DOI: 10.1002/elan.201400688 A Simple and Sensitive Poly-1,5-Diaminonaphthalene Modified Sensor for the Determination of Sulfamethoxazole in Biological Samples Himanshu Chasta [a] and Rajendra N. Goyal* [a] 1 Introduction Sulfamethoxazole (SMZ) [N 1 -(5-methylisoxazol-3-yl) sul- fanilamide] (Scheme 1 a), a sulfonamide drug with anti- bacterial properties, is used for the treatment of human infections. Sulfonamide drugs are pervasively used in vet- erinary care and their use without a proper withdrawal period can cause accumulation of sulfonamides in eggs, milk, meat and honey as well as in fish [1–3]. Sulfona- mide drugs were used as a first chemotherapeutic agent and employed for the systematic prevention and cure of bacterial infection in human beings. Activity of the sulfo- namide drugs has been associated with their competition with p-aminobenzoic acid (PABA) in the synthesis of folic acid for the growth of bacteria. Therefore, sulfa drugs act by inhibiting the bacterial growth rather than directly affecting the bacteria [4]. Recently, it is reported that modern classes of sulfonamides and related sulfonyl derivatives are served as an effective inhibitor for grow- ing tumor cells, or for the medication of different types of cancer [5–7]. SMZ has been extensively used for the treatment of bacterial infections including urinary tract, pneumocystis carinii pneumonia, chronic bronchitis, me- ningococcal meningitis, acute otitis media, Whipples dis- ease and toxoplasmosis as well as in the treatment of op- portunistic infection in transplantation and for AIDS re- lated infection. Nevertheless, SMZ has also been reported to exhibit different types of side effects, like hypersensi- tivity reaction, gastro-intestinal distribution (mainly nausea and vomiting) and various hematological disor- ders such as thrombocytopenia, sulfhemoglobinemia, megaloblastosis, eosinophilia and agranulocytosis [8–12]. Hence, the determination of SMZ in various biological samples and pharmaceutical formulations has been con- sidered of great significance for human health and quality control. Literature survey reveals that various techniques have been used for the determination of SMZ, such as spectro- photometry [13], ratio spectra derivative spectrophotome- try [14], flow injection spectrophotometry [15], gas chro- matography-mass spectrometry [16], capillary electropho- resis [17], liquid chromatography [18], high performance Abstract : Sulfamethoxazole (SMZ), an antibacterial sul- fonamide drug, has been selectively determined using poly-1,5-diaminonaphthalene (p-DAN) modified glassy carbon electrode (GCE). The modified sensor was char- acterized by field emission scanning electron microscopy (FE-SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). SMZ showed linear response in the concentration range of 0.5–150 mM by using square wave voltammetry (SWV) and the detection limit was found to be 0.05 nM with sensitivity of 0.085 mA mM 1 . The proposed sensor has been successfully employed to determine SMZ in the pharmaceutical tab- lets and human urine samples. Keywords: Sulfamethoxazole · 1,5-Diaminonaphthalene · Glassy carbon electrode · Square wave voltammetry Scheme 1. (a) Sulfamethoxazole (SMZ) [N 1 -(5-methylisoxazol- 3-yl) sulfanilamide]; (b) 1,5-DAN. [a] H. Chasta, R. N. Goyal Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee -247667 (India) *e-mail: rngcyfcy@iitr.ac.in www.electroanalysis.wiley-vch.de  2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Electroanalysis 2015, 27, 1 – 10 &1& These are not the final page numbers! ÞÞ Full Paper