A New Sensor Electrode for Caffeine Determination Using Square Wave Voltammetry: Cytosine Modified Glassy Carbon Electrode

In this study, cytosine (CT) modified glassy carbon (GC) electrode was used to investigate the detectability of caffeine (CAF) found in foods such as tea, coffee and soft drinks. Using the cyclic voltammetry (CV) technique, 1 mM CT was prepared in pH 7.2 phosphate buffer solution (PBS) and modified at a scanning rate of 100 mV s-¹ in the potential range of 1.0 V to 2.1 V. CT/GC electrode was characterized by CV, scanning electron microscope (SEM) and electrochemical impedance spectroscopy (EIS) techniques. 1 mM CAF solutions were prepared in different supporting electrolytes such as H₂SO₄, HCl, HNO₃, and CH₃COOH within the potential range of +0.5 V to +1.7 V using square wave voltammetry (SWV) technique. Effect of the supporting electrolyte concentrations were investigated. CAF solutions in the concentration ranges of 0.75 to 0.05 mM and 0.025 to 0.0025 mM were prepared in 100 mM H₂SO₄ supporting electrolyte and calibration graphs were drawn. Line equations were created using the values ​​read from the drawn graphs. Correlation coefficient (R2) values ​​were calculated as 0.9947 and 0.9961, respectively. Using the calibration curves, limit of detection (LOD) and limit of quantification (LOQ) were found as 0.93 µM and 2.79 µM.