ORIGINAL PAPER Ionic silsesquioxane film immobilized on silica applied in the development of carbon paste electrode for determination of methyl parathion Elisangela Muncinelli Caldas • Eliana Weber de Menezes • Ta ˆnia Mara Pizzolato • Silvio Luis Pereira Dias • Tania Maria Haas Costa • Leliz Ticona Arenas • Edilson Valmir Benvenutti Received: 14 November 2013 / Accepted: 16 April 2014 Ó Springer Science+Business Media New York 2014 Abstract A mesoporous silica-based hybrid material composed of silica xerogel modified with an ionic silsesquioxane, which contains the 1,4-diazoniabicy- clo[2.2.2]octane chloride group, was obtained. The sils- esquioxane film is highly dispersed on the surface. This hybrid material was utilized to develop a carbon paste electrode (CPE) for determination of methyl parathion. Transmission FTIR, elemental analysis and N 2 adsorption– desorption isotherms were used for characterization of the material. The electrochemical behavior of methyl parathion was evaluated by cyclic voltammetry and differential pulse voltammetry. It was observed a linear response to methyl parathion in the concentration range from 1.25 9 10 -7 to 2.56 9 10 -6 mol L -1 by employing the carbon paste elec- trode, in Britton–Robinson buffer solution (pH 6). The achieved detection limit (3 SD of the blank divided by the slope of calibration curve) was 0.013 lmol L -1 and sensi- tivity was 6.3 lA lmol L -1 . This result shows the potenti- ality of this electrode for application as electrochemical sensor for methyl parathion. Keywords Charged organosilanes Á Sol–gel Á Water soluble polymers Á Charged silsesquioxane coating Á Organophosphorous pesticides Á Chemically modified electrodes 1 Introduction Organophosphorus pesticides, such as methyl parathion, constitute a group of organic pesticides that present high toxicity [1]. They can cause serious risk for the balance of aquatic systems and even danger to human health due to the contamination generated by residue of farm products [2]. In humans and other mammals, they are inhibitors of acetyl- cholinesterase enzyme, which is essential for the transmis- sion of nervous impulses [3, 4]. Methyl parathion is a toxic substance and releases p-nitrophenol when it is hydrolyzed and it also has the property of inhibiting the enzymatic activity [5]. Chromatographic methods (GC, HPLC) cou- pled with mass spectrometry are the usual methods for organophosphorus pesticides detection [6–8]. These meth- ods are sensitive and allow the quantification and identifi- cation of different organophosphorus compounds but require a tedious sample pretreatment and sophisticated instrument. Therefore, it is essential the development of methods with high sensitivity, selectivity and low-cost for rapid and accurate analysis of organophosphorus pesticides. Electrochemical methods have earned growing interest in the detection of pesticides [9–17]. Electrochemical sensors offer the advantages of low-cost, compact nature, easy sample handling, and even present high sensitivity, since they are alternative methods for the detection and trace-level determination of organophosphorus pesticides [17]. Carbon paste electrodes (CPEs) have been used for electrochemical determination of organophosphorus pesti- cides [17, 18]. The advantages of using CPEs are low-cost, easy preparation, and they also offer a wide potential window with low background current. In addition, CPEs, in the form of chemically modified electrodes, enhance the sensitivity and selectivity for determination of specific analytes [17, 18]. E. M. Caldas Á E. W. de Menezes Á T. M. Pizzolato Á S. L. P. Dias Á T. M. H. Costa Á L. T. Arenas Á E. V. Benvenutti (&) LSS—Laborato ´rio de So ´lidos e Superfı ´cies, Instituto de Quı ´mica, UFRGS, CP 15003, Porto Alegre, RS CEP 91501-970, Brazil e-mail: benvenutti@ufrgs.br 123 J Sol-Gel Sci Technol DOI 10.1007/s10971-014-3367-8