Voltammetric determination of harmaline in natural food products using boron-doped diamond electrode

• BDD electrode was used for the first time for sensitive determination of harmaline.
• Harmaline yielded two irreversible oxidation peaks at +0.9 and +1.2 V (vs. Ag/AgCl).
• Detection limit of 0.08 μmol L−1 was achieved without any modification of electrode.
• Advantages of proposed method: sensitivity, selectivity, precision and accuracy.
• Sensitive electrochemical sensor for quality control analysis of food products.

A novel analytical approach for the sensitive determination of a β-carboline alkaloid, harmaline, was developed using pulse voltammetric techniques with a boron-doped diamond electrode. Cyclic voltammetry showed two irreversible oxidation peaks at about +0.90 and +1.20 V (vs. Ag/AgCl) in Britton–Robinson buffer solution at pH 5. Under optimized experimental conditions, differential pulse and square-wave voltammetry were elaborated for the determination of harmaline in a linear concentration range from 0.2 to 100.7 and from 0.4 to 104.5 μmol L−1, respectively, with detection limits of 0.08 and 0.2 μmol L−1, respectively. The practical feasibility of the developed method was demonstrated by quantification of harmaline in the extracts of natural food products such as Syrian rue (Peganum harmala, also known as esphant, harmal, yüzerlik) seeds, locally used as condiment and medicine in Turkey and the Near and Middle East, and the South American shamanic drink component Ayahuasca liane (Banisteriopsis caapi) with results in good agreement with those obtained by high-performance liquid chromatography as a reference method. The proposed sensor represents an effective electrochemical tool and inexpensive alternative for quality control analysis of food products containing harmaline.