Square Wave Voltammetric Determination of 2-Thiouracil in Pharmaceuticals and Real Samples Using Glassy Carbon Electrode

A simple and rapid method was developed using cyclic and square wave voltammetric techniques for the determination of trace-level sulfur containing compound, 2-thiouracil, at a glassy carbon electrode. 2-thiouracil produced two anodic peaks at 0.334？V and 1.421？V and a cathodic peak at ？0.534？V. The square wave voltammetry of 2-thiouracil gave a good linear response in the range of 1–20？μM with a detection limit of 0.16？μM and quantification limit of 0.53？μM (0.0679？μg/g), which is in good agreement as per IUPAC definition of trace component analysis (100？μg/g). The obtained recoveries range from 98.10% to 102.1%. The proposed method was used successfully for its quantitative determination in pharmaceutical formulations and urine as real samples. 1. Introduction In order to meet the growing demands for the new drugs (less costly, quite effective, and with minimum side effects) to fight against diseases, newer drugs are being pushed into the market at a greater extent that it has become difficult to keep abreast of their merits and demerits; so, a strict control on the quality of the drugs and their therapeutic actions become important. Hence, the pharmaceutical analysis plays a pivotal role in quality assurance. Thiouracil refers both to a specific molecule consisting of a sulfated uracil and a family of molecules based upon the structure. The substance is historically relevant in the preparation of antithyroid drug. Sulfhydryl compounds are known to undergo electrochemical oxidation at solid electrodes, but their oxidation occurs at relatively high potentials [1, 2]. It was characterized for the electrocatalytic oxidation of sulfhydryl compounds. 2-thiouracil (Scheme 1) and its derivatives also act as selective inhibitors of nitric oxide synthase (NOS) [3]. The administration of 2-thiouracil in chicken has been found to cause increase in total protein content and decrease in DNA content [4]. Results of some derivatives of 2-thiouracil, such as propylthiouracil, which was used as antithyroid drug, produced thyroid cancers in human and in some animals such as mice, rats, and hamsters [5]. Several methods have been reported for the determination of 2-thiouracil in complex physiological samples such as liquid chromatography coupled with electrochemical detection [6] and spectral studies [7]. However, these methods suffer from some disadvantages such as high cost, long analysis time, sample pretreatment, low sensitivity and selectivity, which make them unsuitable for routine analysis. In most of the chemical oxidations of 2-thiouracil, S–S linked dimer is