has been inve stigated. Cu(II) speciation studies with various synthetic hydrophilic liga nds (sulphosalicylic acid, hydroxyquinoline sulphonic acid and oxalic acid) and natural ligands such as fulvic acids were done using 1,10-didecyl-1,10 -diazacrown ether -lauric acid/phenyl hexane-toluene on flat and hollow fib re supported liquid membranes. The salient features of the results obtained are that only free metal ions are transported across this SLM and the nega tively charged complexes and neutral complex do not pass through within the time scale of the measurement. Low free metal concentrations can be measur ed and most importantly the experimentally observed values of degree of com plexation(alpha(s)) are in good agreement with the theoretically calculated ones, the correlation, coefficient being 1.01 +/- 0.02. These findings sug gest that SLM can be used as an alternative method for speciation studies i n natural waters.