On the potentiometric response of mercury(II) membrane sensors based on symmetrical thiourea derivatives-Experimental and theoretical approaches

Mercury(II) sensors based on two bis-thioureas: 4,4'-bis-(3-phenylthiourea)diphenyl methane (L-1) and 2-2-[10-[(E)-2-(aminocarbothioyl)hydrazono]-1,4-dihydroxy-9(10H)-anthracenyliden]-1 hydrazinecarbothioamide (L-2) were prepared and studied. The best response characteristics were obtained using the composition-L-2:KTpCIPB:PVC:DOP in the percentage ratio of 3.5:1.5:32:63 (w:w). The electrode exhibited a near Nernstian response of 30.3 mV decade(-1) to mercury ions over the activity range 1.0 x 10(-7) to 1.0 x 10(-2) M with a limit of detection 7.9 x 10(-8) M. The pH independent plateau ranges between 1.5 and 4.0. The proposed sensor revealed fairly good discriminating ability toward Hg2+ ion in comparison with many hard and soft metal ions. It could be applied to determination of mercury in waste water as a real sample. Besides, theoretical calculations performed using the Gaussian 09 programs indicate a S atom is the most favorite reactive site and mainly responsible for the observed electrochemical behaviors in Hg(II)-selective electrodes toward the different cations. (C) 2014 Elsevier B.V. All rights reserved.