Journal of Analytical & Pharmaceutical Research Rhodium Nanoparticles and Halloysite Nanoclay as Electrode Modifiers for Electroanalytical Determination of Paracetamol Submit Manuscript | http://medcraveonline.com Abbreviations: HNC: Halloysite Nanoclay; EIS: Electrochemical Impedance Spectrometry; TEM: Transmission Electron Microscopy; GCE: Glassy Carbon Electrode; CV: Cyclic Voltammetry; LSV: Linear Sweep Voltammetry; SWV: Square- Wave Voltammetry; DPV: Differential Pulse Voltammetry Introduction Despite the known side effects of liver damage, among other issues, paracetamol (N-acetyl-p-aminophenol) continues to be one of the most commonly used drugs worldwide for conditions such as pain and fever and it is often purchased without medical prescription. It is usually administered as a tablet, but it is also available as solutions, suppositories and intravenous preparations. In addition, paracetamol is often taken in association with other drugs like caffeine, tramadol and codeine [1-3]. Given its chemical, commercial and medical significance, several methods of analysis have been developed to determine its content accurately in multiple kinds of samples. Analytical techniques such as spectrophotometry [4-6], chromatography [7-8] and mass spectrometry [9-10] have been employed in the determination of paracetamol, as well as electrochemical techniques [11-13] which offer a reliable, fast and simple method of analysis with no need for complicated sample preparation procedures. Among other areas of research, electroanalytical sensors have been constructed in order to enhance analytical parameters using diverse components. In this context, nanomaterials are notable for their unique electrical, optical and magnetic properties [14- 15]. Several different nanomaterials have been synthesised and applied in the construction of electrochemical sensors. A series of metallic nanoparticles stabilized in a zwitterionic surfactant (ImS3-14) was found to be suitable for this purpose, due to the metallic nature and small size of the particles and because the stabilizer itself, i.e., the zwitterionic surfactant, can be used as a modifier for electrochemical sensors [16-19]. Halloysite nanoclay (HNC) also attracts interest not only due to its effect in enhancing analytical parameters for electrochemical sensors, but also because it is widely available, cost effective and biodegradable [20,21]. The aim of this study was to investigate the suitability of a sensor constructed with a mixture of halloysite nanoclay and rhodium nanoparticles stabilized in zwitterionic surfactant (Rh-(ImS3-14)) for paracetamol determination. Experimental Reagents and solutions All reagents, that is, paracetamol, starch, cellulose, chloroform, RhCl 2 , sodium acetate, sodium phosphate, acetic acid, phosphoric acid and sodium hydroxide, were analytical grade (Sigma-Aldrich) and used without further purification. The halloysite nanoclay was purchased from Sigma-Aldrich and contained nanotubes with 30-70nm of diameter and 1-3µm of length. All solutions were prepared in ultrapure water obtained from a Milli-Q System (Millipore, USA) with a resistivity of 18.2MΩ cm -1 . The Rh- (ImS3-14) reverse micelle solution was synthesized according to a procedure previously described in the literature [19]. The paracetamol tablets were purchased at a local drugstore. Volume 6 Issue 4 - 2017 1 Department of Chemistry, Federal University of Santa Catarina, Brazil 2 Department of Teaching Methodology, Federal University of Santa Catarina, Brazil *Corresponding author: Larissa Moreira Ferreira, Department of Chemistry, Department of Teaching Methodology, Federal University of Santa Catarina, Brazil, Tel: +554837213616; Email: Received: November 22, 2017 | Published: December 05, 2017 Research Article J Anal Pharm Res 2017, 6(4): 00183 Abstract A new electrochemical sensor (HNC-Rh-(ImS3-14)/GCE) was built by coating a glassy carbon electrode (GCE) with a suspension made of rhodium nanoparticles stabilized in zwitterionic surfactant (3-(1-tetradecyl-3-imidazolium) propanesulfonate (ImS3-14)) and halloysite nanoclay (HNC). The sensor was characterized by cyclic voltammetry, electrochemical impedance spectroscopy, transmission electron microscopy and profilometry. The modifier was found to enhance the electroactive surface area and lower the charge transfer resistance in comparison to the bare GCE. The proposed sensor was applied in the electrochemical analysis of paracetamol, with a limit of detection of 82.78 nmol L -1 and a linear range of 0.9 to 10.9µmol L -1 (r 2 = 0.995) under optimized conditions (acetate buffer 0.1mol L -1 , pH 5.0 employing differential pulse voltammetry). Precision studies revealed the proposed sensor is reproducible on an interday/intraday basis showing low relative standard errors. Paracetamol tablets were selected as target sample and the sensor showed good selectivity and low relative error in comparison to the labelled content (RE=1,67%) with recoveries ranging from 107.6 to 123.2%. Keywords: Halloysite nanoclay; Nanoparticles; Paracetamol; Rhodium nanoparticles; Sensor