Automated, Rapid, and Quantitative Dispersive Liquid–Liquid Microextraction (DLLME) of Pharmaceuticals with Hydrogen Effervescence and Spectrophotometric Determination

A novel technique for effervescent-based dispersive liquid–liquid microextraction is reported. Rapid and continuous effervescence, driven by hydrogen bubbles, was utilized to transfer the analyte from the aqueous to the organic phase. The reactivity of magnesium metal with water was exploited to generate a stream of hydrogen bubbles. In this method, an aqueous sample solution, contained in a microcentrifuge tube, was treated with 1 mg of magnesium and 100 µl of 1-undecanol. Microextraction was initiated by the addition of 100 µl of 1 M sodium bicarbonate to induce a rapid stream of hydrogen bubbles. The microcentrifuge tube was cooled to allow the solidification of 1-undecanol which was carefully separated and analyzed. Factors potentially affecting extraction efficiency were optimized, including the magnesium mass, concentration of sodium bicarbonate, extraction time, pH, open/closed system, sample volume, temperature, and analyte concentrations. These studies revealed the required speed and minimum concentration of sodium bicarbonate, as well as the possibility of efficient microextraction without sodium bicarbonate but in acidic conditions or at elevated temperatures (45–50 °C). The analytical performance was assessed and demonstrated to be promising. In the case of the model drug quercetin, the limit of detection (LOD) was determined to be 0.051 µg/ml, the limit of quantification (LOQ) was 0.154 µg/ml, and the extraction efficiency was 100%. The applicability of this method was also evaluated on samples with variable physicochemical properties, demonstrating an automated, fast, and efficient liquid–liquid microextraction protocol.