A rapid, reusable, and portable electrochemical assay for caffeine monitoring in beverage samples based on boron doped diamond and multi walled carbon nanotubes

Despite potential health risks at high doses, caffeine remains the most widely consumed psychoactive drug globally, naturally occurring in more than 60 plants. Accurate determination of caffeine content is crucial to ensure the safety of consumers of caffeine-containing beverages. This work explores two different electrochemical sensors for caffeine determination: screen-printed carbon electrodes modified with multi-walled carbon nanotubes (MWCNT SPEs) and screen-printed sensors with boron-doped diamond electrodes prepared by chemical vapor deposition (BDD SPEs). These sensors offer advantages over traditional methods, potentially providing faster and more portable analysis. Two linear ranges for caffeine determination were observed at BDD SPEs in 0.5 M H₂SO₄. A lower linear range between 20 μM and 80 μM resulted in a limit of detection (LOD) of 3.40 μM and a limit of quantification (LOQ) of 10.30 μM, while a higher linear range between 100 μM to 500 μM provided the LOD of 9.72 μM and the LOQ of 29.45 μM of caffeine. MWCNT SPEs showed the optimal analytical parameters in the Britton-Robinson buffer at pH 2 with a broader linear range from 33 μM to 500 μM; the LOD was 8.65 μM, and the LOQ was 26.20 μM. The determination of caffeine content was successfully conducted in real dietary samples using both sensors, with validation by high-performance liquid chromatography (HPLC) and spectrophotometric analysis.