Maryam Hamtak - Department of Chemistry, School of Science, Alzahra University, Tehran, Iran
Morteza Hosseini - Center of Excellence in Electrochemistry, Faculty of Chemistry, University of Tehran, Tehran, Iran
Lida Fotouhi - Department of Chemistry, School of Science, Alzahra University, Tehran, Iran

A thin layer of a poly (pyrrole-luminol) composite was synthesized, through electrodeposition of luminol and pyrrole in acidic medium on a graphite electrode modified by casting of titanium dioxide (TiO2) nanoparticles with 33 - 35 nm in diameter. The properties of the nanocomposite were studied by FE-SEM and EDX techniques. In alkaline media, luminol undergoes a two-step oxidation process at around 3440V and form excited luminol (3-aminophthalic acid dianion, the ring-opened intermediate form), which in turn emit light at 425 nm [1, 2]. Features of merit include broad linearity from 1pM to 4μM (R2= 34..6) with a limit of detection as low as 3443 pM (S/N=3), good reproducibility (RSD of 44) for the analysis of a 443 μM hydrogen peroxide solution (n=4) and long-term stability. The presence of ascorbic acid at concentrations as high as 133 nM did not produce any electrochemiluminescence signals, which was held as proof of the selective behavior of the electrode modified with Ppy/Plu/TiO2 towards H2O2 using method. The ECL process consumes luminol since this ring opened and the process is not reversible. The sensor was also used in the analysis of H2O2 concentration in mouthwash formulations.