Please cite this article in press as: S. Helali, et al., On-site monitoring of fish spoilage using vanadium pentoxide xerogel modified interdigitated gold electrodes, Electrochim. Acta (2009), doi:10.1016/j.electacta.2009.01.027 ARTICLE IN PRESS G Model EA-14300; No. of Pages 5 Electrochimica Acta xxx (2009) xxx–xxx Contents lists available at ScienceDirect Electrochimica Acta journal homepage: www.elsevier.com/locate/electacta On-site monitoring of fish spoilage using vanadium pentoxide xerogel modified interdigitated gold electrodes S. Helali a , A. Abdelghani a , N. Jaffrezic-Renault b , P.N. Trikalitis c , C.E. Efstathiou d , M.I. Prodromidis e,∗ a Unité de Recherche de Physique des Semiconducteurs et Capteurs, IPEST, Tunisia b Laboratoire de Sciences Analytiques, Université de Claude Bernard, Lyon, France c Department of Chemistry, University of Crete, 71 003, Heraklion Crete, Greece d Department of Chemistry, University of Athens, 157 71, Athens, Greece e Department of Chemistry, University of Ioannina, 45 110, Ioannina, Greece article info Article history: Received 29 September 2008 Received in revised form 15 December 2008 Accepted 10 January 2009 Available online xxx Keywords: Vanadium pentoxide xerogel Interdigitated gold electrodes Ammonia chemical sensor On-site Real-time monitoring of fish spoilage TVB-N abstract The development of a vanadium pentoxide xerogel (VXG)-based sensor for the detection of volatile inor- ganic (ammonia) and organic (dimethylamine, etc.) amines is described. The xerogel film was deposited on interdigitated gold electrodes by dip-coating using an aqueous solution of VXG. The morphology of the sensing layer, its interaction with ammonia, which was used as a model analyte throughout this work, as well as the regeneration of the surface of the sensor electrodes with vapors of HCl were examined with scanning electron microscopy and FTIR spectroscopy. Signal changes, due to changes of the RC-product of the electrochemical cell (Au-VXG-Au), as a result of its interactions with ammonia vapors, were probed with a portable, homemade charge meter, the Multipulser. Exposing the sensor electrodes to various con- centrations of ammonia vapors resulted in proportional changes in the signal output. Finally, the proposed sensors were successfully used for on-site, real-time monitoring of fish spoilage in ambient conditions. © 2009 Published by Elsevier Ltd. 1. Introduction For all kinds of fish and fishery products, freshness is essen- tial for the quality of the final product. Freshness can be explained to some extent by some objective sensory, (bio)chemical, micro- bial and physical parameters, and can therefore be defined as an objective attribute [1]. To date, the freshness of fish is judged by trained assessors, by evaluating various freshness attributes, such as appearance, texture, smell and color, while characteristic sensory changes of the aforementioned attributes occur when fish deterio- rate [2]. Sensory evaluation is currently the most important method for freshness evaluation in the fish sector. Other approaches based on microbial methods, physical measurements (measurement of electrical parameters, monitoring of oxidation–reduction potential, instrumental monitoring of texture and color changes), and chem- ical methods (measurements of lipid oxidation, determination of various volatile compounds, such as C 6 –C 9 alcohols, carbonyl com- pounds and total volatile basic nitrogen compounds) have been also proposed. In addition, the calculation of K value, which is defined as the ratio of the sum of inosine and hypoxanthine concentration ∗ Corresponding author. Tel.: +30 26510 98301. E-mail address: mprodrom@cc.uoi.gr (M.I. Prodromidis). to the total concentration of ATP metabolites, is a widely used tech- nique mostly in a research level. A detailed description of these approaches along with a comprehensive analysis on their inher- ent advantages and disadvantages are provided in the excellent review of Olafsdottir et al. [2]. The possibility to measure and/or estimate fish freshness with a combination of instrumental tech- niques (electronic noses, spectroscopic methods, texture-meters, image analysers, color meters and devices measuring electrical properties) using a multi-sensor device has been also proposed [3]. Microorganisms are the major cause of spoilage of most seafood products. However, only a few members of the microbial commu- nity, the specific spoilage organisms (SSOs), give rise to the offensive off-flavors associated with seafood spoilage [4,5]. Volatile com- pounds such as ammonia, dimethylamine, trimethylamine, which are collectively known as total volatile basic nitrogen (TVB-N), are products of microbial degradation and are considered as poten- tial indicators of fish spoilage (index of freshness). The reference method for the determination of TVB-N, as adopted by the European community involves a rather laborious extraction—steam distil- lation and subsequent titration of the amines with hydrochloric acid [6], while other methods based on flow injection analysis in combination with photometric detectors [7], and solid-phase micro-extraction coupled to gas chromatography with NPD or FID detectors [8] have been also proposed. Although these methods provide satisfactory results and utilize instrumentation with a high 0013-4686/$ – see front matter © 2009 Published by Elsevier Ltd. doi:10.1016/j.electacta.2009.01.027