Abstract
Monitoring of fixed-bed adsorption processes is crucial for the efficient separation of bioactive compounds. Conventional monitoring techniques, such as flow-injection analysis and in-situ spectrophotometric detection, are effective for measuring the total concentration of a specific class of compounds or the concentration of a single compound. Herein, a simple dual-wavelength fiber-optic sensing technique was developed for the simultaneous measurement of quercetin (QE) and gallic acid (GA) concentrations. The established standard curves for QE and GA show strong linearity (R2 = 0.9922 and R2 = 0.9962) within concentration ranges of 5–50 mg/L and 1–35 mg/L, respectively. This technique was innovatively integrated with the fixed-bed adsorption technique for real-time monitoring of QE and GA during the adsorption process. The experimental conditions for the fixed-bed adsorption system were optimized: the adsorbent was LXT-052 macroporous resins, the adsorption solvent was 10% ethanol, the desorption solvent was 60% ethanol, with feed, washing, and desorption flow rates of 1.0 mL/min, 2.0 mL/min, and 1.5 mL/min, respectively. Under the optimized condition, the separation of QE from GA, along with the simultaneous and accurate determination of both compounds, was successfully achieved. The developed method offers the advantage of real-time monitoring, making it ideal for process monitoring in the fixed-bed adsorptive separation of QE and GA, as well as for the design of such fixed-bed adsorption systems.