Electrochimica Acta 117 (2014) 534–540 Contents lists available at ScienceDirect Electrochimica Acta jou rn al hom ep age: www.elsevier.com/locate/elec tacta Determination of the substitution degree of modified chitosan by cyclic voltammetry at the water/dichloroethane interface Ana Agustina Aldana a , Miriam C. Strumia a , Lidia M. Yudi b , Marisa Martinelli a , Ana Valeria Juarez b,∗ a Instituto Multidisciplinario de Biología Vegetal (IMBIV) CONICET-UNC, Departamento de Química Orgánica, Facultad de Ciencias Químicas b Instituto de Investigaciones en Físico Química de Córdoba (INFIQC) CONICET-UNC, Departamento de Físico Química, Facultad de Ciencias Químicas, Ala 1, Pabellón Argentina, Ciudad Universitaria, X5000HUA Córdoba, Argentina a r t i c l e i n f o Article history: Received 15 August 2013 Received in revised form 6 November 2013 Accepted 25 November 2013 Available online 11 December 2013 Keywords: Liquid/liquid interfaces Chitosan quaternized chitosan cationic polyelectrolytes a b s t r a c t The electrochemical behavior of the cationic polymer chitosan-gtmac (Ch-GTMAC), at the polarized water/1,2-dichloroethane interface was studied. This polymer was obtained by nucleophilic reaction of chitosan (Ch) with glycidyltrimethylammonium chloride groups (GTMAC). The voltammetric response was found to be dependent on the concentration of the polymer, on pH of the aqueous phase, and on the nature of the organic electrolyte. The results suggest a weak adsorption of the polymer coupled to the transfer towards the organic phase. Desorption process is quasi-reversible, and there is not interaction between adsorbents. From the analysis of desorption charge, it was possible to determine the substitution degree of the polymer © 2013 Elsevier Ltd. All rights reserved. 1. Introduction Chitosan, the main derivative of chitin, is an attractive linear aminopolysaccharide, composed primarily of repeating units of - (1→4)2-amino-2-deoxy-D-glucose (D-glucosamine). As an unique natural alkali polysaccharide, chitosan has many potential applica- tions including drug delivery, artificial skin, reinforced bone nail, absorbable suture and wound dressing [1–9], due to its distinctive properties, such as biodegradability, biocompatibility, non-toxicity, antibacterial activity, wound healing acceleration ability[10–12]. However, compared with collagen and hyaluronic acid, its natural materials counterparts, the widespread use of chitosan has been restricted. The limited utility of chitosan, principally arises from its insolubility at neutral or high pH values. So, many efforts were made to increase the solubility of chitosan [6,13,14], and to enable a broader application in a wide pH range. In this work, we present the electrochemical behavior of chi- tosan modified with glycidyltrimethylammonium chloride, GTMAC a quaternary ammonium group, which confers a permanent posi- tive charge to the polymer. This modification allows high solubility in a wide pH range. In the last years, the interfacial behavior of polyelectrolytes at liquid/liquid interfaces has been studied by different authors. Among these studies, cationic polymers have gain a lot of interest ∗ Corresponding author. Tel.: +54 0351 4334169–80; fax: +54 0351 4334188. E-mail address: vjuarez@fcq.unc.edu.ar (A.V. Juarez). regarding both, their interaction with others molecules, and their interfacial behavior [15–21]. Principal interest has been paid to the study of the adsorption of biopolymers which includes: heparine [22–24], proteins [25,26], insulin [27], haemoglobin [28–30], myo- globin [31], cytochrome C and ribonuclease A, DNA and his complex [28,30,32–34]. Another research topic is that focused on the study of the interactions between polyelectrolytes and membrane com- ponents such as phospholipid molecules adsorbed at liquid/liquid interfaces [33,35] or nanoparticles [36]. The aim of the present paper is to study the interfacial behavior of chitosan modified with glycidyltrimethylammonium chloride (GTMAC) applying cyclic voltammetry at a water/1,2- dichloroethane interface and analyzing the effect of pH and concentration of all the species. As mentioned above, this modifi- cation allows the solubilization of the polymer at neutral and high pH values. Therefore an important topic is the determination of the degree of substitution resulting from the modification. In this sense we demonstrate that the result obtained from voltammet- ric experiments enable us to infer the substitution degree of the polymer chain with GTMAC. 2. Experimental 2.1. Materials Chitosan, Ch (85% DA, LMW, Aldrich); glycidyltrimethylam- monium chloride, GTMAC (Sigma Aldrich); tetrapentylammonium bromide, TPnABr (Fluka); tetraphenylarsonium chloride, TPhAsCl 0013-4686/$ – see front matter © 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.electacta.2013.11.146