A modern and powerful electrochemical sensing platform for purines determination: Voltammetric determination of uric acid and caffeine in biological samples on miniaturized thick-film boron-doped diamond electrode

In this study, an unmodified and powerful electrochemical sensor was introduced for the first time for the voltammetric determination of purine derivatives uric acid (UA) and caffeine (CAF). The miniaturized thick-film boron-doped diamond (BDD) electrode in tandem with cyclic voltammetry (CV) revealed two irreversible oxidation peaks at + 0.7 V and + 1.5 V for UA and CAF, respectively, in Britton-Robinson (BR) buffer pH 3. Under the optimized experimental conditions, square-wave voltammetry (SWV) and differential pulse voltammetry (DPV) were performed in three measurement modes: selective determination of one analyte in the presence of low concentrations of another one (first and second measurement mode) and the simultaneous determination of both purine derivatives (third measurement mode). Using the suitable values of pulse parameters, the thick-film BDD electrode showed the good linear response in the concentration ranges of (9.2 - 95.0) mu M and (4.6 - 95.7) mu M for the simultaneous quantification of both compounds by SWV and DPV, respectively. The detection limit was determined to be 6.0 mu M and 3.9 mu M for UA and 4.6 mu M and 2.1 mu M for CAF by SWV and DPV, respectively. The selectivity of the proposed sensor was evaluated by the examination of the impact of some inorganic and organic substances, which are commonly present in biological samples, on the current responses of UA and CAF. Finally, the miniaturized thick-film BDD electrode was successfully applied for the electrochemical determination of UA and CAF in human urine and human plasma samples using both pulse techniques with adequate recoveries ranging between 93.7% and 103.3% and without tedious sample pretreatment procedures.

Automated summary

In this study, a powerful electrochemical sensor was introduced for the first time for the determination of uric acid (UA) and caffeine (CAF) using a miniaturized thick-film boron-doped diamond (BDD) electrode in tandem with cyclic voltammetry (CV). The sensor showed good linear response and selectivity, with detection limits determined for both compounds. The sensor was successfully applied for the electrochemical determination of UA and CAF in human urine and plasma samples with adequate recoveries and without the need for tedious sample pretreatment procedures.