Analytical Sciences

Abstract − Analytical Sciences, 18(8), 887 (2002).

Determination of SCN- in Urine and Saliva of Smokers and Non-Smokers by SCN--Selective Polymeric Membrane Containing a Nickel(II)-Azamacrocycle Complex Coated on a Graphite Electrode
Mohammad Reza GANJALI,*1  Mohammad YOUSEFI,*2 Mehran JAVANBAKHT,*2 Tahereh POURSABERI,*2 Masoud SALAVATI-NIASARI,*3 Leila HAJIAGHA-BABAEI,*1 Elnaz LATIFI,*1 and Mojtaba SHAMSIPUR*4
*1 Department of Chemistry, Tehran University, Tehran, Iran
*2 Department of Chemistry, Tarbiat Modarres University, Tehran, Iran
*3 Department of Chemistry, Kashan University, Kashan, Iran
*4 Department of Chemistry, Razi University, Kermanshah, Iran
The construction, performance characteristics, and application of a novel polymeric membrane coated on a graphite electrode with unique selectivity towards SCN- are reported. The electrode was prepared by incorporating Ni(II)-2,2,4,9,9,11-hexamethyltetraazacyclotetradecanediene perchlorate into a plasticized poly(vinyl chloride) membrane. The influences of membrane composition, pH and foreign ions were investigated. The electrode displays a near Nernstian slope (- 57.8 mV decade-1) over a wide concentration range of 1 x 10-7 - 1 x 10-1 M of SCN- ion. The electrode has a detection limit of 4.8 x 10-8 M (2.8 ng/cm3) SCN- and shows response times of about 15 s and 120 s for low to high and high to low concentration sequences, respectively. The proposed sensor shows high selectivity towards SCN- over several common organic and inorganic anions. The electrode revealed a great enhancement in selectivity coefficients and detection limit for SCN-, in comparison with the previously reported electrodes. It was successfully applied to the direct determination of SCN- in milk and biological samples, and as an indicator electrode in titration of Ag+ ions with thiocyanate.