Rehacek V, Hojova L, Marton M, Hotovy I, Michniak P, Vojs M, Stanova A Vojs
Institute of Electronics and Photonics, Faculty of Electrical Engineering and Information Technology, Slovak University of Technology, Ilkovicova 3, 841 04, Bratislava, Slovakia.
Department of Analytical Chemistry, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynska dolina, Ilkovicova 6, 842 15, Bratislava, Slovakia.
Talanta. 2025 Apr 1;285:127297. doi: 10.1016/j.talanta.2024.127297. Epub 2024 Dec 3.
A three-electrode screen-printed sensor with heavily doped microcrystalline boron-doped diamond electrodes grown by chemical vapor deposition on alumina substrates was used to determine the concentration of melatonin by constant current potentiometric stripping analysis. This paper provides a detailed examination of the irreversible oxidation behavior of melatonin by cyclic voltammetry at a boron-doped diamond electrode. The relationship between the current response and the square root of the scan rate confirmed a diffusion-controlled oxidation process. The research highlights the strong effect of electrode pretreatment on electrode properties, demonstrating its influence on electrochemical activity and electron-transfer kinetics. After the electrodes were cathodically pretreated, the melatonin responses increased more than four times compared to the anodically pretreated electrodes. Optimum results were obtained in constant current potentiometric stripping analysis at pH value of 3.0 using the Britton-Robinson buffer solution as an electrolyte. Further optimization of the accumulation potential/time, and stripping current led to improved melatonin detection sensitivity, achieving a significantly lower limit of detection of 14.6 μg L compared to square wave voltammetry (110 μg L). Interference studies assessed the impact of selected organic compounds on melatonin determination. While some compounds like dopamine, l-ascorbic acid, and uric acid showed minimal interference, l-tryptophan and serotonin significantly influenced melatonin responses. The sensor was successfully applied to determine of melatonin in a commercial pharmaceutical supplement. A satisfactory result was obtained by constant current potentiometric stripping analysis as the recovery reached 100.75 % compared to the reference value obtained by the LC-HRMS method. The proposed method, due to the excellent properties of the boron-doped diamond electrode and constant current potentiometric stripping analysis, provides a fast measurement procedure of melatonin with high sensitivity (compared to square wave voltammetry) at a stable background signal. Moreover, the method is insensitive to dissolved oxygen in the electrolyte and only the stripping current of the potentiometric stripping analysis needs to be optimized.
采用一种三电极丝网印刷传感器来通过恒流电位溶出分析法测定褪黑素浓度，该传感器具有通过化学气相沉积法生长在氧化铝基底上的重掺杂微晶硼掺杂金刚石电极。本文通过循环伏安法详细研究了褪黑素在硼掺杂金刚石电极上的不可逆氧化行为。电流响应与扫描速率平方根之间的关系证实了该氧化过程受扩散控制。该研究突出了电极预处理对电极性能的强烈影响，证明了其对电化学活性和电子转移动力学的影响。与阳极预处理的电极相比，阴极预处理后的电极对褪黑素的响应增加了四倍多。使用 Britton-Robinson 缓冲溶液作为电解质，在 pH 值为 3.0 的条件下进行恒流电位溶出分析可获得最佳结果。对富集电位/时间和溶出电流的进一步优化提高了褪黑素的检测灵敏度，与方波伏安法（110 μg/L）相比，检测限显著降低至 14.6 μg/L。干扰研究评估了所选有机化合物对褪黑素测定的影响。虽然多巴胺、L-抗坏血酸和尿酸等一些化合物的干扰极小，但 L-色氨酸和血清素对褪黑素的响应有显著影响。该传感器成功应用于测定市售药物补充剂中的褪黑素。通过恒流电位溶出分析获得了令人满意的结果，与通过 LC-HRMS 方法获得的参考值相比，回收率达到了 100.75%。由于硼掺杂金刚石电极的优异性能和恒流电位溶出分析，所提出的方法在稳定的背景信号下提供了一种快速测量褪黑素的高灵敏度方法（与方波伏安法相比）。此外，该方法对电解质中的溶解氧不敏感，仅需优化电位溶出分析的溶出电流。
