Prospects for using a new sequential chemiluminescence strategy for monitoring the caffeine content in soft and energy drinks via the catalytic activities of different nano‐metal oxides

This article suggests a new sequential injection analysis chemiluminescence (SIA‐CL) strategy for monitoring the caffeine (CAF) content in soft and energy drinks using the catalytic activities of different nano‐metal oxides. The present study describes three different SIA‐CL systems (luminol–ferricyanide (III) coupled with Fe₂O₃ or ZnO nanoparticles (NPs), and luminol–H₂O₂ coupled with CuONPs. All experimental conditions were optimized and the linear concentration ranges of pure CAF were evaluated using the calibration graphs. The selectivity of the developed SIA‐CL systems was studied under the influence of various interfering species that may be present in soft or energy drinks such as sodium ions, sucrose, glucose, sodium benzoate, sodium citrate, riboflavin, niacin, citric, phosphoric and ascorbic acids. International Council for Harmonization (ICH) guidelines were obeyed for the validation of the suggested CL methods. The developed SIA‐CL systems displayed linear relationships over the concentration ranges 1.0–350, 5.0–400 and 10.0–400 μg ml^?1 with Fe₂O₃ NPs, ZnO NPs and CuO NPs, respectively. The recorded lower limits of detection and quantification were 0.7, 2.7 and 7.8 μg ml^?1, and 1.0, 5.0 and 10.0 μg ml^?1 for the previously mentioned SIA‐CL systems. The results revealed high selectivity for CAF determination and were in good agreement with those obtained by other reported methods.