Minoxidil (MN) is a vasodilator used to treat hair loss and severe hypertension. However, its illegal use in cosmetics and pharmaceutical formulations has been reported in several countries. An efficient method for MN detection is of great interest for forensic and pharmaceutical applications. Electrochemical sensors have been reported as an interesting alternative for MN detection in various samples. However, a more in-depth study of the redox processes and a more selective electrochemical detection for MN are still required. In this context, we present, for the first time, the use of nuclear magnetic resonance and Fourier transform infrared spectroscopy analyses for understanding the electrochemical behaviour of MN after electrolysis procedures on a boron-doped diamond electrode (BDDE). Using these combined techniques, we have proposed and confirmed an electrochemical mechanism for all redox processes of MN on a BDDE, where in phosphate buffer (pH 6.0) two oxidation processes at +0.72 V and +0.97 V vs (Ag/AgCl/ sat. KCl) are presented. The last generated product by MN oxidation is reduced on the BDDE surface at -0.01 V with a quasi-reversible redox process. The use of this redox process is the strategy for a selective and sensitive detection of MN on the BDDE. This innovative approach was successfully applied to determine MN in adulterated cosmetics and pharmaceutical formulations, showing a low limit of detection (5.7 µmol. L-1) and high stability of electrochemical responses (RSD < 1.5 %, n = 6) using the same BDDE. Therefore, the proposed method provides a simple, fast and selective method for the identification and quantification of MN in pharmaceutical and forensic samples.

中文翻译：

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使用核磁共振和红外分析对米诺地尔进行伏安法检测，对米诺地尔进行全面的电化学研究：在法医和制药领域的应用


米诺地尔 （MN） 是一种血管扩张剂，用于治疗脱发和严重高血压。然而，一些国家/地区已报告了其在化妆品和药物制剂中的非法使用。一种高效的 MN 检测方法在法医和制药应用中具有重要意义。据报道，电化学传感器是各种样品中 MN 检测的有趣替代方案。然而，仍然需要对氧化还原过程进行更深入的研究和对 MN 进行更具选择性的电化学检测。在此背景下，我们首次提出了使用核磁共振和傅里叶变换红外光谱分析来了解在掺硼金刚石电极 （BDDE） 上进行电解程序后 MN 的电化学行为。使用这些组合技术，我们提出并确认了 BDDE 上 MN 的所有氧化还原过程的电化学机制，其中在磷酸盐缓冲液 （pH 6.0） 中，提出了 +0.72 V 和 +0.97 V vs （Ag/AgCl/ sat. KCl） 的两种氧化过程。通过 MN 氧化生成的最后产物在 -0.01 V 下通过准可逆氧化还原工艺在 BDDE 表面还原。使用这种氧化还原工艺是在 BDDE 上选择性和灵敏地检测 MN 的策略。这种创新方法已成功应用于测定掺假化妆品和药物制剂中的 MN，使用相同的 BDDE 时表现出低检测限 （5.7 μmol. L-1） 和高稳定性的电化学反应 （RSD < 1.5 %， n = 6）。因此，所提出的方法为药物和法医样品中 MN 的鉴定和定量提供了一种简单、快速和选择性的方法。