Semi-synthetic flavonoids, such as rutin and its aglycone, quercetin, are of considerable interest in nutraceuticals, pharmaceuticals, and traditional medicine due to their health benefits. Here, we report the synthesis of hydroxyapatite (HA), its subsequent modification through gamma irradiation, and fabrication of an electrochemical sensor for the selective and simultaneous determination of quercetin (QR) and rutin (RT). Under optimized conditions, the GI-HA modified glassy carbon electrode (GCE) showcased sharp peaks at 0.29 V and 0.39 V corresponding to the oxidation potentials of QR and RT respectively in phosphate-buffered saline at pH 6. The fabricated sensor exhibited the lowest detection limits of 0.02 µM for QR and 0.018 µM for RT over a wide linear concentration range from 0.02 to 800 µM for both compounds. Furthermore, the sensor displayed excellent storage stability, reproducibility, and repeatability, with relative standard deviations of less than 5 %. The practical applicability of the sensor was demonstrated by measuring QR and RT in amaranthus viridis (a perennial medicinal herb), red onions, and pharmaceutical samples. Interestingly, a transition from RT to QR has been observed in the amaranthus viridis during its cooking in water at temperatures ranging from 80 to 100 ℃. Additionally, the sensor demonstrated a notable increase in QR levels in red onions exposed to sunlight over the course of a week. Thus, the 100 kGy GI-HA modified GCE has the potential to monitor QR and RT in food and pharmaceutical samples, either independently or simultaneously.
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