| Description |
Xanthine (XA), hypoxanthine (HXA) and uric acid (UA) are degradation products of purine metabolism. It is commonly known, that abnormalities of the metabolite concentrations in human serum and urine are sensitive indicators of many disorders, such as gout, xanthinuria, hyperuricemia, and perinatal asphyxia. The detection and quantification of XA, HXA and UA in body fluids is very important in the study of homeostasis of the xanthine oxidase (XOD) system and clinical diagnostics [1, 2]. Many techniques were developed for the simultaneous determination of the purine degradation products, e.g. enzymatic methods [2 ,3] high-performance liquid chromatography (HPLC) [2, 4, 5], capillary electrophoresis (CE) [2, 6], and also electrochemistry based methods [2, 7-14]. In the context of electrochemistry, it has been shown that the oxidation processes of purines can be observed and studied using different types of graphite electrodes, e. g. pyrolytic graphite, polymer pencil graphite electrode (pPeGE) or screen printed graphite electrode (SPGE), with good reproducibility. In addition, this electroanalysis is fast, cheap and applicable in medicine and food industry. The aim of our research was the electrochemical determination of HXA, XA and UA at chosen graphite electrodes by using linear sweep voltammetry (LSV) and cyclic voltammetry (CV) in connection with the elimination voltammetry with linear scan (EVLS). The oxidation behaviour of the above-mentioned purine derivatives was investigated not only with respect to pH (pH 2-9; phosphate – acetate buffer) and (micromolar and submicromolar) concentration but also with respect to the type of the graphite electrode used (pPeGE – polymer pencil graphite electrode, BPPGE - basal plane pyrolytic graphite and EPPGE - edge plane pyrolytic graphite). As results from the voltammetric experiments, the oxidation behaviour of purine derivatives is strongly pH-dependent. However, the position of the oxidation signals of XA, HXA, and uric acid allows to distinguish these three important derivatives at all pH values. Based on the concentration dependences, it can be concluded that polymer pencil graphite electrode (pPeGE) is the most sensitive sensor for the determination of purine metabolites, as follows from the comparison of different types of graphite electrodes.
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