Analytical Methods Sensitive determination of carbendazim in orange juice by electrode modified with hybrid material Claudia A. Razzino a , Lívia F. Sgobbi a , Thiago C. Canevari a,⇑ , Juliana Cancino b , Sergio A.S. Machado a a Instituto de Química de São Carlos, Universidade de São Paulo, PO Box 780, 13560-970 São Carlos, SP, Brazil b Instituto de Física de São Carlos, Universidade de São Paulo, PO Box 780, 13560-970 São Carlos, SP, Brazil article info Article history: Received 17 December 2013 Received in revised form 5 August 2014 Accepted 6 August 2014 Available online 27 August 2014 Keywords: Pesticides Carbendazim Mesoporous silica Carbon nanotubes Electrochemical sensor abstract This paper describes the application of a glassy carbon electrode modified with a thin film of mesoporous silica/multiwalled carbon nanotubes for voltammetric determination of the fungicide carbendazim (CBZ). The hybrid material, (SiO 2 /MWCNT), was obtained by a sol–gel process using HF as the catalyst. The amperometric response to CBZ was measured at +0.73 V vs. Ag/AgCl by square wave voltammetry at pH 8.0. SiO 2 /MWCNT/GCE responded to CBZ in the linear range from 0.2 to 4.0 lmol L À1 . The calculated detection limit was 0.056 lmol L À1 , obtained using statistical methods. The SiO 2 /MWCNT/GCE sensor presented as the main characteristics high sensitivity, low detection limit and robustness, allowing CBZ determination in untreated real samples. In addition, this strategy afforded remarkable selectivity for CBZ against ascorbic and citric acid which are the main compounds of the orange juice. The excellent sensitivity and selectivity yielded feasible application for CBZ detection in orange juice sample. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Carbendazim (CBZ, methyl 2-benzimidazolecarbamate) is a benzimidazole fungicide widely used to control citrus black spot (a fungal disease) in Brazil, Mexico and Costa Rica, which are the top three source of orange juice imported into the USA (Buch, Brown, Niva, Sautter, & Sousa, 2013). The European Union has established maximum residue limits (MRLs) for carbendazim in citrus ranging between 100 and 700 ppb (0.52 and 3.6 lmol L À1 ) (Risk Assessment for Safety of Orange Juice Containing Fungicide Carbendazim, 2012). The Environmental Protection Agency (EPA) allowed limited use of CBZ in citrus fruit until 2009. Currently, the use of CBZ is not approved in the USA (Risk Assessment for Safety of Orange Juice Containing Fungicide Carbendazim, 2012). Due to the high consumption of orange juice in the world and the high environmental impact that may result, the control of CBZ levels is extremely important. Several analytical methods are used for CBZ detection such as high-performance liquid chroma- tography (Subhani, Huang, Zhu, & Zhu, 2013; Wen et al., 2013), mass spectroscopy (Domínguez-Álvarez, Mateos-Vivas, García- Gómez, Rodríguez-Gonzalo, & Carabias-Martínez, 2013; Gilbert- López, García-Reyes, & Molina-Díaz, 2012), UV–Vis and fluorescence spectroscopies (del Pozo, Hernández, & Quintana, 2010; Llorent-Martínez, Fernández-de Córdova, Ruiz-Medina, & Ortega-Barrales, 2012). However, these techniques are not suitable for in situ and real-time detection, besides they require complex pre-treatment steps, highly trained operators and time-consuming detection processes. To overcome these drawbacks, electroanalyti- cal techniques have been applied. A variety of modified electrodes have been used to determine trace amounts of CBZ in different matrix, but not in orange juice (Guo, Guo, Li, Wang, & Dong, 2011; Hernandez, Ballesteros, Galan, & Hernandez, 1996; Luo, Wu, & Gou, 2013; Manisankar, Selvanathan, & Vedhi, 2005). Inorganic–organic hybrid material based on mesoporous silica obtained by the sol–gel process have been employed in different areas (Backe, Day, & Field, 2013; Ewlad-Ahmed, Morris, Patwardhan, & Gibson, 2012; Qu, Alvarez, & Li, 2012), including the electroanalytical field (Walcarius, 2013; Walcarius, Mandler, Cox, Collinson, & Lev, 2005). These hybrid materials have the advantage of combining distinct organic and inorganic compo- nents, giving rise to a composite with new properties. The proper- ties of the inorganic–organic hybrid material include high porosity with pore diameters ranging between 2 and 50 nm, which facili- tates the process of mass transfer, as well as high chemical stability and stiffness (Hasanzadeh, Shadjou, Eskandani, & de la Guardia, 2012). The main organic compound used in the synthesis of these hybrid materials is carbon nanotubes (MWCNT). These composites have been the subject of intense research in electrochemical sens- ing, owing to their intrinsic structural, electronic and chemical http://dx.doi.org/10.1016/j.foodchem.2014.08.085 0308-8146/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel./fax: +55 16 3521 3109. E-mail address: tccanevari@gmail.com (T.C. Canevari). Food Chemistry 170 (2015) 360–365 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem