Recebido em 13/12/06; aceito em 5/7/07; publicado na web em 19/12/07 A simple cloud point extraction procedure is presented for the preconcentration of copper in various samples. After complexation by 4-hydroxy-2-mercapto-6-propylpyrimidine (PTU), copper ions are quantitatively extracted into the phase rich in Triton X-114 after centrifugation. Methanol acidified with 0.5 mol L -1 HNO 3 was added to the surfactant-rich phase prior to its analysis by flame atomic absorption spectrometry (FAAS). Analytical parameters including concentrations for PTU, Triton X-114 and HNO 3 , bath temperature, centrifugation rate and time were optimized. The influences of the matrix ions on the recoveries of copper ions were investigated. The detection limits (3SD b /m, n=4) of 1.6 ng mL -1 along with enrichment factors of 30 for Cu were achieved. The proposed procedure was applied to the analysis of environmental samples.

Highly selective poly(vinyl chloride) (PVC) membrane electrodes based on recently synthesized mercury complexes including Hg(Nmpntb) 2 and Hg(Npdntb) 2 as new carriers for iodide-selective electrodes by incorporating the membrane ingredients on the surface of graphite electrodes are reported. The effect of various parameters including the membrane composition, pH and possible interfering anions were investigated on the response properties of the electrodes. Both sensors exhibited Nernstian responses toward iodide over a wide concentration range of 7 Â 10 À7 to 0.1 M and 1 Â 10 À6 to 0.1 M, with slopes of 59.6 AE 0.8 and 58.9 AE 0.9 mV per decade of iodide concentration and detection limit of 3 Â 10 À7 M and 7 Â 10 À7 for Hg(Npdntb) 2 and Hg(Nmpntb) 2 , respectively, over a wide pH range of 3 -11. The sensors have response times of 5 s and can be used for at least 2 months without any considerable divergence in their potential response. The proposed electrodes show good ability to discriminate iodide over several inorganic and organic anions. The electrodes were successfully applied to direct determination of iodide in synthetic mixture, waste water and drinking water and as indicator electrodes in precipitation titrations.

A sensitive and selective procedure is presented for the voltammetric determination of copper(II) ion. The procedure involves an adsorptive accumulation of Cu2+-PPKO on a hanging mercury drop electrode, followed by a stripping voltammetric measurement of reduction current of adsorbed complex at about -0.30 V (vs. SCE). The optimum conditions for the analysis of copper(II) ion include pH (5.8-7.0), 60 microgM PPKO and an accumulation potential of -0.5 V (vs. SCE). The peak current is proportional to the concentration of copper over the range 0.3-76 ng mL(-1) with a detection limit of 0.01ng mL(-1) with an accumulation time of 60 s. The speciation of different forms of complex between copper(II) ion and PPKO, using the Best (Martell program), followed pH measurement were examined. The method was applied to the determination of copper(II) ion content in real samples successfully.

Highly selective poly(vinyl chloride) (PVC) membrane of iodide ion selective electrode based on the application of bis(trans-cinnamaldehyde)-1,3-propanediimine)mercury(II)chloride [Hg(BPPPB)Cl2] as new carrier by coating the membrane ingredient on the surface of graphite electrodes has been reported. The effect of various parameters including membrane composition, pH and possible interfering anions on the response properties of the electrode were examined. At optimum conditions, the proposed sensor exhibited Nernstian responses toward iodide ion in a wide concentration range of 1×10-6to 0.1 M with slopes of 58.0±0.8 mV per decade of iodide concentration over a wide pH range of 3-11 with detection limit of detection of ~8×10-7M. The sensors have stable responses times of ≤ 5 s and give stable response after conditioning in 0.05 M KI for 24 h with its response is stable at least 2 months without any considerable divergence in its potential response characteristics. The electrodes were successfully applied for the direct determination of iodide ion in water sample and as indicator electrodes in precipitation titrations.

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