Determination of Coumarin in Mikania glomerata Infusions by Square-Wave Voltammetry Using a Boron-Doped Diamond Electrode

Infusions of Mikania glomerata Sprengel (guaco) leaves are used in Brazil for the treatment of respiratory diseases. Coumarin is the chemical marker of guaco for quality control purposes. This work proposes a voltammetric methodology to determine coumarin by using a boron-doped diamond electrode. At pH 10 (0.1 mol L-1 Britton-Robinson buffer solution), coumarin is irreversibly oxidized around +1.77 V in a process predominantly controlled by diffusion. The methodology described here presented a linear range from 1.54 to 15.3 µg mL-1 with limits of detection and quantification of 0.20 and 0.62 µg mL-1, respectively. Analysis of variance confirmed the significance of the regression and the absence of lack-of-fit at the confidence level of 95%. Infusion of commercial guaco leaves was directly analyzed, and results were in agreement with high-performance liquid chromatography after applying the paired t-test at a confidence level of 95%.

在巴西，盖裂泽兰（Mikania glomerata Sprengel，俗称guaco）的叶浸剂被用于呼吸系统疾病的治疗。香豆素（Coumarin）是guaco质量控制的化学标志物。本研究提出了一种采用掺硼金刚石电极（boron-doped diamond electrode）检测香豆素的伏安分析方法。在pH=10的0.1 mol·L⁻¹布里顿-罗宾逊缓冲溶液（Britton-Robinson buffer solution）中，香豆素在约+1.77 V电位处发生不可逆氧化反应，该反应主要受扩散过程控制。本方法的线性范围为1.54~15.3 μg·mL⁻¹，检出限与定量限分别为0.20 μg·mL⁻¹和0.62 μg·mL⁻¹。方差分析结果证实，在95%置信水平下，回归方程具有统计学显著性，且不存在失拟现象。直接对市售guaco叶浸剂进行分析，采用配对t检验在95%置信水平下验证，所得结果与高效液相色谱法（high-performance liquid chromatography）的检测结果一致。