Application of a nanostructured platform and imprinted sol-gel film for determination of chlorogenic acid in food samples Carla M. Ribeiro a , Eliane M. Miguel a , Jonadab dos S. Silva b , Cristian B. da Silva b , Marília O.F. Goulart c , Lauro T. Kubota d , Fabiano B. Gonzaga a , Wilney J.R. Santos b , Phabyanno R. Lima b,n a Instituto Nacional de Metrologia, Qualidade e Tecnologia, INMETRO, 25250-020 Duque de Caxias, RJ, Brazil b Instituto Federal de Educação, Ciência e Tecnologia de Alagoas, IFAL, 57020-600 Maceió, AL, Brazil c Universidade Federal de Alagoas, UFAL, 57072-900 Maceió, AL, Brazil d Instituto de Química, UNICAMP, C. Postal 6154,13084-971 Campinas, SP, Brazil article info Article history: Received 19 February 2016 Received in revised form 3 May 2016 Accepted 5 May 2016 Available online 7 May 2016 Keywords: Chlorogenic acid Molecular imprinting siloxane Sol-gel MWCNTs abstract Chlorogenic acid (CGA) is a polyphenol derivative that widely exists in higher plants like fruits, vege- tables, black teas, and some traditional Chinese medicines. In this work, we have proposed a sensitive and selective electrochemical sensor for detection of CGA. The sensor was based on a glassy carbon electrode (GCE) modified with a functional platform by grafting vinyltrimethoxysilane (VTMS) in multi- walled carbon nanotubes (MWCNTs) and covered by a molecularly imprinted siloxane (MIS) film pre- pared using the sol-gel process. The VTMS was grafted onto the surface of the MWCNTs via in situ free radical polymerization. The MIS was obtained from the acid-catalyzed hydrolysis/condensation of a so- lution consisting of tetraethoxysilane (TEOS), phenyltriethoxysilane (PTEOS), (3-aminopropyl)tri- methoxysilane (APTMS), and CGA as a template molecule. The modification procedure was evaluated by differential pulse voltammetry (DPV) and scanning electron microscopy (SEM). Under optimized op- erational conditions, a linear response was obtained covering a concentration ranging from 0.08 μmol L 1 to 500 μmol L 1 with a detection limit (LOD) of 0.032 μmol L 1 . The proposed sensor was applied to CGA determination in coffee, tomato, and apple samples with recoveries ranging from 99.3% to 108.6%, showing a promising potential application in food samples. Additionally, the imprinted sensor showed a significantly higher affinity for target CGA than the non-imprinted siloxane (NIS) sensor. & 2016 Elsevier B.V. All rights reserved. 1. Introduction Chlorogenic acid (CGA) is a well-known substrate of polyphenol oxidases and it has antioxidant, free radical scavenging, mutation suppression, and anti-tumor properties [1]. CGA is found in plants, fruits, and vegetables such as coffee beans, apples, pears, tomatoes, blueberries, potatoes, peanuts, and eggplant [2,3]. Therefore, the determination of CGA is an important factor in different areas and in various foods. Thus, there is a need for new and more versatile analytical methods, since the methods that have already been reported, such as infrared spectrometry [4], thin layer chromato- graphy [5], spectrophotometry [6], 1 H NMR spectroscopy [7], li- quid chromatography [6], gas chromatography [6], and chemilu- minescence [8], are time-consuming, laborious, expensive, and require more complicated instrumentation. On the other hand, electrochemical sensors are becoming im- portant tools in medical, food, biological, and environmental analysis due to their simplicity, high sensitivity, and relatively low cost [9,10]. Furthermore, the sensitivity and specificity of these systems can be improved considerably with the use of suitable electrocatalysts, which improve the interfacial electron transfer. Therefore, a carbon nanotube (CNT) is one type of material that has been broadly recognized as playing a key role in the process of charge transfer. This material can improve interfacial properties providing unique properties to the electrode, including high electroactive surface area [11], low charge transfer resistance [12– 14], and the possibility of functionalization [15,16]. The functio- nalization factor is very important when the immobilization of enzymes, selective recognition elements, and/or redox mediators in the carbon nanotube structure is needed. One strategy that has been used for functionalization is the method of “grafting from” polymers. The “grafting from” approach involves the growing of polymers from the CNT surfaces via in situ polymerization of monomers initiated by chemical species immobilized on the CNT Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/talanta Talanta http://dx.doi.org/10.1016/j.talanta.2016.05.020 0039-9140/& 2016 Elsevier B.V. All rights reserved. n Corresponding author. E-mail address: phaby.lima@gmail.com (P.R. Lima). Talanta 156-157 (2016) 119–125