A permeation liquid membrane system for determination of nickel in seawater

The use of a permeation liquid membrane system for the preconcentration and separation of nickel in natural and sea waters and subsequent determination by atomic absorption spectroscopy is presented. 2-Hydroxybenzaldehyde N-ethylthiosemi-carbazone (2-HBET) in toluene is used as the active component of the liquid membrane. A study strategy based on a simplex design has been followed. Several chemical and physical parameters were optimized. Maximum permeation coefficient was obtained at a feed solution pH of 9.4, 0.3mol l(-1) of HNO(3) in the stripping solution and 1.66mmol l(-1) of 2-HBTE in toluene as carrier. The precision of the method was 4.7% at 95% significance level and a detection limit of 0.012microg l(-1) of nickel was achieved. The preconcentration procedure showed a linear response within the studied concentration range from 3 to 500microg l(-1) of Ni in the feed solution. The method was validated with different spiked synthetic seawater and certified reference water samples: TMDA-62 and LGC 6016, without matrix interferences and showing good concordance with the certified values, being the relative errors -5.9% and -2.2%, respectively. Under optimal conditions, the average preconcentration yield for real seawater samples was 98+/-5%, with a nickel preconcentration factor of 20.83 and metal concentrations ranging between 2.8 and 5.4microg l(-1).