Extraction and pre-concentration of parabens in liquid pharmaceutical samples by dispersive liquid-liquid microextraction based on deep eutectic solvents.

In this paper dispersive liquid-liquid microextraction using deep eutectic solvent (DES), as an extraction solvent, was applied for the pre-concentration and determination of parabens in liquid pharmaceutical samples. A DES composed of a hydrogen bond acceptor [choline chloride (ChCl)] and a hydrogen bond donor (glucose) achieved the highest extraction efficiency. Therefore, this solvent was selected as the extraction solvent. After the synthesis of this solvent, its various properties were investigated. Thermogravimetric analysis, X-ray diffraction, and Fourier transform infrared spectroscopy were used for this purpose and the successful synthesis of the solvent was confirmed. HPLC with photodiode array detection was used for the analysis of paraben species. Parameters affecting the extraction efficiency were monitored and optimized through univariate analysis and experimental design. Under the optimal conditions (pH of aqueous solution 4.5, ethanol as the disperser solvent, and glucose DES as the extraction solvent), the linearity range of 0.1-5000 ng mL was obtained with the coefficient of determination (R ) between 0.993 and 0.9962. Limits of detections ranged from 0.04 to 0.15 ng mL , with relative standard deviations from 1.8% to 6.8%. The developed method was applied to the determination of parabens in liquid pharmaceuticals such as ampule, syrups, and nose drop samples. A certain amount of paraben was added to the tested real samples to increase their shelf life. The relative recoveries in these real samples ranged between 80.9% and 103.1%.