Alkanolamine-based deep eutectic solvent as an efficient extractant for dispersive liquid–liquid microextraction of digoxin in human plasma

A dispersive liquid–liquid microextraction utilizing alkanolamine-based deep eutectic solvent was firstly proposed and introduced to preconcentrate trace level of digoxin in human plasma prior to high performance liquid chromatography analysis with deslanoside as the internal standard. In the procedure, a deep eutectic solvent was prepared with N,N-dimethylethanolamine as a hydrogen bond acceptor and n -heptanol as a hydrogen bond donor. Chemical structures of the prepared deep eutectic solvent were characterized by infrared spectroscopy and proton nuclear magnetic resonance spectroscopy. The experimental parameters affecting the extraction performance, including deep eutectic solvent composition, volume of extraction solvent, pH of aqueous sample solution, salt concentration and extraction time, were investigated and optimized. Under the optimum conditions, the method showed good linearity in the range of 0.32–80 ng/mL, precision (relative standard deviations 1.0 %–15 %), accuracy (relative errors −6.4 %–8.5 %) and acceptable extraction recoveries (80.3 %–81.4 %). In addition, satisfactory lower limit of quantification (0.32 ng/mL) and stability were achieved, while matrix effect was not observed in human plasma for the proposed method. It showed that the developed method was efficient, fast and eco-friendly, which provides a potential alternative for the preconcentration and determination of digoxin in complex biological matrices.