Selective Simultaneous Determination of Paracetamol and Uric Acid Using a Glassy Carbon Electrode Modified with Multiwalled Carbon Nanotube/Chitosan Composite Ali Babaei ,* a, b David J. Garrett, b Alison J. Downard* b a Permanent address: Department of Chemistry, University of Arak, Private Bag 879, Arak 38156, Iran b Department of Chemistry, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand *e-mail: a-babaei@araku.ac.ir; Alison.downard@canterbury.ac.nz Received: July 3, 2010; & Accepted: September 10, 2010 Abstract A multiwalled carbon nanotube/chitosan modified glassy carbon electrode (MWCNTs-CHT/GCE) has been used for simultaneous determination of paracetamol (PAR) and uric acid (UA). The measurements were carried out using differential pulse voltammetry (DPV), cyclic voltammetry (CV) and chronoamperometry (CA). DPV meas- urements showed a linear relationship between oxidation peak current and concentration of PAR and UA in phos- phate buffer (pH 7) over the concentration range 2 mM to 250 mM, and 10 mM to 400 mM, respectively. The analyti- cal performance of this sensor has been evaluated for detection of PAR and UA in human serum and human urine with satisfactory results. Keywords: Paracetamol, Uric acid, Carbon nanotubes, Chitosan, Modified glassy carbon DOI: 10.1002/elan.201000406 1 Introduction We have recently reported application of a glassy carbon electrode modified with multiwalled carbon nanotube/chi- tosan (MWCNTs-CHT) as a new sensor for simultaneous determination of paracetamol and mefenamic acid [1]. Our studies revealed that the oxidation peaks of the ana- lytes were strongly overlapped at a glassy carbon elec- trode (GCE) but were well-separated, and had signifi- cantly higher currents, at the MWCNTs-CHT surface. These results suggest that the MWCNTs-CHT/GCE may be useful for other important analyses which are difficult or impossible at unmodified GCE. The MWCNTs-CHT/GCE sensor is constructed by dis- persing MWCNTs in chitosan and drop-coating onto GCE. Carbon nanotubes are an excellent immobilization substance because of their significant mechanical strength, high surface area, excellent electrical conductivi- ty, good chemical stability, and high ability for immobili- zation of different electron transfer mediators [2–5]. Combining polymers with nanoscale inorganic and organ- ic solids leads to production of nanocomposite materials with unique mechanical, electrical, magnetic and adhesive properties [6, 7]. Chitosan is a polysaccharide biopolymer which is biocompatible, biodegradable, nontoxic, chemi- cally inert and low cost. In addition to these attractive properties, it displays excellent film-forming ability, high water permeability and has good adhesion to surfaces [8]. Because chitosan-CNTs can form a stable complex through noncovalent binding, the stability of CNTs in aqueous chitosan solution is greatly improved. As a result CNTs can be uniformly distributed in a chitosan film [9– 12]. Paracetamol (PAR) or acetaminophen is a popular medicine to relieve mild to moderate pain and also has a gentle effect on the stomach lining [13–15]. It has been reported that PAR is a useful drug in osteoarthritis thera- py [16]. At normal therapeutic doses PAR is rapidly and completely metabolized to form inactive metabolites which would be eliminated in the urine in body. However at higher doses of PAR produces toxic metabolite accu- mulation, that may cause severe and sometimes fatal hep- atoxicity [17–19]. It can also cause skin rashes and inflam- mation of the pancreas [20]. Several analytical techniques such as titrimetry [16], spectrophotometry [21], spectro- fluorometry [22], voltammetry [1], HPLC [23], TLC [24], colorimetry [25] and Fourier transform infra red spectros- copy [26] have been proposed for the determination of PAR. As the primary end product of purine metabolism, uric acid (UA) is a fluid of great importance in human diagno- sis. In a healthy human body the typical concentration of UA in urine is around 2 mM, whereas in blood it is in the range of 120–450 mM [27, 28]. An abnormal concentration of UA is associated with a number of clinical situations such as gout, hyperuricemia, cardiovascular and kidney diseases [29, 30]. As an important disease marker, simple methods for the determination of UA are important. Var- ious techniques have been used to accomplish this, such Electroanalysis 2011, 23, No. 2, 417 – 423  2011 Wiley-VCH Verlag GmbH &Co. KGaA, Weinheim 417 Full Paper