Highly sensitive and ultra-selective amperometric nitrite sensor using cyclometalated Rh(III)-complex/CNTs modified glassy carbon electrode integrated with flow injection analysis

Abstract

A highly sensitive and ultra selective amperometric nitrite sensor was fabricated based on immobilization of novel cyclometalated Rh(III) complex, [Rh(phpy-κ2N,C2′)2(phen-dione)]PF6,where phpy-κ2N,C 2′ is pyridine-2-yl-2-phenyl and phen-dione is 1,10- phenantroline-5,6-dione onto glassy carbon electrode (GCE) modified with multi-walled carbon nanotubes. The modified electrode shows stable and well defined redox couple with surface confined characteristic at wide pH range and it showed excellent electrocatalytic activity toward both oxidation and reduction of nitrite. Under optimized condition in amperometric measurement at applied potential 0.8V, the detection limit and sensitivity were 23nM, 0.3μA/μM at concentration range up to 300μM, while for applied potential −0.5V, detection limit, sensitivity and concentration range were 80nM, 0.6μA/μM and 0.25–15μM, respectively. Furthermore, the proposed sensor shows excellent anti-interference ability towards various reducing and oxidizing compounds such as uric acid, ascorbic acid, glucose, SO32−, I−, ICH2COO−, IO3−, B4O72−, Br−, SCN−,Cl−, BrO3−,Cr6+, Hg2+, Cr3+, As3+, Ag+, Ni2+ Mn2+,Cd2+,Pb2+,Zn2+, Co2+ and Fe3+ at concentration ratio 100–1000. The practical application of the sensor as amperometric detector for flow injection analysis systems was evaluated. Finally, the proposed sensor was successfully applied to the detection of nitrite in real samples with obtained satisfactory results.